title: Heterogeneity and linkage of equine C4 and steroid 21-hydroxylase genes.
abstract: The fourth component of complement (C4) is polymorphic in most species studied, and is encoded by a gene or genes within the MHC. In man and mouse there are two closely linked C4 and steroid 21-hydroxylase (21-OH) genes. Therefore we have used Southern blotting to determine whether equine C4 and 21-OH genes are linked. C4 restriction fragment length polymorphism (RFLP) was found with the enzymes EcoRI and BamHI. Comparison of the sizes of EcoRI-digested fragments of genomic DNA hybridizing with C4 and 21-OH probes revealed that equine C4 and 21-OH genes are separated by no more than 13 kb. Further, there is no evidence of C4 and 21-OH gene duplication in the horse. Segregation of ELA and different polymorphic forms of equine C4 suggest that C4 and 21-OH genes are within the MHC. It is likely that equine MHC supratypes will provide improved markers of disease susceptibility.
mesh_terms: D000818:Animals; D003181:Complement C4 / Q000235:genetics*; D004262:DNA Restriction Enzymes; D005796:Genes; D008040:Genetic Linkage; D006736:Horses / Q000235:genetics*; D007158:Immunologic Techniques; D008214:Lymphocytes / Q000276:immunology; D008285:Major Histocompatibility Complex; D009693:Nucleic Acid Hybridization; D010375:Pedigree; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D013255:Steroid 21-Hydroxylase / Q000235:genetics*; D013250:Steroid Hydroxylases / Q000235:genetics*
chemical_list: D003181:Complement C4; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase; D004262:DNA Restriction Enzymes