Novel GLI2 mutations identified in patients with Combined Pituitary Hormone Deficiency (CPHD): Evidence for a pathogenic effect by functional characterization.

CONTEXT: The Gli-family of zinc-finger transcription factors regulates the Sonic Hedgehog (Shh) signalling pathway that plays a key role in early pituitary and ventral forebrain development. Heterozygous GLI2 loss of function mutations in humans have been reported in holoprosencephaly (HPE), HPE-like phenotypes associated with pituitary anomalies and combined pituitary hormone deficiency with or without other extra-pituitary findings. OBJECTIVE: The aim of this study was the search for GLI2 mutations in a cohort of Italian CPHD patients and the assessment of a pathogenic role for the identified variants through in vitro studies. PATIENTS: One hundred forty-five unrelated CPHD patients diagnosed with or without extra-pituitary manifestations were recruited from different Italian centres. METHODS: The GLI2 mutation screening was carried out through direct sequencing of all the 13 exons and intron-exon boundaries. Luciferase reporter assays were performed to evaluate the role of the detected missense variants. RESULTS: Five different novel heterozygous non-synonymous GLI2 variants were identified in five patients. The mutations were three missense (p.Pro386Leu, p.Tyr575His, p.Ala593Val), one frameshift (p.Val1111Glyfs*19) and one nonsense (p.Arg1226X). The latter two mutants are likely pathogenic since they lead to a truncated protein. The in vitro functional study of the plasmids bearing two of the three missense variants (namely p.Tyr575His and p.Ala593Val) revealed a significant reduction in transcriptional activity. CONCLUSION: In conclusion, the analysis of GLI2 in individuals with CPHD led to the identification of five variations with a likely negative impact on the GLI2 protein, confirming that GLI2 is an important causative gene in CPHD. The functional in vitro study analysis performed on the missense variations were useful to strengthen the hypothesis of pathogenicity.

Frequency of genetic defects in combined pituitary hormone deficiency: a systematic review and analysis of a multicentre Italian cohort.

OBJECTIVE: Combined pituitary hormonal deficiency (CPHD) can result from mutations within genes that encode transcription factors. This study evaluated the frequency of mutations in these genes in a cohort of 144 unrelated Italian patients with CPHD and estimated the overall prevalence of mutations across different populations using a systematic literature review. MATERIAL AND METHODS: A multicentre study of adult and paediatric patients with CPHD was performed. The PROP1, POU1F1, HESX1, LHX3 and LHX4 genes were analysed for the presence of mutations using direct sequencing. We systematically searched PubMed with no date restrictions for studies that reported genetic screening of CPHD cohorts. We only considered genetic screenings with at least 10 individuals. Data extraction was conducted in accordance with the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). RESULTS: Global mutation frequency in Italian patients with CPHD was 2·9% (4/136) in sporadic cases and 12·5% (1/8) in familial cases. The worldwide mutation frequency for the five genes calculated from 21 studies was 12·4%, which ranged from 11·2% in sporadic to 63% in familial cases. PROP1 was the most frequently mutated gene in sporadic (6·7%) and familial cases (48·5%). CONCLUSION: The frequency of defects in genes encoding pituitary transcription factors is quite low in Italian patients with CPHD and other western European countries, especially in sporadic patients. The decision of which genes should be tested and in which order should be guided by hormonal and imaging phenotype, the presence of extrapituitary abnormalities and the frequency of mutation for each gene in the patient-referring population.