Human-specific ARHGAP11B increases size and folding of primate neocortex in the fetal marmoset

Decoding human brain evolution: Insights from genomics

The human brain has undergone remarkable structural and functional specializations compared to that of nonhuman primates (NHPs), underlying the advanced cognitive abilities unique to humans. However, the cellular and genetic basis driving these specializations remains largely unknown. Comparing humans to our closest living relatives, chimpanzee and other great apes, is essential for identifying truly human-specific features. Recent comparative studies with closely related NHPs at the single-cell resolution using multimodal genomic profiling, assisted with high-throughput functional screening have provided unprecedented insights into human-specific brain features and their genetic underpinnings. In this review, we synthesize the current knowledge of human brain evolution at cellular and molecular levels, emphasizing how genetic changes have shaped these adaptations. We also discuss the emerging opportunities presented by new technologies and comprehensive atlases for advancing our understanding of human brain evolution.

A dyad of human-specific NBPF14 and NOTCH2NLB orchestrates cortical progenitor abundance crucial for human neocortex expansion

We determined the roles of two coevolved and coexpressed human-specific genes, NBPF14 and NOTCH2NLB, on the abundance of the cortical progenitors that underlie the evolutionary expansion of the neocortex, the seat of higher cognitive abilities in humans. Using automated microinjection into apical progenitors (APs) of embryonic mouse neocortex and electroporation of APs in chimpanzee cerebral organoids, we show that NBPF14 promotes the delamination of AP progeny, by promoting oblique cleavage plane orientation during AP division, leading to increased abundance of the key basal progenitor type, basal radial glia. In contrast, NOTCH2NLB promotes AP proliferation, leading to expansion of the AP pool. When expressed together, NBPF14 and NOTCH2NLB exert coordinated effects, resulting in expansion of basal progenitors while maintaining self-renewal of APs. Hence, these two human-specific genes orchestrate the behavior of APs, and the lineages of their progeny, in a manner essential for the evolutionary expansion of the human neocortex.

Unbuckling Mechanics of Epithelial Monolayers under Compression

When cell sheets fold during development, their apical or basal surfaces constrict and cell shapes approach the geometric singularity in which these surfaces vanish. Here, we reveal the mechanical consequences of this geometric singularity for tissue folding in a minimal vertex model of an epithelial monolayer. In simulations of the buckling of the epithelium under compression and numerical solutions of the corresponding continuum model, we discover an "unbuckling" bifurcation: at large compression, the buckling amplitude can decrease with increasing compression. By asymptotic solution of the continuum equations, we reveal that this bifurcation comes with a large stiffening of the epithelium. Our results thus provide the mechanical basis for absorption of compressive stresses by tissue folds such as the cephalic furrow during germband extension in Drosophila.

The Principle of Cortical Development and Evolution

Human's robust cognitive abilities, including creativity and language, are made possible, at least in large part, by evolutionary changes made to the cerebral cortex. This paper reviews the biology and evolution of mammalian cortical radial glial cells (primary neural stem cells) and introduces the concept that a genetically step wise process, based on a core molecular pathway already in use, is the evolutionary process that has molded cortical neurogenesis. The core mechanism, which has been identified in our recent studies, is the extracellular signal-regulated kinase (ERK)-bone morphogenic protein 7 (BMP7)-GLI3 repressor form (GLI3R)-sonic hedgehog (SHH) positive feedback loop. Additionally, I propose that the molecular basis for cortical evolutionary dwarfism, exemplified by the lissencephalic mouse which originated from a larger gyrencephalic ancestor, is an increase in SHH signaling in radial glia, that antagonizes ERK-BMP7 signaling. Finally, I propose that: (1) SHH signaling is not a key regulator of primate cortical expansion and folding; (2) human cortical radial glial cells do not generate neocortical interneurons; (3) human-specific genes may not be essential for most cortical expansion. I hope this review assists colleagues in the field, guiding research to address gaps in our understanding of cortical development and evolution.

Whole-genome sequencing analysis of Japanese autism spectrum disorder trios

AIM

Autism spectrum disorder (ASD) is a genetically and phenotypically heterogeneous neurodevelopmental disorder with a strong genetic basis. Conducting the first comprehensive whole-genome sequencing (WGS) analysis of Japanese ASD trios, this study aimed to elucidate the clinical significance of pathogenic variants and enhance the understanding of ASD pathogenesis.

METHODS

WGS was performed on 57 Japanese patients with ASD and their parents, investigating variants ranging from single-nucleotide variants to structural variants (SVs), short tandem repeats (STRs), mitochondrial variants, and polygenic risk score (PRS).

RESULTS

Potentially pathogenic variants that could explain observed phenotypes were identified in 18 patients (31.6%) overall and in 10 of 23 patients (43.5%) with comorbid intellectual developmental disorder (IDD). De novo variants in PTEN, CHD7, and HNRNPH2 were identified in patients referred for genetic counseling who exhibited previously reported phenotypes, including one patient with ASD who had profound IDD and macrocephaly with PTEN L320S. Analysis of the AlphaFold3 protein structure indicated potential inhibition of intramolecular interactions within PTEN. SV analysis identified deletions in ARHGAP11B and TMLHE. A pathogenic de novo mitochondrial variant was identified in a patient with ASD who had a history of encephalitis and cognitive decline. GO enrichment analysis of genes with nonsense variants and missense variants (Missense badness, PolyPhen-2, and Constraint >1) showed associations with regulation of growth and ATP-dependent chromatin remodeler activity. No reportable results were obtained in the analysis of STR and PRS.

CONCLUSION

Characterizing the comprehensive genetic architecture and phenotypes of ASD is a fundamental step towards unraveling its complex biology.

The Role of Preoperative Chronic Hypertension in Neurocognitive Decline after Cardiac Surgery: A Retrospective Cohort Study

INTRODUCTION

Patients frequently experience transient postoperative neurocognitive decline (NCD) after cardiac surgery with cardiopulmonary bypass. The goal of this study is to describe preoperative high blood pressure as a risk factor for NCD and use genomic expression to uncover its contribution to the pathophysiology of NCD.

METHODS

This is a retrospective analysis of cohort study at a single academic center. Patients undergoing cardiac surgery with the use of cardiopulmonary bypass were administered the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) preoperatively, at postoperative day four, and four weeks postoperatively. Electronic medical records were reviewed for all recorded blood pressure from the year preceding surgery and intraoperative blood pressures. Blood samples were collected six hours preoperatively and six hours postoperatively to assess messenger ribonucleic acid expression.

RESULTS

Eighty-seven patients completed postoperative day four testing, of whom thirty-seven experienced NCD (42.5%). Chronically elevated systolic blood pressure over the year preceding surgery was correlated with greater negative change in RBANS score at postoperative day four (P=0.03). Upon genomic analysis, macrophage markers were upregulated preoperatively, and anti-inflammatory and neuroprotective genes were downregulated postoperatively among patients who had a mean systolic blood pressure ≥ 130 mmHg.

CONCLUSION

Chronic exposure to elevated preoperative systolic blood pressure may increase the risk of NCD. The contributing role of preoperative hypertension in NCD may be partly explained by reduced attenuation of oxidative stress, increased inflammation, and reduced neuroprotection and heme metabolism postoperatively. This must be considered when assessing patient risks for cardiac surgery.

Cis-Regulatory Evolution of CCNB1IP1 Driving Gradual Increase of Cortical Size and Folding in primates

Neocortex expansion has a concerted relationship with folding, underlying evolution of human cognitive functions. However, molecular mechanisms underlying this significant evolutionary process remains unknown. Here, using tree shrew as an outgroup of primates, we identify a new regulator CCNB1IP1, which acquired its expression before the emergence of primates. Following the evolution of cis-regulatory elements, the CCNB1IP1 expression has steadily increased over the course of primate brain evolution, mirroring the gradual increase of neocortex. Mechanistically, we elucidated that CCNB1IP1 expression can cause an increase in neural progenitors through shortening G1 phase. Consistently, the CCNB1IP1 knock-in mouse model exhibited traits associated with enhanced learning and memory abilities. Together, our study reveals how changes in CCNB1IP1 expression may have contributed to the gradual evolution in primate brain.

The Control of Cortical Folding: Multiple Mechanisms, Multiple Models

The cerebral cortex develops through a carefully conscripted series of cellular and molecular events that culminate in the production of highly specialized neuronal and glial cells. During development, cortical neurons and glia acquire a precise cellular arrangement and architecture to support higher-order cognitive functioning. Decades of study using rodent models, naturally gyrencephalic animal models, human pathology specimens, and, recently, human cerebral organoids, reveal that rodents recapitulate some but not all the cellular and molecular features of human cortices. Whereas rodent cortices are smooth-surfaced or lissencephalic, larger mammals, including humans and nonhuman primates, have highly folded/gyrencephalic cortices that accommodate an expansion in neuronal mass and increase in surface area. Several genes have evolved to drive cortical gyrification, arising from gene duplications or de novo origins, or by alterations to the structure/function of ancestral genes or their gene regulatory regions. Primary cortical folds arise in stereotypical locations, prefigured by a molecular "blueprint" that is set up by several signaling pathways (e.g., Notch, Fgf, Wnt, PI3K, Shh) and influenced by the extracellular matrix. Mutations that affect neural progenitor cell proliferation and/or neurogenesis, predominantly of upper-layer neurons, perturb cortical gyrification. Below we review the molecular drivers of cortical folding and their roles in disease.

Human-specific genetic hallmarks in neocortical development: focus on neural progenitors

The evolutionary expansion of the neocortex in the ape lineage is the basis for the development of higher cognitive abilities. However, the human brain has uniquely increased in size and degree of folding, forming an essential foundation for advanced cognitive functions. This raises the question: what factors distinguish humans from our closest living primate relatives, such as chimpanzees and bonobos, which exhibit comparatively constrained cognitive capabilities? In this review, we focus on recent studies examining (modern) human-specific genetic traits that influence neural progenitor cells, whose behavior and activity are crucial for shaping cortical morphology. We emphasize the role of human-specific genetic modifications in signaling pathways that enhance the abundance of apical and basal progenitors, as well as the importance of basal progenitor metabolism in their proliferation in human. Additionally, we discuss how changes in neuron morphology contribute to the evolution of human cognition and provide our perspective on future directions in the field.

Reconstructing human-specific regulatory functions in model systems

Uniquely human physical traits, such as an expanded cerebral cortex and changes in limb morphology that allow us to use tools and walk upright, are in part due to human-specific genetic changes that altered when, where, and how genes are expressed during development. Over 20 000 putative regulatory elements with potential human-specific functions have been discovered. Understanding how these elements contributed to human evolution requires identifying candidates most likely to have shaped human traits, then studying them in genetically modified animal models. Here, we review the progress and challenges in generating and studying such models and propose a pathway for advancing the field. Finally, we highlight that large-scale collaborations across multiple research domains are essential to decipher what makes us human.

Comparative single-cell analyses identify shared and divergent features of human and mouse kidney development

The mammalian kidney maintains fluid homeostasis through diverse epithelial cell types generated from nephron and ureteric progenitor cells. To extend a developmental understanding of the kidney's epithelial networks, we compared chromatin organization (single-nuclear assay for transposase-accessible chromatin sequencing [ATAC-seq]; 112,864 nuclei) and gene expression (single-cell/nuclear RNA sequencing [RNA-seq]; 109,477 cells/nuclei) in the developing human (10.6-17.6 weeks; n = 10) and mouse (post-natal day [P]0; n = 10) kidney, supplementing analysis with published mouse datasets from earlier stages. Single-cell/nuclear datasets were analyzed at a species level, and then nephron and ureteric cellular lineages were extracted and integrated into a common, cross-species, multimodal dataset. Comparative computational analyses identified conserved and divergent features of chromatin organization and linked gene activity, identifying species-specific and cell-type-specific regulatory programs. In situ validation of human-enriched gene activity points to human-specific signaling interactions in kidney development. Further, human-specific enhancer regions were linked to kidney diseases through genome-wide association studies (GWASs), highlighting the potential for clinical insight from developmental modeling.

The chromodomain protein CDYL confers forebrain identity to human cortical organoids by inhibiting neuronatin

Fate determination of neural stem cells (NSCs) is crucial for cortex development and is closely linked to neurodevelopmental disorders when gene expression networks are disrupted. The transcriptional corepressor chromodomain Y-like (CDYL) is widely expressed across diverse cell populations within the human embryonic cortex. However, its precise role in cortical development remains unclear. Here, we show that CDYL is critical for human cortical neurogenesis and that its deficiency leads to a substantial increase in gamma-aminobutyric acid (GABA)-ergic neurons in cortical organoids. Subsequently, neuronatin (NNAT) is identified as a significant target of CDYL, and its abnormal expression obviously influences the fate commitment of cortical NSCs. Cross-species comparisons of CDYL targets unravel a distinct developmental trajectory between human cortical organoids and the mouse cortex at an analogous stage. Collectively, our data provide insight into the evolutionary roles of CDYL in human cortex development, emphasizing its critical function in maintaining the fate of human cortical NSCs.

Unraveling mechanisms of human brain evolution

Evolutionary changes in human brain structure and function have enabled our specialized cognitive abilities. How these changes have come about genetically and functionally has remained an open question. However, new methods are providing a wealth of information about the genetic, epigenetic, and transcriptomic differences that set the human brain apart. Combined with in vitro models that allow access to developing brain tissue and the cells of our closest living relatives, the puzzle pieces are now coming together to yield a much more complete picture of what is actually unique about the human brain. The challenge now will be linking these observations and making the jump from correlation to causation. However, elegant genetic manipulations are now possible and, when combined with model systems such as organoids, will uncover a mechanistic understanding of how evolutionary changes at the genetic level have led to key differences in development and function that enable human cognition.

What Makes Us Human: Insights from the Evolution and Development of the Human Neocortex

"What makes us human?" is a central question of many research fields, notably anthropology. In this review, we focus on the development of the human neocortex, the part of the brain with a key role in cognition, to gain neurobiological insight toward answering this question. We first discuss cortical stem and progenitor cells and human-specific genes that affect their behavior. We thus aim to understand the molecular foundation of the expansion of the neocortex that occurred in the course of human evolution, as this expansion is generally thought to provide a basis for our unique cognitive abilities. We then review the emerging evidence pointing to differences in the development of the neocortex between present-day humans and Neanderthals, our closest relatives. Finally, we discuss human-specific genes that have been implicated in neuronal circuitry and offer a perspective for future studies addressing the question of what makes us human.

Gene expansions contributing to human brain evolution

Genomic drivers of human-specific neurological traits remain largely undiscovered. Duplicated genes expanded uniquely in the human lineage likely contributed to brain evolution, including the increased complexity of synaptic connections between neurons and the dramatic expansion of the neocortex. Discovering duplicate genes is challenging because the similarity of paralogs makes them prone to sequence-assembly errors. To mitigate this issue, we analyzed a complete telomere-to-telomere human genome sequence (T2T-CHM13) and identified 213 duplicated gene families likely containing human-specific paralogs (>98% identity). Positing that genes important in universal human brain features should exist with at least one copy in all modern humans and exhibit expression in the brain, we narrowed in on 362 paralogs with at least one copy across thousands of ancestrally diverse genomes and present in human brain transcriptomes. Of these, 38 paralogs co-express in gene modules enriched for autism-associated genes and potentially contribute to human language and cognition. We narrowed in on 13 duplicate gene families with human-specific paralogs that are fixed among modern humans and show convincing brain expression patterns. Using long-read DNA sequencing revealed hidden variation across 200 modern humans of diverse ancestries, uncovering signatures of selection not previously identified, including possible balancing selection of CD8B. To understand the roles of duplicated genes in brain development, we generated zebrafish CRISPR "knockout" models of nine orthologs and transiently introduced mRNA-encoding paralogs, effectively "humanizing" the larvae. Morphometric, behavioral, and single-cell RNA-seq screening highlighted, for the first time, a possible role for GPR89B in dosage-mediated brain expansion and FRMPD2B function in altered synaptic signaling, both hallmark features of the human brain. Our holistic approach provides important insights into human brain evolution as well as a resource to the community for studying additional gene expansion drivers of human brain evolution.

Role of cell metabolism in the pathophysiology of brain size-associated neurodevelopmental disorders

Cell metabolism is a key regulator of human neocortex development and evolution. Several lines of evidence indicate that alterations in neural stem/progenitor cell (NPC) metabolism lead to abnormal brain development, particularly brain size-associated neurodevelopmental disorders, such as microcephaly. Abnormal NPC metabolism causes impaired cell proliferation and thus insufficient expansion of NPCs for neurogenesis. Therefore, the production of neurons, which is a major determinant of brain size, is decreased and the size of the brain, especially the size of the neocortex, is significantly reduced. This review discusses recent progress understanding NPC metabolism, focusing in particular on glucose metabolism, fatty acid metabolism and amino acid metabolism (e.g., glutaminolysis and serine metabolism). We provide an overview of the contributions of these metabolic pathways to brain development and evolution, as well as to the etiology of neurodevelopmental disorders. Furthermore, we discuss the advantages and disadvantages of various experimental models to study cell metabolism in the developing brain.

Brain enlargement with rostral bias in larvae from a spontaneously occurring female variant line of Xenopus; role of aberrant embryonic Wnt/β-catenin signaling

Increased brain size and its rostral bias are hallmarks of vertebrate evolution, but the underlying developmental and genetic basis remains poorly understood. To provide clues to understanding vertebrate brain evolution, we investigated the developmental mechanisms of brain enlargement observed in the offspring of a previously unrecognized, spontaneously occurring female variant line of Xenopus that appears to reflect a genetic variation. Brain enlargement in larvae from this line showed a pronounced rostral bias that could be traced back to the neural plate, the primordium of the brain. At the gastrula stage, the Spemann organizer, which is known to induce the neural plate from the adjacent dorsal ectoderm and give it the initial rostrocaudal patterning, was expanded from dorsal to ventral in a large proportion of the offspring of variant females. Consistently, siamois expression, which is required for Spemann organizer formation, was expanded laterally from dorsal to ventral at the blastula stage in variant offspring. This implies that the active region of the Wnt/β-catenin signaling pathway was similarly expanded in advance on the dorsal side, as siamois is a target gene of this pathway. Notably, the earliest detectable change in variant offspring was in fertilized eggs, in which maternal wnt11b mRNA, a candidate dorsalizing factor responsible for activating Wnt/β-catenin signaling in the dorsal embryonic region, had a wider distribution in the vegetal cortical cytoplasm. Since lateral spreading of wnt11b mRNA, and possibly that of other potential maternal dorsalizing factors in these eggs, is expected to facilitate lateral expansion of the active region of the Wnt/β-catenin pathway during subsequent embryonic stages, we concluded that aberrant Wnt/β-catenin signaling could cause rostral-biased brain enlargement via expansion of siamois expression and consequent expansion of the Spemann organizer in Xenopus. Our studies of spontaneously occurring variations in brain development in Xenopus would provide hints for uncovering genetic mutations that drive analogous morphogenetic variations during vertebrate brain evolution.

Indirect neurogenesis in space and time

During central nervous system (CNS) development, neural progenitor cells (NPCs) generate neurons and glia in two different ways. In direct neurogenesis, daughter cells differentiate directly into neurons or glia, whereas in indirect neurogenesis, neurons or glia are generated after one or more daughter cell divisions. Intriguingly, indirect neurogenesis is not stochastically deployed and plays instructive roles during CNS development: increased generation of cells from specific lineages; increased generation of early or late-born cell types within a lineage; and increased cell diversification. Increased indirect neurogenesis might contribute to the anterior CNS expansion evident throughout the Bilateria and help to modify brain-region size without requiring increased NPC numbers or extended neurogenesis. Increased indirect neurogenesis could be an evolutionary driver of the gyrencephalic (that is, folded) cortex that emerged during mammalian evolution and might even have increased during hominid evolution. Thus, selection of indirect versus direct neurogenesis provides a powerful developmental and evolutionary instrument that drives not only the evolution of CNS complexity but also brain expansion and modulation of brain-region size, and thereby the evolution of increasingly advanced cognitive abilities. This Review describes indirect neurogenesis in several model species and humans, and highlights some of the molecular genetic mechanisms that control this important process.

A molecular and cellular perspective on human brain evolution and tempo

The evolution of the modern human brain was accompanied by distinct molecular and cellular specializations, which underpin our diverse cognitive abilities but also increase our susceptibility to neurological diseases. These features, some specific to humans and others shared with related species, manifest during different stages of brain development. In this multi-stage process, neural stem cells proliferate to produce a large and diverse progenitor pool, giving rise to excitatory or inhibitory neurons that integrate into circuits during further maturation. This process unfolds over varying time scales across species and has progressively become slower in the human lineage, with differences in tempo correlating with differences in brain size, cell number and diversity, and connectivity. Here we introduce the terms 'bradychrony' and 'tachycrony' to describe slowed and accelerated developmental tempos, respectively. We review how recent technical advances across disciplines, including advanced engineering of in vitro models, functional comparative genetics and high-throughput single-cell profiling, are leading to a deeper understanding of how specializations of the human brain arise during bradychronic neurodevelopment. Emerging insights point to a central role for genetics, gene-regulatory networks, cellular innovations and developmental tempo, which together contribute to the establishment of human specializations during various stages of neurodevelopment and at different points in evolution.

Insights from the past: the work of Hans von Alten on the evolution of brain structure, ecological adaptation, and cognition in hymenopteran species

In his treatise on arthropod brains, Hans von Alten (1910) focuses on a specific functional group of insects-the flying Hymenoptera-which exhibit a spectrum of lifestyles ranging from solitary to social. His work presents a distinctive comparative neuro-anatomical approach rooted in an eco-evolutionary and eco-behavioral background. We regard his publication as an exceptionally valuable source of information and seek to inspire the research community dedicated to the study of the insect brain to explore its insights further, even after more than 110 years. We have translated and annotated his work, expecting it to engage researchers not just with its remarkable drawings but also with its substantive content and exemplary research strategy. The present text is designed to complement von Alten's publication, situating it within the temporal context of nineteenth-century and early twentieth-century studies, and to draw connections to contemporary perspectives, especially concerning a central brain structure: the mushroom body.

Functional synergy of a human-specific and an ape-specific metabolic regulator in human neocortex development

Metabolism has recently emerged as a major target of genes implicated in the evolutionary expansion of human neocortex. One such gene is the human-specific gene ARHGAP11B. During human neocortex development, ARHGAP11B increases the abundance of basal radial glia, key progenitors for neocortex expansion, by stimulating glutaminolysis (glutamine-to-glutamate-to-alpha-ketoglutarate) in mitochondria. Here we show that the ape-specific protein GLUD2 (glutamate dehydrogenase 2), which also operates in mitochondria and converts glutamate-to-αKG, enhances ARHGAP11B's ability to increase basal radial glia abundance. ARHGAP11B + GLUD2 double-transgenic bRG show increased production of aspartate, a metabolite essential for cell proliferation, from glutamate via alpha-ketoglutarate and the TCA cycle. Hence, during human evolution, a human-specific gene exploited the existence of another gene that emerged during ape evolution, to increase, via concerted changes in metabolism, progenitor abundance and neocortex size.

Human restricted CHRFAM7A gene increases brain efficiency

Introduction

CHRFAM7A, a uniquely human fusion gene, has been associated with neuropsychiatric disorders including Alzheimer's disease, schizophrenia, anxiety, and attention deficit disorder. Understanding the physiological function of CHRFAM7A in the human brain is the first step to uncovering its role in disease. CHRFAM7A was identified as a potent modulator of intracellular calcium and an upstream regulator of Rac1 leading to actin cytoskeleton reorganization and a switch from filopodia to lamellipodia implicating a more efficient neuronal structure. We performed a neurocognitive-MRI correlation exploratory study on 46 normal human subjects to explore the effect of CHRFAM7A on human brain.

Methods

Dual locus specific genotyping of CHRFAM7A was performed on genomic DNA to determine copy number (TaqMan assay) and orientation (capillary sequencing) of the CHRFAM7A alleles. As only the direct allele is expressed at the protein level and affects α7 nAChR function, direct allele carriers and non-carriers are compared for neuropsychological and MRI measures. Subjects underwent neuropsychological testing to measure motor (Timed 25-foot walk test, 9-hole peg test), cognitive processing speed (Symbol Digit Modalities Test), Learning and memory (California Verbal Learning Test immediate and delayed recall, Brief Visuospatial Memory Test-Revised immediate and delayed recall) and Beck Depression Inventory-Fast Screen, Fatigue Severity Scale. All subjects underwent MRI scanning on the same 3 T GE scanner using the same protocol. Global and tissue-specific volumes were determined using validated cross-sectional algorithms including FSL's Structural Image Evaluation, using Normalization, of Atrophy (SIENAX) and FSL's Integrated Registration and Segmentation Tool (FIRST) on lesion-inpainted images. The cognitive tests were age and years of education-adjusted using analysis of covariance (ANCOVA). Age-adjusted analysis of covariance (ANCOVA) was performed on the MRI data.

Results

CHRFAM7A direct allele carrier and non-carrier groups included 33 and 13 individuals, respectively. Demographic variables (age and years of education) were comparable. CHRFAM7A direct allele carriers demonstrated an upward shift in cognitive performance including cognitive processing speed, learning and memory, reaching statistical significance in visual immediate recall (FDR corrected p = 0.018). The shift in cognitive performance was associated with smaller whole brain volume (uncorrected p = 0.046) and lower connectivity by resting state functional MRI in the visual network (FDR corrected p = 0.027) accentuating the cognitive findings.

Conclusion

These data suggest that direct allele carriers harbor a more efficient brain consistent with the cellular biology of actin cytoskeleton and synaptic gain of function. Further larger human studies of cognitive measures correlated with MRI and functional imaging are needed to decipher the impact of CHRFAM7A on brain function.

Oxygen and the Spark of Human Brain Evolution: Complex Interactions of Metabolism and Cortical Expansion across Development and Evolution

Scientific theories on the functioning and dysfunction of the human brain require an understanding of its development-before and after birth and through maturation to adulthood-and its evolution. Here we bring together several accounts of human brain evolution by focusing on the central role of oxygen and brain metabolism. We argue that evolutionary expansion of human transmodal association cortices exceeded the capacity of oxygen delivery by the vascular system, which led these brain tissues to rely on nonoxidative glycolysis for additional energy supply. We draw a link between the resulting lower oxygen tension and its effect on cytoarchitecture, which we posit as a key driver of genetic developmental programs for the human brain-favoring lower intracortical myelination and the presence of biosynthetic materials for synapse turnover. Across biological and temporal scales, this protracted capacity for neural plasticity sets the conditions for cognitive flexibility and ongoing learning, supporting complex group dynamics and intergenerational learning that in turn enabled improved nutrition to fuel the metabolic costs of further cortical expansion. Our proposed model delineates explicit mechanistic links among metabolism, molecular and cellular brain heterogeneity, and behavior, which may lead toward a clearer understanding of brain development and its disorders.

A 25-year odyssey of genomic technology advances and structural variant discovery

This perspective focuses on advances in genome technology over the last 25 years and their impact on germline variant discovery within the field of human genetics. The field has witnessed tremendous technological advances from microarrays to short-read sequencing and now long-read sequencing. Each technology has provided genome-wide access to different classes of human genetic variation. We are now on the verge of comprehensive variant detection of all forms of variation for the first time with a single assay. We predict that this transition will further transform our understanding of human health and biology and, more importantly, provide novel insights into the dynamic mutational processes shaping our genomes.

Temporal transcriptomic dynamics in developing macaque neocortex

Despite intense research on mice, the transcriptional regulation of neocortical neurogenesis remains limited in humans and non-human primates. Cortical development in rhesus macaque is known to recapitulate multiple facets of cortical development in humans, including the complex composition of neural stem cells and the thicker supragranular layer. To characterize temporal shifts in transcriptomic programming responsible for differentiation from stem cells to neurons, we sampled parietal lobes of rhesus macaque at E40, E50, E70, E80, and E90, spanning the full period of prenatal neurogenesis. Single-cell RNA sequencing produced a transcriptomic atlas of developing parietal lobe in rhesus macaque neocortex. Identification of distinct cell types and neural stem cells emerging in different developmental stages revealed a terminally bifurcating trajectory from stem cells to neurons. Notably, deep-layer neurons appear in the early stages of neurogenesis, while upper-layer neurons appear later. While these different lineages show overlap in their differentiation program, cell fates are determined post-mitotically. Trajectories analysis from ventricular radial glia (vRGs) to outer radial glia (oRGs) revealed dynamic gene expression profiles and identified differential activation of BMP, FGF, and WNT signaling pathways between vRGs and oRGs. These results provide a comprehensive overview of the temporal patterns of gene expression leading to different fates of radial glial progenitors during neocortex layer formation.

Development and evolution of the primate neocortex from a progenitor cell perspective

The generation of neurons in the developing neocortex is a major determinant of neocortex size. Crucially, the increase in cortical neuron numbers in the primate lineage, notably in the upper-layer neurons, contributes to increased cognitive abilities. Here, we review major evolutionary changes affecting the apical progenitors in the ventricular zone and focus on the key germinal zone constituting the foundation of neocortical neurogenesis in primates, the outer subventricular zone (OSVZ). We summarize characteristic features of the OSVZ and its key stem cell type, the basal (or outer) radial glia. Next, we concentrate on primate-specific and human-specific genes, expressed in OSVZ-progenitors, the ability of which to amplify these progenitors by targeting the regulation of the cell cycle ultimately underlies the evolutionary increase in upper-layer neurons. Finally, we address likely differences in neocortical development between present-day humans and Neanderthals that are based on human-specific amino acid substitutions in proteins operating in cortical progenitors.

Neocortical neurogenesis in development and evolution-Human-specific features

In this review, we focus on human-specific features of neocortical neurogenesis in development and evolution. Two distinct topics will be addressed. In the first section, we discuss the expansion of the neocortex during human evolution and concentrate on the human-specific gene ARHGAP11B. We review the ability of ARHGAP11B to amplify basal progenitors and to expand a primate neocortex. We discuss the contribution of ARHGAP11B to neocortex expansion during human evolution and its potential implications for neurodevelopmental disorders and brain tumors. We then review the action of ARHGAP11B in mitochondria as a regulator of basal progenitor metabolism, and how it promotes glutaminolysis and basal progenitor proliferation. Finally, we discuss the increase in cognitive performance due to the ARHGAP11B-induced neocortical expansion. In the second section, we focus on neocortical development in modern humans versus Neanderthals. Specifically, we discuss two recent findings pointing to differences in neocortical neurogenesis between these two hominins that are due to a small number of amino acid substitutions in certain key proteins. One set of such proteins are the kinetochore-associated proteins KIF18a and KNL1, where three modern human-specific amino acid substitutions underlie the prolongation of metaphase during apical progenitor mitosis. This prolongation in turn is associated with an increased fidelity of chromosome segregation to the apical progenitor progeny during modern human neocortical development, with implications for the proper formation of radial units. Another such key protein is transketolase-like 1 (TKTL1), where a single modern human-specific amino acid substitution endows TKTL1 with the ability to amplify basal radial glia, resulting in an increase in upper-layer neuron generation. TKTL1's ability is based on its action in the pentose phosphate pathway, resulting in increased fatty acid synthesis. The data imply greater neurogenesis during neocortical development in modern humans than Neanderthals due to TKTL1, in particular in the developing frontal lobe.

Divergent Evolutionary Rates of Primate Brain Regions as Revealed by Genomics and Transcriptomics

Although the primate brain contains numerous functionally distinct structures that have experienced diverse genetic changes during the course of evolution and development, these changes remain to be explored in detail. Here we utilize two classic metrics from evolutionary biology, the evolutionary rate index (ERI) and the transcriptome age index (TAI), to investigate the evolutionary alterations that have occurred in each area and developmental stage of the primate brain. We observed a higher evolutionary rate for those genes expressed in the non-cortical areas during primate evolution, particularly in human, with the highest rate of evolution being exhibited at brain developmental stages between late infancy and early childhood. Further, the transcriptome age of the non-cortical areas was lower than that of the cerebral cortex, with the youngest age apparent at brain developmental stages between late infancy and early childhood. Our exploration of the evolutionary patterns manifest in each brain area and developmental stage provides important reference points for further research into primate brain evolution.

Toward a better understanding of how a gyrified brain develops

The size and shape of the cerebral cortex have changed dramatically across evolution. For some species, the cortex remains smooth (lissencephalic) throughout their lifetime, while for other species, including humans and other primates, the cortex increases substantially in size and becomes folded (gyrencephalic). A folded cortex boasts substantially increased surface area, cortical thickness, and neuronal density, and it is therefore associated with higher-order cognitive abilities. The mechanisms that drive gyrification in some species, while others remain lissencephalic despite many shared neurodevelopmental features, have been a topic of investigation for many decades, giving rise to multiple perspectives of how the gyrified cerebral cortex acquires its unique shape. Recently, a structurally unique germinal layer, known as the outer subventricular zone, and the specialized cell type that populates it, called basal radial glial cells, were identified, and these have been shown to be indispensable for cortical expansion and folding. Transcriptional analyses and gene manipulation models have provided an invaluable insight into many of the key cellular and genetic drivers of gyrification. However, the degree to which certain biomechanical, genetic, and cellular processes drive gyrification remains under investigation. This review considers the key aspects of cerebral expansion and folding that have been identified to date and how theories of gyrification have evolved to incorporate this new knowledge.

Towards correlative archaeology of the human mind

Retracing human cognitive origins started out at the systems level with the top-down interpretation of archaeological records spanning from man-made artifacts to endocasts of ancient skulls. With emerging evolutionary genetics and organoid technologies, it is now possible to deconstruct evolutionary processes on a molecular/cellular level from the bottom-up by functionally testing archaic alleles in experimental models. The current challenge is to complement these approaches with novel strategies that allow a holistic reconstruction of evolutionary patterns across human cognitive domains. We argue that computational neuroarcheology can provide such a critical mesoscale framework at the brain network-level, linking molecular/cellular (bottom-up) to systems (top-down) level data for the correlative archeology of the human mind.

An evolutionary perspective on complex neuropsychiatric disease

The forces of evolution-mutation, selection, migration, and genetic drift-shape the genetic architecture of human traits, including the genetic architecture of complex neuropsychiatric illnesses. Studying these illnesses in populations that are diverse in genetic ancestry, historical demography, and cultural history can reveal how evolutionary forces have guided adaptation over time and place. A fundamental truth of shared human biology is that an allele responsible for a disease in anyone, anywhere, reveals a gene critical to the normal biology underlying that condition in everyone, everywhere. Understanding the genetic causes of neuropsychiatric disease in the widest possible range of human populations thus yields the greatest possible range of insight into genes critical to human brain development. In this perspective, we explore some of the relationships between genes, adaptation, and history that can be illuminated by an evolutionary perspective on studies of complex neuropsychiatric disease in diverse populations.

Genetics of human brain development

Brain development in humans is achieved through precise spatiotemporal genetic control, the mechanisms of which remain largely elusive. Recently, integration of technological advances in human stem cell-based modelling with genome editing has emerged as a powerful platform to establish causative links between genotypes and phenotypes directly in the human system. Here, we review our current knowledge of complex genetic regulation of each key step of human brain development through the lens of evolutionary specialization and neurodevelopmental disorders and highlight the use of human stem cell-derived 2D cultures and 3D brain organoids to investigate human-enriched features and disease mechanisms. We also discuss opportunities and challenges of integrating new technologies to reveal the genetic architecture of human brain development and disorders.

Possible roles of deep cortical neurons and oligodendrocytes in the neural basis of human sociality

Sociality is an instinctive property of organisms that live in relation to others and is a complex characteristic of higher order brain functions. However, the evolution of the human brain to acquire higher order brain functions, such as sociality, and the neural basis for executing these functions and their control mechanisms are largely unknown. Several studies have attempted to evaluate how human sociality was acquired during the course of evolution and the mechanisms controlling sociality from a neurodevelopment viewpoint. This review discusses these findings in the context of human brain evolution and the pathophysiology of autism spectrum disorder (ASD). Comparative genomic studies of postmortem primate brains have demonstrated human-specific regulatory mechanisms underlying higher order brain functions, providing evidence for the contribution of oligodendrocytes to human brain function. Functional analyses of the causative genes of ASD in animal models have demonstrated that the neural basis of social behavior is associated with layer 6 (L6) of the neocortex and oligodendrocytes. These findings demonstrate that both neurons and oligodendrocytes contribute to the neural basis and molecular mechanisms underlying human brain evolution and social functioning. This review provides novel insights into sociability and the corresponding neural bases of brain disorders and evolution.

Shaping the brain: The emergence of cortical structure and folding

The cerebral cortex-the brain's covering and largest region-has increased in size and complexity in humans and supports higher cognitive functions such as language and abstract thinking. There is a growing understanding of the human cerebral cortex, including the diversity and number of cell types that it contains, as well as of the developmental mechanisms that shape cortical structure and organization. In this review, we discuss recent progress in our understanding of molecular and cellular processes, as well as mechanical forces, that regulate the folding of the cerebral cortex. Advances in human genetics, coupled with experimental modeling in gyrencephalic species, have provided insights into the central role of cortical progenitors in the gyrification and evolutionary expansion of the cerebral cortex. These studies are essential for understanding the emergence of structural and functional organization during cortical development and the pathogenesis of neurodevelopmental disorders associated with cortical malformations.

Fetal head-down posture may explain the rapid brain evolution in humans and other primates: An interpretative review

Evolutionary cerebrovascular consequences of upside-down postural verticality of the anthropoid fetus have been largely overlooked in the literature. This working hypothesis-based report provides a literature interpretation from an aspect that the rapid evolution of the human brain has been promoted by fetal head-down position due to maternal upright and semi-upright posture. Habitual vertical torso posture is a feature not only of humans, but also of monkeys and non-human apes that spend considerable time in a sitting position. Consequently, the head-down position of the fetus may have caused physiological craniovascular hypertension that stimulated expansion of the intracranial vessels and acted as an epigenetic physiological stress, which enhanced neurogenesis and eventually, along with other selective pressures, led to the progressive growth of the anthropoid brain and its organization. This article collaterally opens a new insight into the conundrum of high cephalopelvic proportions (i.e., the tight fit between the pelvic birth canal and fetal head) in phylogenetically distant lineages of monkeys, lesser apes, and humans. Low cephalopelvic proportions in non-human great apes could be accounted for by their energetically efficient horizontal nest-sleeping and consequently by their larger body mass compared to monkeys and lesser apes that sleep upright. One can further hypothesize that brain size varies in anthropoids according to the degree of exposure of the fetus to postural verticality. The supporting evidence for this postulation includes a finding that in fossil hominins cerebral blood flow rate increased faster than brain volume. This testable hypothesis opens a perspective for research on fetal postural cerebral hemodynamics.

Protooncogenic Role of ARHGAP11A and ARHGAP11B in Invasive Ductal Carcinoma: Two Promising Breast Cancer Biomarkers

Invasive duct carcinoma (IDC) is one of the most common types of breast cancer (BC) in women worldwide, with a high risk of malignancy, metastasis, recurrence, and death. So far, molecular patterns among IDC cases have not been fully defined. However, extensive evidence has shown that dysregulated Rho family small GTPases (Rho GTPases) including Rho GTPase activating proteins (RhoGAPs) have important roles in the invasive features of IDCs. In the current study, we analyzed the expression levels of two RhoGAP genes, ARHGAP11A and ARHGAP11B, in The Cancer Genome Atlas (TCGA) breast cancer (BRCA) and also our 51 IDC tumors compared to their matched normal tissues using quantitative polymerase chain reaction (qPCR). Our TCGA data analysis revealed higher expression of ARHGAP11A and ARHGAP11B in various cancers comprising BCs. Also, we found correlations between these genes and other genes in TCGA-BRCA. Moreover, our methylation analysis showed that their promotor methylation had a negative correlation with their overexpression. QPCR revealed their significant upregulation in our tumor samples. Furthermore, we found that the expression level of ARHGAP11A was considerably lower in women who were breastfeeding. Moreover, it had overexpression in cases who had regular menstrual cycles and early age (younger than 14) at menarche. However, ARHGAP11B had a higher expression in HER2-positive tumors versus HER2-positive and ER-positive tumors. Our study found possible protooncogenic roles for these genes and their involvement in IDC pathogenesis and malignancy. Therefore, they can be considered novel prognostic and diagnostic biomarkers for IDC.

Neurogenesis in primates versus rodents and the value of non-human primate models

Neurogenesis, the process of generating neurons from neural stem cells, occurs during both embryonic and adult stages, with each stage possessing distinct characteristics. Dysfunction in either stage can disrupt normal neural development, impair cognitive functions, and lead to various neurological disorders. Recent technological advancements in single-cell multiomics and gene-editing have facilitated investigations into primate neurogenesis. Here, we provide a comprehensive overview of neurogenesis across rodents, non-human primates, and humans, covering embryonic development to adulthood and focusing on the conservation and diversity among species. While non-human primates, especially monkeys, serve as valuable models with closer neural resemblance to humans, we highlight the potential impacts and limitations of non-human primate models on both physiological and pathological neurogenesis research.

Brain developmental and cortical connectivity changes in transgenic monkeys carrying the human-specific duplicated gene SRGAP2C

Human-specific duplicated genes contributed to phenotypic innovations during the origin of our own species, such as an enlarged brain and highly developed cognitive abilities. While prior studies on transgenic mice carrying the human-specific SRGAP2C gene have shown enhanced brain connectivity, the relevance to humans remains unclear due to the significant evolutionary gap between humans and rodents. In this study, to investigate the phenotypic outcome and underlying genetic mechanism of SRGAP2C, we generated transgenic cynomolgus macaques (Macaca fascicularis) carrying the human-specific SRGAP2C gene. Longitudinal MRI imaging revealed delayed brain development with region-specific volume changes, accompanied by altered myelination levels in the temporal and occipital regions. On a cellular level, the transgenic monkeys exhibited increased deep-layer neurons during fetal neurogenesis and delayed synaptic maturation in adolescence. Moreover, transcriptome analysis detected neotenic expression in molecular pathways related to neuron ensheathment, synaptic connections, extracellular matrix and energy metabolism. Cognitively, the transgenic monkeys demonstrated improved motor planning and execution skills. Together, our findings provide new insights into the mechanisms by which the newly evolved gene shapes the unique development and circuitry of the human brain.

Spatiotemporal molecular dynamics of the developing human thalamus

The thalamus plays a central coordinating role in the brain. Thalamic neurons are organized into spatially distinct nuclei, but the molecular architecture of thalamic development is poorly understood, especially in humans. To begin to delineate the molecular trajectories of cell fate specification and organization in the developing human thalamus, we used single-cell and multiplexed spatial transcriptomics. We show that molecularly defined thalamic neurons differentiate in the second trimester of human development and that these neurons organize into spatially and molecularly distinct nuclei. We identified major subtypes of glutamatergic neuron subtypes that are differentially enriched in anatomically distinct nuclei and six subtypes of γ-aminobutyric acid-mediated (GABAergic) neurons that are shared and distinct across thalamic nuclei.

Human-specific genetics: new tools to explore the molecular and cellular basis of human evolution

Our ancestors acquired morphological, cognitive and metabolic modifications that enabled humans to colonize diverse habitats, develop extraordinary technologies and reshape the biosphere. Understanding the genetic, developmental and molecular bases for these changes will provide insights into how we became human. Connecting human-specific genetic changes to species differences has been challenging owing to an abundance of low-effect size genetic changes, limited descriptions of phenotypic differences across development at the level of cell types and lack of experimental models. Emerging approaches for single-cell sequencing, genetic manipulation and stem cell culture now support descriptive and functional studies in defined cell types with a human or ape genetic background. In this Review, we describe how the sequencing of genomes from modern and archaic hominins, great apes and other primates is revealing human-specific genetic changes and how new molecular and cellular approaches - including cell atlases and organoids - are enabling exploration of the candidate causal factors that underlie human-specific traits.

Generation of a tyrosine hydroxylase-2A-Cre knockin non-human primate model by homology-directed-repair-biased CRISPR genome editing

Non-human primates (NHPs) are the closest animal model to humans; thus, gene engineering technology in these species holds great promise for the elucidation of higher brain functions and human disease models. Knockin (KI) gene targeting is a versatile approach to modify gene(s) of interest; however, it generally suffers from the low efficiency of homology-directed repair (HDR) in mammalian cells, especially in non-expressed gene loci. In the current study, we generated a tyrosine hydroxylase (TH)-2A-Cre KI model of the common marmoset monkey (marmoset; Callithrix jacchus) using an HDR-biased CRISPR-Cas9 genome editing approach using Cas9-DN1S and RAD51. This model should enable labeling and modification of a specific neuronal lineage using the Cre-loxP system. Collectively, the current study paves the way for versatile gene engineering in NHPs, which may be a significant step toward further biomedical and preclinical applications.

Loss of Twist1 and balanced retinoic acid signaling from the meninges causes cortical folding in mice

Secondary lissencephaly evolved in mice due to effects on neurogenesis and the tangential distribution of neurons. Signaling pathways that help maintain lissencephaly are still poorly understood. We show that inactivating Twist1 in the primitive meninges causes cortical folding in mice. Cell proliferation in the meninges is reduced, causing loss of arachnoid fibroblasts that express Raldh2, an enzyme required for retinoic acid synthesis. Regionalized loss of Raldh2 in the dorsolateral meninges is first detected when folding begins. The ventricular zone expands and the forebrain lengthens at this time due to expansion of apical radial glia. As the cortex expands, regionalized differences in the levels of neurogenesis are coupled with changes to the tangential distribution of neurons. Consequentially, cortical growth at and adjacent to the midline accelerates with respect to more dorsolateral regions, resulting in cortical buckling and folding. Maternal retinoic acid supplementation suppresses cortical folding by normalizing forebrain length, neurogenesis and the tangential distribution of neurons. These results suggest that Twist1 and balanced retinoic acid signaling from the meninges are required to maintain normal levels of neurogenesis and lissencephaly in mice.

Spatiotemporal molecular dynamics of the developing human thalamus

The thalamus plays a central coordinating role in the brain. Thalamic neurons are organized into spatially-distinct nuclei, but the molecular architecture of thalamic development is poorly understood, especially in humans. To begin to delineate the molecular trajectories of cell fate specification and organization in the developing human thalamus, we used single cell and multiplexed spatial transcriptomics. Here we show that molecularly-defined thalamic neurons differentiate in the second trimester of human development, and that these neurons organize into spatially and molecularly distinct nuclei. We identify major subtypes of glutamatergic neuron subtypes that are differentially enriched in anatomically distinct nuclei. In addition, we identify six subtypes of GABAergic neurons that are shared and distinct across thalamic nuclei.

One-Sentence Summary

Single cell and spatial profiling of the developing thalamus in the first and second trimester yields molecular mechanisms of thalamic nuclei development.

Clade-specific genes and the evolutionary origin of novelty; new tools in the toolkit

Clade-specific (a.k.a. lineage-specific) genes are very common and found at all taxonomic levels and in all clades examined. They can arise by duplication of previously existing genes, which can involve partial truncations or combinations with other protein domains or regulatory sequences. They can also evolve de novo from non-coding sequences, leading to potentially truly novel protein domains. Finally, since clade-specific genes are generally defined by lack of sequence homology with other proteins, they can also arise by sequence evolution that is rapid enough that previous sequence homology can no longer be detected. In such cases, where the rapid evolution is followed by constraint, we consider them to be ontologically non-novel but likely novel at a functional level. In general, clade-specific genes have received less attention from biologists but there are increasing numbers of fascinating examples of their roles in important traits. Here we review some selected recent examples, and argue that attention to clade-specific genes is an important corrective to the focus on the conserved developmental regulatory toolkit that has been the habit of evo-devo as a field. Finally, we discuss questions that arise about the evolution of clade-specific genes, and how these might be addressed by future studies. We highlight the hypothesis that clade-specific genes are more likely to be involved in synapomorphies that arose in the stem group where they appeared, compared to other genes.

Genomic structural variation: A complex but important driver of human evolution

Structural variants (SVs)-including duplications, deletions, and inversions of DNA-can have significant genomic and functional impacts but are technically difficult to identify and assay compared with single-nucleotide variants. With the aid of new genomic technologies, it has become clear that SVs account for significant differences across and within species. This phenomenon is particularly well-documented for humans and other primates due to the wealth of sequence data available. In great apes, SVs affect a larger number of nucleotides than single-nucleotide variants, with many identified SVs exhibiting population and species specificity. In this review, we highlight the importance of SVs in human evolution by (1) how they have shaped great ape genomes resulting in sensitized regions associated with traits and diseases, (2) their impact on gene functions and regulation, which subsequently has played a role in natural selection, and (3) the role of gene duplications in human brain evolution. We further discuss how to incorporate SVs in research, including the strengths and limitations of various genomic approaches. Finally, we propose future considerations in integrating existing data and biospecimens with the ever-expanding SV compendium propelled by biotechnology advancements.

Comparative landscape of genetic dependencies in human and chimpanzee stem cells

Comparative studies of great apes provide a window into our evolutionary past, but the extent and identity of cellular differences that emerged during hominin evolution remain largely unexplored. We established a comparative loss-of-function approach to evaluate whether human cells exhibit distinct genetic dependencies. By performing genome-wide CRISPR interference screens in human and chimpanzee pluripotent stem cells, we identified 75 genes with species-specific effects on cellular proliferation. These genes comprised coherent processes, including cell-cycle progression and lysosomal signaling, which we determined to be human-derived by comparison with orangutan cells. Human-specific robustness to CDK2 and CCNE1 depletion persisted in neural progenitor cells and cerebral organoids, supporting the G1-phase length hypothesis as a potential evolutionary mechanism in human brain expansion. Our findings demonstrate that evolutionary changes in human cells reshaped the landscape of essential genes and establish a platform for systematically uncovering latent cellular and molecular differences between species.

Comparative physiological anthropogeny: exploring molecular underpinnings of distinctly human phenotypes

Anthropogeny is a classic term encompassing transdisciplinary investigations of the origins of the human species. Comparative anthropogeny is a systematic comparison of humans and other living nonhuman hominids (so-called "great apes"), aiming to identify distinctly human features in health and disease, with the overall goal of explaining human origins. We begin with a historical perspective, briefly describing how the field progressed from the earliest evolutionary insights to the current emphasis on in-depth molecular and genomic investigations of "human-specific" biology and an increased appreciation for cultural impacts on human biology. While many such genetic differences between humans and other hominids have been revealed over the last two decades, this information remains insufficient to explain the most distinctive phenotypic traits distinguishing humans from other living hominids. Here we undertake a complementary approach of "comparative physiological anthropogeny," along the lines of the preclinical medical curriculum, i.e., beginning with anatomy and considering each physiological system and in each case considering genetic and molecular components that are relevant. What is ultimately needed is a systematic comparative approach at all levels from molecular to physiological to sociocultural, building networks of related information, drawing inferences, and generating testable hypotheses. The concluding section will touch on distinctive considerations in the study of human evolution, including the importance of gene-culture interactions.