8235 Mutations in EMX2, a Homeodomain Transcription Factor, Cause Idiopathic Hypogonadotropic Hypogonadism

Abstract Disclosure: M. Stamou: None. M. Tompkin: None. H. Bow: None. H. Brand: None. L. Plummer: None. M. Talkowski: None. Y. Shen: None. D. Wu: None. R. Balasubramanian: None. S. Wray: None. S.B. Seminara: None. The genetic etiology of infertility remains largely unknown. To identify novel human infertility genes, we applied a de novo rare variant analysis in 142 parent-proband trios with idiopathic hypogonadotropic hypogonadism (IHH), a Mendelian disease caused by Gonadotropin Releasing Hormone (GnRH) deficiency. The discovery pipeline identified 43 rare de novo copy number variants (CNVs-deletions) spanning 263 genes and 213 rare de novo single nucleotide variants (SNVs) in 191 genes. Four genes were found to be affected by both rare de novo CNVs and SNVs among unrelated sporadic IHH probands. A rare variant association testing for protein truncating variants (PTVs) in the IHH cohort (N=1,394) compared to gnomAD controls (N=125,784) revealed that 3/4 genes demonstrated enrichment for PTVs in the IHH cohort compared to controls: the 2 known for IHH genes (ANOS1 and FGFR1) and one novel candidate gene, EMX2. IHH probands with de novo EMX2 variants demonstrated developmental delay and hearing loss. Common EMX2 variants were linked to delayed puberty/infertility, hearing loss and Parkinson’s disease in a phenome-wide association study of the Massachusetts General Brigham Biobank (N=65,253). Emx2 lineage tracing was conducted on Emx2Cre/+; RosatdT/+ and Emx2Cre/-; RosatdT/+ mouse embryos at embryonic day(E) 13.5. The tdT reporter was co-expressed in neuroendocrine GnRH (nGnRH) cells as they migrated from the olfactory pit to the nasal forebrain junction. WT and KO embryos from Emx2+/- matings were immunostained for GnRH across E12.5, E13.5, E14.5 and E16. The total number of nGnRH cells was greater in the Emx2 KO mice compared to WT littermates. However, by E16.5, fewer nGnRH cells were detected in the forebrain of Emx2 KO, compared to WT (WT= 496±28, KO=384±147, p=0.0125). Thus, failure of nGnRH neurons to enter the forebrain could contribute to the IHH pathogenesis. In conclusion, by utilizing a de novo variant analysis and a mouse model, EMX2 was uncovered as a novel gene for human infertility. Presentation: 6/1/2024