Knockout mice with pituitary malformations help identify human cases of hypopituitarism
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). 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 and identified 51 genes that cause recessive, embryonic pituitary malformations in embryonic lethal or subviable knockout mice. 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, MORC2A and MKS1, not previously associated with CH.  This provides proof-of-principle that recessive lethal mouse mutants are an excellent source of candidate genes for congenital hypopituitarism in children Overall design: Embryonic pituitary glands were dissected at e12.5 and e14.5 and used for transcript analysis by scRNAseq