EP1076 - ECE_2982 - LATS1 and LATS2 are dispensable for pituitary gonadotrope function

Abstract

The Hippo signaling pathway is a highly conserved kinase cascade that regulates vital biological and pathological processes in mammals. The pathway's transcriptional co-activators, Yes-associated protein 1 (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ), play a central role in mediating these functions, as they represent the final downstream effectors of Hippo signaling. We recently demonstrated that conditional deletion of YAP and TAZ in murine pituitary gland gonadotrope cells results in increased circulating luteinizing hormone (LH) levels in both sexes. Increased testosterone levels, testicular weight, and sperm concentration were observed in males, while females presented a hyperfertility phenotype characterized by higher ovulation rates and larger litter sizes. Although these findings advanced our understanding of Hippo signaling in gonadotrope cells, the upstream mechanisms regulating YAP and TAZ activity remain to be elucidated. In the Hippo signaling pathway, the canonical upstream kinases that regulate YAP and TAZ are the large tumor suppressor homolog kinases 1 and 2 (LATS1 and LATS2). To directly assess the role of these kinases in gonadotrope cells, Lats1 and Lats2 were conditionally knocked-out in murine gonadotropes using the GnRH receptor–IRES-Cre (GRIC) driver and a ROSA mTmG fluorescent reporter. Deletion was firstly successful validated by fluorescence-activated cell sorting (FACS)–isolated gonadotropes from 12-16-week-old mice, which showed significant reduction in expression levels of both genes. Serum, gonads, and pituitaries were then collected from 10-12-week-old male mice and 8-10-week-old females at diestrus. Unexpectedly, hormonal analyses indicated no differences between controls and knock-out mice in LH or FSH levels in either males or females. Consequently, no reproductive phenotypic anomalies were observed in either sex. Curiously, RT-PCR analyses of pituitaries showed that YAP/TAZ target genes were not altered following Lats1 and Lats2 deletion. Taken together, these results suggest that, unlike many other cell types, YAP and TAZ activity does not appear to be regulated by LATS1 and LATS2 in gonadotropes. We are currently using bulk RNA sequencing on FACS-sorted gonadotropes from control and knock-out mice to determine if there are unappreciated roles for LATS1 and LATS2 in these cells.