Summaries of Completed Studies
Hip Dysplasia is a common disease of dogs that ultimately leads to osteoarthritis (OA), a serious debilitating condition, which at present, is treated by symptomatic management of pain. Accidental injuries also lead to the development of OA. Cartilage degeneration is fundamental to the pathogenesis of OA. We propose to study the transcriptional control of MMP-1, a major enzyme involved in the degradation of articular cartilage. Expression of MMP-1 gene and the corresponding protein is markedly increased under osteoarthritic condition. Because cytokines like IL-1 and TNF-a increase expression of MMP-1 and biomechanical factors also influence its expression in osteoarthritic, unstable joints, the objectives are to understand what components of the promoter region of canine MMP-1 gene are influenced by these factors. At present no data is available on canine MMP-1 gene regulation. This proposal is aimed towards understanding the regulation of canine MMP-1 gene expression in response to biomechanical stress and cytokines by isolating canine MMP-1 gene, identifying the regulatory elements in the promoter responsive to biomechanical stress and cytokines, and analyzing MMP-1 expression in chondrocytes of articular cartilage from normal and osteoarthritic dogs with the intent to develop novel therapeutic drugs to combat this disease.
Genome maps are essential for identifying disease genes. The current canine map is composed of several thousand markers, and as a result, has proven useful for localizing several disease genes. A much more highly refined map is necessary if we are to actually clone disease genes of interest (not just identify their location) and, subsequently, develop appropriate genetic tests. This proposal aims at developing the technology to do that, focusing on a test case on chromosome one, where two genes associated with hip dysplasia in the Portuguese Water Dog have been mapped. The goal is to determine the location and linear order of many hundred small variants calld ""SNPs"" throughout chromosome one. The resulting SNP map can then be used 1) by ourselves to identify the culprit gene(s) in PWD and 2) by anyone studying hip dysplasia in any breed of dog to determine if the same chromosomal region that is mutated in the Portuguese Water Dog is similarly responsible for disease in other breeds.
Cranial cruciate ligament disease (CCLD) is the cause of limping in nearly 20 percent of all dogs that are taken by their owners to veterinarians for lameness. CCLD causes instability in the knee, swelling and pain. Surgery to stabilize a torn CCL costs individual dog owners thousands of dollars and the dog owning public tens of millions of dollars each year and even with surgery, debilitating arthritis occurs and progresses. CCLD commonly occurs in particular breeds of dogs (e.g. Labrador Retreiver, Rottweiler, and Newfoundland) while other breeds (e.g. Greyhound, German Shepherd) rarely develop this problem. When a disease is seen with increased frequency in particular breeds of dogs, this supports the probability that a disease, in this case CCLD, is hereditary. Using this information we have already collected pedigrees and genetic material (DNA) from normal and CCLD affected Newfoundlands. The pedigrees will be used to determine a pattern of inheritance (i.e. simple recessive, sex-linked) for CCLD. The DNA will be used to search for genetic markers that differ between normal and affected dogs and may serve as disease predictors. These markers will then allow identification of carriers of CCLD, and potentially reduction or elimination of CCLD from the dog population.
Identification of chromosomal regions associated with cranial cruciate ligament rupture in a population of Newfoundlands.
Wilke VL, Zhang S, Evans RB, Conzemius MG, Rothschild MF.
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
Abstract - Am J Vet Res. 2009 Aug;70(8):1013-7.
OBJECTIVE: To identify chromosomal regions associated with cranial cruciate ligament rupture (CCLR) in a population of Newfoundlands.
ANIMALS: 90 client-owned Newfoundlands.
PROCEDURES: A pedigree was constructed for dogs that did or did not have CCLR (determined on the basis of physical examination and radiographic findings). From this pedigree, affected and unaffected dogs were selected for genotyping on the basis of their predicted statistical likelihood of being homozygous CCLR-unaffected (n = 53) or homozygous CCLR-affected (37) dogs. Genotyping was performed for 532 microsatellite markers (MSATs). Comparisons of genotypes and allele frequencies were made between CCLR-affected and CCLR-unaffected dogs.
RESULTS: In the selected population, 495 MSATs were informative with a mean interval between markers of 5.5 centimorgans. Eighty-six MSATs were significantly associated with the CCLR trait, whereas 4 markers (located on 4 chromosomes) were significantly associated with the trait when false discovery rate (q value) was controlled at the 0.05 level. Subsequent initial validation confirmed significant trait association for 3 of the 4 MSATs.
CONCLUSIONS AND CLINICAL RELEVANCE: In the population of Newfoundlands, 4 MSATs that were located on 4 chromosomes were significantly associated with the CCLR trait. Three of those markers were validated in part via genotyping additional closely located markers. The MSATs that were associated with the CCLR trait were identified in all regions (except for those on chromosome 24). Newfoundlands with CCLR could be used to study the disease process associated with anterior cruciate ligament injuries that occur in young female human athletes.
Lymphoma is one of the most common cancers seen in the dog. Current methods of classifying lymphoma neither explain nor predict its variable clinical behavior. While the majority of canine lymphomas appear microscopically similar and affected dogs show similar clinical signs, the clinical course of the disease can vary significantly in patients with microscopically identical tumors with identical clinical signs. This heterogeneity in behavior is particularly evident with respect to response to chemotherapy. Although the majority of patients initially respond well to chemotherapy, some are disease-free for a few months, while others remain disease-free over two years. Clearly, microscopic and initial clinical appearances inadequately explain the variable clinical behavior. In order to better understand and explain these differences, we will create and develop a specialized dog lymphoma gene microarray; a new tool that can be used to determine which groups of genes are important in different sub-types of lymphoma. Ultimately, by identifying these important groups of genes, we hope to 1) provide better prognostic information regarding individual tumor clinical behavior, 2) identify important groups of genes that characterize unique lymphoma sub-types, and 3) identify new molecules or genes that can be targets for development of new drugs to treat lymphoma.