Maternally transmitted histocompatibility antigen of mice: a hydrophobic peptide of a mitochondrially encoded protein

Area of Science:

• Immunology
• Genetics
• Cell Biology

Background:

• Maternal factors (MTF) are maternally inherited antigens.
• MTF is believed to be encoded by mitochondrial genes.
• Previous research suggested MTF's role as a minor histocompatibility antigen.

Purpose of the Study:

• To investigate the genetic basis of MTF variations.
• To determine the specific gene and protein responsible for MTF.
• To understand the mechanism of MTF presentation to cytotoxic T cells.

Main Methods:

• Sequencing of entire mitochondrial genomes from four MTF strains (Mtf alpha, Mtf beta, Mtf gamma, Mtf delta).
• Comparative sequence analysis to identify genetic variations.
• Synthetic peptide incubation assays with target cells and cytotoxic T cells (CTLs).

Main Results:

• A single nucleotide polymorphism was found in the ND1 gene, affecting amino acid 6 of the ND1 protein across all four strains.
• Synthetic peptides corresponding to the variable ND1 region induced target cell lysis by strain-specific CTLs.
• This allelic variation in ND1 protein is directly responsible for MTF.

Conclusions:

• MTF is caused by allelic variation in the mitochondrially encoded ND1 protein.
• Cells can present peptides derived from mitochondrial proteins as histocompatibility antigens.
• This finding provides a molecular basis for understanding MTF and its role in immune responses.