Molecular genetic analysis of the major histocompatibility complex in an ELA typed horse family

Summary. Restriction fragment length polymorphism was studied in an ELA typed horse family which included a stallion, a mare with two full-sibs, another mare with three full-sibs and, in addition, three paternal half-sibs. DNA samples from all individuals were investigated by Southern blot analysis using three restriction enzymes (EcoRI, HindIII or TaqI) and human cDNA class I, class II (DRβ) and class III (C4) probes. In addition, a genomic class II DQα probe was used. Fragments hybridized with the various probes revealed the existence of DNA sequences homologous to HLA class I, DRβ, DQα and C4 genes in the horse. Polymorphic fragments were found when DNA was hybridized with class I and class II probes irrespective of the enzyme used; but hybridization with the C4 probe did not reveal variability. All polymorphic fragments segregated according to the ELA serological specificities, thus indicating a close linkage between the different revealed subregions. Banding patterns suggest that the horse possesses about 20–30 class I genes, probably more than one DRβ and DQα genes and possibly only one C4 gene. The high degree of polymorphism observed suggests that molecular DNA typing may represent a potentially powerful aid to decision in parentage control determination.