Deletion of nephrocystin 4 exacerbates cardiac function and survival rate in a mouse model of cardio-renal syndrome

Abstract Background Cardiorenal syndrome (CRS), characterized by cardiac and renal dysfunction, is an increasing health problem associated with high mortality rate. Nephrocystin 4 (NPHP4) gene is the major cause of end-stage renal disease in children. We have reported NPHP4 single nucleotide polymorphism is the genetic risk for CRS and subsequent cardiovascular events in general population. However, the functional role of Nphp4 in the development of CRS has never been examined yet. Methods and Results We generated systemic Nphp4 knockout (KO) mice deleting exon 3 to 8 using CRISPR-Cas9 system. RNA sequence analysis of heart and kidney tissues demonstrated that gene-sets related to mitochondrial function were significantly downregulated in Nphp4 KO mice compared to their wild-type (WT) littermates. Nphp4 KO mice showed less cardiac hypertrophy, however, exacerbated cardiac function and survival compared to WT mice in a CRS model induced by thoracic transverse aortic constriction. Nphp4 located in endosome and cell membrane in H9C2 cardiomyocytes. Immunoprecipitation confirmed protein interaction between Nphp4 and HECT-type E3 ligase Itch. Furthermore, we found that Itch targeted Lats2 and insulin-like growth factor-1 receptor in cardiomyocytes. Knockdown of Nphp4 activated Hippo signaling and worsened mitochondrial function in H9C2 cardiomyocytes through the inhibition of Itch-dependent Lats2 degradation. Knockdown of Nphp4 inhibited insulin-like growth factor-1 signaling through the disturbance of Itch-mediated endosome function. Conclusions Deletion of Nphp4 impaired compensatory cardiac hypertrophy and exacerbated cardiac function and survival in a mouse CRS model through mitochondrial dysfunction. Nphp4 mediated Hippo signaling and insulin-like growth factor-1 signaling through the interaction with Itch. NPHP4 could be the novel therapeutic target in CRS.figure1figure2