ABSTRACT
CONTEXT: Loss-of-function mutations of makorin RING finger protein 3 (MKRN3) are the most common monogenic cause of familial central precocious puberty (CPP). OBJECTIVE: To describe the clinical and hormonal features of a large cohort of patients with CPP due to MKRN3 mutations and compare the characteristics of different types of genetic defects. METHODS: Multiethnic cohort of 716 patients with familial or idiopathic CPP screened for MKRN3 mutations using Sanger sequencing. A group of 156 Brazilian girls with idiopathic CPP (ICPP) was used as control group. RESULTS: Seventy-one patients (45 girls and 26 boys from 36 families) had 18 different loss-of-function MKRN3 mutations. Eight mutations were classified as severe (70% of patients). Among the 71 patients, first pubertal signs occurred at 6.2â ±â 1.2 years in girls and 7.1â ±â 1.5 years in boys. Girls with MKRN3 mutations had a shorter delay between puberty onset and first evaluation and higher follicle-stimulating hormone levels than ICPP. Patients with severe MKRN3 mutations had a greater bone age advancement than patients with missense mutations (2.3â ±â 1.6 vs 1.6â ±â 1.4 years, Pâ =â .048), and had higher basal luteinizing hormone levels (2.2â ±â 1.8 vs 1.1â ±â 1.1 UI/L, Pâ =â .018) at the time of presentation. Computational protein modeling revealed that 60% of the missense mutations were predicted to cause protein destabilization. CONCLUSION: Inherited premature activation of the reproductive axis caused by loss-of-function mutations of MKRN3 is clinically indistinct from ICPP. However, the type of genetic defect may affect bone age maturation and gonadotropin levels.
Subject(s)
Puberty, Precocious/genetics , Ubiquitin-Protein Ligases/genetics , Case-Control Studies , Child , Child, Preschool , Cohort Studies , Family , Female , Genetic Association Studies , Humans , Hypothalamic Diseases/epidemiology , Hypothalamic Diseases/genetics , Loss of Function Mutation , Male , Mutation, Missense , Puberty, Precocious/epidemiologyABSTRACT
BACKGROUND: Central precocious puberty (CPP) has been associated with loss-of-function mutations in 2 paternally expressed genes (MKRN3 and DLK1). Rare defects in the DLk1 were also associated with poor metabolic phenotype at adulthood. OBJECTIVE: Our aim was to investigate genetic and biochemical aspects of DLK1 in a Spanish cohort of children with CPP without MKRN3 mutations. PATIENTS: A large cohort of children with idiopathic CPP (Spanish PUBERE Registry) was studied. Genomic deoxyribonucleic acid was obtained from 444 individuals (168 index cases) with CPP and their close relatives. Automatic sequencing of MKRN3 and DLK1 genes were performed. RESULTS: Five rare heterozygous mutations of MKRN3 were initially excluded in girls with familial CPP. A rare allelic deletion (c.401_404â +â 8del) in the splice site junction of DLK1 was identified in a Spanish girl with sporadic CPP. Pubertal signs started at 5.7 years. Her metabolic profile was normal. Familial segregation analysis showed that the DLK1 deletion was de novo in the affected child. Serum DLK1 levels were undetectable (<0.4 ng/mL), indicating that the deletion led to complete lack of DLK1 production. Three others rare allelic variants of DLK1 were also identified (p.Asn134=; g.-222 C>A and g.-223 G>A) in 2 girls with CPP. However, both had normal DLK1 serum levels. CONCLUSION: Loss-of-function mutations of DLK1 represent a rare cause of CPP, reinforcing a significant role of this factor in human pubertal timing.