Functional SNPs within the Intron 1 of the PROP1 Gene Contribute to Combined Growth Hormone Deficiency (CPHD).

Context:Mutations within the PROP1 gene represent one of the main causes of familial combined pituitary hormone deficiency (CPHD). However, most of the cases are sporadic with an unknown genetic cause.Objective:The aim of this study was the search for low penetrance variations within and around a conserved regulatory element in the intron 1 of PROP1, contributing to a multifactorial form of the disease in sporadic patients.Methods and Patients:A fragment of 570 bp encompassing the conserved region was sequenced in 107 CPHD patients and 294 controls, and an association study was performed with the four identified variants, namely c.109+435G>A (rs73346254), c.109+463C>T (rs4498267), c.109+768C>G (rs4431364), and c.109+915_917ins/delTAG (rs148607624). The functional role of the associated polymorphisms was evaluated by luciferase reporter gene expression analyses and EMSA.Results:A statistically significant increased frequency was observed in the patients for rs73346254A (P = 5 × 10(-4)) and rs148607624delTAG (P = 0.01) alleles. Among all the possible allele combinations, only the haplotype bearing both risk alleles showed a significantly higher frequency in the patients vs. controls (P = 4.7 × 10(-4)) and conferred a carrier risk of 4.19 (P = 1.2 × 10(-4)). This haplotype determined a significant decrease of the luciferase activity in comparison with a basal promoter and the other allelic combinations in GH4C and MCF7 cells (P = 4.6 × 10(-6); P = 5.5 × 10(-4), respectively). The EMSA showed a differential affinity for nuclear proteins for the alternative alleles of the two associated variations.Conclusions:Variations with a functional significance conferring susceptibility to CPHD have been identified in the PROP1 gene, indicating a multifactorial origin of this disorder in sporadic cases.