A Novel Compound Heterozygous CYP17A1 Variant Causes 17α-Hydroxylase/17, 20-Lyase Deficiency

• Published in: Frontiers in genetics Vol. 10; p. 996
• Main Authors: Chen, Hong, Yuan, Ke, Zhang, Bingtao, Jia, Zexiao, Chen, Chun, Zhu, Yilin, Sun, Yaping, Zhou, Hui, Huang, Wendong, Liang, Li, Yan, Qingfeng, Wang, Chunlin
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 22.10.2019
• Subjects: 17α-hydroxylase/17,20-lyase deficiency; congenital adrenal hyperplasia; CYP17A1 gene; Genetics; rhabdomyolysis; variant
• DOI: 10.3389/fgene.2019.00996
• ISSN: 1664-8021

Background: Congenital adrenal hyperplasia (CAH) encompasses a group of autosomal recessive diseases characterized by enzyme deficiencies, within steroid hormone anabolism, which lead to disorders in cortisol synthesis. The 17α-hydroxylase/17,20-lyase deficiency (17-OHD) is an uncommon form of CAH caused by variants in the CYP17A1 gene. Aims: We report a novel compound heterozygous CYP17A1 variant and its association with the pathogenesis of 17-OHD. Methods: The patient was assessed for medical history, clinical manifestations, physical examination, laboratory examination, karyotype analysis, and adrenal computed tomography. Mutation screening was conducted using whole-exome sequencing (WES) and Sanger sequencing. The wild-type and mutant CYP17A1 complementary DNAs (cDNAs) were amplified and cloned into a pcDNA3.1(+) vector. These plasmids were transfected transiently into HEK-293T cells. Quantitative PCR and Western blotting analysis were performed to measure the expression level of P450c17. An enzymatic activity assay was conducted to measure the content of 17-hydroxyprogesterone (17-OHP) and dehydroepiandrosterone (DHEA) in medium using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Results: The proband was characterized by 17-OHD with rhabdomyolysis, hypokalemia, and adrenal insufficiency. Novel compound heterozygous variants of the CYP17A1 gene (c.1304T > C/p.Phe435Ser and c.1228delG/p.Asp410Ilefs*9) were identified. The enzymatic activity assay revealed that this variant resulted in a complete deficiency of 17α-hydroxylase and 17,20-lyase activity. This was consistent with the hormonal characteristics of the proband’s blood. Conclusions: These results suggest that the compound heterozygous variant of c.1304T > C and c.1228delG of the CYP17A1 gene can lead to 17-OHD. Our findings thus provide a novel insight into the clinical evaluations and molecular basis of 17-OHD.