BACKGROUND Dysfunction in inwardly rectifying potassium channel Kir4.1 has been implicated in SeSAME syndrome, an autosomal-recessive (AR), rare, multi-systemic disorder. However, not all neurological, intellectual disability, and comorbid phenotypes in SeSAME syndrome can be mechanistically linked solely to Kir4.1 dysfunction. METHODS We therefore performed whole-exome sequencing and identified additional genetic risk-elements that might exert causative effects either alone or in concert with Kir4.1 in a family diagnosed with SeSAME syndrome. RESULTS Two variant prioritization pipelines based on AR inheritance and runs of homozygosity (ROH), identified two novel homozygous variants in KCNJ10 and PI4KB and five rare homozygous variants in PVRL4, RORC, FLG2, FCRL1, NIT1 and one common homozygous variant in HSPA6 segregating in all four patients. The novel mutation in KCNJ10 resides in the cytoplasmic domain of Kir4.1, a seat of phosphatidylinositol bisphosphate (PIP2) binding. The mutation altered the subcellular localization and stability of Kir4.1 in patient-specific lymphoblastoid cells (LCLs) compared to parental controls. Barium-sensitive endogenous K+ currents in patient-specific LCLs using whole-cell patch-clamp electrophysiology revealed membrane depolarization and defects in inward K+ ion conductance across the membrane, thereby suggesting a loss-of-function effect of KCNJ10 variant. CONCLUSION Altogether, our findings implicate the role of new genes in SeSAME syndrome without electrolyte imbalance and thereby speculate the regulation of Kir4.1 channel activity by PIP2 and integrin-mediated adhesion signaling mechanisms.

中文翻译：

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没有电解质失衡的SeSAME综合征的KCNJ10和PI4KB中的两个新突变的鉴定和功能表征。

背景技术内向整流钾通道Kir4.1的功能障碍与SeSAME综合征有关，SeSAME综合征是一种常染色体隐性（AR）罕见的多系统疾病。但是，并不是机械地将SeSAME综合征中的所有神经，智力障碍和合并表型仅与Kir4.1功能障碍相关联。方法因此，我们进行了全外显子组测序，并确定了可能单独或与Kir4.1一起在诊断为SeSAME综合征的家庭中发挥致病作用的其他遗传风险因素。结果基于AR遗传和纯合运行（ROH）的两个变体优先排序管道，在KCNJ10和PI4KB中鉴定了两个新的纯合变体，在PVRL4，RORC，FLG2，FCRL1，NIT1中鉴定了五个罕见的纯合变体，在HSPA6分离中鉴定了一个常见的纯合变体。全部四个病人。KCNJ10中的新突变位于Kir4.1的胞质结构域中，磷脂酰肌醇双磷酸（PIP2）结合位点。与父母对照相比，该突变改变了患者特异性淋巴母细胞（LCL）中Kir4.1的亚细胞定位和稳定性。使用全细胞膜片钳电生理学的患者特异性LCL中钡敏感的内源性K +电流揭示了膜去极化和跨膜的内向K +离子电导率的缺陷，从而提示了KCNJ10变体的功能丧失作用。结论总之，我们的发现暗示了新基因在没有电解质失衡的SeSAME综合征中的作用，从而推测了PIP2和整联蛋白介导的粘附信号转导机制对Kir4.1通道活性的调节。