整合遗传学与功能分析揭示新型STXBP3变异在伴免疫缺陷的极早发型炎症性肠病中的致病效应

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中文摘要

背景： 极早发型炎症性肠病（VEOIBD）常由单基因缺陷驱动。突触融合蛋白结合蛋白3（STXBP3）基因的致病变异已被认为与VEOIBD相关；然而，特定变异类型与临床表现之间的关系仍不完全清楚。本研究旨在明确一名VEOIBD患者的遗传病因，并探讨STXBP3相关疾病可能的基因型-表型相关性。
方法： 我们对一名表现为VEOIBD、感音神经性听力损失和免疫缺陷的男婴进行了三联全外显子组测序（trio-WES）。利用RNA测序（RNA-seq）、逆转录聚合酶链反应（RT-PCR）、蛋白质印迹和免疫共沉淀（co-IP）实验研究所识别变异的功能后果。我们进行了系统性文献综述，分析所有已报道STXBP3病例的临床特征和遗传方式。
结果： 识别出STXBP3中的一个新型杂合剪接位点变异（c.1022_1029 + 3del）。RNA-seq和RT-PCR证实该变异导致异常剪接，引起外显子12跳跃并产生截短蛋白。Co-IP显示该异常蛋白与STX4的结合能力降低。对13例患者的综合分析揭示了可能的基因型-表型相关性：剪接位点和移码变异主要呈常染色体显性（AD）遗传模式，与VEOIBD、感音神经性听力损失和免疫缺陷相关；相反，错义变异通常呈常染色体隐性（AR）遗传模式，与VEOIBD和先天性畸形相关。鉴于队列较小，这些比较仅为描述性，并非旨在建立明确的基因型-表型关联。
结论： 我们识别出一个新型致病性STXBP3变异，并验证了其功能影响。观察到的AD与AR病例之间的差异为理解STXBP3相关疾病提供了一个初步的、产生假设的框架，仍需在更大队列中验证。

英文摘要

BACKGROUND: Very early onset inflammatory bowel disease (VEOIBD) is frequently driven by monogenic defects. Pathogenic variants in the syntaxin-binding protein 3 (STXBP3) gene have been implicated in VEOIBD; however, the relationship between specific variant types and clinical manifestations remains incompletely understood. This study aimed to identify the genetic cause in a patient with VEOIBD and explore the possible genotype-phenotype correlations of STXBP3-related disorders.
METHODS: We performed trio-whole-exome sequencing (trio-WES) on a male infant presenting with VEOIBD, sensorineural hearing loss, and immunodeficiency. Functional consequences of the identified variant were investigated using RNA sequencing (RNA-seq), reverse transcription-polymerase chain reaction (RT-PCR), western blotting and co-immunoprecipitation (co-IP) assay. A systematic literature review was conducted to analyze clinical features and inheritance patterns across all reported STXBP3 cases.
RESULTS: A novel heterozygous splice-site variant in STXBP3 (c.1022_1029 + 3del) was identified. RNA-seq and RT-PCR confirmed that this variant causes aberrant splicing, leading to the skipping of exon 12 and the production of a truncated protein. Co-IP showed that the aberrant protein reduced the ability to bind STX4. The comprehensive analysis of 13 patients revealed possible genotype-phenotype correlations: splice-site and frameshift variants were observed predominantly follow an autosomal dominant (AD) pattern associated with VEOIBD, sensorineural hearing loss, and immunodeficiency; conversely, missense variants generally follow an autosomal recessive (AR) pattern linked to VEOIBD, and congenital malformations. Given the small cohort, these comparisons were descriptive and were not intended to establish definitive genotype-phenotype associations.
CONCLUSIONS: We identified a novel pathogenic STXBP3 variant and validated its impact on its function. The observed differences between AD and AR cases provided a preliminary, hypothesis-generating framework for understanding STXBP3-related disease, which require validation in larger cohorts.