Structure of wild-type and mutant mouse beta 2-microglobulin genes

Area of Science:

• Immunogenetics
• Molecular Biology

Background:

• Beta 2-microglobulin (B2M) is a crucial component of the MHC class I complex.
• Its genetic organization in mice shares similarities with H-2 and immunoglobulin domains.

Purpose of the Study:

• To investigate the genetic basis for the loss of cell-surface antigen expression in a mutant mouse cell line.
• To analyze the molecular defects underlying the absence of beta 2-microglobulin and H-2 expression.

Main Methods:

• Gene cloning and sequencing of the mouse beta 2-microglobulin gene.
• Analysis of a mutant cell line using Southern blot hybridization.
• Assessing cell-surface expression of thymus leukemic antigen, beta 2-microglobulin, and H-2.

Main Results:

• The mouse beta 2-microglobulin gene comprises four coding regions and three intervening sequences.
• A mutant cell line exhibited no detectable cytoplasmic beta 2-microglobulin.
• Southern blot analysis indicated defects in both copies of the beta 2-microglobulin gene in the mutant cells.

Conclusions:

• Genetic defects within the beta 2-microglobulin locus are responsible for the observed loss of multiple cell-surface antigens.
• This study links the concomitant loss of thymus leukemic antigen, beta 2-microglobulin, and H-2 to mutations in the beta 2-microglobulin gene.