A reference population designed for molecular genetic mapping of the chicken genome was produced by backcrossing a partially inbred Red Jungle Fowl (JF) line to a highly inbred White Leghorn (WL) line. The parental lines were chosen to maximize the expected genetic polymorphisms between them. Two full-sib F^ males, produced by crossing a JF male with a WL female, were each individually mated to about 10 WL females to produce 400 progeny. All the progeny were classified for segregation of three loci controlling color phenotype and six blood group loci, some of which have been mapped by classical methods. Segregation of these nine loci did not differ significantly from the expected 1:1 ratio with one exception. At least 20 mL of whole blood was stored from all the parents and progeny to provide DNA for molecular analysis. Screening of the parental lines and Fi crosses by Southern blot with cloned genes and by the random amplified polymorphic DNA (RAPD) procedure revealed a large number of molecular markers mat were parental line-specific. A preliminary analysis of 16 backcross progeny classified for polymorphisms at 2 color loci, 6 blood group loci, 16 loci detected by cloned chicken genes, and 4 loci detected by the RAPD method has been completed. Segregation at 27 out of 28 loci did not differ significantly from the expected 1:1 ratio, showing that two alternative alleles were detected at each locus. Five pairs of linked loci were detected (P < .01). Thus, this population is polymorphic and gives simple segregation for two types of molecular probes, providing a good resource for collaborative mapping of the chicken genome. (
University of California, Davis (UCD) line 200 White Leghorn Chickens spontaneously develop a syndrome that has many analogous features to human progressive systemic sclerosis. This syndrome is characterized by progressive involution of comb, dermal fibrosis, and distal polyarthritis. These three features occur within 6 wk after hatching, and are accompanied by a 40% mortality as a result of vaso-occlusive disease, with development of secondary infection of peripheral gangrenous lesions. Birds that survive greater than 2 mo after hatching progressively develop fibrosis of the esophagous and mononuclear infiltration of heart and kidney, with prominent occlusion of small and medium sized blood vessels. In addition, line 200 chickens develop rheumatoid factors, antinuclear antibodies, and antibodies to collagen, but do not have antibodies to thymocytes, DNA, or extractable nuclear antigens. Moreover, antinuclear antibodies when studied using HEp-2 cells as substrate demonstrate predominantly a speckled pattern. This syndrome of line 200 chickens is not detectable in F1 crosses to several UCD inbred lines. F1 X parental line BC1 backcrosses have an approximately 50% incidence of disease, suggesting that this syndrome is inherited as autosomal recessive. However, only 4% of F2 generation birds show abnormal symptoms, suggesting the presence of modifying genes. There is no appearance of IgG deposition, as determined by immunofluorescence, in either skin, blood vessels, esophagus, or heart. However, approximately 20% of chickens have a glomerulonephritis; this feature appears to be a terminal event and does not appear clinically significant. Although this syndrome of line 200 chickens has several features that are in sharp distinction to human scleroderma, the presence of common immunologic and pathologic denominators suggest that this spontaneous disease may be an appropriate model to develop a better understanding of autoimmune connective tissue diseases.
Chicken B-G-subregion cDNA probes were used to analyze restriction fragment length polymorphisms (RFLP) of the B-G subregion of the chicken major histocompatibility complex. Genomic DNA from chickens representing 17 of the 27 standard B haplotypes were digested with restriction endonucleases and analyzed in Southern hybridizations with two cDNA clones from the B-G subregion. Each B-G genotype was found to produce a unique pattern of restriction fragments in these Southern hybridizations. With 15 of the 17 genotypes examined, the different genotypes could be readily distinguished in hybridizations produced with DNA digested with a single restriction enzyme, PVU II. The two additional genotypes produced nearly identical patterns in PVU II preparations and with three additional enzymes as well, but were readily distinguishable in Eco RI digestions. For many of the haplotypes, samples from several individuals in different flocks were examined. In every instance, genotyping by RFLP pattern was found to confirm the B-G allele assigned serologically.
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