The Locus Isolation And Polymorphism Of MHC Class Ⅱ Gene In The Chinese Alligator

Chinese alligator (Alligator sinensis) is an endangered species that is endemic to China. In the history, it used to distributed in the Yangtse and Yellow River drainage area widely. As a result of habitat loss and serious illegal hunting, the wild population has been close to extinct during the past decades. In the 1970's, the Anhui Research Center of Chinese Alligator Reproduction and Changxing Nature Breeding Research Center for Chinese alligator were established successively. By now, although the captive population has been greately developed, it's quality is very low.The major histocompatibility complex (MHC) is a group of closely linked loci present in remarkably similar form in all mammals and perhaps in all vertebrates. It is hetero-dimer gene encoding glycoprotein which presents peptides to T4 cell, and plays a central role in immune system. MHC, especially MHC II, has a very high polymorphism, so we can make it a kind of molecular marker of genetics used to investigate the genetic construction and genetic variability of a subpopulation. It plays a very important role in conservation genetics.In this study, we separated a locus of MHC class II a-chain genes and four loci of MHC class IIβ-chain genes from the Chinese alligator, one of which is pseudo gene. Then we designed and picked out three pairs of locus primers for the three loci of the five we separated. Then we use the three pairs of locus primers to investigate the site polymorphism of 59 Chinese alligators, 49 of which came from the Changxing subpopulation, the other 10 came from the USA. As a result, we found all of the three loci took on monomorphism among the 59 individuals scored, which suggested the diversity of MHC in the captive Chinese alligator has been extremely low. So it is necessary to take all kinds of countermeasure on purpose to protect and increase it.