Molecular analysis of novel PROP1 mutations associated with Combined Pituitary Hormone Deficiency.

Objective: Homozygous mutations in the gene encoding the pituitary transcription factor PROP1 are associated with combined pituitary hormone deficiency in both mice and humans with a highly variable phenotype with respect to the severity and time of initiation of pituitary hormone deficiency. We have ascertained three pedigrees with PROP1 mutations from a large cohort of patients with variable degrees of combined pituitary hormone deficiency who were screened for mutations in PROP1. Results: Affected individuals from all three pedigrees were found to harbour novel PROP1 mutations. We have identified two siblings in one family who were homozygous for an intronic mutation (c.343-11C>G) that disrupts correct splicing resulting in the loss of exon 3 from the PROP1 transcript. Two siblings from a second, unrelated family are compound heterozygotes for two point mutations in the coding region, a missense mutation (p.R125W) that leads to impaired transcriptional activation, and a deletion of a single nucleotide (c.310delC) resulting in a frameshift and non-functional mutant protein. Additionally, we identified a homozygous deletion of the PROP1 locus in two patients born to consanguineous parents. Conclusion: Mutations in PROP1 are a frequent cause of familial combined pituitary hormone deficiency. We have described four novel mutations in PROP1 in 3 pedigrees, all resulting in PROP1 deficiency by different mechanisms. The phenotypic variation observed in association with PROP1 mutations both within and between families, together with the evolving nature of hormone deficiencies and sometimes changing pituitary morphology indicates a need for continual monitoring of these patients.