Date of Award

5-2023

Document Type

Thesis

Department

Genetics and Biochemistry

Abstract

In dogs, a white base coat with black patches is termed harlequin patterning. In the Great Dane, harlequin is caused by a mutation in the ubiquitin-proteasome system, a highly complex process through which damaged proteins are degraded1. All harlequins are also heterozygous for the Merle allele of SILV, which harbors a retrotransposon that leads to production of abnormal protein2. In melanocytes with impaired protein degradation, aberrant SILV is thought to cause cell death, resulting in the characteristic white base coat of a harlequin dog1. We identified a novel, spontaneous form of harlequin patterning in a family of Australian shepherds. To identify the genetic cause, we generated genome-wide SNP profiles and identified 32 chromosomal regions with genotype patterns consistent with the known mode of inheritance: heterozygous in the sire and harlequin offspring (n=4) and absent from the non-harlequin merles (n=2). We generated whole genome and skin transcriptome sequences from a harlequin dog to identify candidate causal variants. High quality, heterozygous variants were filtered against multibreed VCFs representing nearly 2000 canines to identify protein coding changes private to the harlequin Australian shepherds. Seven variants were evaluated through in silico programs for variant effect and sequenced to confirm inheritance pattern. We identified a candidate causal variant in BRCA1, an E3 ubiquitin ligase. To quantify the impact of the variant we will synthesize mutant SILV and evaluate the effectiveness of both mutant and wild type BRCA1 at performing ubiquitination.

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