The KCASH2KO mice: a new mouse model with mild cerebellar Hedgehog-dependent phenotype and spermatozoa abnormalities

KCASH2 gene participates in the modulation of the Hedgehog (Hh) pathway, which plays a role in development, embryogenesis and tumorigenesis. In particular, KCASH2 protein prevents the transcriptional Gli1 activity, interacting with the E3 ubiquitin Ligase Cullin 3, mediating histone-deacetylase 1 (HDAC1) ubiquitin-dependent degradation, which would otherwise deacetylate Gli1 enhancing their transcriptional activity. In the present work, we generated KCASH2 knockout mice (KCASH2KO) to evaluate in vivo effect of KCASH2 deletion on the Shh pathway and cerebellar development. KCASH2 expression was present in differentiated cerebellar granule cells, and histological analysis highlighted a larger thickness of the internal granule layer (IGL) in the IV-V cerebellar lobules in the adult KCASH2KO mice cerebellum, confirming the KCASH2 loss determines a prolonged proliferation of granule cells precursors (GCP) during post natal development. Behavioural experiments have highlighted a significant alteration in cerebellum functions; indeed that the loss of KCASH2 induces in male KCASH2KO a delayed learning and in female KCASH2KO a diversity in procedural navigational strategy compared to WT siblings. Our observations demonstrate that KCASH2 acts in vivo as negative regulator of Hh pathway and suggest, for the fist time, the role of the Hh pathway alteration in such behavioural disorders related to cerebellar function. During the characterization of the KCASH2KO mouse, we unveiled a potential physiological role of KCASH2 in spermatozoa development and function. We have demonstrated that KCASH2 is expressed in Leydig cells and in Epididymal Epithelium cells and we have observed anomalies in KCASH2KO mice spermatozoa morphology (increased atipicity) and sperm mobility (dyskinesia).