RGCC balances self‐renewal and neuronal differentiation of neural stem cells in the developing mammalian neocortex

During neocortical development, neural stem cells (NSCs) divide symmetrically to self‐renew at the early stage and then divide asymmetrically to generate post‐mitotic neurons. The molecular mechanisms regulating the balance between NSC self‐renewal and neurogenesis are not fully understood. Using mouse in utero electroporation (IUE) technique and in vitro human NSC differentiation models including cerebral organoids (hCOs), we show here that regulator of cell cycle (RGCC) modulates NSC self‐renewal and neuronal differentiation by affecting cell cycle regulation and spindle orientation. RGCC deficiency hampers normal cell cycle process and dysregulates the mitotic spindle, thus driving more cells to divide asymmetrically. These modulations diminish the NSC population and cause NSC pre‐differentiation that eventually leads to brain developmental malformation in hCOs. We further show that RGCC might regulate NSC spindle orientation by affecting the organization of centrosome and microtubules. Our results demonstrate that RGCC is essential to maintain the NSC pool during cortical development and suggest that RGCC defects could have etiological roles in human brain malformations.     

Cryo‐EM structures of perforin‐2 in isolation and assembled on a membrane suggest a mechanism for pore formation

Perforin‐2 (PFN2, MPEG1) is a key pore‐forming protein in mammalian innate immunity restricting intracellular bacteria proliferation. It forms a membrane‐bound pre‐pore complex that converts to a pore‐forming structure upon acidification; but its mechanism of conformational transition has been debated. Here we used cryo‐electron microscopy, tomography and subtomogram averaging to determine structures of PFN2 in pre‐pore and pore conformations in isolation and bound to liposomes. In isolation and upon acidification, the pre‐assembled complete pre‐pore rings convert to pores in both flat ring and twisted conformations. On membranes, in situ assembled PFN2 pre‐pores display various degrees of completeness; whereas PFN2 pores are mainly incomplete arc structures that follow the same subunit packing arrangements as found in isolation. Both assemblies on membranes use their P2 β‐hairpin for binding to the lipid membrane surface. Overall, these structural snapshots suggest a molecular mechanism for PFN2 pre‐pore to pore transition on a targeted membrane, potentially using the twisted pore as an intermediate or alternative state to the flat conformation, with the capacity to cause bilayer distortion during membrane insertion.     

Special AT‐rich sequence‐binding protein 2 (Satb2) synergizes with Bmp9 and is essential for osteo/odontogenic differentiation of mouse incisor mesenchymal stem cells

ObjectivesMouse incisor mesenchymal stem cells (MSCs) have self‐renewal ability and osteo/odontogenic differentiation potential. However, the mechanism controlling the continuous self‐renewal and osteo/odontogenic differentiation of mouse incisor MSCs remains unclear. Special AT‐rich sequence‐binding protein 2 (SATB2) positively regulates craniofacial patterning, bone development and regeneration, whereas SATB2 deletion or mutation leads to craniomaxillofacial dysplasia and delayed tooth and root development, similar to bone morphogenetic protein (BMP) loss‐of‐function phenotypes. However, the detailed mechanism underlying the SATB2 role in odontogenic MSCs is poorly understood. The aim of this study was to investigate whether SATB2 can regulate self‐renewal and osteo/odontogenic differentiation of odontogenic MSCs.Materials and methods Satb2 expression was detected in the rapidly renewing mouse incisor mesenchyme by immunofluorescence staining, quantitative RT‐PCR and Western blot analysis. Ad‐Satb2 and Ad‐siSatb2 were constructed to evaluate the effect of Satb2 on odontogenic MSCs self‐renewal and osteo/odontogenic differentiation properties and the potential role of Satb2 with the osteogenic factor bone morphogenetic protein 9 (Bmp 9) in vitro and in vivo.Results Satb2 was found to be expressed in mesenchymal cells and pre‐odontoblasts/odontoblasts. We further discovered that Satb2 effectively enhances mouse incisor MSCs self‐renewal. Satb2 acted synergistically with the potent osteogenic factor Bmp9 in inducing osteo/odontogenic differentiation of mouse incisor MSCs in vitro and in vivo.Conclusions Satb2 promotes self‐renewal and osteo/odontogenic differentiation of mouse incisor MSCs. Thus, Satb2 can cooperate with Bmp9 as a new efficacious bio‐factor for osteogenic regeneration and tooth engineering.     

Influence of plant reproductive systems on the evolution of hummingbird pollination

Many hummingbird‐pollinated plant species evolved from bee‐pollinated ancestors independently in many different habitats in North and South America. The mechanisms leading to these transitions are not completely understood. We conducted pollination and germination experiments and analyzed additional reproductive traits in three sister species pairs of which one species is bee‐ and the other hummingbird‐pollinated. All hummingbird‐pollinated species showed higher seed set and germination rates in cross‐pollinated than in self‐pollinated flowers. In the self‐compatible, bee‐pollinated sister species this difference did not exist. As expected, seed set and germination rate were higher after cross‐pollination in the largely self‐incompatible genus Penstemon independently of the pollination syndrome. However, the bird‐pollinated species produce only half of the amount of ovules and pollen grains per flower compared to the bee‐pollinated sister species. This indicates that hummingbird pollination is much more efficient in self‐incompatible populations because hummingbirds waste less pollen and provide higher outcrossing rates. Therefore, hummingbird pollination is less resource costly. Overall, we suggest that hummingbirds may increase the reproductive success compared to bees, influencing the evolution of hummingbird pollination in ecosystems with diverse bee assemblages.     

Temperature‐induced multi‐species cohort effects in sympatric snakes

In reptiles, reproductive maturity is often determined by size rather than age. Consequently, growth early in life may influence population dynamics through effects on generation time and survival to reproduction. Because reproductive phenology and pre‐ and post‐natal growth are temperature dependent, environmental conditions may induce multi‐species cohort effects on body size in sympatric reptiles. I present evidence of this using 10 years of neonatal size data for three sympatric viviparous snakes, Dekay''s Brown snakes (Storeria dekayi), Red‐bellied Snakes (S. occipitomaculata), and Common Garter snakes (Thamnophis sirtalis). End‐of‐season neonatal size varied in parallel across species such that snout–vent length was 36%–61% greater and mass was 65%–223% greater in years when gestating females could achieve higher April–May (vs. June–July or August–September) operative temperatures. Thus, temperature had a larger impact during follicular enlargement and ovulation than during gestation or post‐natal growth. Multi‐species cohort effects like these may affect population dynamics and the magnitude of these effects may increase with climate change.     

Sexual selection,feather wear,and time constraints on the pre‐basic molt explain the acquisition of the pre‐alternate molt in European passerines

Avian feathers need to be replaced periodically to fulfill their functions, with natural, social, and sexual selection presumably driving the evolution of molting strategies. In temperate birds, a common pattern is to molt feathers immediately after the breeding season, the pre‐basic molt. However, some species undergo another molt in winter‐spring, the pre‐alternate molt. Using a sample of 188 European passerine species, Bayesian phylogenetic mixed models, and correlated evolution analyses, we tested whether the occurrence of the pre‐alternate molt was positively associated with proxies for sexual selection (sexual selection hypothesis) and nonsexual social selection (social selection hypothesis), and with factors related to feather wear (feather wear hypothesis) and time constraints on the pre‐basic molt (time constraints hypothesis). We found that the pre‐alternate molt was more frequent in migratory and less gregarious species inhabiting open/xeric habitats and feeding on the wing, and marginally more frequent in species with strong sexual selection and those showing a winter territorial behavior. Moreover, an increase in migratory behavior and sexual selection intensity preceded the acquisition of the pre‐alternate molt. These results provide support for the feather wear hypothesis, partial support for the sexual selection and time constraints hypotheses, and no support for the social selection hypothesis.     

How rapidly do self‐compatible populations evolve selfing? Mating system estimation within recently evolved self‐compatible populations of Azorean Tolpis succulenta (Asteraceae)

Genome‐wide genotyping and Bayesian inference method (BORICE) were employed to estimate outcrossing rates and paternity in two small plant populations of Tolpis succulenta (Asteraceae) on Graciosa island in the Azores. These two known extant populations of T. succulenta on Graciosa have recently evolved self‐compatibility. Despite the expectation that selfing would occur at an appreciable rate (self‐incompatible populations of the same species show low but nonzero selfing), high outcrossing was found in progeny arrays from maternal plants in both populations. This is inconsistent with an immediate transition to high selfing following the breakdown of a genetic incompatibility system. This finding is surprising given the small population sizes and the recent colonization of an island from self‐incompatible colonists of T. succulenta from another island in the Azores, and a potential paucity of pollinators, all factors selecting for selfing through reproductive assurance. The self‐compatible lineage(s) likely have high inbreeding depression (ID) that effectively halts the evolution of increased selfing, but this remains to be determined. Like their progeny, all maternal plants in both populations are fully outbred, which is consistent with but not proof of high ID. High multiple paternity was found in both populations, which may be due in part to the abundant pollinators observed during the flowering season.     

A structural inventory of native ribosomal ABCE1‐43S pre‐initiation complexes

In eukaryotic translation, termination and ribosome recycling phases are linked to subsequent initiation of a new round of translation by persistence of several factors at ribosomal sub‐complexes. These comprise/include the large eIF3 complex, eIF3j (Hcr1 in yeast) and the ATP‐binding cassette protein ABCE1 (Rli1 in yeast). The ATPase is mainly active as a recycling factor, but it can remain bound to the dissociated 40S subunit until formation of the next 43S pre‐initiation complexes. However, its functional role and native architectural context remains largely enigmatic. Here, we present an architectural inventory of native yeast and human ABCE1‐containing pre‐initiation complexes by cryo‐EM. We found that ABCE1 was mostly associated with early 43S, but also with later 48S phases of initiation. It adopted a novel hybrid conformation of its nucleotide‐binding domains, while interacting with the N‐terminus of eIF3j. Further, eIF3j occupied the mRNA entry channel via its ultimate C‐terminus providing a structural explanation for its antagonistic role with respect to mRNA binding. Overall, the native human samples provide a near‐complete molecular picture of the architecture and sophisticated interaction network of the 43S‐bound eIF3 complex and the eIF2 ternary complex containing the initiator tRNA.     

CDT1 is the major functional regulatory subunit of the pre‐replication complex in zygotes

Pre‐replication complex (pre‐RC) is critical for DNA replication initiation. CDT1 and MCM2 are the subunits of pre‐RC, and proper regulation of CDT1 and MCM2 are necessary for DNA replication and cell proliferation. The present study aimed to explore the role of CDT1 and MCM2 in oocyte meiotic maturation and early embryonic development. The depletion and overexpression of Cdt1 and Mcm2 in oocyte and zygote were achieved by microinjecting specific siRNA and mRNA to explored their functions in oocyte meiotic maturation and embryonic development. Then, we examined the effect of CDT1 and MCM2 on other signal pathways by immunostaining the expression of related maker genes. We showed that neither depletion nor overexpression of Cdt1 affected oocyte meiotic progressions. The CDT1 was degraded in S phase and remained at a low level in G2 phase of zygote. Exogenous expression of Cdt1 in G2 phase led to embryo attest at zygote stage. Mechanistically, CDT1 overexpression induced DNA re‐replication and thus DNA damage check‐point activation. Protein abundance of MCM2 was stable throughout the cell cycle, and embryos with overexpressed MCM2 could develop to blastocysts normally. Overexpression or depletion of Mcm2 also had no effect on oocyte meiotic maturation. Our results indicate that pre‐RC subunits CDT1 and MCM2 are not involved in oocyte meiotic maturation. In zygote, CDT1 but not MCM2 is the major regulator of DNA replication in a cell cycle dependent manner. Furthermore, its'' degradation is essential for zygotes to prevent from DNA re‐replication in G2 stage.

Pre‐replication complex (pre‐RC) is formed in G1 phase during which CDT1 is localized in nucleus. When zygote enters S phase, CDT1 is degraded and stays at a low level in G2 phase. However, the expression of exogenous Cdt1 mRNA in G2 phase of fertilized egg, mimicking events in which CDT1 degradation is disrupted, pre‐RC reassembles and leads to DNA re‐replication, and thus DNA damage check point activation, which results in embryo arrest at G2/M phase.     

Context‐dependency in carnivore co‐occurrence across a multi‐use conservation landscape

Carnivore intraguild dynamics depend on a complex interplay of environmental affinities and interspecific interactions. Context‐dependency is commonly expected with varying suites of interacting species and environmental conditions but seldom empirically described. In South Africa, decentralized approaches to conservation and the resulting multi‐tenure conservation landscapes have markedly altered the environmental stage that shapes the structure of local carnivore assemblages. We explored assemblage‐wide patterns of carnivore spatial (residual occupancy probability) and temporal (diel activity overlap) co‐occurrence across three adjacent wildlife‐oriented management contexts—a provincial protected area, a private ecotourism reserve, and commercial game ranches. We found that carnivores were generally distributed independently across space, but existing spatial dependencies were context‐specific. Spatial overlap was most common in the protected area, where species occur at higher relative abundances, and in game ranches, where predator persecution presumably narrows the scope for spatial asymmetries. In the private reserve, spatial co‐occurrence patterns were more heterogeneous but did not follow a dominance hierarchy associated with higher apex predator densities. Pair‐specific variability suggests that subordinate carnivores may alternate between pre‐emptive behavioral strategies and fine‐scale co‐occurrence with dominant competitors. Consistency in species‐pairs diel activity asynchrony suggested that temporal overlap patterns in our study areas mostly depend on species'' endogenous clock rather than the local context. Collectively, our research highlights the complexity and context‐dependency of guild‐level implications of current management and conservation paradigms; specifically, the unheeded potential for interventions to influence the local network of carnivore interactions with unknown population‐level and cascading effects.     

Internalizing psychopathology and all‐cause mortality: a comparison of transdiagnostic vs. diagnosis‐based risk prediction

Previous studies have documented the utility of a transdiagnostic internalizing factor in predicting important future outcomes (e.g., subsequent mental disorder diagnoses). To date, however, no study has investigated whether an internalizing factor predicts mortality risk. Also, while pre­vious studies of mortality risk have emphasized its associations with particular internalizing disorders, no study has assessed how the transdiagnostic internalizing factor vs. disorder‐specific variance differently predict that risk. The primary aims of this study were to explore: a) whether the internalizing factor predicts mortality risk, b) whether particular internalizing psychopathologies uniquely predict mortality risk over and beyond the transdiagnostic internalizing factor, and c) whether there is a significant interaction of internalizing with self‐reported health in the prediction of mortality risk. We utilized a large national sample of American adults from the Midlife in the United States (MIDUS), a longitudinal study that examined midlife development of individuals across multiple waves between 1995 and 2015. Data were analyzed for the 6,329 participants who completed the phone interview and self‐administered questionnaire in MIDUS 1 (1995‐1996) and were then followed up until October 31, 2015 or until death. To investigate the association between internalizing and mortality risk, we used the semi‐parametric proportional hazards Cox model, where survival time was regressed on a latent internalizing factor. Overall findings indicate that a transdiagnostic internalizing factor significantly predicts mortality risk over a 20‐year period (hazard ratio, HR=1.12, 95% CI: 1.05‐1.16, p<0.01) and that internalizing outperforms disorder‐specific variance (e.g., depression‐specific variance) in the prediction of that risk. Further, there was a significant interaction between transdiagnostic internalizing and self‐reported health, whereby internalizing psychopathology had a specific association with early death for individuals with excellent self‐reported health condition (HR=1.50, 95% CI: 1.17‐1.84, p<0.05). This highlights the clinical utility of using the transdiagnostic internalizing factor for prediction of an important future outcome, and supports the argument that internalizing psychopathology can be a meaningful liability to explore in public health practice.     

No hybrid snowcocks in the Altai—Hyper‐variable markers can be problematic for phylogenetic inference

A recent article in Ecology and Evolution featured the discovery of hybrid snowcocks (Tetraogallus) and speculated on the hybrid origin of an extant species (T. altaicus). Comprehensive re‐analyses of original data from the latter paper reliably refute the phylogenetic hypothesis taken as firm evidence of a past hybridization event in these birds. The new re‐analyses showed that there is no evidence of hybridization in these snowcocks from the data available so far.     

NONO enhances mRNA processing of super‐enhancer‐associated GATA2 and HAND2 genes in neuroblastoma

High‐risk neuroblastoma patients have poor survival rates and require better therapeutic options. High expression of a multifunctional DNA and RNA‐binding protein, NONO, in neuroblastoma is associated with poor patient outcome; however, there is little understanding of the mechanism of NONO‐dependent oncogenic gene regulatory activity in neuroblastoma. Here, we used cell imaging, biochemical and genome‐wide molecular analysis to reveal complex NONO‐dependent regulation of gene expression. NONO forms RNA‐ and DNA‐tethered condensates throughout the nucleus and undergoes phase separation in vitro, modulated by nucleic acid binding. CLIP analyses show that NONO mainly binds to the 5′ end of pre‐mRNAs and modulates pre‐mRNA processing, dependent on its RNA‐binding activity. NONO regulates super‐enhancer‐associated genes, including HAND2 and GATA2. Abrogating NONO RNA binding, or phase separation activity, results in decreased expression of HAND2 and GATA2. Thus, future development of agents that target RNA‐binding activity of NONO may have therapeutic potential in this cancer context.     

Genetic confirmation of a hybrid between two highly divergent cardinalid species: A rose‐breasted grosbeak (Pheucticus ludovicianus) and a scarlet tanager (Piranga olivacea)

Using low‐coverage whole‐genome sequencing, analysis of vocalizations, and inferences from natural history, we document a first‐generation hybrid between a rose‐breasted grosbeak (Pheucticus ludovicianus) and a scarlet tanager (Piranga olivacea). These two species occur sympatrically throughout much of eastern North America, although were not previously known to interbreed. Following the field identification of a putative hybrid, we use genetic and bioacoustic data to show that a rose‐breasted grosbeak was the maternal parent and a scarlet tanager was the paternal parent of the hybrid, whose song was similar to the latter species. These two species diverged >10 million years ago, and thus it is surprising to find a hybrid formed under natural conditions in the wild. Notably, the hybrid has an exceptionally heterozygous genome, with a conservative estimate of a heterozygous base every 100 bp. The observation that this hybrid of such highly divergent parental taxa has survived until adulthood serves as another example of the capacity for hybrid birds to survive with an exceptionally divergent genomic composition.     

1‐Undecene from Pseudomonas aeruginosa is an olfactory signal for flight‐or‐fight response in Caenorhabditis elegans

Animals possess conserved mechanisms to detect pathogens and to improve survival in their presence by altering their own behavior and physiology. Here, we utilize Caenorhabditis elegans as a model host to ask whether bacterial volatiles constitute microbe‐associated molecular patterns. Using gas chromatography–mass spectrometry, we identify six prominent volatiles released by the bacterium Pseudomonas aeruginosa. We show that a specific volatile, 1‐undecene, activates nematode odor sensory neurons inducing both flight and fight responses in worms. Using behavioral assays, we show that worms are repelled by 1‐undecene and that this aversion response is driven by the detection of this volatile through AWB odor sensory neurons. Furthermore, we find that 1‐undecene odor can induce immune effectors specific to P. aeruginosa via AWB neurons and that brief pre‐exposure of worms to the odor enhances their survival upon subsequent bacterial infection. These results show that 1‐undecene derived from P. aeruginosa serves as a pathogen‐associated molecular pattern for the induction of protective responses in C. elegans.     

The splicing‐regulatory lncRNA NTRAS sustains vascular integrity

Vascular integrity is essential for organ homeostasis to prevent edema formation and infiltration of inflammatory cells. Long non‐coding RNAs (lncRNAs) are important regulators of gene expression and often expressed in a cell type‐specific manner. By screening for endothelial‐enriched lncRNAs, we identified the undescribed lncRNA NTRAS to control endothelial cell functions. Silencing of NTRAS induces endothelial cell dysfunction in vitro and increases vascular permeability and lethality in mice. Biochemical analysis revealed that NTRAS, through its CA‐dinucleotide repeat motif, sequesters the splicing regulator hnRNPL to control alternative splicing of tight junction protein 1 (TJP1; also named zona occludens 1, ZO‐1) pre‐mRNA. Deletion of the hnRNPL binding motif in mice (Ntras ^∆CA/∆CA) significantly repressed TJP1 exon 20 usage, favoring expression of the TJP1α‐ isoform, which augments permeability of the endothelial monolayer. Ntras ^∆CA/∆CA mice further showed reduced retinal vessel growth and increased vascular permeability and myocarditis. In summary, this study demonstrates that NTRAS is an essential gatekeeper of vascular integrity.     

A geographical perspective on the relationship between Impatiens spur lengths and bill lengths of sunbirds in Afrotropical mountains

Trait matching—a correlation between the morphology of plants and their pollinators—has been frequently observed in pollination interactions. Different intensities of natural selection in individual regions should cause such correlations to be observable across different local assemblages. In this study, we focused on matching between spur lengths of the genus Impatiens and bill lengths of sunbirds in tropical Africa. For 25 mountain and island locations, we compiled information about the composition and traits of local Impatiens and sunbird assemblages. We found that assemblage mean and maximum values of bill lengths were positively correlated with mean and maximum spur lengths across locations. Moreover, our results suggest that the positive correlations hold only for forest sunbird assemblages sharing the same habitat with Impatiens species. We further show that long‐billed sunbirds seem to locally match the morphology of multiple Impatiens plant species, not vice versa. Our observation implies that trait matching significantly contributes to structuring of Impatiens–sunbird pollination systems. We suggest that special habitat preferences together with spatial isolation of mountain environment might play a role in this case.