Galnt17 loss-of-function leads to developmental delay, abnormal coordination, activity, and social interactions, with cerebellar vermis pathology

GALNT17 encodes a N-acetylgalactosaminyltransferase (GalNAc-T) protein specifically involved in mucin-type O-linked glycosylation of target proteins, a process important for cell adhesion, cell signaling, neurotransmitter activity, neurite outgrowth, and neurite sensing. GALNT17, also known as WBSCR17, is located at the edge of the Williams-Beuren Syndrome (WBS) critical region and adjacent to the AUTS2 locus, genomic regions associated with neurodevelopmental phenotypes that are thought to be co-regulated. Although previous data have implicated Galnt17 in neurodevelopment, the in vivo functions of this gene have not been investigated. In this study, we have analyzed behavioral, brain pathology, and molecular phenotypes exhibited by Galnt17 knockout (Galnt17-/-) mice. We show that Galnt17-/- mutants exhibit developmental neuropathology within the cerebellar vermis, along with abnormal activity, coordination, and social interaction deficits. Transcriptomic and protein analysis revealed reductions in both mucin type O-glycosylation and heparan sulfate synthesis in the developing mutant cerebellum along with disruption of pathways central to neuron differentiation, axon pathfinding, and synaptic signaling, consistent with the mutant neuropathology. These brain and behavioral phenotypes and molecular data confirm a specific role for Galnt17 in brain development and suggest new clues to factors that could contribute to phenotypes in certain WBS and AUTS2 syndrome patients. RNA Sequencing was performed on RNA samples collected from individual cerebellums of male, 14-day old (P14), mice. Two mouse strains were sampled in biological triplicate, Wbscr17-/- and B6C3 w/t control. Paired end RNA Libraries were prepared and sequenced on a Hiseq 4000 sequencer with a read length of 2x150bp.GALNT17编码N-乙酰半乳糖胺基转移酶（N-acetylgalactosaminyltransferase，简称GalNAc-T），该蛋白特异性参与靶蛋白的黏蛋白型O-连接糖基化修饰，这一过程对细胞黏附、细胞信号转导、神经递质活性、神经突生长及神经突感知均具有重要作用。 GALNT17又名WBSCR17，定位于威廉姆斯-比伦综合征（Williams-Beuren Syndrome，简称WBS）关键区域的边缘，且紧邻AUTS2基因座；上述两个基因组区域均与神经发育表型相关，且被认为存在共调控关系。 尽管已有研究提示Galnt17参与神经发育过程，但该基因的体内功能尚未得到深入研究。 本研究针对Galnt17敲除（Galnt17-/-）小鼠所呈现的行为学、脑病理学及分子表型展开了系统分析。 结果显示，Galnt17-/-突变小鼠存在小脑蚓部发育性神经病理学异常，同时伴随活动异常、协调能力缺陷以及社交互动障碍。 转录组学与蛋白质组学分析表明，发育中的突变小鼠小脑内，黏蛋白型O-糖基化与硫酸乙酰肝素合成水平均出现下调，同时神经元分化、轴突导向以及突触信号传导核心通路均受到干扰，这与突变小鼠的神经病理学表型高度一致。 上述脑与行为表型及分子层面的数据证实了Galnt17在脑发育中的特异性功能，并为阐明部分WBS及AUTS2综合征患者表型的潜在致病因素提供了新的研究线索。 本研究针对14日龄（P14）雄性小鼠的单个小脑组织提取的RNA样本开展了RNA测序。 实验设置两个小鼠品系的生物学重复样本：Wbscr17-/-敲除小鼠与B6C3野生型（w/t）对照小鼠，每组均设置3次生物学重复。 构建双端RNA测序文库后，使用HiSeq 4000测序仪进行测序，测序读长为2×150 bp。