Molecular Screening of MKRN3, DLK1, and KCNK9 Genes in Girls with Idiopathic Central Precocious Puberty

Background: Mutations in the imprinted gene MKRN3 have been described as a common genetic cause of idiopathic central precocious puberty (CPP), in particular in familial cases. However, the exact prevalence of mutations is unknown. Single nucleotide polymorphisms in 2 other imprinted genes, DLK1 and KCNK9, have been associated with age at menarche. We investigated the prevalence of mutations in MKRN3, DLK1, and KCNK9 genes in a cohort of girls with idiopathic CPP. Methods: MKRN3, DLK1, and KCNK9 coding regions were sequenced in 60 girls with idiopathic CPP (familial in 23 cases). Results: Three mutations, including a new one, in MKRN3 were found in 2 familial cases (c.1229G>A; p.Cys410Ter and c.477_485del; p.Pro160Cysfs*14) (8.7%) and in 1 sporadic case (c.982C>T; p.Arg328Cys) (2.8%). We did not find rare variants in DLK1 and KCNK9 genes. Conclusions: (1) The prevalence of MKRN3 mutations in our cohort was similar to that reported in the literature in sporadic cases but lower than previously described in familial ones. This could be due to different inheritance patterns of families studied; (2) we expanded the phenotype of MKRN3 defects describing 3 more patients with MKRN3 mutations; and (3) point mutations in DLK1 and KCNK9 at least do not seem to be a common cause of CPP in girls.