POLYMORPHISM OF THE SECOND EXON OF THE ELA-DQB GENE IN THE HORSE

Insitute of Animal Breeding and Genetics, Faculty of Veterinary Medicine, Palackeho 1/3 612 42 Brno, Czech Republic

In our previous studies, polymorphism of the horse major histocompatibility complex ELA-DQB gene was investigated by using the polymerase chain reaction - single strand conformation polymorphism (PCR-SSCP) with horse-specific primers. SSCP patterns from ELA homozygous horses with known nucleotide sequences (Szalai et al. 1993) were compared with those obtained from different horses of various breeds. Horses with SSCP patterns differing from the former were selected. Their non-identity was confirmed by differences in SSCP patterns from individual clones. The second exon was amplified by PCR, subcloned and sequenced with an automatic DNA sequencer. The results revealed existence of additional new ELA-DQB alleles as defined by nucleotide sequences. A phylogenetic tree was constructed. The variation was observed mainly at polymorphic sites described previously by Szalai et al. 1993. However, additional polymorphic sites were observed. The results support the idea of a considerable extent of polymorphism at the horse major histocompatibility class II DQB locus. Three types of clones differing by their SSCP patterns as well as by their nucleotide sequences were identified in one Akhal-Teke horse. Studies of other horses either with SSCP patterns identical to those of the new alleles detected or with complex SSCP patterns (i.e. with more than four SSCP bands) are in progress in order to confirm existence of the new alleles and to investigate possible existence of a second ELA-DQB locus.