1996 Fiscal Year Final Research Report Summary
Origin and Evolution of MHC
| Project/Area Number |
07044288
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | Nagoya City University |
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Principal Investigator |
NONAKA Masaru Nagoya City University, Medical School, Associate Professor, 医学部, 助教授 (40115259)
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| Co-Investigator(Kenkyū-buntansha) |
OZAKI Yasuhiko Nagoya City University, Medical School, Research Associate, 医学部, 助手 (50254280)
CAMPBELL R.Duncan University of Oxford, MRC,Special Appointment Grade, MRC, Special Ap
FLAJNIK Martin University of Miami, School of Medicine, Professor, 医学部, 教授
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| Project Period (FY) |
1995 – 1996
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| Keywords | MHC / complement / lower vertebrate / evolution |
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| Research Abstract |
The major histocompatibility complex (MHC), best described in mammals, is a large genetic region encompassing more than 4000kb in human. The Xenopus MHC is known to be remarkably similar to its mammalian counterparts. Class Ia, class IIa, class IIb, complement Bf, C4, heat shock protein 70 (HSP70), the proteasome subunit LMP7 genes all map to the Xenopus MHC,demonstrating that the overall organization and the basic genetic components were present at the time of the divergence of amphibians and mammals 300-350 million years ago. Furthermore, I detected a recombinant in previous family studies that demonstrated that the Xenopus LMP7/class II genes could be separated from the Bf/HSP70/class I suggesting that even the gene order is similar to that of mammals.
I found a second recombinant in another family where class II/LMP7/C4/class I genes cosegregate away from the Bf/HSP70 loci. Barring a double crossover, this recombinant implies that the class Ia gene is physically associated with the Xenopus class II region. This result is gratifying since the class I processing genes are found in the class II region in all species so far examined, and because class I and class II genes clearly have been derived from a common ancestor. An association with class II/III regions also may explain the remarkably deep and stable MHC-linked class I lineage in Xenopus ; I predict that the translocation of class I to the distal end of the MHC later in vertebrate evolution bestowed on class I genes the capacity to duplicate and diverge, hence giving rise to the celebrated class I plasticity found in mammals.
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