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Lindhout FW, Krienen FM, Pollard KS, Lancaster MA. A molecular and cellular perspective on human brain evolution and tempo. Nature 2024; 630:596-608. [PMID: 38898293 DOI: 10.1038/s41586-024-07521-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 04/29/2024] [Indexed: 06/21/2024]
Abstract
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.
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Affiliation(s)
- Feline W Lindhout
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
| | - Fenna M Krienen
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Katherine S Pollard
- Gladstone Institutes, San Francisco, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
- Department of Epidemiology & Biostatistics, Institute for Computational Health Sciences, and Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
| | - Madeline A Lancaster
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
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2
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Zug R, Uller T. Evolution and dysfunction of human cognitive and social traits: A transcriptional regulation perspective. EVOLUTIONARY HUMAN SCIENCES 2022; 4:e43. [PMID: 37588924 PMCID: PMC10426018 DOI: 10.1017/ehs.2022.42] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/11/2022] [Accepted: 09/11/2022] [Indexed: 11/07/2022] Open
Abstract
Evolutionary changes in brain and craniofacial development have endowed humans with unique cognitive and social skills, but also predisposed us to debilitating disorders in which these traits are disrupted. What are the developmental genetic underpinnings that connect the adaptive evolution of our cognition and sociality with the persistence of mental disorders with severe negative fitness effects? We argue that loss of function of genes involved in transcriptional regulation represents a crucial link between the evolution and dysfunction of human cognitive and social traits. The argument is based on the haploinsufficiency of many transcriptional regulator genes, which makes them particularly sensitive to loss-of-function mutations. We discuss how human brain and craniofacial traits evolved through partial loss of function (i.e. reduced expression) of these genes, a perspective compatible with the idea of human self-domestication. Moreover, we explain why selection against loss-of-function variants supports the view that mutation-selection-drift, rather than balancing selection, underlies the persistence of psychiatric disorders. Finally, we discuss testable predictions.
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Affiliation(s)
- Roman Zug
- Department of Biology, Lund University, Lund, Sweden
| | - Tobias Uller
- Department of Biology, Lund University, Lund, Sweden
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3
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Wexler BE. Returning to basic principles to develop more effective treatments for central nervous system disorders. Exp Biol Med (Maywood) 2022; 247:856-867. [PMID: 35172621 PMCID: PMC9158240 DOI: 10.1177/15353702221078291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Development of new treatments for diseases of the central nervous system (CNS) is
stalled. Of candidate drugs developed through costly preclinical research, 93%
fail clinical trials. Hoped-for improvements in diagnosis or treatment from
decades of positron emission tomography (PET) and functional magnetic resonance
imaging (fMRI) imaging have yet to materialize. To understand what we are doing
wrong, I begin with recognition that all aspects of life, including the brain
and mind, are physical phenomena consistent with processes described by
physicists. Two processes, emergence and entropy, are of particular relevance in
complex arrangements of matter that constitute life in general and the brain in
particular. The human brain functions through dynamically reconfiguring and
hierarchically organized neural functional systems with emergent properties of
cognition, emotion, and conscious experience. These systems are shaped and
maintained by negentropic environmental input transformed by sensory receptors
into neural signals that trigger epigenetic neuroplastic processes. CNS diseases
produce clinical disorders by disrupting these systems. As researchers seek
appropriate levels of system organization at which to characterize and treat
illness, focus has been on medications that impact processes at lower levels or
transcranial electric or magnetic stimulation that impact broad contiguous
swaths of tissue. Neither align with the brain’s neurosystem organization and
therefore lack specificity necessary to be effective and to limit side effects.
Digital neurotherapies (DNTs), in contrast, align with neurosystem organization
and achieve the needed specificity using the same input pathways and
neuroplastic processes that created the neural systems organization to repair
it. The omission of DNTs from major systems-based initiatives represents
powerful residua of dualist thinking. Interventions based on perceptual and
cognitive processes are not thought of as being as physical as drugs or electric
or magnetic stimulation through the skull. In fact, they are examples of the
most basic processes that create and support life itself.
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Quiver MH, Lachance J. Adaptive eQTLs reveal the evolutionary impacts of pleiotropy and tissue-specificity while contributing to health and disease. HGG ADVANCES 2022; 3:100083. [PMID: 35047867 PMCID: PMC8756519 DOI: 10.1016/j.xhgg.2021.100083] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 12/21/2021] [Indexed: 11/24/2022] Open
Abstract
Large numbers of expression quantitative trait loci (eQTLs) have recently been identified in humans, and many of these regulatory variants have large allele frequency differences between populations. Here, we conducted genome-wide scans of selection to identify adaptive eQTLs (i.e., eQTLs with large population branch statistics). We then tested if tissue pleiotropy affects whether eQTLs are more or less likely to be adaptive and identified tissues that have been key targets of positive selection during the last 100,000 years. Top adaptive eQTL outliers include rs1043809, rs66899053, and rs2814778 (a SNP that is associated with malaria resistance). We found that effect sizes of eQTLs were negatively correlated with population branch statistics and that adaptive eQTLs affect two-thirds as many tissues as do non-adaptive eQTLs. Because the tissue breadth of an eQTL can be viewed as a measure of pleiotropy, these results imply that pleiotropy inhibits adaptation. The proportion of eQTLs that are adaptive varies by tissue, and we found that eQTLs that regulate expression in testis, thyroid, blood, or sun-exposed skin are enriched for signatures of positive selection. By contrast, eQTLs that regulate expression in the cerebrum or female-specific tissues have a relative lack of adaptive outliers. Scans of selections also reveal that many adaptive eQTLs are closely linked to disease-associated loci. Taken together, our results indicate that eQTLs have played an important role in recent human evolution.
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Affiliation(s)
- Melanie H Quiver
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Joseph Lachance
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
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5
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Hamann E, Pauli CS, Joly-Lopez Z, Groen SC, Rest JS, Kane NC, Purugganan MD, Franks SJ. Rapid evolutionary changes in gene expression in response to climate fluctuations. Mol Ecol 2020; 30:193-206. [PMID: 32761923 PMCID: PMC7818422 DOI: 10.1111/mec.15583] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 07/20/2020] [Accepted: 07/30/2020] [Indexed: 12/12/2022]
Abstract
There is now abundant evidence of rapid evolution in natural populations, but the genetic mechanisms of these changes remain unclear. One possible route to rapid evolution is through changes in the expression of genes that influence traits under selection. We examined contemporary evolutionary gene expression changes in plant populations responding to environmental fluctuations. We compared genome‐wide gene expression, using RNA‐seq, in two populations of Brassica rapa collected over four time points between 1997 and 2014, during which precipitation in southern California fluctuated dramatically and phenotypic and genotypic changes occurred. By combining transcriptome profiling with the resurrection approach, we directly examined evolutionary changes in gene expression over time. For both populations, we found a substantial number of differentially expressed genes between generations, indicating rapid evolution in the expression of many genes. Using existing gene annotations, we found that many changes occurred in genes involved in regulating stress responses and flowering time. These appeared related to the fluctuations in precipitation and were potentially adaptive. However, the evolutionary changes in gene expression differed across generations within and between populations, indicating largely independent evolutionary trajectories across populations and over time. Our study provides strong evidence for rapid evolution in gene expression, and indicates that changes in gene expression can be one mechanism of rapid evolutionary responses to selection episodes. This study also illustrates that combining resurrection studies with transcriptomics is a powerful approach for investigating evolutionary changes at the gene regulatory level, and will provide new insights into the genetic basis of contemporary evolution. see also the Perspective by Emily B. Josephs.
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Affiliation(s)
- Elena Hamann
- Department of Biological Sciences, Fordham University, Bronx, NY, USA.,Department of Genetics and Odum School of Ecology, University of Georgia, Athens, GA, USA
| | - Christopher S Pauli
- Department of Ecology and Evolution, The University of Colorado at Boulder, Boulder, CO, USA
| | - Zoé Joly-Lopez
- Department of Biology, Center for Genomics and Systems Biology, New York University, NY, USA
| | - Simon C Groen
- Department of Biology, Center for Genomics and Systems Biology, New York University, NY, USA
| | - Joshua S Rest
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, USA
| | - Nolan C Kane
- Department of Ecology and Evolution, The University of Colorado at Boulder, Boulder, CO, USA
| | - Michael D Purugganan
- Department of Biology, Center for Genomics and Systems Biology, New York University, NY, USA
| | - Steven J Franks
- Department of Biological Sciences, Fordham University, Bronx, NY, USA
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Housman G, Gilad Y. Prime time for primate functional genomics. Curr Opin Genet Dev 2020; 62:1-7. [PMID: 32544775 DOI: 10.1016/j.gde.2020.04.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 04/21/2020] [Accepted: 04/24/2020] [Indexed: 12/14/2022]
Abstract
Functional genomics research is continually improving our understanding of genotype-phenotype relationships in humans, and comparative genomics perspectives can provide additional insight into the evolutionary histories of such relationships. To specifically identify conservation or species-specific divergence in humans, we must look to our closest extant evolutionary relatives. Primate functional genomics research has been steadily advancing and expanding, in spite of several limitations and challenges that this field faces. New technologies and cheaper sequencing provide a unique opportunity to enhance and expand primate comparative studies, and we outline possible paths going forward. The potential human-specific insights that can be gained from primate functional genomics research are substantial, and we propose that now is a prime time to expand such endeavors.
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Affiliation(s)
- Genevieve Housman
- Section of Genetic Medicine, Department of Medicine, University of Chicago, 5841 S. Maryland Ave., N417, MC6091, Chicago, IL 60637 USA.
| | - Yoav Gilad
- Section of Genetic Medicine, Department of Medicine, University of Chicago, 5841 S. Maryland Ave., N417, MC6091, Chicago, IL 60637 USA; Department of Human Genetics, University of Chicago, Cummings Life Science Center, 928 E. 58th St., Chicago, IL 60637 USA
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7
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Bauernfeind AL, Babbitt CC. Metabolic changes in human brain evolution. Evol Anthropol 2020; 29:201-211. [PMID: 32329960 DOI: 10.1002/evan.21831] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 08/30/2019] [Accepted: 03/13/2020] [Indexed: 12/23/2022]
Abstract
Because the human brain is considerably larger than those of other primates, it is not surprising that its energy requirements would far exceed that of any of the species within the order. Recently, the development of stem cell technologies and single-cell transcriptomics provides novel ways to address the question of what specific genomic changes underlie the human brain's unique phenotype. In this review, we consider what is currently known about human brain metabolism using a variety of methods from brain imaging and stereology to transcriptomics. Next, we examine novel opportunities that stem cell technologies and single-cell transcriptomics provide to further our knowledge of human brain energetics. These new experimental approaches provide the ability to elucidate the functional effects of changes in genetic sequence and expression levels that potentially had a profound impact on the evolution of the human brain.
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Affiliation(s)
- Amy L Bauernfeind
- Department of Neuroscience, Washington University Medical School, St. Louis, Missouri, USA.,Department of Anthropology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Courtney C Babbitt
- Department of Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
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8
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Genes dysregulated in the blood of people with Williams syndrome are enriched in protein-coding genes positively selected in humans. Eur J Med Genet 2020; 63:103828. [DOI: 10.1016/j.ejmg.2019.103828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 11/09/2019] [Accepted: 12/21/2019] [Indexed: 12/29/2022]
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Swain-Lenz D, Berrio A, Safi A, Crawford GE, Wray GA. Comparative Analyses of Chromatin Landscape in White Adipose Tissue Suggest Humans May Have Less Beigeing Potential than Other Primates. Genome Biol Evol 2020; 11:1997-2008. [PMID: 31233101 PMCID: PMC6648876 DOI: 10.1093/gbe/evz134] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2019] [Indexed: 12/20/2022] Open
Abstract
Humans carry a much larger percentage of body fat than other primates. Despite the central role of adipose tissue in metabolism, little is known about the evolution of white adipose tissue in primates. Phenotypic divergence is often caused by genetic divergence in cis-regulatory regions. We examined the cis-regulatory landscape of fat during human origins by performing comparative analyses of chromatin accessibility in human and chimpanzee adipose tissue using rhesus macaque as an outgroup. We find that many regions that have decreased accessibility in humans are enriched for promoter and enhancer sequences, are depleted for signatures of negative selection, are located near genes involved with lipid metabolism, and contain a short sequence motif involved in the beigeing of fat, the process in which lipid-storing white adipocytes are transdifferentiated into thermogenic beige adipocytes. The collective closing of many putative regulatory regions associated with beigeing of fat suggests a mechanism that increases body fat in humans.
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Affiliation(s)
| | | | - Alexias Safi
- Duke Center for Genomic and Computational Biology, Duke University
| | - Gregory E Crawford
- Duke Center for Genomic and Computational Biology, Duke University.,Division of Medical Genetics, Department of Pediatrics, Duke University
| | - Gregory A Wray
- Biology Department, Duke University.,Duke Center for Genomic and Computational Biology, Duke University
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10
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Pizzollo J, Nielsen WJ, Shibata Y, Safi A, Crawford GE, Wray GA, Babbitt CC. Comparative Serum Challenges Show Divergent Patterns of Gene Expression and Open Chromatin in Human and Chimpanzee. Genome Biol Evol 2018; 10:826-839. [PMID: 29608722 PMCID: PMC5848805 DOI: 10.1093/gbe/evy041] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/19/2018] [Indexed: 12/13/2022] Open
Abstract
Humans experience higher rates of age-associated diseases than our closest living evolutionary relatives, chimpanzees. Environmental factors can explain many of these increases in disease risk, but species-specific genetic changes can also play a role. Alleles that confer increased disease susceptibility later in life can persist in a population in the absence of selective pressure if those changes confer positive adaptation early in life. One age-associated disease that disproportionately affects humans compared with chimpanzees is epithelial cancer. Here, we explored genetic differences between humans and chimpanzees in a well-defined experimental assay that mimics gene expression changes that happen during cancer progression: A fibroblast serum challenge. We used this assay with fibroblasts isolated from humans and chimpanzees to explore species-specific differences in gene expression and chromatin state with RNA-Seq and DNase-Seq. Our data reveal that human fibroblasts increase expression of genes associated with wound healing and cancer pathways; in contrast, chimpanzee gene expression changes are not concentrated around particular functional categories. Chromatin accessibility dramatically increases in human fibroblasts, yet decreases in chimpanzee cells during the serum response. Many regions of opening and closing chromatin are in close proximity to genes encoding transcription factors or genes involved in wound healing processes, further supporting the link between changes in activity of regulatory elements and changes in gene expression. Together, these expression and open chromatin data show that humans and chimpanzees have dramatically different responses to the same physiological stressor, and how a core physiological process can evolve quickly over relatively short evolutionary time scales.
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Affiliation(s)
- Jason Pizzollo
- Molecular and Cellular Biology Graduate Program, University of Massachusetts Amherst.,Department of Biology, University of Massachusetts Amherst
| | | | - Yoichiro Shibata
- Division of Medical Genetics, Department of Pediatrics, Duke University
| | - Alexias Safi
- Division of Medical Genetics, Department of Pediatrics, Duke University
| | - Gregory E Crawford
- Division of Medical Genetics, Department of Pediatrics, Duke University.,Center for Genomic and Computational Biology, Duke University
| | - Gregory A Wray
- Department of Biology, Duke University.,Center for Genomic and Computational Biology, Duke University.,Department of Evolutionary Anthropology, Duke University
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