Mrm2, also known as RRMJ2 and encoded by FTSJ2, is a mitochondrial methyltransferase. It is involved in the modification of nucleotides in the 16S rRNA A-loop, an essential part of the peptidyl transferase center, and is crucial for the biogenesis and function of the large subunit of the mitochondrial ribosome [2]. Defects in Mrm2 can disrupt mitochondrial translation, which is essential for oxidative phosphorylation [2]. Yeast models have been valuable in studying Mrm2-related functions and mutations [4,5].

In human studies, variants in Mrm2 have been associated with various disorders. In two families, DYAF11 and M, with dystonic or involuntary movement disorders, specific Mrm2 variants were identified. In Family DYAF11, a donor splice-site variant c.8 + 1G>T led to an aberrant alternative acceptor splice-site usage in a subset of transcripts, causing a frameshift. In Family M, a missense variant c.242C>T (p.(Ala81Val)) affected a conserved amino acid [1]. Additionally, a 7-year-old boy with a MELAS-like syndrome was found to have a damaging mutation c.567G>A (p.Gly189Arg) in Mrm2 [3]. Knockout yeast models for the orthologous gene showed respiration defects and reduced 2'-O-methyl modification at the equivalent position in yeast mitochondrial 21S rRNA [3].

In conclusion, Mrm2 is essential for mitochondrial ribosome biogenesis and function through its role in 16S rRNA modification. Studies on Mrm2, especially using yeast models as a research model, have revealed its association with complex dystonic syndromes and MELAS-like phenotypes, contributing to our understanding of the molecular mechanisms underlying these diseases.