Functional Characterization of a Heterozygous GLI2 Missense Mutation in Patients With Multiple Pituitary Hormone Deficiency

Journal of Clinical Endocrinology and Metabolism

CONTEXT
The GLI2 transcription factor is a major effector protein of the sonic hedgehog pathway and suggested to play a key role in pituitary development. Genomic GLI2 aberrations that mainly result in truncated proteins have been reported to cause holoprosencephaly or holoprosencephaly-like features, sometimes associated with hypopituitarism.

OBJECTIVE
Our objective was to determine the frequency of GLI2 mutations in patients with multiple pituitary hormone deficiency (MPHD).

DESIGN
Patients were selected from participants in the Genetics and Neuroendocrinology of Short Stature International Study (GeNeSIS) program. Patients with mutations within established candidate genes were excluded.

PATIENTS
A total of 165 patients with MPHD defined as GH deficiency and at least 1 additional pituitary hormone deficiency were studied regardless of the presence of extrapituitary clinical manifestations.

MAIN OUTCOME MEASURES
Prevalence of GLI2 variations in MPHD patients was assessed and detailed phenotypic characterization is given. Transcriptional activity of identified GLI2 variants was evaluated by functional reporter assays.
Results:In 5 subjects, 4 heterozygous missense variants were identified, of which 2 are unpublished so far. One variant, p.R516P, results in vitro in a complete loss of protein function. In addition to GH deficiency, the carrier of the mutation demonstrates deficiency of thyrotrope and gonadotrope function, a maldescended posterior pituitary lobe, and polydactyly, but no midline defects.

CONCLUSIONS
For the first time, we show that heterozygous amino acid substitutions within GLI2 may lead to MPHD with mild extrapituitary findings. The phenotype of GLI2 mutations is variable, and penetrance is incomplete. GLI2 mutations are associated with anterior pituitary hypoplasia, and frequently, ectopy of the posterior lobe occurs.