Knockout mice with pituitary malformations help identify human cases of hypopituitarism.

BACKGROUND: Congenital hypopituitarism (CH) and its associated syndromes, septo-optic dysplasia (SOD) and holoprosencephaly (HPE), are midline defects that cause significant morbidity for affected people. Variants in 67 genes are associated with CH, but a vast majority of CH cases lack a genetic diagnosis. Whole exome and whole genome sequencing of CH patients identifies sequence variants in genes known to cause CH, and in new candidate genes, but many of these are variants of uncertain significance (VUS). METHODS: The International Mouse Phenotyping Consortium (IMPC) is an effort to establish gene function by knocking-out all genes in the mouse genome and generating corresponding phenotype data. We used mouse embryonic imaging data generated by the Deciphering Mechanisms of Developmental Disorders (DMDD) project to screen 209 embryonic lethal and sub-viable knockout mouse lines for pituitary malformations. RESULTS: Of the 209 knockout mouse lines, we identified 51 that have embryonic pituitary malformations. These genes not only represent new candidates for CH, but also reveal new molecular pathways not previously associated with pituitary organogenesis. We used this list of candidate genes to mine whole exome sequencing data of a cohort of patients with CH, and we identified variants in two unrelated cases for two genes, MORC2 and SETD5, with CH and other syndromic features. CONCLUSIONS: The screening and analysis of IMPC phenotyping data provide proof-of-principle that recessive lethal mouse mutants generated by the knockout mouse project are an excellent source of candidate genes for congenital hypopituitarism in children.

FOXO1 regulates expression of Neurod4 in the pituitary gland.

Pituitary gland function is regulated by the activity of various transcription factors that control cell fate decisions leading to cellular differentiation and hormone production. FOXO1 is necessary for normal somatotrope differentiation and function. Recent in vivo data implicate FOXO1 in the regulation of genes important for somatotrope differentiation including Gh1, Neurod4, and Pou1f1. In the current study, the somatotrope-like cell line GH3 was treated with a FOXO1 inhibitor, resulting in significant reduction in Neurod4 and Gh1 expression. Consistent with these findings, CRISPR/Cas9-mediated deletion of Foxo1 in GH3 cells significantly reduced expression of Gh1 and Neurod4. Chromatin immunoprecipitation sequencing identifies novel FOXO1 binding sites associated with the Neurod4, Gh1, and Pou1f1 genes. The FOXO1 binding site in the Neurod4 gene exhibits enhancer activity in somatotrope-like cells but not in gonadotrope-like cells. These data strongly suggest FOXO1 directly contributes to the transcriptional control of genes important for somatotrope differentiation.