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.

Introduction: Hypopituitarism is defined as a deficiency of one or more pituitary hormones. Pathogenic allelic variants in genes implicated in pituitary development were associated in 15% of the patients with congenital hypopituitarism (CH). To improve the molecular diagnosis we performed whole exome sequencing of ten patients born from consanguineous parents with CH. One patient with GH, TSH, ACTH and LH/FSH deficiencies presented an allelic variant c.865G>A, p.V289I in CDH2 gene (exon 7) in homozygous state that was absent in populational databanks. CDH2 produces an N-cadherin protein implicated in cellular adhesion and is responsible for epithelial-mesenchymal transition during pituitary development and differentiation. Aim: To analyze the CDH2 gene in a cohort of unrelated patients with CH. Methods: We selected 143 patients with CH from a single Brazilian center. Genomic DNA, extracted by salting out technique, was submitted to PCR amplification of 15 coding regions, except CG rich exon 1, of the CDH2 gene followed by the Sanger sequencing. Rare allelic variant frequency (MAF<1%) was searched in the populational data bank (ExAC, gnomAD, ABraom). Bioinformatic sites (Human Splicing Finder, Polyphen2, Mutation Taster and Mutation assessor) were used to look for deleterious effects. Results: Three allelic variants were found in this cohort. The allelic variant CDH2 (c.865G>A, p.V289I) was found in heterozygous state in a male patient with short stature diagnosed with GH and TSH deficiencies at the age of 11 that evolved with LH/FSH and ACTH deficiencies. Family segregation showed 3 among 11 normal siblings heterozygous carriers. This variant is rare, in heterozygous state, in populational data bank and it was predicted as deleterious or possibly harmful. The allelic variant c.1202C> A (p.A401D), in exon 9, was found in heterozygous state in a female patient with isolated GH deficiency and intellectual disability. The variant was absent in the databases and predicted as deleterious or disease-causing. The variant was absent in the mother and stepsister and the father was not available for testing. The c.1430_1431delCCinsTG allelic variant (p.P477L) was found in heterozygous state in a patient with septo-optic dysplasia, GH, TSH and ACTH deficiencies. It was absent in the databases and was predicted as deleterious or disease causing. The Human Splicing Finder predicted exonic splicing enhancer breakdown leading to the loss of 93 nucleotides. Normal mother is heterozygous carrier suggesting incomplete penetrance. Conclusion: Heterozygous variants in CDH2 were found in 2% of a cohort of Brazilian patients with congenital hypopituitarism and none in homozygous or compound heterozygous state. Further CDH2 analyses in unrelated patients from different ethnic backgrounds are needed to establish the role CDH2 variants in the etiology of congenital hypopituitarism.

Context: Congenital hypopituitarism is a genetically heterogeneous condition. Whole exome sequencing (WES) is a promising approach for molecular diagnosis of patients with this condition. Objectives: To conduct WES in a patient with congenital hypopituitarism born to consanguineous parents, CDH2 screening in a cohort of patients with congenital hypopituitarism, and functional testing of a novel CDH2 variant. Design: Genomic DNA from a proband and her consanguineous parents was analyzed by WES. Copy number variants were evaluated. The genetic variants were filtered for population frequency (ExAC, 1000 genomes, gnomAD and ABraOM), in silico prediction of pathogenicity, and gene expression in pituitary and/or hypothalamus. Genomic DNA from 145 patients was screened for CDH2 by Sanger sequencing. Results: One female patient with deficiencies in GH, TSH, ACTH, LH, and FSH and ectopic posterior pituitary gland contained a rare homozygous c.865G>A (p.Val289Ile) variant in CDH2. To determine whether the p.Val289Ile variant in CDH2 affects cell adhesion properties, we stably transfected L1 fibroblast lines, labeled the cells with lipophilic dyes, and quantified aggregation. Large aggregates formed in cells expressing wild type CDH2, but aggregation was impaired in cells transfected with variant CDH2 or non-transfected. Conclusion: A homozygous CDH2 allelic variant was found in 1 hypopituitarism patient, and the variant impaired cell aggregation function in vitro. No disease-causing variants were found in 145 other patients screened for CDH2 variants. Thus, CDH2 is a candidate gene for hypopituitarism that needs to be tested in different populations.