A mouse mutation that dysregulates neighboring Galnt17 and Auts2 genes is associated with phenotypes related to the human AUTS2 syndrome

AUTS2 was originally discovered as the gene disrupted by a translocation in human twins with Autism spectrum disorder (ASD), intellectual disability, and epilepsy. Since that initial finding, AUTS2-linked mutations and variants have been associated with a very broad array of neuropsychiatric disorders, suggesting that AUTS2 is required for fundamental steps of neurodevelopment. However, genotype-phenotype correlations in this region are complicated, because most mutations could also involve neighboring genes. Of particular interest in this regard is the nearest downstream neighbor of AUTS2, GALNT17, encoding a brain-expressed N-acetylgalactosaminyltransferase of unknown brain function. Here we describe a mouse (Mus musculus) mutation, T(5G2;8A1)GSO (abbreviated 16Gso), a reciprocal translocation that breaks between Auts2 and Galnt17 and dysregulates both genes. Despite this complex regulatory effect, 16Gso homozygotes model certain human AUTS2-linked phenotypes very well. In addition to abnormalities in growth, craniofacial structure, learning and memory, and behavior, 16Gso homozygotes display distinct pathologies of the cerebellum and hippocampus that are similar to those associated with ASD and other types of neurological disease associated with this genomic region. Analyzing the mutant cerebellar and hippocampal transcriptomes, we identified disturbances in pathways related to neurite and synapse maturation, neurotransmitter signaling, and cellular stress, suggesting possible cellular mechanisms for 16Gso phenotypes. These pathways, coupled with the translocation's selective effects on Auts2 isoforms and coordinated dysregulation of Galnt17, suggest novel hypotheses regarding the etiology of the human "AUTS2 syndrome" and the wide array of neurodevelopmental disorders linked to variance in this genomic region. We collected cerebellum (CB) and hippocampus (HC) from 16Gso homozyotes and wild type (WT) animals at postnatal day 14 (P14) and P35. RNA from three animals of each genotype and age was used to generate Illumina RNA-seq libraries. We compared mutant and WT gene expression at each age in each tissue to identify differentially expressed genes.AUTS2最初被发现为在患有自闭症谱系障碍（Autism Spectrum Disorder, ASD）、智力障碍及癫痫的人类双胞胎中，因染色体易位而发生断裂破坏的基因。自该初始发现以来，与AUTS2相关的突变与变异已被关联到极为广泛的神经精神疾病谱系，这提示AUTS2对神经发育的核心环节至关重要。然而该区域内的基因型-表型关联较为复杂，因为多数突变可能同时波及邻近基因。此方面尤为值得关注的是AUTS2最近的下游邻位基因GALNT17，其编码一种在大脑中表达、但脑内功能尚未明确的N-乙酰半乳糖胺基转移酶（N-acetylgalactosaminyltransferase）。本研究描述了一种小鼠（Mus musculus）突变体T(5G2;8A1)GSO（简写为16Gso），该突变属于相互易位，其断点位于Auts2与Galnt17之间，并对这两个基因均造成表达失调。尽管存在这种复杂的调控效应，16Gso纯合子小鼠仍能很好地模拟部分人类AUTS2相关表型。除生长发育异常、颅面结构异常、学习记忆障碍与行为异常外，16Gso纯合子小鼠还表现出小脑与海马体的特异性病理改变，此类改变与该基因组区域相关的ASD及其他神经系统疾病的病理特征相似。通过对突变体小脑与海马体的转录组进行分析，本研究鉴定出与神经突成熟、突触形成、神经递质信号传导及细胞应激相关的通路异常，这为16Gso表型提供了潜在的细胞机制解释。上述通路，结合易位对Auts2剪接异构体的选择性调控效应，以及Galnt17的协同表达失调，为人类"AUTS2综合征"的病因学，以及该基因组区域变异相关的广泛神经发育障碍，提供了全新的研究假说。本研究分别在出生后第14天（P14）与第35天（P35），采集16Gso纯合子与野生型（Wild Type, WT）小鼠的小脑（Cerebellum, CB）与海马体（Hippocampus, HC）组织。取每种基因型与年龄组的3只动物的RNA构建Illumina RNA测序文库，随后在每个年龄、每个组织中比较突变体与野生型的基因表达水平，以鉴定差异表达基因。