The Major Histocompatibility Complex of Frogs

Flainik, Martin F.; Pasquier, Louis Du

doi:10.1111/j.1600-065x.1990.tb00036.x

Cited by 51 publications

(25 citation statements)

References 52 publications

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“…However, the functional Xenopus MHC loci have been diploidized, (Du Pasquiet et al 1977;Du Pasquier and Blomberg 1982). The reasons and mechanisms for the silencing of MHC loci in polyploid animals are not known, but there seems to be a selective pressure to maintain a low number of expressed functional MHC genes, not only in Xenopus but in all vertebrates (Flajnik and Du Pasquier 1990;Nowak et al 1992); individuals have few functional MHC genes but each species possesses, instead, many polymorphic alleles. Two opposing pressures may determine why the MHC is multi-alMic rather than multigenic, in spite of the fact that one might expect to have many expressed MHC loci to diversify the T-cell repertoire during positive selection (von Boehmer 1992) and to allow presentation of a large array of peptides derived from pathogens.…”

Section: Resultsmentioning

confidence: 99%

“…1989;Wurst et al 1989;Gaskins et al 1990;Cameron et al 1990;Milner and Campbell 1991), and because HSP70 has been implicated in antigen processing and presentation and may have a peptide-binding region homologous to the MttC class I, we investigated whether the MHC and Hsp70 gene families are linked in Xenopus. This amphibian is a suitable model with which to perform such linkage studies, since the MHC has been well defined at the functional, biochemical, and genetic levels (Flajnik and Du Pasquier 1990). By carrying out these mapping studies, we hoped to establish a minimal estimate of the age of the physical association between MHC class I and class II genes and Hsp70 genes.…”

Section: Introductionmentioning

confidence: 99%

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Hsp70 genes are linked to the Xenopus major histocompatibility complex

1994

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Some of the inducible forms of the heat shock protein 70 (Hsp70) gene family are encoded in the class III region of the major histocompatibility complex (MHC) of mammals. This study was undertaken to determine whether Hsp70 genes are linked to the MHC of Xenopus, an amphibian last sharing a common ancestor with mammals 300-350 million years ago. Segregation analyses involving seven haplotypes demonstrated the linkage of two or three inducible Hsp70 genes to the frog MHC. Another Hsp70 gene is not closely linked to the MHC. We conclude that the physical association of MHC class I and class II genes with Hsp70 genes is ancient.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hsp70 genes are linked to the Xenopus major histocompatibility complex

1994

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“…The Xenopus MHC is remarkably similar to its mouse and human counterparts (8). Classes Ia (9), II␤ (10), and class II␣ (ref.…”

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confidence: 99%

Major histocompatibility complex gene mapping in the amphibianXenopusimplies a primordial organization

Nonaka

Namikawa

Kato

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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One of the most provocative recent discoveries in immunology was the description of a genetic linkage in the major histocompatibility complex (MHC) between structurally unrelated genes whose products are involved in processing and presentation of antigens for recognition by T lymphocytes. Genes encoding MHC class I molecules, which bind and present at the cell surface proteolytic fragments of cytosolic proteins, are linked to nonhomologous genes whose products are involved in the production and subsequent transfer of such fragments into the endoplasmic reticulum. In mammals, the class I presentation and processing genes are found in different regions of the MHC. To examine the evolutionary origins of this genetic association, linkage studies were carried out with Xenopus, an amphibian last sharing an ancestor with mammals over 350 million years ago. In contrast to mammals, the single copy Xenopus class I gene is located between the class II and III regions, speculated to be in close linkage with the processing and transport genes. In addition to suggesting a primordial organization of genes involved in class I antigen presentation, these linkage studies further provide insight into the origins of the MHC class III region and the phenomenon of class I gene instability in the mammalian MHC.

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“…13). (i) Tadpoles, although immunocompetent, do not display cell-surface expression of MHC class I until metamorphosis; class II molecules, in contrast, are expressed at all stages of life albeit with a different tissue distribution (14,15).…”

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Evolution of the major histocompatibility complex: molecular cloning of major histocompatibility complex class I from the amphibian Xenopus.

Flajnik

Canel

Kramer

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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Class I major histocompatibility complex (MHC) cDNA clones have been isolated from an expression library derived from mRNA of an MHC homozygous Xenopus laevis. The nucleotide and predicted amino acid sequences show definite similarity to MHC class I molecules of higher vertebrates. The immunoglobulin-like a-3 domain is more similar to the immunoglobulin-like domains of mammalian class II (3 chains than to those of mammalian class I molecules, and a tree based on nucleotide sequences of representative MHC genes is presented.

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The Major Histocompatibility Complex of Frogs

Cited by 51 publications

References 52 publications

Hsp70 genes are linked to the Xenopus major histocompatibility complex

Hsp70 genes are linked to the Xenopus major histocompatibility complex

Major histocompatibility complex gene mapping in the amphibianXenopusimplies a primordial organization

Evolution of the major histocompatibility complex: molecular cloning of major histocompatibility complex class I from the amphibian Xenopus.

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