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Sophie Morier-Genoud of the University of Reims Champagne-Ardenne and Valentin Ovsienko of the Centre National de la Recherche Scientifique, Reims, are awarded the 2025 AMS David P. Robbins Prize for their paper “$q$-deformed rationals and $q$-continued fractions,” published in Forum of Mathematics, Sigma.

“In this groundbreaking work .. it is shown that the new concept has striking connections and applications to a wide range of mathematical areas,” according to the prize citation. “The paper has subsequently inspired a profusion of significant further research developments.”

From the citation

The David P. Robbins Prize is awarded to Sophie Morier-Genoud and Valentin Ovsienko for their paper “$q$-deformed rationals and $q$-continued fractions,” published in Forum of Mathematics, Sigma, in 2020.

The authors provide an entirely novel and natural definition of a $q$-analog of the rational numbers. Although a $q$-analog of the integers has been used extensively since the work of Euler, a satisfactory and meaningful $q$-analog of the rationals had remained elusive until this paper. The definition also leads to a natural $q$-analog of the real numbers and has a wide range of fascinating and far-reaching applications.

A $q$-analog of a mathematical concept is a generalization of the concept which depends on a new parameter $q$ in such a way that the original concept is recovered when $q$ is set to 1, and various interesting or useful properties also arise.

Response of Sophie Morier-Genoud

I am thrilled and honored to receive the 2025 David P. Robbins Prize. This is a fantastic recognition and a great encouragement to keep doing what I like to do. I always had a lot of fun doing mathematics and I feel privileged to do it as a profession. 

I am grateful to everyone who helped me in making this path possible. 

I would like to thank all my collaborators and colleagues in the Math Department at the University of Reims and also everywhere in the world who show interest in the math we are doing and contribute to enrich the theory of $q$-numbers.

Response of Valentin Ovsienko

I am deeply moved to receive this prize, named in honor of David P. Robbins, the creator of mathematical concepts that will forever remain among the most beautiful.

My scientific life has been spent trying to connect different topics in algebra, geometry, and mathematical physics. The $q$-numbers, which is a combinatorial notion, are the result of my journey with my younger and much smarter collaborator Sophie Morier-Genoud, following this route. We tried to better understand connections between cluster algebra, Coxeter friezes, Conway’s ideas, the Jones polynomial... We realized that it is impossible to $q$-deform a singular object, but only an infinite sequence of them! In order to $q$-deform rationals, one needs to count them all. We chose the way of counting determined by continued fractions and the action of the modular group.

Working on this subject has been and remains the happiest part of my scientific life. I was captivated by $q$-rationals and I was completely haunted by $q$-irrationals. This happiness, enhanced by interest of other researchers, in itself is reward enough. 

My collaboration with Sophie produced a variety of results, including two energetic children, Lisa and Anatole; the $q$-numbers are also little kids who need to grow up!

Biographical sketch of Sophie Morier-Genoud

Sophie Morier-Genoud is currently full professor at the University of Reims Champagne-Ardenne in France. She completed her PhD at the University of Lyon (2006) under the supervision of Philippe Caldero. She was T.H. Hildebrandt Assistant Professor at the University of Michigan (2006-2008), postdoctoral fellow of the Fondation Sciences Mathématiques de Paris (2008-2009) and associate professor at Sorbonne Université (2009-2021). Her research work is mainly related to algebraic combinatorics and representation theory. She currently serves as an editor for the column “Gems and Curiosities” of the Mathematical Intelligencer.

Biographical sketch of Valentin Ovsienko

Valentin Ovsienko was born in 1964 in the Soviet Union. He received his PhD in 1989 from Moscow State University under the supervision of Alexandre Kirillov. Ovsienko is currently in Reims, Champagne, as a senior researcher at the French Centre National de la Recherche Scientifique. He worked in projective differential geometry, infinite-dimensional Lie algebras, integrable systems, octonions, and, more recently, in combinatorics. Together with Sophie Morier-Genoud, he is the editor of the column “Gems and Curiosities” of the Mathematical Intelligencer, and he invites everyone to write beautiful articles for it.

About the prize

The David P. Robbins Prize is awarded every three years for a paper with the following characteristics: It reports on novel research in algebra, combinatorics, or discrete mathematics and has a significant experimental component; and it is on a topic which is broadly accessible and provides a simple statement of the problem and clear exposition of the work. Papers published within the six calendar years preceding the year in which the prize is awarded are eligible for consideration.

The 2025 prize will be presented at the 2025 Joint Mathematics Meetings in Seattle.

Learn more about the prize and previous recipients.

Contact: AMS Communications.

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The American Mathematical Society is dedicated to advancing research and connecting the diverse global mathematical community through our publications, meetings and conferences, MathSciNet, professional services, advocacy, and awareness programs.

The two branches of the Kennedy pathways (CDP-choline and CDP-ethanolamine) are the predominant pathways responsible for the synthesis of the most abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively, in mammalian membranes. Recently, hereditary diseases associated with single gene mutations in the Kennedy pathways have been identified. Interestingly, genetic diseases within the same pathway vary greatly, ranging from muscular dystrophy to spastic paraplegia to a childhood blinding disorder to bone deformations. Indeed, different point mutations in the same gene (PCYT1; CCTα) result in at least three distinct diseases. In this review, we will summarize and review the genetic diseases associated with mutations in genes of the Kennedy pathway for phospholipid synthesis. These single-gene disorders provide insight, indeed direct genotype-phenotype relationships, into the biological functions of specific enzymes of the Kennedy pathway. We discuss potential mechanisms of how mutations within the same pathway can cause disparate disease.

Recent studies have suggested that innate immune responses exhibit characteristics associated with memory linked to modulations in both vertebrates and invertebrates. However, the diverse evolutionary paths taken, particularly within the invertebrate taxa, should lead to similarly diverse innate immunity memory processes. Our understanding of innate immune memory in invertebrates primarily comes from studies of the fruit fly Drosophila melanogaster, the generality of which is unclear. Caenorhabditis elegans typically inhabits soil harboring a variety of fatal microbial pathogens; for this invertebrate, the innate immune system and aversive behavior are the major defensive strategies against microbial infection. However, their characteristics of immunological memory remains infantile. Here we discovered an immunological memory that promoted avoidance and suppressed innate immunity during reinfection with bacteria, which we revealed to be specific to the previously exposed pathogens. During this trade-off switch of avoidance and innate immunity, the chemosensory neurons AWB and ADF modulated production of serotonin and dopamine, which in turn decreased expression of the innate immunity-associated genes and led to enhanced avoidance via the downstream insulin-like pathway. Therefore, our current study profiles the immune memories during C. elegans reinfected by pathogenic bacteria and further reveals that the chemosensory neurons, the neurotransmitter(s), and their associated molecular signaling pathways are responsible for a trade-off switch between the two immunological memories.

Distinct cell types emerge from embryonic stem cells through a precise and coordinated execution of gene expression programs during lineage commitment. This is established by the action of lineage specific transcription factors along with chromatin complexes. Numerous studies have focused on epigenetic factors that affect embryonic stem cells (ESC) self-renewal and pluripotency. However, the contribution of chromatin to lineage decisions at the exit from pluripotency has not been as extensively studied. Using a pooled epigenetic shRNA screen strategy, we identified chromatin-related factors critical for differentiation toward mesodermal and endodermal lineages. Here we reveal a critical role for the chromatin protein, ARID4B. Arid4b-deficient mESCs are similar to WT mESCs in the expression of pluripotency factors and their self-renewal. However, ARID4B loss results in defects in up-regulation of the meso/endodermal gene expression program. It was previously shown that Arid4b resides in a complex with SIN3A and HDACS 1 and 2. We identified a physical and functional interaction of ARID4B with HDAC1 rather than HDAC2, suggesting functionally distinct Sin3a subcomplexes might regulate cell fate decisions Finally, we observed that ARID4B deficiency leads to increased H3K27me3 and a reduced H3K27Ac level in key developmental gene loci, whereas a subset of genomic regions gain H3K27Ac marks. Our results demonstrate that epigenetic control through ARID4B plays a key role in the execution of lineage-specific gene expression programs at pluripotency exit.

Thoracic great vessels such as the aorta and subclavian arteries are formed through dynamic remodeling of embryonic pharyngeal arch arteries (PAAs). Previous work has shown that loss of a basic helix-loop-helix transcription factor Hey1 in mice causes abnormal fourth PAA development and lethal great vessel anomalies resembling congenital malformations in humans. However, how Hey1 mediates vascular formation remains unclear. In this study, we revealed that Hey1 in vascular endothelial cells, but not in smooth muscle cells, played essential roles for PAA development and great vessel morphogenesis in mouse embryos. Tek-Cre–mediated Hey1 deletion in endothelial cells affected endothelial tube formation and smooth muscle differentiation in embryonic fourth PAAs and resulted in interruption of the aortic arch and other great vessel malformations. Cell specificity and signal responsiveness of Hey1 expression were controlled through multiple cis-regulatory regions. We found two distal genomic regions that had enhancer activity in endothelial cells and in the pharyngeal epithelium and somites, respectively. The novel endothelial enhancer was conserved across species and was specific to large-caliber arteries. Its transcriptional activity was regulated by Notch signaling in vitro and in vivo, but not by ALK1 signaling and other transcription factors implicated in endothelial cell specificity. The distal endothelial enhancer was not essential for basal Hey1 expression in mouse embryos but may likely serve for Notch-dependent transcriptional control in endothelial cells together with the proximal regulatory region. These findings help in understanding the significance and regulation of endothelial Hey1 as a mediator of multiple signaling pathways in embryonic vascular formation.

α-Linked galactose is a common carbohydrate motif in nature that is processed by a variety of glycoside hydrolases from different families. Terminal Galα1–3Gal motifs are found as a defining feature of different blood group and tissue antigens, as well as the building block of the marine algal galactan λ-carrageenan. The blood group B antigen and linear α-Gal epitope can be processed by glycoside hydrolases in family GH110, whereas the presence of genes encoding GH110 enzymes in polysaccharide utilization loci from marine bacteria suggests a role in processing λ-carrageenan. However, the structure–function relationships underpinning the α-1,3-galactosidase activity within family GH110 remain unknown. Here we focus on a GH110 enzyme (PdGH110B) from the carrageenolytic marine bacterium Pseudoalteromonas distincta U2A. We showed that the enzyme was active on Galα1–3Gal but not the blood group B antigen. X-ray crystal structures in complex with galactose and unhydrolyzed Galα1–3Gal revealed the parallel β-helix fold of the enzyme and the structural basis of its inverting catalytic mechanism. Moreover, an examination of the active site reveals likely adaptations that allow accommodation of fucose in blood group B active GH110 enzymes or, in the case of PdGH110, accommodation of the sulfate groups found on λ-carrageenan. Overall, this work provides insight into the first member of a predominantly marine clade of GH110 enzymes while also illuminating the structural basis of α-1,3-galactoside processing by the family as a whole.

Heme oxygenase-2 (HO2) and -1 (HO1) catalyze heme degradation to biliverdin, CO, and iron, forming an essential link in the heme metabolism network. Tight regulation of the cellular levels and catalytic activities of HO1 and HO2 is important for maintaining heme homeostasis. HO1 expression is transcriptionally regulated; however, HO2 expression is constitutive. How the cellular levels and activity of HO2 are regulated remains unclear. Here, we elucidate the mechanism of post-translational regulation of cellular HO2 levels by heme. We find that, under heme-deficient conditions, HO2 is destabilized and targeted for degradation, suggesting that heme plays a direct role in HO2 regulation. HO2 has three heme binding sites: one at its catalytic site and the others at its two heme regulatory motifs (HRMs). We report that, in contrast to other HRM-containing proteins, the cellular protein level and degradation rate of HO2 are independent of heme binding to the HRMs. Rather, under heme deficiency, loss of heme binding to the catalytic site destabilizes HO2. Consistently, an HO2 catalytic site variant that is unable to bind heme exhibits a constant low protein level and an enhanced protein degradation rate compared with the WT HO2. Finally, HO2 is degraded by the lysosome through chaperone-mediated autophagy, distinct from other HRM-containing proteins and HO1, which are degraded by the proteasome. These results reveal a novel aspect of HO2 regulation and deepen our understanding of HO2's role in maintaining heme homeostasis, paving the way for future investigation into HO2's pathophysiological role in heme deficiency response.

Investigations of bacterial resistance strategies can aid in the development of new antimicrobial drugs as a countermeasure to the increasing worldwide prevalence of bacterial antibiotic resistance. One such strategy involves the TipA class of transcription factors, which constitute minimal autoregulated multidrug resistance (MDR) systems against diverse antibiotics. However, we have insufficient information regarding how antibiotic binding induces transcriptional activation to design molecules that could interfere with this process. To learn more, we determined the crystal structure of SkgA from Caulobacter crescentus as a representative TipA protein. We identified an unexpected spatial orientation and location of the antibiotic-binding TipAS effector domain in the apo state. We observed that the α6–α7 region of the TipAS domain, which is canonically responsible for forming the lid of antibiotic-binding cleft to tightly enclose the bound antibiotic, is involved in the dimeric interface and stabilized via interaction with the DNA-binding domain in the apo state. Further structural and biochemical analyses demonstrated that the unliganded TipAS domain sterically hinders promoter DNA binding but undergoes a remarkable conformational shift upon antibiotic binding to release this autoinhibition via a switch of its α6–α7 region. Hence, the promoters for MDR genes including tipA and RNA polymerases become available for transcription, enabling efficient antibiotic resistance. These insights into the molecular mechanism of activation of TipA proteins advance our understanding of TipA proteins, as well as bacterial MDR systems, and may provide important clues to block bacterial resistance.

Aspergillus terreus is an allergenic fungus, in addition to causing infections in both humans and plants. However, the allergens in this fungus are still unknown, limiting the development of diagnostic and therapeutic strategies. We used a proteomic approach to search for allergens, identifying 16 allergens based on two-dimensional immunoblotting with A. terreus susceptible patient sera. We further characterized triose-phosphate isomerase (Asp t 36), one of the dominant IgE (IgE)-reactive proteins. The gene was cloned and expressed in Escherichia coli. Phylogenetic analysis showed Asp t 36 to be highly conserved with close similarity to the triose-phosphate isomerase protein sequence from Dermatophagoides farinae, an allergenic dust mite. We identified four immunodominant epitopes using synthetic peptides, and mapped them on a homology-based model of the tertiary structure of Asp t 36. Among these, two were found to create a continuous surface patch on the 3D structure, rendering it an IgE-binding hotspot. Biophysical analysis indicated that Asp t 36 shows similar secondary structure content and temperature sensitivity with other reported triose-phosphate isomerase allergens. In vivo studies using a murine model displayed that the recombinant Asp t 36 was able to stimulate airway inflammation, as demonstrated by an influx of eosinophils, goblet cell hyperplasia, elevated serum Igs, and induction of Th2 cytokines. Collectively, our results reveal the immunogenic property of Asp t 36, a major allergen from A. terreus, and define a new fungal allergen more broadly. This allergen could serve as a potent candidate for investigating component resolved diagnosis and immunotherapy.

Identification of antibody-binding epitopes is crucial to understand immunological mechanisms. It is of particular interest for allergenic proteins with high cross-reactivity as observed in the lipid transfer protein (LTP) syndrome, which is characterized by severe allergic reactions. Art v 3, a pollen LTP from mugwort, is frequently involved in this cross-reactivity, but no antibody-binding epitopes have been determined so far. To reveal human IgE-binding regions of Art v 3, we produced three murine high-affinity mAbs, which showed 70–90% coverage of the allergenic epitopes from mugwort pollen–allergic patients. As reliable methods to determine structural epitopes with tightly interacting intact antibodies under native conditions are lacking, we developed a straightforward NMR approach termed hydrogen/deuterium exchange memory (HDXMEM). It relies on the slow exchange between the invisible antigen-mAb complex and the free 15N-labeled antigen whose 1H-15N correlations are detected. Due to a memory effect, changes of NH protection during antibody binding are measured. Differences in H/D exchange rates and analyses of mAb reactivity to homologous LTPs revealed three structural epitopes: two partially cross-reactive regions around α-helices 2 and 4 as well as a novel Art v 3–specific epitope at the C terminus. Protein variants with exchanged epitope residues confirmed the antibody-binding sites and revealed strongly reduced IgE reactivity. Using the novel HDXMEM for NMR epitope mapping allowed identification of the first structural epitopes of an allergenic pollen LTP. This knowledge enables improved cross-reactivity prediction for patients suffering from LTP allergy and facilitates design of therapeutics.

18 August 2020

27 August 2020

Climate migration: Ways ahead from the next generation The World Today rsoppelsa.drupal 25 May 2022

Ella Dennis and Mike Higgins talk to young activists seeking solutions as global warming wreaks havoc in sub-Saharan Africa

Africa has the lowest carbon emissions per capita yet the highest rate of temperature increase in the world. Rising levels of desertification, drought and flooding are already forcing millions of Africans to relocate to find more stable livelihoods. 

The continent’s youth will bear the brunt of this climate migration problem. It is estimated that by 2050, Africa will be home to 86 million internal climate migrants.

How is climate migration already affecting sub-Saharan Africa and what frameworks could tackle it? To begin to answer those questions, five young activists from across the region, who are members of Chatham House’s Common Futures Conversations, took part in a panel discussion at the world’s first youth-led Conference on Climate Migration, convened in April by the Alliance for Citizen Engagement, a nonpartisan think tank based in the US. 

The conversation and follow-up discussions focused on a common problem – climate migration brings people into conflict and puts pressure on infrastructure. 

In Kenya, droughts have left 3.5 million people hungry and the chronic flooding of several lakes in the Rift Valley has displaced hundreds of thousands, said Gerald Muchiri, 29, a social scientist from Kenya. One result has been outbreaks of violence between pastoralists such as the Orma people and the farmers of the Pokomo community, said Laura Mukhwana, 33, a PhD student in Kenya. She believes this violence is likely to worsen. ‘Inter-group conflicts will pose even larger security concerns for surrounding communities as climate migration intensifies,’ she said.

Suleman Nuhu, 24, a farmer and veterinary student from Nigeria, said farmer-herder conflicts were his country’s most significant climate-migration issue. The movement of nomadic tribes from the north had affected him personally: ‘Nomads have trespassed on [my family’s] farms many times while moving with their livestock, destroying our crops.’ 

Changes in climate also force people to move from rural to urban areas. Nigeria, for instance, struggles with the so-called ‘Lagos problem’, said Temiloluwa Lawal, 25, a lawyer and researcher from Nigeria. An estimated 22 million people, a number that is rising fast, are crammed into a city smaller than Greater London. While not on the same scale, Zimbabwe experiences comparable challenges, said Tinotenda Dube, 29, a Zimbabwean finance director. Thanks to drought, unemployed rural migrants arriving in cities ‘put excessive pressure on service delivery against a low tax base,’ he said. ‘People, including close family members of mine, are crowded in dilapidated homes because they cannot afford to pay rent for decent housing.’ 

But there is hope, say the activists. Dube believes that affordable housing is an ‘integral component of [tackling] the climate migration crisis’. 

In Zimbabwe, he has developed a low-cost home finance model that, he said, has helped more than 250 low-income households find good-quality accommodation. Alongside this initiative, Dube has co-founded a property and construction company, Solinfra Zimbabwe Private Ltd, to provide low-cost housing. 

Muchiri is taking action in Kenya, founding an NGO called Social Assistance Welfare to tackle public health issues, he said: ‘As climate migration becomes more intense, I expect preventable health issues to increase throughout the region, and thus see Social Assistance Welfare as an important mitigation.’

In Nigeria, Nuhu noted that to help reduce conflict between farmers and herders social-media campaigns are encouraging pastoralists to move from nomadic livestock farming to more efficient intensive systems, using ranching and grazing reserves. ‘As for food security problems, the best mitigation is to reduce reliance on rain-fed agriculture through irrigation schemes,’ he said. 

All five agreed that, in their experience, the youth of sub-Saharan Africa could be better informed about climate migration. But they took encouragement from the fact the young are passionate about tackling issues arising from the broader climate crisis. 

In Kenya, Mukhwana pointed to successful youth projects around agro-forestry and tree-planting. She added that there is ‘a growing movement of urban youth who are advocating for climate justice, such as the Kenyan Youth Environmental Network and Fridays for the Future Kenya’. It was pleasing too, she said, that when the Kenyan government revised its contributions to the Paris Climate Accords it staged a week-long youth conference to include their opinions.

‘Overall, I am quite hopeful about how the youth are mobilizing themselves in Kenya,’ she added.

Find out more about Chatham House’s Common Futures Conversations
 

Why Ethiopia must close its political gender gap The World Today mhiggins.drupal 29 July 2022

Women urgently need to gain access to high office if the country hopes to survive, say Hilina Berhanu Degefa and Emebet Getachew.

At the end of 2021, Prime Minister Abiy Ahmed’s government announced the formation of a three-year national dialogue to address Ethiopia’s political crisis, looking at the ongoing civil war and conflict, inflation, unemployment, drought and other urgent domestic issues. 

But, while efforts have been made to ensure the participation of women in this dialogue, it must be more than symbolic otherwise gaps in meaningful gender inclusion could have significant implications on the very survival of the country.
 
One of the challenges for meaningful inclusion is that Ethiopia is a highly patriarchal society. Patriarchal norms and practices permeate all aspects of the country’s social, economic and political life. Women constitute over half of the Ethiopian population and represent 41 per cent of the national parliament.

Nevertheless, most political parties, including those with liberal credentials, are exclusively governed by men, with women taking almost no part in key decision-making processes. As a result, women are relegated to the margins of political and economic activities. 

Though there has been little systematic study of the structural challenges faced by Ethiopian women in politics, women members of political parties encounter many barriers, including political violence, male-coded norms and sexist discourses across Ethiopian society.
 
The nature and scale of political violence perpetrated against women is particularly disempowering and affects their ability to participate in political spaces.

While attitudes to gender equality, sexual violence and gender discrimination are often trivialized, they remain ever-present threats in women’s lives. As late as 2016, a significant minority of men still believed wife-beating to be justified in certain situations. Even when women overcome social pressure to pursue their political ambitions, patriarchal views and practices within political party structures about the role of women significantly undermine their active participation and engagement. 

The political space is even more inaccessible to women with disabilities and in conflict and climate-related crises such as among internally displaced people and in pastoral communities. Male-coded norms ingrained at both party and community levels remain a significant concern. Specifically, sex in exchange for candidacy, inconsiderate working schedules affecting women with children and denial of access to equal information and financial resources are frequently reported as major internal hurdles among political parties.

Closing the gender gap could offer Ethiopia a new beginning

Many political initiatives designed to tackle these gender imbalances often have been driven by short-term political considerations without proper gender-gap assessment and policy analysis. In most cases, the authorities have viewed gender-targeted reforms as acts of benevolence, dispensed by the government, without adopting the legal and financial measures necessary to ensure sustainability and impact.
 
Take, for example, Abiy’s appointment of a 50:50 gender-balanced cabinet in 2018. At the time, much was made about its transformative potential, with the prime minister attracting widespread global approval. Yet, a cabinet reshuffle in 2021 reduced female representation to 36.3 per cent, with far less scrutiny or accountability.

This indicates that gender equality in Ethiopia is not considered a priority but rather an endeavour for more opportune, ‘stable’ times. Without thorough measures that create the conditions for real change, the aspiration of having a gender-balanced cabinet will always be challenging to translate into lasting equal representation.
 
The proposed national dialogue presents an ideal opportunity for Ethiopian women to begin reshaping attitudes and closing the gender gap through their inclusion and participation in the political process. To do so, three issues must be addressed.
 
First, the varying rights of women need to be consolidated, including on identity, constitutional reform and economic issues .

Second, gender equality considerations must be absorbed into mainstream political discourse at all levels.

Third, the experiences of women in the recent war, other ongoing conflicts and past and lingering legacies of political violence targeting women from specific communities, must be acknowledged and remedied. 

If Ethiopia is indeed serious about addressing its asymmetric gender power dynamics, this national dialogue provides an excellent opportunity to begin the process. Genuine participation of women as independent actors, with their own agency, could offer Ethiopia a new beginning.

A new vision for African agency in sustainable development Expert comment LJefferson 18 October 2022

Change is necessary not only in global economic structures and attitudes – but in African governance too.

The conventional notion that Africa is mostly a consumer of norms and practices designed by the Global North has been repeatedly challenged and is increasingly being debunked. Increased African agency in international affairs is today a well-established and documented reality. But Africa’s influence still does not match the scale of the challenges that it faces on its pathway to sustainable development. 

Pushing for African agency in sustainable development also warrants a critical assessment of how ‘sustainable development’ should be defined, and how it can be achieved in terms of actual poverty reduction and real improvement in the lives of local poor Africans. Sustainable development has been a political catchphrase for over 30 years – but a genuine transition towards sustainability has yet to begin.

African agency today

Historically, there have been structural limitations on the agency of African stakeholders to shape development pathways. Chief among them, donor-recipient power dynamics have persistently promoted dependency and sustained institutional corruption. Many African countries are also challenged by economic incentives and infrastructure that have favoured the market demands and supply chains of former colonial powers, which largely remain reliant on natural resource extraction, and are marked by limited investment in value-addition activities and technology development.

Today, however, African agency is being exerted in a more assertive fashion. The African Union (AU), individual African states, civil society, the private sector and eminent and ordinary persons are all displaying Africa’s agency in steering global sustainable development priorities, namely by proposing their own development agenda, The African Union Agenda 2063, adopted in 2013. This was followed by the UN Sustainable Development Goals (Agenda 2030), which in many ways mirror Agenda 2063 – a clear demonstration of the influence of Africa in the global arena. 

Agenda 2063 is a strategic roadmap for Africa ‘to build an integrated, prosperous and peaceful Africa, driven and managed by its own citizens and development goals representing a dynamic force in the international arena’. Prepared following a broad-based participatory consultation, it advocates for inclusion and empowerment and provides an excellent vision for African countries and African people. The SDGs address several of the key shortcomings of their predecessor – the MDGs – and incorporate a broader and more transformative agenda that more adequately reflects the complex challenges of the 21st century and the need for structural reforms in the global economy and governance norms.

In international forums on sustainable development, African countries are increasingly using their collective voice to change the discourse on how development can and should be done. For instance, by championing innovative solutions for carbon markets, African policy leaders are enabling access to climate finance for development while preserving Africa’s natural wealth.

In the post-COVID era, championing investments in and leadership of Africa’s global health architecture demonstrates a desire that in the next pandemic, Africa CDC, AMA and continental manufacturers will play leading roles in determining Africa’s public health strategy and implementation.

In trade, building on the groundwork led by the regional economic commissions, the AfCFTA will catalyse and scale regional integration, trade and cooperation, leading to promising new modes of supply chain and self-sufficiency.

Encouraging signs, but persistent shortcomings

Encouraging signs that African agency is gaining momentum cannot disguise the fact that Africa has yet to move from rhetoric to implementation in the realm of sustainable development. Continental visions often fail to go beyond declarations of intent, and have only limited influence on governance systems or national structural transformation, and African states remain vulnerable to economic shocks emanating from the global system.

Change will require governance systems that are coordinated, transparent, efficient, and inclusive, as well as tools, processes, and means (material, technical, and human) for successful implementation. There is an urgent need for a new governance paradigm in Africa and internationally, dealing with long-term social change.

Notably, African agency should not be only seen as emanating from government, but also as being exerted by independent civil society organizations and committed ordinary individuals. Effective agency needs to be multi-faceted and multi-actor, and depends on the inclusiveness of African governments and their willingness to work with civil society in their strategic engagements with external partners.

Both Agenda 2063 and the SDGs hold the potential for transformation, but implementation will depend on continued advocacy to hold authorities to account and change the dominant discourse, logic and rules of engagement at global, regional, national, and local levels. There is a need for a dynamic new model of African ‘development’.

Time for a new vision

Africa’s economic landscape is changing rapidly, with new regional and local value chains, and integrated regional economic corridors to link countries, minimize the burden of high-cost production and logistics, and boost real incomes and international competitiveness. But Africa continues to face structural challenges, including the need for large investment projects – at a time when Africa remains a net exporter of capital.

Donors and development partners must reflect upon their prior modes of engagement and commit to genuine and equitable relationships with African states. Such partnerships must reflect mutual respect of ideas and accountability, and commit to making space in international forums and multi-lateral arrangements for African people and countries to realize their own visions for progress.

But African leaders and actors must also recognize that with the advent of resources and agency comes responsibility for results and outcomes, notably the need to improve governance. Gaps in accountability, widespread corruption, and lack of successful implementation and sustainability of projects must be addressed.

Africa’s maritime agency cannot be overlooked Expert comment LJefferson 3 November 2022

Increasing maritime awareness has already delivered impact, but consistency and continental leadership are needed to realize the sector’s full potential.

Africa’s 48,000 kilometres of coastline, shared among 38 coastal states, are resource rich and hold some of the world’s most strategic sea lanes, including the approaches to the Suez Canal, which carries 12 per cent of worldwide trade, and the Gulf of Guinea, a critical route for global energy. But despite the vast potential this represents, piracy and maritime insecurity have dominated the narrative of Africa’s coasts, and further propagated the image of African states as beholden to external intervention.

Yet African agency is established and evolving in the sector, with African littoral states enhancing their capacity to face collective security threats and exercising increasing autonomy in responding to the recent rush of external actors looking for port facilities and military bases. Enhanced continental coordination, consistency and leadership can help Africa’s maritime endowment become a resource that can bring sustainable benefit across the continent.  

Agency beyond piracy: the Gulf of Aden and Western Indian Ocean

Piracy became the dominant frame of reference for the East African maritime space as a result of the crisis off the coast of Somalia, which peaked between 2008 and 2012. In 2008, the UN Security Council (UNSC) took the unprecedented step of authorizing international naval operations in Somali territorial waters, contributing to a gradual reduction in attacks. There have been no successful hijackings reported since 2017.

But progress has not just been down to international assistance. Somalia is prioritizing increased domestic enforcement capacity – as demonstrated in the establishment of  a new specialized maritime unit and the wider region enhanced collaboration and information sharing through the Djibouti Code of Conduct of 2009, amended in 2017.

South Africa’s recent admission as a new signatory demonstrates its continued relevance. In March 2022, the UNSC authorization lapsed, following pressure from the Somali government. Although it is not yet clear whether Somali efforts will be sufficient to repress piracy in the long term, this reverse was a clear statement of Somalia’s agency at a level unthinkable during the outset of the crisis.

As the immediate threat of piracy has quietened, broader geopolitical dynamics have come to the fore, notably in a surge by external actors to establish strategic ports and military bases. Here too, African states have demonstrated enhanced agency, for better or worse. Consider Djibouti’s unilateral seizure of a container terminal from an Emirati firm, Sudan’s review of Russian and Turkish deals for maritime facilities, Tanzania’s rejection of a Chinese-led port investment, or the Seychelles withdrawing agreement for an Indian naval base.

Such examples point to a growing awareness of the value of maritime resources within African states, alongside a willingness and ability to push back against external imposition – and indeed to innovate in finding solutions beyond infrastructure and ‘hard’ security. In 2018, the Seychelles launched the world’s first sovereign blue bond to fund sustainable marine projects. That other countries are seeking to replicate this model points to the potentially global impact of African leadership on maritime issues.

Regional cooperation or competition in the Gulf of Guinea?

The Gulf of Guinea is likewise resource rich and geographically strategic, and has faced diverse maritime security threats including piracy, smuggling, illegal fishing, oil theft and pollution. Gulf of Guinea states put in place several initiatives to promote security, including the Yaoundé Code of Conduct (YCoC), signed by 25 states in 2013, that led to information-sharing and cooperation on interdiction, investigation and prosecution. But crime in the Gulf of Guinea nonetheless reached an all-time high in 2020, suffering 130 of the 135 maritime kidnappings recorded worldwide, due to the non-binding nature of the YCoC and gaps in capacity and finance.

Though external actors have become increasingly engaged, including the EU, US, France, Denmark, and the G7++ Group of Friends of the Gulf of Guinea (FOGG), states within the region, especially those most affected by piracy and armed robbery, have nonetheless demonstrated leadership. Nigeria, Ghana, and Cote D’Ivoire have all developed maritime security strategies; Nigeria launched its Deep Blue Project to secure Nigerian waters; Ghana has strengthened its navy; and Togo has changed its laws and judicial system to allow the arrest and prosecution of ships and persons. Maritime security incidents have consequently reduced in 2022.

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Visual Abstract

Felicia Grasso
Dec 1, 2020; 19:1986-1996
Research

Madison T Wright
Nov 18, 2020; 0:RA120.002168v1-mcp.RA120.002168
Research

Mingkun Yang
Nov 24, 2020; 0:RA120.002144v1-mcp.RA120.002144
Research

Qin Zhang
Nov 17, 2020; 0:RA120.002325v1-mcp.RA120.002325
Research

Kailun Fang
Nov 30, 2020; 0:RA120.002081v1-mcp.RA120.002081
Research

Colin T. McDowell
Nov 24, 2020; 0:RA120.002256v1-mcp.RA120.002256
Research

Congcong Lu
Nov 17, 2020; 0:R120.002257v1-mcp.R120.002257
Review

Adult progenitor cell populations typically exist in a quiescent state within a controlled niche environment. However, various stresses or forms of damage can disrupt this state, which often leads to dysfunction and aging. We built a glucocorticoid (GC)-induced liver damage model of mice, found that GC stress induced liver damage, leading to consequences for progenitor cells expansion. However, the mechanisms by which niche factors cause progenitor cells proliferation are largely unknown. We demonstrate that, within the liver progenitor cells niche, Galectin-3 (Gal-3) is responsible for driving a subset of progenitor cells to break quiescence. We show that GC stress causes aging of the niche, which induces the up-regulation of Gal-3. The increased Gal-3 population increasingly interacts with the progenitor cell marker CD133, which triggers focal adhesion kinase (FAK)/AMP-activated kinase (AMPK) signaling. This results in the loss of quiescence and leads to the eventual stemness exhaustion of progenitor cells. Conversely, blocking Gal-3 with the inhibitor TD139 prevents the loss of stemness and improves liver function. These experiments identify a stress-dependent change in progenitor cell niche that directly influence liver progenitor cell quiescence and function.

Gle1 is a conserved, essential regulator of DEAD-box RNA helicases, with critical roles defined in mRNA export, translation initiation, translation termination, and stress granule formation. Mechanisms that specify which, where, and when DDXs are targeted by Gle1 are critical to understand. In addition to roles for stress-induced phosphorylation and inositol hexakisphosphate binding in specifying Gle1 function, Gle1 oligomerizes via its N-terminal domain in a phosphorylation-dependent manner. However, a thorough analysis of the role for Gle1 self-association is lacking. Here, we find that Gle1 self-association is driven by two distinct regions: a coiled-coil domain and a novel 10-amino acid aggregation-prone region, both of which are necessary for proper Gle1 oligomerization. By exogenous expression in HeLa cells, we tested the function of a series of mutations that impact the oligomerization domains of the Gle1A and Gle1B isoforms. Gle1 oligomerization is necessary for many, but not all aspects of Gle1A and Gle1B function, and the requirements for each interaction domain differ. Whereas the coiled-coil domain and aggregation-prone region additively contribute to competent mRNA export and stress granule formation, both self-association domains are independently required for regulation of translation under cellular stress. In contrast, Gle1 self-association is dispensable for phosphorylation and nonstressed translation initiation. Collectively, we reveal self-association functions as an additional mode of Gle1 regulation to ensure proper mRNA export and translation. This work also provides further insight into the mechanisms underlying human gle1 disease mutants found in prenatally lethal forms of arthrogryposis.

Kinases are critical components of intracellular signaling pathways and have been extensively investigated with regard to their roles in cancer. p21-activated kinase-1 (PAK1) is a serine/threonine kinase that has been previously implicated in numerous biological processes, such as cell migration, cell cycle progression, cell motility, invasion, and angiogenesis, in glioma and other cancers. However, the signaling network linked to PAK1 is not fully defined. We previously reported a large-scale yeast genetic interaction screen using toxicity as a readout to identify candidate PAK1 genetic interactions. En masse transformation of the PAK1 gene into 4,653 homozygous diploid Saccharomyces cerevisiae yeast deletion mutants identified ∼400 candidates that suppressed yeast toxicity. Here we selected 19 candidate PAK1 genetic interactions that had human orthologs and were expressed in glioma for further examination in mammalian cells, brain slice cultures, and orthotopic glioma models. RNAi and pharmacological inhibition of potential PAK1 interactors confirmed that DPP4, KIF11, mTOR, PKM2, SGPP1, TTK, and YWHAE regulate PAK1-induced cell migration and revealed the importance of genes related to the mitotic spindle, proteolysis, autophagy, and metabolism in PAK1-mediated glioma cell migration, drug resistance, and proliferation. AKT1 was further identified as a downstream mediator of the PAK1-TTK genetic interaction. Taken together, these data provide a global view of PAK1-mediated signal transduction pathways and point to potential new drug targets for glioma therapy.

AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism that phosphorylates a wide range of proteins to maintain cellular homeostasis. AMPK consists of three subunits: α, β, and γ. AMPKα and β are encoded by two genes, the γ subunit by three genes, all of which are expressed in a tissue-specific manner. It is not fully understood, whether individual isoforms have different functions. Using RNA-Seq technology, we provide evidence that the loss of AMPKβ1 and AMPKβ2 lead to different gene expression profiles in human induced pluripotent stem cells (hiPSCs), indicating isoform-specific function. The knockout of AMPKβ2 was associated with a higher number of differentially regulated genes than the deletion of AMPKβ1, suggesting that AMPKβ2 has a more comprehensive impact on the transcriptome. Bioinformatics analysis identified cell differentiation as one biological function being specifically associated with AMPKβ2. Correspondingly, the two isoforms differentially affected lineage decision toward a cardiac cell fate. Although the lack of PRKAB1 impacted differentiation into cardiomyocytes only at late stages of cardiac maturation, the availability of PRKAB2 was indispensable for mesoderm specification as shown by gene expression analysis and histochemical staining for cardiac lineage markers such as cTnT, GATA4, and NKX2.5. Ultimately, the lack of AMPKβ1 impairs, whereas deficiency of AMPKβ2 abrogates differentiation into cardiomyocytes. Finally, we demonstrate that AMPK affects cellular physiology by engaging in the regulation of hiPSC transcription in an isoform-specific manner, providing the basis for further investigations elucidating the role of dedicated AMPK subunits in the modulation of gene expression.

Akt3 regulates mitochondrial content in endothelial cells through the inhibition of PGC-1α nuclear localization and is also required for angiogenesis. However, whether there is a direct link between mitochondrial function and angiogenesis is unknown. Here we show that Akt3 depletion in primary endothelial cells results in decreased uncoupled oxygen consumption, increased fission, decreased membrane potential, and increased expression of the mitochondria-specific protein chaperones, HSP60 and HSP10, suggesting that Akt3 is required for mitochondrial homeostasis. Direct inhibition of mitochondrial homeostasis by the model oxidant paraquat results in decreased angiogenesis, showing a direct link between angiogenesis and mitochondrial function. Next, in exploring functional links to PGC-1α, the master regulator of mitochondrial biogenesis, we searched for compounds that induce this process. We found that, sildenafil, a phosphodiesterase 5 inhibitor, induced mitochondrial biogenesis as measured by increased uncoupled oxygen consumption, mitochondrial DNA content, and voltage-dependent anion channel protein expression. Sildenafil rescued the effects on mitochondria by Akt3 depletion or pharmacological inhibition and promoted angiogenesis, further supporting that mitochondrial homeostasis is required for angiogenesis. Sildenafil also induces the expression of PGC-1 family member PRC and can compensate for PGC-1α activity during mitochondrial stress by an Akt3-independent mechanism. The induction of PRC by sildenafil depends upon cAMP and the transcription factor CREB. Thus, PRC can functionally substitute during Akt3 depletion for absent PGC-1α activity to restore mitochondrial homeostasis and promote angiogenesis. These findings show that mitochondrial homeostasis as controlled by the PGC family of transcriptional activators is required for angiogenic responses.

The tenovins are a frequently studied class of compounds capable of inhibiting sirtuin activity, which is thought to result in increased acetylation and protection of the tumor suppressor p53 from degradation. However, as we and other laboratories have shown previously, certain tenovins are also capable of inhibiting autophagic flux, demonstrating the ability of these compounds to engage with more than one target. In this study, we present two additional mechanisms by which tenovins are able to activate p53 and kill tumor cells in culture. These mechanisms are the inhibition of a key enzyme of the de novo pyrimidine synthesis pathway, dihydroorotate dehydrogenase (DHODH), and the blockage of uridine transport into cells. These findings hold a 3-fold significance: first, we demonstrate that tenovins, and perhaps other compounds that activate p53, may activate p53 by more than one mechanism; second, that work previously conducted with certain tenovins as SirT1 inhibitors should additionally be viewed through the lens of DHODH inhibition as this is a major contributor to the mechanism of action of the most widely used tenovins; and finally, that small changes in the structure of a small molecule can lead to a dramatic change in the target profile of the molecule even when the phenotypic readout remains static.

Priyanka Tripathi
Dec 30, 2020; 0:jlr.RA120001190v1-jlr.RA120001190
Research Articles

Stephanie E. Hood
Dec 1, 2020; 61:1720-1732
Research Articles

Melissa Gómez
Dec 1, 2020; 61:1658-1674
Research Articles

Jiayan Guo
Dec 1, 2020; 61:1764-1775
Research Articles

Montgomery Blencowe
Dec 23, 2020; 0:jlr.RA120000713v1-jlr.RA120000713
Research Articles

Oktawia Nilsson
Nov 17, 2020; 0:jlr.RA120000920v1-jlr.RA120000920
Research Articles

Babunageswararao Kanuri
Nov 17, 2020; 0:jlr.RA120001101v1-jlr.RA120001101
Research Articles