Project description:Background - One of the causal mechanisms underlying neurodevelopmental disorders (NDDs) is chromatin modification, and the genes that regulate chromatin. AT-Rich Interactive Domain 1B (ARID1B), a chromatin modifier, has been shown to be reduced in autism spectrum disorder (ASD) and to affect rare and inherited genetic variation in a broad set of NDDs. Methods - A novel preclinical mouse model of Arid1b deficiency was created and validated to characterize and define neuroanatomical, behavioural and tran¬scriptional phenotypes. Neuroanatomy was assessed ex vivo in adult animals and in vivo longitudinally from birth to adulthood. Behavioural testing was also performed throughout development and tested all aspects of motor, learning, sociability, repetitive behaviours, seizure susceptibility and general milestones delays. Results – We validated decreased Arid1b mRNA and protein in Arid1b+/- mice, with signatures of increased axonal and synaptic gene expression and decreased transcriptional regulator and RNA processing expression in adult Arid1b+/- cerebellum. During neonatal development, Arid1b+/- mice exhibited robust impairments in ultrasonic vocalizations (USVs) and metrics of developmental growth. In addition, a striking sex dependence was observed throughout development; males had an early emergence of this neuroanatomical phenotype at postnatal day 7, whereas females had a delayed emergence around postnatal day 40. Behaviourally, as adults, Arid1b+/- mice showed low motor skills in open field exploration and normal three chambered approach. Arid1b+/- mice had learning and memory deficits in novel object recognition but not in visual discrimination and reversal touchscreen tasks. Social interactions in the male-female social dyad with USVs revealed social deficits on some but not all parameters. No repetitive behaviours were observed. Brains of adult Arid1b+/- mice had a smaller cerebellum and a larger hippocampus and corpus callosum. These results stand in contrast to previously reported data highlighting losses in corpus callosum volume in mice. Limitations – The behaviour and neuroimaging analyses were done on separate cohorts of mice, which did not allow a direct correlation between the imaging and behavioural findings, and the transcriptomic analyses was exploratory, with no validation of altered expression beyond Arid1b. Conclusions – This study represents a full validation and investigation of a novel model of Arid1b+/- haploinsufficiency throughout development and highlights the importance of examining both sexes throughout development in NDDs.

Project description:Shank3 is an abundant excitatory postsynaptic scaffolding proteins implicated in various neurodevelopmental and psychiatric disorders, including ASD, Phelan-McDermid syndrome, intellectual disability, and schizophrenia. Shank3-mutant mice with a homozygous deletion of exons 14-16 (Shank3-HM mice) show ASD-like behavioral deficits and altered synaptic and neuronal functions, but little is known about how different ages, brain regions, and gene dosages contribute to transcriptomic phenotypes in these mice. Here, we performed RNA-Seq-based transcriptomic analyses of the prefrontal cortex, hippocampus, and striatum in adult Shank3 heterozygous- and homozygous-mutant mice. In addition, juvenile and adult Shank3 homozygous-mutant forebrain transcriptomes were compared. Juvenile and adult forebrain transcriptomes from Shank3 homozygous-mutant mice showed the patterns that are opposite and similar to those observed in ASD: reverse-ASD and ASD-like patterns, respectively. Here, the juvenile reverse-ASD pattern involved synaptic gene upregulations and ribosomal and mitochondrial downregulations, whereas the adult ASD-like pattern involved opposite changes. Gene set enrichment analyses (GSEA) of brain regional transcripts in adult Shank3-HT and Shank3-HM mice revealed that the cortical, hippocampal, and striatal transcripts show distinctly altered biological functions and ASD-related/risk gene expressions. The cortex and striatum display ASD-like patterns whereas the hippocampus displays reverse-ASD patterns. The cortical ASD-like pattern more strongly involves ASD-risk genes whereas the striatal ASD-like pattern more strongly involves astrocyte/microglia genes. Shank3-HT and Shank3-HM transcripts in a given brain region display largely similar patterns in biological functions and ASD-related/risk gene expressions, suggestive of small gene dosage effects. These results suggest that heterozygous and homozygous Shank3 deletions in mice lead to age, brain region, and gene dosage-differential transcriptomic changes.

Project description:Newborn neurons enter an extended maturation stage, during which they acquire excitability characteristics crucial for development of presynaptic and postsynaptic connectivity. In contrast to earlier specification programs, little is known aboutthe regulatory mechanisms that control neuronal maturation. The Pet-1 ETS (E26 transformation-specific) factor is continuously expressed in serotonin (5-HT) neurons and initially acts in postmitotic precursors to control acquisition of 5-HT transmitter identity. Using a combination of RNA sequencing, electrophysiology, and conditional targeting approaches, we determined gene expression patterns in maturing flow-sorted 5-HT neurons and the temporal requirements for Pet-1 in shaping these patterns for functional maturation of mouse 5-HT neurons. We report a profound disruption of postmitotic expression trajectories in Pet-1 / neurons, which prevented postnatal maturation of 5-HT neuron passive and active intrinsic membrane properties, G-protein signaling, and synaptic responses to glutamatergic, lysophosphatidic, and adrenergic agonists. Unexpectedly, conditional targeting revealed a postnatal stage-specific switch in Pet-1 targets from 5-HT synthesis genes to transmitter receptor genes required for afferent modulation of 5-HT neuron excitability. 5-HT1a autoreceptor expression depended transiently on Pet-1, thus revealing an early postnatal sensitive period for control of 5-HT excitability genes. Chromatin immunoprecipitation followed by sequencing revealed that Pet-1 regulates 5-HT neuron maturation through direct gene activation and repression. Moreover, Pet-1 directly regulates the 5-HT neuron maturation factor Engrailed 1, which suggests Pet-1 orchestrates maturationthrough secondary postmitotic regulatoryfactors. The early postnatal switch in Pet-1targets uncovers a distinct neonatal stage-specific function for Pet-1, during which it promotes maturation of 5-HT neuron excitability. 5-HT neuron mRNA profiles of E11.5, E15.5, and postnatal (P1-P3) wild type (WT) and Pet-1-/- mice were generated by deep sequencing, in triplicate, using Illumina HiSeq 2500. Myc-tagged Pet-1 ChIP-seq was performed on E12.5 to E14.5 hindbrains and sequencing using NextSeq 500.

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Whole-brain transcriptome of Arid1b heterozygote mutation mice age of postnatal day 3

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