Contribution of LHX4 mutations to pituitary deficits in a cohort of 417 unrelated patients

Context:LHX4 encodes a LIM-homeodomain transcription factor implicated in early pituitary development. In humans, only 13 heterozygous LHX4 mutations have been associated with congenital hypopituitarism.Objective:To evaluate the prevalence of LHX4 mutations in patients with hypopituitarism, and to precise the associated phenotypes. To characterize the functional impact of the identified variants and the respective role of the two LIM domains of LHX4.Patients and design:We screened 417 unrelated patients with isolated growth hormone deficiency or combined pituitary hormone deficiency associated with ectopic posterior pituitary and/or sella turcica anomalies for LHX4 mutations (Sanger sequencing). In vitro studies were performed to assess the functional consequences of the identified variants.Results:We identified seven heterozygous variations (p.(Tyr131*), p.(Arg48Thrfs*104), c.606+1G>T, p.Arg65Val, p.Thr163Pro, p.Arg221Gln, and p.Arg235Gln) associated with variable expressivity and, in five of them, incomplete penetrance. The p.(Tyr131*), p.(Arg48Thrfs*104), p.Ala65Val, p.Thr163Pro and p.Arg221Gln LHX4 mutants are unable to transactivate the POU1F1 and GH promoters. As suggested by transactivation, subcellular localization and protein-protein interaction studies, p.Arg235Gln is probably a rare polymorphism. Co-immunoprecipitation studies identified LHX3 as a potential protein partner of LHX4. As revealed by functional studies of LIM-defective recombinant LHX4 proteins, the LIM1 and LIM2 domains are not redundant.Conclusion:This study, performed in the largest cohort of patients screened so far for LHX4 mutations, describes six new disease-causing mutations responsible for congenital hypopituitarism. LHX4 mutations were found to be associated with variable expressivity and most of them with incomplete penetrance; their contribution to pituitary deficits associated with an ectopic posterior pituitary and/or a sella turcica defect is ∼1.4% in the 417 probands tested.