21-Hydroxylase deficiency: Mutational spectrum and Genotype-Phenotype relations analyses by next-generation sequencing and multiplex ligation-dependent probe amplification.

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) is autosomal recessive disorder of cortisol biosynthesis. Genetic defects in CYP21A2 cause 21OHD. The aim of this study was to determine spectrum of mutations in CYP21A2 in a large cohort and analyze the genotype-phenotype correlation to assess predictive characteristics of genotype. We investigated a total of 113 patients with 21OHD. Next-generation sequencing and Multiplex ligation-dependent probe amplification of the CYP21A2 gene were performed in patients and their parents. The genotypes were categorized into Groups 0, A, B, and C according to the residual 21-hydroxylase activities. In this study, the group A was divided into two subgroups as A1 and A2. Three novel variants were found. The genotype-phenotype correlation of the mutation classification was 91.5%. Positive predictivity of subgroups A1 was higher than groups A and subgroups A2. Our study reports genotype-phenotype correlations in the largest 21OHD cohort in Turkey. This correlation sustained when we analyzed our data in combination with metadata from other published studies. This study confirms that CYP21A2 genotyping with next-generation sequencing and MLPA can accurately and reliably confirm the diagnosis of 21OHD. We propose a new classification by dividing group A into two new subgroups to better predict the phenotype. In light of this very high genotype-phenotype correlation, with their ever-increasing availability, declining cost, and turnaround time, we propose that molecular genetic studies can be more economical and practical alternative to the current initial diagnostic laboratory studies based on assays of intermediary steroid metabolites.

Prevalence and associated phenotypes of PLXNA1 variants in normosmic and anosmic idiopathic hypogonadotropic hypogonadism.

Idiopathic hypogonadotropic hypogonadism (IHH) can be divided into two major forms, normosmic IHH and Kallmann syndrome (KS). Genetic mutations are responsible for the majority of IHH. PLXNA1 has recently been implicated in the GnRH neuron migration and the etiology of KS. We aimed to investigate the prevalence and associated phenotypes of PLXNA1 variants in a large cohort of IHH patients. We screened the whole exome data of 215 IHH patients in a single center for causative PLXNA1 variants. Our studies showed eight novel (p.Arg836His, p.Lys1451Arg, p.Val287Met, p.Val536Ile, p.Ser1850Arg, p.Ile1701Val, p.Arg319Trp, and p.Pro485Leu) and two previously described (p.Arg528Trp and p.Gly720Glu) heterozygous PLXNA1 variants in nine affected individuals from seven unrelated families. Only three of nine patients were anosmic (KS) while the remaining patients showed normal olfactory function (nIHH). Seven of nine patients (77.7%) harbored additional one or two variants in other nIHH/KS-associated genes, including PROKR2, IGSF10, HS6ST1, SEMA3E, CCDC141, FGFR1, NRP1, POLR3A, and SRA1. Our findings indicate that PLXNA1 variants cause not only anosmic but also normosmic IHH with a relatively high prevalence (3.9%). Heterozygous missense PLXNA1 variants appear to be involved together with other IHH gene variants in bringing about the IHH disease phenotype.