Validation of DNA test for hip dysplasia failed in Danish Labrador Retrievers.

Canine hip dysplasia is characterized by poor hip joint conformation and laxity. The disease is a complex trait influenced by both genetics and environment. Diagnosis and quantification of hip dysplasia are performed by radiographic examination of the hip joint and the diagnosis is used for making breeding decisions in many breeds. A prognostic genetic test (the Dysgen test) based on seven associated SNPs has been developed in a study based on Spanish Labrador Retrievers. In our study this test has been evaluated in 39 Danish Labrador Retrievers with known radiographic hip score: 14 with hip dysplasia (grade D or E) and 25 without hip dysplasia (grade A or B). There was no significant correlation between the Dysgen test results and the radiographic hip status (P = 0.3203) in these dogs, indicating that Dysgen test results obtained for Danish Labrador Retrievers have no prognostic value.

Expression of matrix metalloproteinase-9 and -12 in porcine lung infections.

Matrix metalloproteinases (MMPs) play a variety of roles during organogenesis, in the immune response and during acute and chronic diseases as well as in tissue remodelling. During the last decade, the pig has become used increasingly as a model for human diseases; however, studies on the expression of porcine MMPs are limited. In the present study species-specific antibodies were produced to investigate the expression of MMP-9 and MMP-12 immunohistochemically in lungs from pigs infected with Actinobacillus pleuropneumoniae, Pasteurella multocida and Staphylococcus aureus. The immunolabelling of lung tissues (one infected and one control pig representing each infection) was evaluated for cellular distribution and intensity, which was scored semiquantitatively. When compared with healthy, non-infected controls, the expression of both MMP-9 and MMP-12 was higher in infected lungs. The highest expressions were seen in the alveolar epithelium (MMP-9) and alveolar macrophages (MMP-12). These results are in accordance with studies of human lungs.

Evaluation of the porcine melanocortin 4 receptor (MC4R) gene as a positional candidate for a fatness QTL in a cross between Landrace and Hampshire.

Melanocortin 4 receptor (MC4R) is expressed in the appetite-regulating areas of the brain where it is central in the regulation of feed intake and energy balance. A mutation in MC4R causing an Asp298Asn substitution has been associated with fatness, high daily gain and feed intake in the pig. In a previously performed genome scan based on a Hampshire x Landrace cross, we detected one quantitative trait loci (QTL) affecting carcass fat/meat ratio and one QTL affecting the biceps femoris muscle, both close to the position of MC4R on porcine chromosome 1. In this study, the two lines were found to be close to fixation for alternative alleles of the Asp298Asn polymorphism. Additional QTL analyses supported our hypothesis of MC4R as a positional candidate gene but only for the fat/meat QTL. The Asp298Asn polymorphism was also evaluated as a selection target for daily gain in a Danish pig breeding population that included four breeds (Hampshire, Duroc, Landrace and Yorkshire). Over a 12-year period (1990-2002), a significant increase in the allele frequency of 298Asn was found in Landrace and Duroc, whereas a non-significant decrease in the 298Asn allele frequency was observed in Yorkshire. The Hampshire breed was fixed for the 298Asn allele in 1990. The high 298Asn allele frequencies in Hampshire, Landrace and Duroc are most likely due to selection for daily gain, whereas selection for daily gain in the Yorkshire breed apparently focuses on other loci.

Genome-wide identification of quantitative trait loci in a cross between Hampshire and Landrace I: carcass traits.

We report the identification of quantitative trait loci (QTL) affecting carcass composition, carcass length, fat deposition and lean meat content using a genome scan across 462 animals from a combined intercross and backcross between Hampshire and Landrace pigs. Data were analysed using multiple linear regression fitting additive and dominance effects. This model was compared with a model including a parent-of-origin effect to spot evidence of imprinting. Several precisely defined muscle phenotypes were measured in order to dissect body composition in more detail. Three significant QTL were detected in the study at the 1% genome-wide level, and twelve significant QTL were detected at the 5% genome-wide level. These QTL comprise loci affecting fat deposition and lean meat content on SSC1, 4, 9, 10, 13 and 16, a locus on SSC2 affecting the ratio between weight of meat and bone in back and weight of meat and bone in ham and two loci affecting carcass length on SSC12 and 17. The well-defined phenotypes in this study enabled us to detect QTL for sizes of individual muscles and to obtain information of relevance for the description of the complexity underlying other carcass traits.