Genomic analyses of induced hypercholesterolemia and atherosclerosis in a mixed breed colony of dogs and developmental abnormalities in the Havanese

• Other Authors: Murphy, Keith E., Kerwin, Sharon C., Kier, Ann B., Long, Charles R.
• Format: Book
• Language: English
• Published: 2009
• Subjects: canine; genetics; microsatellite; microarray; Rasch measurement; Canis lupus
• Online Access: http://hdl.handle.net/1969.1/ETD-TAMU-2516

The domestic dog, Canis lupus familiaris, is a unique model system for the dissection of hereditary diseases. Selective breeding practices have created more than 300 distinct breeds of dogs, born from a desire to create specific physical and behavioral characteristics. Breeds represent closed breeding populations and the extensive records maintained for members of each breed (e.g., multi-generational pedigrees, veterinary medical records) present an incredible tool for genetic research. Two closed populations were used in the work presented here: a colony of mixed-breed dogs segregating resistance and sensitivity to cholesterol feeding, and a purebred pet population of Havanese experiencing a high frequency of developmental abnormalities. Estimates of heritability were calculated for each disease to evaluate the degree of phenotypic variation attributable to genetics among dogs in the populations used. A heritability of 0.55 (? 0.16) was identified for cholesterol resistance and sensitivity in the mixed-breed colony. The small sample size prevented the use of complex segregation analyses to examine mode of transmission. A heritability of 0.36 (? 0.26) was calculated for the composite phenotype in the Havanese, encompassing the spectrum of abnormalities in the breed. Polygenic inheritance was identified for the composite phenotype, but the action of a major gene was identified by complex segregation analyses in the Havanese. Complex diseases preclude the use of a candidate gene approach, owing to the multitude of genes involved in the disease process. Whole genome screens provide a practical approach to the identification of chromosomal region(s) associated with a disease phenotype by narrowing the search for candidate gene(s). The Minimal Screening Set ? 2 (MSS-2) was used in the present studies to evaluate the segregation of microsatellite markers in pedigrees for both the mixed-breed colony and the Havanese. No significant LOD scores were identified, though suggestive LOD scores were obtained in both analyses. A canine-specific oligonucleotide microarray was used to create gene expression profiles for developmental abnormalities in the Havanese and for cholesterol sensitivity in the mixed-breed colony dogs. Distinct expression profiles were generated for each group, and several genes of interest were identified as being both differentially expressed (>?2-fold change) and statistically significant (p-value<0.05).