Variant detection and runs of homozygosity in next generation sequencing data elucidate the genetic background of Lundehund syndrome

Background: The Lundehund is a highly specialized breed characterized by a unique flexibility of the joints and polydactyly in all four limbs. The extremely small population size and high inbreeding has promoted a high frequency of diseased dogs affected by the Lundehund syndrome (LS), a severe gastro-enteropathic disease. Results: Comprehensive analysis of bead chip and whole-genome sequencing data for LS in the Lundehund resulted in a genome-wide association signal on CFA 34 and LS-specific runs of homozygosity (ROH) in this region. Filtering analysis for variants with predicted high or moderate effects revealed a missense mutation in LEPREL1 1. 2 Mb proximal to the region of the genome-wide association, which was shown to be significantly associated with LS. LS-affected Lundehund harbored the mutant LEPREL1: g. 139212C>G genotype A/A whereas all controls of other breeds showed the C/C wild type. In addition, ROH analysis for the Lundehund indicated a high enrichment of genes in potential signatures of selection affecting protein activation and immunoregulatory processes like NOD1 potentially involved in LS breed disposition. Conclusions: Sequencing results for Lundehund specific traits reveal a potential causative mutation for LS in the neuropeptide operating gene LEPREL1 and suggests it as a precursor of the inflammatory process. Analyses of ROH regions give an insight into the genetic background of characteristic traits in the Lundehund that remain to be elucidated in the future.