Endocrine Abstracts

Introduction: Gonadotropin-releasing hormone (GnRH) is the master hypothalamic hormone regulating the reproductive axis. GnRH insufficiency causes absent puberty with low levels of sex steroids, known as hypogonadotropic hypogonadism (HH). Recently, pathogenic variants in SOX11 (SRY-box transcription factor 11) were identified to underlie a novel neurodevelopmental disorder with congenital HH. SOX11 is expressed in both the developing pituitary and hypothalamus, but its role in reproductive development and function is unknown. This project aims to investigate the mechanisms by which SOX11 deficiency effects hypothalamic-pituitary-gonadal axis biology using cellular and mouse models.

Methods: We have generated two new transgenic lines to genetically delete Sox11. These mice models have tissue specific knockout of Sox11 in the pituitary gland (Prop1.2i^Cre/+;Sox11^Flox/Flox;Rosa26^Tomato/+) and in GnRH neurons (GnRH^Cre/+;Sox11^Flox/Flox;Rosa26^Tomato/+). Additionally, we have generated Gn11 CRISPR-Cas9 cell lines to examine the effect of knockdown of Sox11 expression in a developing GnRH neuronal cell line.

Results: Tissue expression studies showed Sox11 localisation in wildtype pituitary and hypothalamus at embryonic day 18.5. Western blot and immunofluorescence staining demonstrated Sox11 protein expression in immature (Gn11) and mature (GT1-7) GnRH neurons, and also in non-reproductive neuronal (SHY5Y) cell lines. In mice with tissue-specific knockout of Sox11 in the pituitary gland, histology of postnatal day 1 hypothalamic-pituitary axis revealed morphological abnormalities of the pituitary as compared to control mice. The Prop1.2i^Cre/+; Sox11^Flox/Flox;Rosa26^Tomato/+ pituitary mouse model showed a significant delay in balanopreputial separation (males, P = 0.0086), vaginal opening (females, P = 0.0100) and first estrous (females, P = 0.0086), compared to control littermates, consistent with delayed timing of sexual maturation and puberty onset. Body weight was not significantly different at the time of puberty onset between knockout or control mice. Ongoing analysis will further examine both knockout mouse and cellular models.

Conclusion: These data suggest that Sox11 deficiency leads to defective pituitary development with delayed puberty in males and females.