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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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Kautt AF, Chen J, Lewarch CL, Hu C, Turner K, Lassance JM, Baier F, Bedford NL, Bendesky A, Hoekstra HE. Evolution of gene expression across brain regions in behaviourally divergent deer mice. Mol Ecol 2024:e17270. [PMID: 38263608 DOI: 10.1111/mec.17270] [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: 09/30/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 01/25/2024]
Abstract
The evolution of innate behaviours is ultimately due to genetic variation likely acting in the nervous system. Gene regulation may be particularly important because it can evolve in a modular brain-region specific fashion through the concerted action of cis- and trans-regulatory changes. Here, to investigate transcriptional variation and its regulatory basis across the brain, we perform RNA sequencing (RNA-Seq) on ten brain subregions in two sister species of deer mice (Peromyscus maniculatus and P. polionotus)-which differ in a range of innate behaviours, including their social system-and their F1 hybrids. We find that most of the variation in gene expression distinguishes subregions, followed by species. Interspecific differential expression (DE) is pervasive (52-59% of expressed genes), whereas the number of DE genes between sexes is modest overall (~3%). Interestingly, the identity of DE genes varies considerably across brain regions. Much of this modularity is due to cis-regulatory divergence, and while 43% of genes were consistently assigned to the same gene regulatory class across subregions (e.g. conserved, cis- or trans-regulatory divergence), a similar number were assigned to two or more different gene regulatory classes. Together, these results highlight the modularity of gene expression differences and divergence in the brain, which may be key to explain how the evolution of brain gene expression can contribute to the astonishing diversity of animal behaviours.
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Affiliation(s)
- Andreas F Kautt
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Jenny Chen
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Caitlin L Lewarch
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Caroline Hu
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Kyle Turner
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Jean-Marc Lassance
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Felix Baier
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Nicole L Bedford
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Andres Bendesky
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Hopi E Hoekstra
- Department of Organismic & Evolutionary Biology, Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
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