Project description:In mammals, fine motor control is essential for skilled behavior, and is subserved by specialized subdivisions of the primary motor cortex (M1) and other components of the brain’s motor circuitry. We profiled the epigenomic state of several components of the Rhesus macaque motor system, including subdivisions of M1 corresponding to hand and orofacial control. We compared this to open chromatin data from M1 in rat, mouse, and human. We found broad similarities as well as unique specializations in open chromatin regions (OCRs) between M1 subdivisions and other brain regions, as well as species- and lineage-specific differences reflecting their evolutionary histories. By distinguishing shared mammalian M1 OCRs from primate- and human-specific specializations, we highlight gene regulatory programs that could subserve the evolution of skilled motor behaviors such as speech and tool use. Further, in order to predict candidate enhancers in additional species for which primary data was not available, we developed machine learning models trained on genome sequence across species.
Project description:Motor neuron (MN), together with interneuron, are the two major neuronal types in spinal cord. MNs control muscle movement and are essential for breathing, walking and fine motor skills. Malfunction of MNs is frequently associated with neuronal diseases such as spinal muscular atrophy and amyotrophic lateral sclerosis. To establish normal function, MNs need to be differentiated properly from neural progenitor cells. Thus, it is of great importance to study the mechanism for MN specification. This study focuses on Mnx1 - a conserved homeobox transcription factor gets expressed during MN specification. Mnx1 is also the most widely used MN marker. Previous studies reported that Mnx1 mutation in mouse causes early lethality - probably by affecting the controlling over respiratory system. However, the exact role of Mnx1 for MN identity remains poorly understood. Taking advantage of a recently developed in vitro model for efficient MN induction from mouse ES cells, we combined experimental and OMICs techniques to systematically investigate the molecular function of Mnx1. We identified thousands of Mnx1 binding sites - many are co-bound by core MN factor Lhx3 and Isl1 and lack active histone marks. Disruption of Mnx1 causes increased expression of 85 genes - while only 14 genes get down-regulated. Up-regulated genes are enriched with neuronal functions, usually get expressed during MN differentiation, and tend to have higher expression in motor neurons and brain compared with other tissues – indicating Mnx1 may fine tune neuronal genes to desired level. However, only a dozen of regions with increased H3K27ac marks are bound by Mnx1, and only two up-regulated genes (Pbx3 and Pou6f2) are identified as putative direct targets of Mnx1 - both are core neuronal factors with the potential to regulate other differential neuronal genes. These results suggest that Mnx1 may contribute to MN identity by fine-tuning the expression of many neuronal genes through direct regulation of a few core neuronal transcription factors. In summary, this study represents the first systematic investigation about the molecular function of the core MN factor Mnx1. It clarifies the mechanism of Mnx1 for MN identity, and also improves the understanding about the regulation mode of homeobox transcription factors.
Project description:While genome sequencing has identified numerous non-coding alterations between primate species, which of these are regulatory and potentially relevant to the evolution of the human brain is unclear. Here, we annotate cis-regulatory elements (CREs) in the human, rhesus macaque and chimpanzee genome using ChIP-sequencing in different anatomical parts of the adult brain. We find high similarity in the genomic positioning of CREs between rhesus macaque and humans, suggesting that the majority of these elements were already present in a common ancestor 25 million years ago. Most of the observed regulatory changes between humans and rhesus macaque occurred prior to the ancestral separation of humans and chimpanzee, leaving a modest set of regulatory elements with predicted human-specificity. Our data refine previous predictions and hypotheses on the consequences of genomic changes between primate species, and allow the identification of regulatory alterations relevant to the evolution of the brain. ChIP-Sequencing for H3K27ac on 8 distinct brain regions from human (three biological replicates per brain region), chimpanzee (two biological replicates per brain region) and rhesus macaque (three biological replicates per brain region).
Project description:While genome sequencing has identified numerous non-coding alterations between primate species, which of these are regulatory and potentially relevant to the evolution of the human brain is unclear. Here, we annotate cis-regulatory elements (CREs) in the human, rhesus macaque and chimpanzee genome using ChIP-sequencing in different anatomical parts of the adult brain. We find high similarity in the genomic positioning of CREs between rhesus macaque and humans, suggesting that the majority of these elements were already present in a common ancestor 25 million years ago. Most of the observed regulatory changes between humans and rhesus macaque occurred prior to the ancestral separation of humans and chimpanzee, leaving a modest set of regulatory elements with predicted human-specificity. Our data refine previous predictions and hypotheses on the consequences of genomic changes between primate species, and allow the identification of regulatory alterations relevant to the evolution of the brain.
Project description:The Aristaless-related homeobox (ARX) gene is a transcription factor involved in the development of GABAergic and cholinergic neurons in the forebrain. ARX mutations have been associated with a wide spectrum of neurodevelopemental disorders in humans, among which the most frequent, the 24 bp duplication in the protein polyalanine tract 2 (c.428_451dup24), gives rise to intellectual disability (ID), fine motor defects with or without epilepsy. To understand the physiological and functional consequences of this mutation, we generated and characterized a humanized mouse model carrying the c.428_451dup24 duplication (Arxdup24/0). Arxdup24/0 males presented with hyperactivity, enhanced stereotypies and altered contextual fear memory. Specific fine motor skills were also affected in Arxdup24/0 males, with reaching and grasping abilities alteration and fine motor coordination and balance defect. Transcriptome analysis of Arxdup24/0 forebrains at E15.5 showed a down-regulation of genes specifically expressed in interneurons associated with an up-regulation of interneuron silenced genes, suggesting abnormal interneuron development. Accordingly, interneuron migration and development were altered particularly in the cortex and the striatum between stages E15.5, P0 and adult. We also revealed a perturbation of the inhibitory/excitatory balance in Arxdup24/0 basolateral amygdala. Altogether, we showed that the c.428_451dup24 mutation modifies Arx function with a direct consequence on interneuron development, leading to hyperactivity and defects in precise motor movement control and in associative memory. Finally, we presented a new review of the clinical features of 33 male patients with ARX c.428_451dup24 mutation and showed striking similarities between their clinical features and the mouse phenotype.
Project description:Gene expression differences are shaped by selective pressures and contribute to phenotypic differences between species. We identified 964 copy number differences (CNDs) of conserved sequences across 3 primate species and examined their potential effects on gene expression profiles. Samples with copy number different genes had significantly different expression than samples with neutral copy number. Genes encoding regulatory molecules differed in copy number and were associated with significant expression differences. Additionally, we identified 127 CNDs which were processed pseudogenes and some of which were expressed. Furthermore, there were copy number different regulatory regions such as ultraconserved elements and long intergenic noncoding RNAs with the potential to affect expression. We postulate that CNDs of these conserved sequences fine-tune developmental pathways by altering the levels of RNA. Gene expression patterns were compared between human, chimpanzee and rhesus macaque lymphoblastoid cell lines using RNA-Seq. Samples from 6 individuals of each species were used. The 6 human samples were previously published as a part of GEO record GSE19480 (samples GSM485426, GSM485428, GSM485468, GSM485410, GSM485413 and GSM485414). The 6 chimpanzee and 6 rhesus macaquesamples are included in the current record (GSE38572).
Project description:Gene expression differences are shaped by selective pressures and contribute to phenotypic differences between species. We identified 964 copy number differences (CNDs) of conserved sequences across 3 primate species and examined their potential effects on gene expression profiles. Samples with copy number different genes had significantly different expression than samples with neutral copy number. Genes encoding regulatory molecules differed in copy number and were associated with significant expression differences. Additionally, we identified 127 CNDs which were processed pseudogenes and some of which were expressed. Furthermore, there were copy number different regulatory regions such as ultraconserved elements and long intergenic noncoding RNAs with the potential to affect expression. We postulate that CNDs of these conserved sequences fine-tune developmental pathways by altering the levels of RNA.
Project description:Gene expression differences are shaped by selective pressures and contribute to phenotypic differences between species. We identified 964 copy number differences (CNDs) of conserved sequences across 3 primate species and examined their potential effects on gene expression profiles. Samples with copy number different genes had significantly different expression than samples with neutral copy number. Genes encoding regulatory molecules differed in copy number and were associated with significant expression differences. Additionally, we identified 127 CNDs which were processed pseudogenes and some of which were expressed. Furthermore, there were copy number different regulatory regions such as ultraconserved elements and long intergenic noncoding RNAs with the potential to affect expression. We postulate that CNDs of these conserved sequences fine-tune developmental pathways by altering the levels of RNA.
Project description:The human genome is composed of 4.5 million transposable elements (TE). The requirement for a TE to propagate through the genome during evolution is to be expressed to be retro-transpose into germ cells or pre-implantation embryo. Thus, many evolutionarily young TEs still contain DNA binding sites for pluripotency factors and are transiently expressed in the pre-implantation embryo. We observed that these and many other primate-restricted transposable elements have alternative binding sites for cell-type-specific transcription factors that allow them to be transcribed during human gastrulation. Furthermore, we have demonstrated that they can also serve as cell-type-specific enhancers and induce the expression of KRAB-Zinc Finger repressors of similar evolutionary age. This mechanism allows the domestication of TEs containing cell-type-specific binding sites and their incorporation into the shaping of human developmental-specific transcription networks.