Chromosomal localization of Cd1d genes in the mouse

Analysis of the genomic structure of the porcine CD1 gene cluster

CD1 is an MHC class I-like protein that presents lipid antigens to T cell receptors. We determined 470,187 bp of the genomic sequence encompassing the region encoding porcine CD1 genes. We identified 16 genes in this region and newly identified CD1A2, CD1B, CD1C, CD1D, and CD1E. Porcine CD1 genes were located in clusters between KIRREL and olfactory receptor (OR) genes, as observed in humans, although they were divided into two regions by a region encoding OR genes. Comparison of the genomic sequences of CD1 gene loci in pigs with other mammals showed that separation of the CD1 gene cluster by ORs was observed only in pigs. CD1A duplication in the porcine genome was estimated to have occurred after the divergence of the human and porcine. This analysis of the genomic sequence of the porcine CD1 family will contribute to our understanding of the evolution of mammalian CD1 genes.

The molecular biology of CD1

CD1 were the first human differentiation antigens to be identified by monoclonal antibodies. In this review, we summarize some key results from the molecular study of CD1, with particular reference to their relationship to MHC antigens, and to the existence of two distinct groups of CD1 molecules.

Genomics, Isoforms, Expression, and Phylogeny of the MHC Class I-Related MR1 Gene

A growing number of non-MHC-encoded class I-related molecules have been shown to perform diverse, yet essential, functions. These include T cell presentation of bacterially derived glycolipidic Ags by CD1, transcytosis of maternal IgG by the neonatal Fc receptor, enriched presence and plausible function within exocrine fluids of the Zn-α2-glycoprotein, subversion of NK cytolytic activity by the CMV UL18 gene product, and, finally, crucial involvement in iron homeostasis of the HFE gene. A recently described member of this family is the MHC class-I related (MR1) gene. The most notable feature of MR1 is undoubtedly its relatively high degree of sequence similarity to the MHC-encoded classical class I genes. The human chromosome 1q25.3 MR1 locus gives rise not only to the originally reported 1,263-bp cDNA clone encoding a putative 341-amino acid polypeptide chain, but to many additional transcripts in various tissues as well. Here we define the molecular identity of all human and murine MR1 isoforms generated through a complex scenario of alternative splicing, some encoding secretory variants lacking the Ig-like α3 domain. Moreover, we show ubiquitous transcription of these MR1 variants in several major cell lineages. We additionally report the complete 18,769-bp genomic structure of the MR1 locus, localize the murine orthologue to a syntenic segment of chromosome 1, and provide evidence for conservation of a single-copy MR1 gene throughout mammalian evolution. The 90% sequence identity between the human and mouse MR1 putative ligand binding domains together with the ubiquitous expression of this gene favor broad immunobiologic relevance.

Two Mhc class I and two Mhc class II genes map to the chicken Rfp-Y system outside the B complex

Gene sequences highly similar to major histocompatibility complex (Mhc) class I and class II genes were recently recognized as mapping to a site in the genome of the chicken separate from the Mhc class I, class II, and B-G genes of the major histocompatibility (B) complex. The present study was undertaken to see whether this complex of Mhc-like genes designated as restriction fragment pattern Y (Rfp-Y) might reside in one of three clusters of cosmid clones contained within the molecular map of chicken Mhc genes, since only two of the three clusters can be assigned to the B system. To determine whether the third cluster (cluster II/IV) might contain Rfp-Y, a subclone (18.1) from within cluster II/IV near a polymorphic lectin gene was used to analyze the DNA of families in which Rfp-Y haplotypes are known to be segregating. The restriction fragment polymorphisms revealed by the 18.1 probe were found to segregate in parallel with the restriction fragment polymorphisms defining the Rfp-Y haplotypes, thus establishing the location of Rfp-Y within cosmid cluster II/IV. Two of six Mhc class I genes and two of five Mhc class II genes map to cosmid cluster II/IV, so a substantial fraction of chicken Mhc genes, including at least one that may be expressed, are located in a chromosomal region separate from the B system. In further linkage analyses, Rfp-Y was found to assort independently from more than 400 markers in the present linkage map of the chicken genome.