MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II-A GENE POLYMORPHISM IN THE STRIPED BASS

Adaptions of the polymerase chain reaction were used to isolate cDNA s equences encoding the Major histocompatibility complex (Mhc) class II A gene(s) of the striped bass (Morone saxatilis). Four complete Mhc cl ass II A genes were cloned and sequenced from a specimen originating i n the Roanoke River, North Carolina, and another three A genes from a specimen originating from the Santee-Cooper Reservoir, South Carolina, identifying a total of seven unique sequences. The sequence suggests the presence of at least two Mhc class II A loci. The extensive sequen ce variability observed between the seven different Mhc class II clone s was concentrated in the alpha 1 encoding domain. The encoded alpha 2 , transmembrane, and cytoplasmic regions of all seven striped bass gen es correlated well with those of known vertebrate Mhc class II protein s. Overall, the striped bass sequences showed greatest similarity to t he Mhc class II A genes of the zebrafish. Southern blot analysis demon strated extensive polymorphism in the Mhc class II A genes in members of a Roanoke river-caught population of striped bass versus a lesser d egree of polymorphism in an aquacultured Santee-Cooper population of s triped bass.