Abstract
17α-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 17α-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 17α-hydroxylase/17, 20-lyase enzyme activity by aberrant mRNA splicing to an intronic pseudo-exon, causing a frame shift and early termination.
Highlights
The UPLC-MS/MS system was used in the multiples reaction monitoring mode (MRM) and steroids were measured in the positive ion mode except aldosterone which was measured in the negative mode
Analysis of DNA from her mother and paternal uncle showed that the p.R358X mutation derived from the father while mutation IVS1 +2T.C was inherited from her mother (Fig. 1)
The CYP17A1 p.R358X mutation has been reported in one girl of Korean descent with combined 17a-hydroxylase/17,20-lyase deficiency, who presented with primary amenorrhea, sexual infantilism, and hypertension [14]
Summary
17a-hydroxylase deficiency (17OHD), a rare autosomal recessive disease caused by CYP17A1 gene mutation, accounts for about 1% of all congenital adrenal hyperplasia and is characterized by hypertension, hypokalemia, and sexual infantilism [1]. The CYP17A1 enzyme catalyzes two different enzymatic reactions: 17a-hydroxylation of progesterone and pregnenolone and the 17,20 lyase reaction for the conversion of 17-hydroxypregnenolone to dehydroepiandrosterone (DHEA). Defects in these two enzymatic reactions lead to decreased glucocorticoid and sex steroid production with mineralocorticoid excess, primarily 11deoxycorticosterone and corticosterone, as well as 18-hydroxydeoxycorticosterone and 18-hydroxycorticosterone. We describe a patient with a first intron splice donor site mutation and characterize the aberrant splicing in transfected cells and in lymphoblastoid cells derived from the patient
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