An unique exonic splicing mutation in the CYPI7AI gene as the cause of steroid 17α-hydroxylase deficiency / 中华内分泌代谢杂志

ABSTRACT

Objective To analyze CYP17A1 gene mutation in a patient with 46,XY disordered sex development and to explore the possible influence on the phenotype of the patient.Methods Eight exons of CYP17AI gene in the patient and her parents were amplified and directly sequenced.In order to construct Mini-gene system,PCR fragments containing wildtype and mutant splicing sites were inserted in expression vector,and then transfected into cells.RT-PCR was used to observe the influence of splicing site mutation.Wildtype and aberrant splicing CYP17A1 cDNA expression plasmids were constructed and transfected into cells respectively,and CYP17A1 enzyme activity was tested in vitro.Results Mutation analysis revealed compound heterozygous CYP17A1 mutations,with Y329fs in one allele and a synonymous substitution( c.1263G＞AGCG＞GCA) in another allele.In vitro analysis showed that the synonymous substitution induced a novel splicing site,which resulted in aberrant splicing of CYP17A1 mRNA and lacked six or seven amino acids after 415 in splicing product.In vitro transfection and enzyme activity experiment showed that the aberrant splicing product abolished the enzyme activity completely.However,this mutation did not completely influence splicing.The patient also had a part of normal splicing product,which was a coincidence to the phenotype of the patient.Conclusion This is the first description of an exonic splicing mutation in CYP17A1 relevant to the 17ot-hydroxylase deficiency phenotype.The functional study of the aberrant splicing variant has been initiated.