A novel Anks6 nonsense mutation promotes polycystic kidney disease in Han:SPRD-Cy rats and its homozygosity is prenatally lethal

Methods

We identified an ostensibly healthy Sprague–Dawley rat line with a mutation that modifies PKD expressivity in Han:SPRD-Cy rats, which we named Mcy (modifier of Cy). We used whole genome sequencing and segregation analysis to identify the Mcy mutation, quantitative PCR and mRNA sequencing to evaluate its effects on gene expression, western blotting and immunohistochemistry to assess its protein consequences, and ultrasound and histology to examine its impact on rat embryonic development.

Results: We identified a nonsense mutation in the ankyrin repeat and sterile alpha motif domain containing 6 (Anks6) gene as the genetic basis of the Mcy phenotype. While rats heterozygous for the Mcy mutation do not develop PKD, those homozygous for the Mcy mutation exhibit laterality defects and die prenatally at E16.5 due to apparent perturbation of cardiovascular development. Compound heterozygotes for the Mcy and Cy mutations develop PKD much more rapidly than Cy heterozygotes and in a timeframe consistent with Cy homozygotes.

Transcripts with the mutant Mcy allele appear to undergo nonsense-mediated decay, and no ANKS6 protein is detected. However, gene expression patterns in the kidneys did not differ significantly between age-matched wild-type and Mcy-carrier rats, indicating that ANKS6 insufficiency does not cause PKD. Conclusions: We identified a novel Anks6 nonsense mutation that indicates that the absence of wild-type ANKS6 accelerates PKD development in the Han:SPRD-Cy rat, and that complete ANKS6 deficiency prevents normal embryonic development in rats.