SUN-089 Novel Genetic and Biochemical Findings of DLK1 Deficiency in Children with Central Precocious Puberty - a Collaborative Brazilian-Spanish Study

Background: Delta-like 1 homolog (DLK1), also known as pre-adipocyte factor 1 (Pref-1), is part of the Notch signaling pathway that controls many developmental processes. Loss-of-function mutations of DLK1 have been identified in children with central precocious puberty (CPP), as well as in women who had precocious menarche (≤ 9 years) with an unfavorable metabolic profile. Objective: To investigate genetic and biochemical aspects of DLK1 in a cohort of children with CPP. Patients: A large cohort of Spanish children with idiopathic CPP (Spanish PUBERE Registry) was studied. Genomic DNA was obtained from 444 individuals, including 168 index cases with CPP and their close relatives. Automatic sequencing of the coding region (5 exons) of DLK1 was performed in all index cases. Serum DLK1 levels were measured by using a soluble DLK1 enzyme-linked immunosorbent assay (ELISA). Results: A rare allelic deletion (c.401_404 + 8del) of a splice site junction of DLK1 was identified in a girl with sporadic CPP. Pubertal signs appeared at 5.7 years of age with progressive puberty (basal LH: 1.7 mIU/mL, peak LH: 32.77 mIU/mL; basal FSH: 6.32 mIU/mL, peak FSH: 19.89 mIU/mL), BA/CA 1.7 years; normal cranial MRI). She received LHRH analogues (6.3 - 10.1 years of CA) with no side effects. At 14.9 years of age height and BMI are 152.9 cms and 18 kg/m(2), respectively, presenting regular menses. Familial segregation analysis showed that the affected child was the only carrier of this deletion characterizing a de novo mutation (biological paternity and maternity were confirmed by microsatellite analysis). Serum DLK1 levels were undetectable (<0.4 ng/mL) in this girl, supporting that the deletion lead to complete lack of DLK1 production. Her father, mother and sister had normal serum DLK1 levels (ranged 6.36 ng/mL to 8.98 ng/mL). Two rare consecutive nucleotide changes in the promoter region of the DLK1 gene (c.-222 C>A and c.-223 G>A) were also identified in an adopted child with CPP. They are located in a transcription factor binding site for SP1 (a zinc finger transcription factor). Pubertal signs appeared at 6.7 years of age with progressive puberty (Basal LH: 0.5 mIU/mL, peak LH: 15.9 mIU/mL, basal FSH: 1.52 mIU/mL, peak FSH: 6.56 mIU/mL, BA/CA 1.4 years; normal cranial MRI). She is under therapy with LHRH analogues with no side effects. Conclusion: Novel DLK1 findings were identified in the Spanish cohort of children with CPP, reinforcing a significant role of this factor in human pubertal timing.