STK36 splice site variant in an Australian Shepherd dog with primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) represents a group of diseases characterized by impaired movement of cilia and subsequent health problems in diverse organ systems, notably the respiratory tract. Almost 50 candidate genes for PCD are known in humans. In this study, we investigated an Australian Shepherd dog with a history of recurrent respiratory infections and nasal discharge. A transmission electron microscopy investigation led to the diagnosis of PCD with central pair defect, in which the normal 9:2 arrangement of respiratory cilia was altered and reduced to a 9:0 arrangement. Whole genome sequencing data from the affected dog was obtained and searched for variants in PCD candidate genes that were not present in 918 control genomes from different breeds. This revealed a homozygous single base pair exchange at a splice site of STK36, XM_038585732.1:c.2868-1G>A. The mutant allele was absent from 281 additionally genotyped Australian Shepherd dogs. RT-PCR confirmed aberrant splicing in the affected dog with the skipping of exon 20 and the insertion of a cryptic exon, which is predicted to lead to a premature stop codon and truncation of 36% of the STK36 wild-type open reading frame, XP_038441660.1:(p.Met957Profs*11). STK36 variants were previously reported to cause PCD in humans and mice. The knowledge from other species together with the absence of the mutant allele in more than 1000 control dogs suggests STK36:c.2868-1G>A as the most likely candidate variant for PCD in the investigated case.