Context: LHX4 is a LIM homeodomain transcription factor involved in pituitary ontogenesis. Only a few heterozygous LHX4 mutations have been reported to be responsible for congenital pituitary hormone deficiency.

Subjects and Methods: 136 patients with congenital hypopituitarism associated with malformations of brain structures, pituitary stalk or posterior pituitary gland were screened for LHX4 mutations.

Results: Three novel allelic variants that cause predicted changes in protein sequence of LHX4 (2.3%) were found (p.Thr99fs, p.Thr90Met, and p.Gly370Ser). On the basis of functional studies, p.Thr99fs mutation was responsible for the patients' phenotype, whereas p.Thr90Met and p.Gly370Ser were likely polymorphisms. Patients bearing the heterozygous p.Thr99fs mutation had variable phenotypes: two brothers presented somatolactotroph and thyrotroph deficiencies, with pituitary hypoplasia and poorly developed sella turcica; the youngest brother (propositus) also had corpus callosum hypoplasia and ectopic neurohypophysis; their father only had somatotroph deficiency and delayed puberty with pituitary hyperplasia. Functional studies showed that the mutation induced a complete loss of transcriptional activity on POU1F1 promoter and a lack of DNA binding. Cotransfection of p.Thr99fs mutant and wild-type LHX4 failed to evidence any dominant negative effect, suggesting a mechanism of haploinsufficiency. We also identified prolactin and growth hormone promoters as potential target genes of LHX4 and found that the p.Thr99fs mutant was also unable to transactivate these promoters.

Conclusions: The present report describes three new exonic LHX4 allelic variants with at least one being responsible of congenital hypopituitarism. It also extends the phenotypic heterogeneity associated with LHX4 mutations, which includes variable anterior pituitary hormone deficits as well as pituitary and extrapituitary abnormalities.