Disruption and pseudoautosomal localization of the major histocompatibility complex in monotremes

Juliane C Dohm,Frank Grützner,Heinz Himmelbauer,Richard Reinhardt,Enkhjargal Tsend-Ayush

doi:10.1186/gb-2007-8-8-r175

Abstract

The characterization and chromosomal mapping of major histocompatibility complex (MHC)-containing BAC clones from platypus and the short-beaked echidna reveals new insights into the evolution of both the mammalian MHC and monotreme sex chromosomes.

Highlights

The monotremes, represented by the duck-billed platypus and the echidnas, are the most divergent species within mammals, featuring a flamboyant mix of reptilian, mammalian and specialized characteristics
The same is true for the three other human class I gene clusters and their counterparts in other eutherian genomes, all of which locate at the same position, that is, are flanked by the same framework genes, even though not all of them contain active class I gene loci
Identification of BAC clones from the platypus and echidna major histocompatibility complex (MHC) We identified bacterial artificial chromosome (BAC) clones from the platypus MHC by hybridization with oligonucleotide probes designed from the platypus class I gene Oran2-1 [16], the class II gene DZB [17], and from the MHC framework genes Bat1 and Pou5f1 encoding a DEAD-Box helicase and a stem cell transcription factor, respectively

Summary

Introduction

The monotremes, represented by the duck-billed platypus and the echidnas, are the most divergent species within mammals, featuring a flamboyant mix of reptilian, mammalian and specialized characteristics. The central framework gene region, located between the class II region and the class I region that encodes the HLA-B and HLA-C genes in human, is known as the class III region (flanked by the genes Btnl and Bat1/Mccd; Figure 1a) This genomic architecture of MHC regions is remarkably well conserved in eutherian mammals. The position of the human HLA-B,C class I gene cluster matches rat RT1-CE, mouse H2-D,L,Q, swine SLA6,7,8 and ovine β [4,5,6,7,8] In each of these species, this particular class I gene block is flanked by the Bat1/Mccd and Pou5f1 framework genes. The fact that only certain positions of the MHC support 'homing' of class I genes has previously been recognized and is known as the framework hypothesis [9]

Methods

Results

Discussion

Conclusion