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- Title
Major Histocompatibility Complex Genes Map to Two Chromosomes in an Evolutionarily Ancient Reptile, the Tuatara Sphenodon punctatus.
- Authors
Miller, Hilary C.; O'Meally, Denis; Ezaz, Tariq; Amemiya, Chris; Marshall-Graves, Jennifer A.; Edwards, Scott
- Abstract
Major histocompatibility complex (MHC) genes are a central component of the vertebrate immune system and usually exist in a single genomic region. However, considerable differences inMHCorganization and size exist between different vertebrate lineages. Reptiles occupy a key evolutionary position for understanding how variation in MHC structure evolved in vertebrates, but information on the structure of the MHC region in reptiles is limited. In this study, we investigate the organization and cytogenetic location of MHC genes in the tuatara (Sphenodon punctatus), the sole extant representative of the early-diverging reptilian order Rhynchocephalia. Sequencing and mapping of 12 clones containing class I and IIMHCgenes from a bacterial artificial chromosome library indicated that the coreMHCregion is located on chromosome 13q. However, duplication and translocation ofMHC genesoutsideof thecore regionwasevident,because additional class IMHCgeneswerelocatedonchromosome4p. Wefound a total of seven class I sequences and 11 class II b sequences,with evidence for duplication and pseudogenization of genes within the tuatara lineage. The tuataraMHC is characterized by high repeat content and low gene density compared with other species and we found no antigen processing or MHC framework genes on the MHC gene-containing clones.Our findings indicate substantial differences in MHC organization in tuatara compared with mammalian and avian MHCs and highlight the dynamic nature of the MHC. Further sequencing and annotation of tuatara and other reptile MHCs will determine if the tuatara MHC is representative of nonavian reptiles in general.
- Subjects
REPTILES; MAJOR histocompatibility complex; COMPARATIVE genomics
- Publication
G3: Genes | Genomes | Genetics, 2015, Vol 5, Issue 7, p1439
- ISSN
2160-1836
- Publication type
Article
- DOI
10.1534/g3.115.017467