Investigation of genetic diversity in wild colonies of naked mole-rats (Heterocephalus glaber) by DNA fingerprinting

DNA from 20 individuals from four wild colonies of naked mole-rats, Heterocephalus glaber, a highly social subterranean rodent, was analysed for polymorphism of the length of restriction fragments of class I major histocompatibility complex genes and minisatellite DNA. Both of these regions of the genome have been shown to be highly variable between individuals in other mammalian species. Minisatellite DNA gives rise to ‘genetic fingerprints’ specific to the individual, which have been used in the study of demographic population genetics, while certain major histocompatibility complex genes are responsible for producing an individual's immunological tissue type. In some rodents it has been reported that the major histocompatibility complex is involved in generating urinary odours unique to a particular animal, and may therefore play an important role in social and reproductive behaviour. The minisatellite probe employed in this study revealed limited restriction fragment length polymorphism in the DNA of naked mole-rats, both within and between colonies. Of the two class I major histocompatibility complex probes, both showed a lack of polymorphism within colonies, while one revealed a single difference in the restriction fragment pattern between one colony and the other three. This probe also revealed a possible variation in copy number of genes in some individuals. The lack of bands on the restriction fragment pattern also indicated that the naked mole-rat has few genes homologous to the class I major histocompatibility complex of the mouse. The absence of variability in naked mole-rat DNA in these normally highly polymorphic loci suggests that these animals are highly inbred, and that there may be little or no genetic diversity within and between closely neighbouring colonies in the wild. Summary DNA from 20 individuals from four wild colonies of naked mole-rats, Heterocephalus glaber, were analysed for restriction fragment length polymorphism of class I major histocompatibility complex genes and minisatellite DNA, both of which have been shown to be highly variable between individuals in other species. The minisatellite probe employed in this study revealed limited polymorphism in the DNA of naked mole-rats, both within and between neighbouring colonies. Of the two class I major histocompatibility complex probes, both showed a lack of polymorphism within colonies, while one revealed a single difference in the restriction fragment pattern between one colony and the other three. This probe also revealed a possible variation in copy number of genes in some individuals. The low numbers of bands on the restriction fragment pattern also indicated that the naked mole-rat MHC I, in contrast to that of other mammalian species, may contain relatively few genes homologous to the class I major histocompatibility complex of the mouse. The absence of variability in naked mole-rat DNA in these normally highly polymorphic loci suggests that there may be little or no genetic diversity either within or between closely neighbouring colonies of naked mole-rats in the wild. The lack of polymorphism in the MHC I questions its possible role in individual odour recognition in this species of rodent.