Related Experiment Videos
Evolution of the Mhc class I region: the framework hypothesis.
1Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235-9050, USA. amadou@utsw.swmed.edu
Immunogenetics
|March 18, 1999
Summary
The human and mouse major histocompatibility complex (Mhc) regions show conserved gene frameworks but divergent class I gene sequences. This suggests Mhc evolution occurs within a stable gene framework, allowing independent class I sequence evolution.
Area of Science:
- Comparative genomics
- Evolutionary biology
- Immunogenetics
Background:
- The major histocompatibility complex (Mhc) is crucial for immune responses.
- Comparing the Mhc regions of different species aids in understanding its evolution.
- Previous comparisons were limited by focusing solely on Mhc class I genes.
Purpose of the Study:
- To compare the Mhc regions of humans and mice.
- To investigate the evolutionary stability and divergence of Mhc regions.
- To propose a model explaining the observed patterns of Mhc evolution.
Main Methods:
- Comparative mapping of the Mhc region in humans and mice.
- Identification and analysis of both Mhc class I and non-class I genes.
- Phylogenetic analysis of Mhc gene sequences.
Main Results:
- Mhc class II and III regions are highly conserved (orthologous) between humans and mice.
- Mhc class I genes are paralogous and have undergone significant reorganization.
- A comparative map reveals homologous locations for non-orthologous class I sequences, framed by conserved genes.
Conclusions:
- Conserved genes form a 'framework' limiting Mhc region alterations.
- Homologous positions for class I genes represent 'permissive sites' for evolutionary change.
- Independent evolution of Mhc class I sequences occurs within this framework via duplication and deletion.