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Diabetes and Endocrinology - Nephrology - Pediatrics and Child Health - Physiology

CYP17A1 Intron Mutation Causing Cryptic Splicing in 17a-Hydroxylase Deficiency
Published: Monday, September 26, 2011
Author: Daw-Yang Hwang et al.

by Daw-Yang Hwang, Chi-Chih Hung, Felix G. Riepe, Richard J. Auchus, Alexandra E. Kulle, Paul-Martin Holterhus, Mei-Chyn Chao, Mei-Chuan Kuo, Shang-Jyh Hwang, Hung-Chun Chen

17a-hydroxylase/17, 20-lyase deficiency (17OHD) is an autosomal recessive disease causing congenital adrenal hyperplasia and a rare cause of hypertension with hypokalemia. The CYP17A1 gene mutation leads to 17OHD and its clinical features. We described an 18 y/o female with clinical features of 17a-hydroxylase/17, 20-lyase deficiency and characterized the functional consequences of an intronic CYP17A1 mutation. The coding regions and flanking intronic bases of the CYP17A1 gene were amplified by PCR and sequenced. The patient is a compound heterozygote for the previously described p.R358X and IVS1 +2T>C mutations. A first intron splice donor site mutation was re-created in minigene and full-length expression vectors. Pre-mRNA splicing of the variant CYP17A1 intron was studied in transfected cells and in a transformed lymphoblastoid cell line. When the full-length CYP17A1 gene and minigene containing the intronic mutation was expressed in transfected cells, the majority (>90%) of mRNA transcripts were incorrectly spliced. Only the p.R358X transcript was detected in the EBV-transformed lymphoblastoid cell line. The IVS1 +2T>C mutation abolished most 17a-hydroxylase/17, 20-lyase enzyme activity by aberrant mRNA splicing to an intronic pseudo-exon, causing a frame shift and early termination.