Supplementary Material for: Whole Exome Sequencing of a multiplex family of Indian origin identifies variants in the RAI1 and FLII genes within the 17p11.2 region in siblings with autism and Smith Magenis Syndrome

Introduction: Autism Spectrum Disorders (ASDs) is a complex neurodevelopmental disorder characterized by restrictive repetitive behaviour and impairment in social and communication skills. It is extremely heterogeneous with a strong genetic preponderance. It is clinically highly convoluted, represented with multiple comorbid conditions and syndromic features. More than 100 genes have been identified till date.
Method: Whole exome sequencing (WES) has emerged as a valuable tool in evaluating the genetic underpinnings of ASDs, be it the syndromic or the idiopathic variants. In the current study, we performed WES on a multiplex family of Indian origin to investigate the disease aetiology in the siblings (S1 (Female) and S2 (Male)) exhibiting ASD syndromic features, at both clinical and genetic aspects.
Results: Exome sequencing identified a missense variant (NM_030665.4:c.5320C>T; p.Arg1774Trp) in S1 resulting in RAI1 haploinsufficiency. Validation by Sanger Sequencing confirmed that the variant was true positive and maternally transmitted in the subject. Likewise, we report an inherited missense variant at the same locus (17p11.2) corresponding to the FLII gene (NM_002018.4:c.2030A>C;p.Glu677Ala) in the other sibling, S2. Both the variants were reported in the Smith Magenis Syndrome (SMS) critical region justifying its contribution to the presentation of the syndromic SMS features. These WES findings were consistent with the clinical findings that imply SMS features in both siblings.
Conclusions: The current study employs WES to provide insights into the genetic complexity associated with syndromic ASD and how that contribute to the disease heterogeneity. Moving forward, combinatorial approaches and findings from syndromic ASDs can potentially act as indicators to understand the genetic and phenotypic variations seen in the idiopathic ASD.

# 引言
自闭症谱系障碍（Autism Spectrum Disorders, ASDs）是一类复杂的神经发育障碍，以局限重复行为、社交与沟通技能受损为核心特征。该疾病具有高度异质性，且遗传倾向显著；临床表型极为复杂，常伴随多种共病状态与综合征性特征，迄今已发现超过100个相关致病基因。

# 方法
全外显子组测序（Whole Exome Sequencing, WES）已成为评估自闭症谱系障碍遗传基础的重要工具，涵盖综合征型与特发型亚型。本研究针对一个印度血统的多发家系开展全外显子组测序，从临床与遗传学层面探究表现出自闭症谱系障碍综合征特征的两名同胞（女性S1与男性S2）的疾病病因。

# 结果
全外显子组测序在S1中检测到一处错义变异（NM_030665.4:c.5320C>T; p.Arg1774Trp），导致RAI1基因单倍体剂量不足。经桑格测序（Sanger Sequencing）验证，该变异为真阳性变异，且为母系遗传。同样，本研究在另一名同胞S2中报道了位于同一染色体位点（17p11.2）的遗传性错义变异，对应FLII基因（NM_002018.4:c.2030A>C;p.Glu677Ala）。上述两处变异均位于史密斯-马吉利综合征（Smith Magenis Syndrome, SMS）关键区域，证实其与综合征性史密斯-马吉利综合征表型的发生密切相关。本研究的全外显子组测序结果与两名同胞均存在史密斯-马吉利综合征表型的临床发现一致。

# 结论
本研究采用全外显子组测序，深入解析了综合征性自闭症谱系障碍相关的遗传复杂性及其对疾病异质性的贡献。未来，综合征性自闭症谱系障碍的联合研究策略与相关研究发现，或可作为理解特发性自闭症谱系障碍中遗传与表型变异的重要参考依据。