PDF(Pubmed)
Abstract：
Heterozygous variants in SLC6A1, encoding the GAT-1 GABA transporter, are associated with seizures, developmental delay, and autism. The majority of affected individuals carry missense variants, many of which are recurrent germline de novo mutations, raising the possibility of gain-of-function or dominant-negative effects. To understand the functional consequences, we performed an in vitro GABA uptake assay for 213 unique variants, including 24 control variants. De novo variants consistently resulted in a decrease in GABA uptake, in keeping with haploinsufficiency underlying all neurodevelopmental phenotypes. Where present, ClinVar pathogenicity reports correlated well with GABA uptake data; the functional data can inform future reports for the remaining 72% of unscored variants. Surface localization was assessed for 86 variants; two-thirds of loss-of-function missense variants prevented GAT-1 from being present on the membrane while GAT-1 was on the surface but with reduced activity for the remaining third. Surprisingly, recurrent de novo missense variants showed moderate loss-of-function effects that reduced GABA uptake with no evidence for dominant-negative or gain-of-function effects. Using linear regression across multiple missense severity scores to extrapolate the functional data to all potential SLC6A1 missense variants, we observe an abundance of GAT-1 residues that are sensitive to substitution. The extent of this missense vulnerability accounts for the clinically observed missense enrichment; overlap with hypermutable CpG sites accounts for the recurrent missense variants. Strategies to increase the expression of the wild-type SLC6A1 allele are likely to be beneficial across neurodevelopmental disorders, though the developmental stage and extent of required rescue remain unknown.
摘要：
SLC6A1中的杂合变体，编码GAT-1GABA转运蛋白，与癫痫发作有关，发育迟缓,和自闭症。大多数受影响的个体携带错义变体，其中许多是反复发生的种系从头突变，提高功能增益或显性负面影响的可能性。要了解功能后果，我们对213个独特变体进行了体外GABA摄取测定，包括24个对照变体。从头变体一致导致GABA摄取减少，与所有神经发育表型潜在的单倍体不足保持一致。Wherepresent,ClinVar致病性报告与GABA摄取数据密切相关；功能数据可以为剩余72％的未评分变体的未来报告提供信息。评估了86种变体的表面定位；三分之二的功能丧失错义变体阻止GAT-1存在于膜上，而GAT-1在表面上，但其余三分之一的活性降低。令人惊讶的是,从头复发错义变异体显示中度功能丧失效应,降低GABA摄取,没有显性阴性或功能获得效应的证据.使用多个错义严重程度评分的线性回归将功能数据外推到所有潜在的SLC6A1错义变体，我们观察到大量对取代敏感的GAT-1残基。这种错义脆弱性的程度解释了临床观察到的错义富集；与超可变CpG位点的重叠解释了复发性错义变体。增加野生型SLC6A1等位基因表达的策略可能对神经发育障碍有益，尽管所需救援的发展阶段和程度仍然未知。
