Background: Congenital adrenal hyperplasia, one of the most frequent autosome recessive disorders, is caused by defects in steroidogenic enzymes involved in the cortisol biosynthesis. Approximately 95% of cases are caused by a deficiency of the 21-hydroxylase enzyme. Its deficiency leads to androgen excess, consequently, to virilization and rapid somatic growth with accelerated skeletal maturation. Mutations in CYP21A2 are responsible for different forms of 21-hydroxylase deficiency.
Objective and hypotheses: The aim of this study was to investigate CYP21A2 mutations in nonclassical patients and evaluate haplotypes concerning novel or rare mutations.
Method: Fifty-three patients and their families were investigated by CYP21A2 amplification and sequencing.
Results and Conclusion: Genotypes identified in this study were divided in four groups: homozygous for p.Val281Leu (51%); compound heterozygous for p.Val281Leu and classical mutations (37%); compound heterozygous p.Val281Leu and other non-classical mutation (9%); and, compound heterozygous for different non-classical mutations (2%). Furthermore, ten haplotypes, defined by 13 SNVs in intron 2 and one in exon 3 of CYP21A2 gene, were identified. Although their functional roles have not been evaluated, in silico analysis for adrenal specific splicing enhancers and silencers using the algorithm SpliceAid 2.0 (http://126.96.36.199/splicing_tissue.html) indicate that they might influence the rate of intron 2 splicing because they cause significant changes in the normal binding-protein pattern which is important for the splicing to occur correctly and in a proper rate. In addition, haplotypes defined by SNVs in 5′ regulatory region outside the 126 pb defined as minimal promoter region have been identified in compound heterozygosis with p.Val281Leu. Due to the importance of the regulatory region for the gene expression the investigation on the role of each haplotype might give clues to better understand cases where genotype shows only heterozygosis for nonclassical mutations.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology