We sought to explore whether complex genetic alterations in the FAS gene escaping standard sequencing or mutations in other FAS pathway-related genes could explain these cases.
Genetic analysis included whole FAS gene sequencing, copy number variation analysis, and sequencing of FAS cDNA and other FAS pathway-related genes. It was guided by FAS expression analysis on CD57+DNT, which can predict somatic loss of heterozygosity (sLOH).
Nine of 16 patients with ALPS-U lacked FAS expression on CD57+DNT predicting heterozygous \"loss-of-expression\" FAS mutations plus acquired somatic second hits in the FAS gene, enriched in DNT. Indeed, 7 of 9 analyzed patients carried deep intronic mutations or large deletions in the FAS gene combined with sLOH detectable in DNT; 1 patient showed a FAS exon duplication. Three patients had reduced FAS expression, and 2 of them harbored mutations in the FAS promoter, which reduced FAS expression in reporter assays. Three of the 4 ALPS-U patients with normal FAS expression carried heterozygous FADD mutations with sLOH.
A combination of serum biomarkers and DNT phenotyping is an accurate means to identify patients with ALPS who are missed by routine exome sequencing.
目的:我们的目的是探讨逃避标准测序的FAS基因的复杂遗传改变或其他FAS途径相关基因的突变是否可以解释这些病例。
方法:遗传分析包括全FAS基因测序,FAScDNA和其他FAS通路相关基因的拷贝数变异分析和测序。以CD57+DNT的FAS表达分析为指导,可以预测体细胞杂合性丢失(sLOH)。
结果:16例ALPS-U患者中有9例缺乏CD57DNT上的FAS表达,预测FAS突变的杂合子“表达缺失”加上FAS基因的获得性体细胞二次命中,富含DNT。的确,7/9分析的患者在FAS基因中携带深度内含子突变或大缺失,并在DNT中检测到sLOH,1例患者出现FAS外显子重复.3例患者FAS表达降低,其中两个在FAS启动子中存在突变,这降低了报道分子测定中的FAS表达。4例FAS表达正常的ALPS-U患者中有3例携带sLOH杂合FADD突变。
结论:血清生物标志物和DNT表型的组合是鉴定常规外显子组测序漏诊的ALPS患者的准确方法。
结论:通过扩展遗传分析检测复杂的FAS途径基因改变允许西罗莫司靶向治疗。