Craniofrontonasal syndrome (CFNS) is an X-linked disorder caused by EFNB1 mutations in which females are more severely affected than males. Severe male phenotypes are associated with mosaicism, supporting cellular interference for sex bias in this disease. Although many variants have been found in the coding region of EFNB1, only 2 pathogenic variants have been identified in the same nucleotide in 5'UTR, disrupting the stop codon of an upstream open reading frame (uORF). uORFs are known to be part of a wide range of post-transcriptional regulation processes, and just recently, their association with human diseases has come to light. In the present study, we analyzed EFNB1 in a female patient with typical features of CFNS. We identified a variant, located at c.-411, creating a new upstream ATG (uATG) in the 5'UTR of EFNB1, which is predicted to alter an existing uORF. Dual-luciferase reporter assays showed significant reduction in protein translation, but no difference in the mRNA levels. Our study demonstrates, for the first time, the regulatory impact of uATG formation on EFNB1 levels and suggests that this should be the target region in molecular diagnosis of CFNS cases without pathogenic variants in the coding and splice sites regions of EFNB1.

中文翻译：

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在EFNB1的5'UTR中引入新型uATG引起的颅前鼻综合征。

颅前鼻综合征（CFNS）是由EFNB1突变引起的X连锁疾病，其中女性受到的影响比男性严重。严重的男性表型与镶嵌症有关，支持该疾病中性偏见的细胞干扰。尽管在EFNB1的编码区中发现了许多变体，但在5'UTR的同一核苷酸中仅鉴定出2个致病变体，破坏了上游开放阅读框（uORF）的终止密码子。众所周知，uORF是许多转录后调控过程的一部分，而最近，它们与人类疾病的联系才被发现。在本研究中，我们分析了具有CFNS典型特征的女性患者的EFNB1。我们确定了一个变体，位于c.-411，在EFNB1的5'UTR中创建了一个新的上游ATG（uATG），预计会改变现有的uORF。双重荧光素酶报告基因测定显示蛋白质翻译显着减少，但mRNA水平无差异。我们的研究首次证明了uATG形成对EFNB1水平的调节作用，并建议这应该是CFNS病例分子诊断中的目标区域，而EFNB1的编码和剪接位点区域没有致病性变异。