CHARACTERIZATION OF CLASS-II-A AND CLASS-II-B GENES IN A GYNOGENETIC CARP CLONE

A prerequisite for carrying out functional studies on major histocompa tibility complex (Mhc) molecules of fish is the availability of geneti cally well-defined homozygous strains. Previously we have applied gyno genetic reproduction to generate isogenic carp, denoted clone A410. Th is clone has recently been demonstrated to express a single class I ge ne, Cyca-UA101, and in the present study two class II B and two class II A transcripts were obtained. The two class II B transcripts, Cyca- D(CB3)B and Cyca-D(CB4)B, as well as the class II A transcripts, Cyca- D(10A)A and Cyca-D(15A)A, appear to be bona fide class II transcripts, based on the presence of conserved protein characteristics of the inf erred class II molecules. With the isolation of class II A sequences, representatives of all major classes of Mhc genes have been identified in the carp. To assess the relationship between the different class I I genes, segregation studies, comparison of cDNA and intron 1 sequence data, and phylogenetic analyses were undertaken. These showed that th e class II B transcripts, Cyca-D(CB3)B and Cyca-D(CB4)B, are derived f rom related, closely linked loci. In addition, these studies indicated that the previously described Cyca-DAB01 and Cyca-DAB*02 are also cl osely linked, but that this linked pair segregates independently from the Cyca-D(CB3)B and Cyca-D(CB4)B loci. The class II A transcripts are most likely derived from separate loci and do not represent alleles, as they were found not to segregate in the individuals of the clone wh ich was generated by meiogenetic gynogenesis.