Sequence analysis of mouse mitochondrial chloramphenicol-resistant mutants

Area of Science:

• Mitochondrial genetics
• Molecular biology
• Genomics

Background:

• Mitochondrial DNA (mtDNA) mutations can lead to drug resistance and cellular dysfunction.
• Chloramphenicol resistance (CAP-R) is a key phenotype studied in mitochondrial genetics.
• Understanding the molecular basis of CAP-R is crucial for deciphering mitochondrial gene function.

Purpose of the Study:

• To determine the specific nucleotide sequence changes in the mitochondrial 16S rRNA gene of mouse CAP-R mutants.
• To investigate the relationship between these mutations and the observed CAP-R phenotype.
• To elucidate the functional consequences of these mutations within the ribosomal RNA peptidyltransferase domain.

Main Methods:

• DNA sequencing of the 3' halves of mitochondrial 16S rRNA genes from four independent mouse CAP-R mutants.
• Analysis of nucleotide base changes and their locations within the rRNA gene.
• Assessment of heteroplasmy in mtDNA populations.

Main Results:

• Four distinct single-nucleotide changes were identified in the 16S rRNA genes of the CAP-R mutants.
• Mutations included G-to-A transitions, an A-to-T transversion, and a T-to-C transition at specific nucleotide positions.
• Three mutants exhibited heteroplasmy, with both wild-type and mutant mtDNA copies present.
• All identified mutations are located within the ribosomal RNA peptidyltransferase domain.

Conclusions:

• Specific single base changes in the mitochondrial 16S rRNA gene are responsible for chloramphenicol resistance in mice.
• These mutations, located in the peptidyltransferase domain, explain the pleiotropic effects observed in CAP-R mutants, including partial respiration deficiency.
• The findings provide molecular insights into mammalian mitochondrial drug resistance and its associated cellular phenotypes.