Neuroanatomy and Behaviour in Mice with a Haploinsufficiency of AT-Rich Interactive Domain 1B (ARID1B) Throughout Development

One of the causal mechanisms underlying neurodevelopmental disorders (NDDs) is chromatin modification, and genes that regulate chromatin modify and control events regulating the formation of neural connections. 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. For this work, a novel preclinical mouse model of Arid1b deficiency was created and molecularly validated to characterize and define neuroanatomical, behavioural and transcriptional phenotypes. Brains of adult Arid1b +/- mice had a smaller cerebellum along with a larger hippocampus and corpus callosum. In addition, a notable sex dependence was observed throughout development; males had an early emergence of the neuroanatomical phenotype around postnatal day 7, whereas females had a delayed emergence of the phenotype around postnatal day 40. Behavioural assays relevant to NDD were conducted during neonatal development and adulthood to evaluate general health, anxiety-like, motor, cognitive, and social behaviours in Arid1b +/- mice. During neonatal development, Arid1b +/- mice exhibited robust impairments in ultrasonic vocalizations (USVs) and metrics of developmental growth. 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 surprisingly 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. This study represents a full investigation of Arid1b +/- haploinsufficiency throughout development and highlights the importance of examining both sexes throughout development in NDDs.