Clinical and genetic characterization of familial central precocious puberty

Author(s)

Flavia Rezende Tinano

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2023-09-14
• Advisor: Ana Claudia Latrônico Xavier

Abstract

Context: Central precocious puberty (CPP) results from the reactivation of the hypothalamic-pituitary-gonadal (HPG) axis and is considered familial when it affects more than one family member. The recognition of this inherited condition increased after the identification of autosomal dominant CPP with paternal transmission caused by mutations in the MKRN3 and DLK1 genes. Recently, rare variants in the MECP2 gene were identified in children with familial and sporadic CPP. While the mechanisms by which MKRN3 regulates puberty onset have been partially elucidated in recent years, the manner by which DLK1 and MECP2 influence pubertal timing have not been determined. Despite the large number of families with maternal transmission of CPP reported, its genetic basis remains unknown. Objectives: To characterize the inheritance and estimate the prevalence of familial CPP in a large multiethnic cohort; to compare clinical and hormonal features, as well as treatment response to GnRH analogs (GnRHa), in children with distinct modes of transmission; to investigate the genetic basis of familial CPP; and to investigate the mechanism by which MKRN3, DLK1and MECP2 influences pubertal onset. Methods: We retrospectively studied 586 children with a diagnosis of CPP. Patients with familial CPP (n=276) were selected for clinical and genetic analysis. The genetic evaluation included analysis of data from 204 patients who underwent sequencing of the MKRN3 and DLK1 genes and 118 individuals (from 58 families) who underwent large-scale parallel sequencing. Functional studies were performed in wild-type (WT), global Dlk1 knockout (Dlk1-KO) and specific central nervous system Dlk1 knockout (Dlk1-cKO) mice. Hypothalamic expression of the Mkrn3, Dlk1 and Mecp2 genes was analyzed in male and female WT mice with postnatal ages (PN) 10, 15, 22, 30 and 60 days by mRNA (Mkrn3, Dlk1 and Mecp2) and protein (Mkrn3 and Dlk1) quantification in the medium-basal hypothalamus and pre-optic area. Circulating serum Dlk1 was measured and compared among WT males and females of different ages (PN10 to 60), as well as WT females at different stages of pubertal maturation, and between Dlk1-KO and Dlk1-cKO mice. Results: The prevalence of familial CPP was estimated at 22%. The maternal and paternal modes of transmission were the most frequent (39 and 38%, respectively), followed by the undetermined (19%) and simultaneously maternal and paternal (4%) forms of transmission. Pedigree analyses of families with maternal transmission suggested an autosomal dominant inheritance with greater penetrance in females. Clinical and hormonal features, as well as treatment response to GnRHa, were similar among patients with different forms of transmission of familial CPP. MKRN3 loss-of-function mutations were the most prevalent cause of familial CPP, followed by DLK1 loss-of-function mutations, both affecting exclusively families with paternal transmission. Rare variants of uncertain significance were identified in CPP families with maternal transmission. A decrease in Mkrn3 and Mecp2 hypothalamic expression, and an increase in Dlk1 expression, was seen in male and female mice toward adulthood. Conversely, circulating Dlk1 levels decreased with progression of age and pubertal maturation in WT mice. Dlk1-KO mice had undetectable or extremely low serum Dlk1 levels, while Dlk1-cKO mice had similar or higher serum Dlk1 levels than controls. Conclusions: Familial CCP was prevalent in our study, with a similar frequency of maternal and paternal transmission. MKRN3 and DLK1 loss-of-function mutations were the major causes of familial CPP with paternal transmission. No definitive monogenic cause was associated with maternally transmitted CCP. The reduction in hypothalamic expression of the Mkrn3 and Mecp2 genes before pubertal onset in mice suggests that these factors may inhibit the HPG axis. The role of Dlk1 remains unclear, but current findings suggest a role for its peripheral circulating form in pubertal inhibition (AU)

• FAPESP's process: 21/12205-2 - Investigation of genetic basis of Familial Central Precocious Puberty of maternal inheritance
• Grantee: Flávia Rezende Tinano
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)