BACKGROUND The X-chromosome gene USP9X encodes a deubiquitylating enzyme that has been associated with neurodevelopmental disorders primarily in female subjects. USP9X escapes X inactivation, and in female subjects de novo heterozygous copy number loss or truncating mutations cause haploinsufficiency culminating in a recognizable syndrome with intellectual disability and signature brain and congenital abnormalities. In contrast, the involvement of USP9X in male neurodevelopmental disorders remains tentative. METHODS We used clinically recommended guidelines to collect and interrogate the pathogenicity of 44 USP9X variants associated with neurodevelopmental disorders in males. Functional studies in patient-derived cell lines and mice were used to determine mechanisms of pathology. RESULTS Twelve missense variants showed strong evidence of pathogenicity. We define a characteristic phenotype of the central nervous system (white matter disturbances, thin corpus callosum, and widened ventricles); global delay with significant alteration of speech, language, and behavior; hypotonia; joint hypermobility; visual system defects; and other common congenital and dysmorphic features. Comparison of in silico and phenotypical features align additional variants of unknown significance with likely pathogenicity. In support of partial loss-of-function mechanisms, using patient-derived cell lines, we show loss of only specific USP9X substrates that regulate neurodevelopmental signaling pathways and a united defect in transforming growth factor β signaling. In addition, we find correlates of the male phenotype in Usp9x brain-specific knockout mice, and further resolve loss of hippocampal-dependent learning and memory. CONCLUSIONS Our data demonstrate the involvement of USP9X variants in a distinctive neurodevelopmental and behavioral syndrome in male subjects and identify plausible mechanisms of pathogenesis centered on disrupted transforming growth factor β signaling and hippocampal function.

中文翻译：

---

USP9X 功能部分丧失会导致男性神经发育和行为障碍，并与 TGFβ 信号传导相关

背景 X 染色体基因 USP9X 编码一种去泛素化酶，该酶主要与女性受试者的神经发育障碍相关。USP9X 逃脱了 X 失活，并且在女性受试者中，从头杂合拷贝数丢失或截短突变导致单倍体不足，最终导致可识别的综合征，伴有智力障碍和特征性大脑和先天性异常。相比之下，USP9X 在男性神经发育障碍中的参与仍处于初步阶段。方法 我们使用临床推荐的指南来收集和探讨与男性神经发育障碍相关的 44 个 USP9X 变异的致病性。使用患者来源的细胞系和小鼠的功能研究来确定病理机制。结果 十二个错义变异显示出致病性的有力证据。我们定义了中枢神经系统的特征表型（白质紊乱、胼胝体薄和心室增宽）；言语、语言和行为发生显着改变的整体性延迟；肌张力减退; 关节过度活动；视觉系统缺陷；以及其他常见的先天性和畸形特征。计算机和表型特征的比较将未知意义的其他变异与可能的致病性联系起来。为了支持部分功能丧失机制，我们使用患者来源的细胞系，仅显示调节神经发育信号通路的特定 USP9X 底物的丢失以及转化生长因子 β 信号传导的联合缺陷。此外，我们在 Usp9x 大脑特异性敲除小鼠中发现了雄性表型的相关性，并进一步解决了海马依赖性学习和记忆的丧失。结论 我们的数据证明 USP9X 变异参与男性受试者独特的神经发育和行为综合征，并确定了以转化生长因子 β 信号传导和海马功能破坏为中心的可能发病机制。