SAT-LB58 Molecular Investigation of Recessive Inheritance by Exome Sequencing of Patients With Congenital Hypopituitarism

Abstract

Background: Growth hormone deficiency (GHD) occurs in ~ 1/8000 individuals, and 14% of the patients have mutations in five major candidate genes. However, over 30 genes have been implicated in hypopituitarism. WES (Whole Exome Sequencing) is a promising approach for molecular diagnosis of patients with GHD because it offers the opportunity to screen for all known genes in addition to novel disease gene discovery. Methods: WES was performed for 13 unrelated patients with congenital hypopituitarism born from consanguineous parents. The variants were filtered assuming autosomal recessive inheritance, rare variants in population databases, in silico analysis predicted as deleterious and pituitary and/or hypothalamus gene expression. To determine whether variants in CDH2 that were predicted to be deleterious were functionally significant, L1 fibroblast lines that have no endogenous CDH2 protein were stably transfected with either human wild type or variant CDH2, the transfected cells were labelled with lipophilic dyes, and cell adhesion properties were assessed. Results: Homozygous pathogenic or likely pathogenic allelic variants were found in 2 of the 13 patients. First, a female patient with GH, TSH, ACTH and LH/ FSH deficiencies presenting ectopic posterior pituitary lobe, non-visualized stalk, and hypoplastic anterior pituitary lobe had two homozygous rare variants predicted as deleterious: PLA2G4A p.Asn703Lys and CDH2 c.865G>A (p.Val289Ile). Only CDH2 is known to be expressed in the pituitary, and Pla2g4a null mice have a pleiotropic phenotype without obvious hypopituitarism. The CDH2 variant is rare and classified as deleterious. Sanger sequencing of CDH2 in four family members of the affected proband revealed that the unaffected parents and two unaffected siblings were heterozygous carriers. The effect of the CDH2 variant on cell aggregation was assessed in cell culture. Large cell aggregates formed in cells transfected with wild type CDH2, but cell aggregates were small or absent in cells that were either non-transfected or transfected with the CDH2 variant. Second, a patient with isolated GHD and no MRI abnormalities was identified with a rare, likely deleterious, homozygous GH1 c.171delT (p. Phe 57Leufs*43) variant. He had a sister who died at the age of 5 and had features of GHD. Conclusion: In a cohort of congenital hypopituitarism from consanguineous parents we had 15% molecular diagnosis using WES. We identified a variant in a known gene, GH1 c.171delT and a variant in a novel gene, CDH2 p.Val289I.