Respiration Refined: Cells derive energy from redox reactions mediated by mitochondrial enzymes that form the electron transport chain. The enzymes can form large complexes, known as supercomplexes, whose function has been controversial. Lapuente-Brun et al. (p. 1567 ) discovered that a mouse protein, supercomplex assembly factor I (SCAFI), specifically modulates assembly of respiratory complexes into supercomplexes. Formation of the supercomplexes appears to cause electrons to be processed differently, depending on the substrate from which they are derived.

The existence of reliable mtDNA reference sequences for each species is of great relevance in a variety of fields, from phylogenetic and population genetics studies to pathogenetic determination of mtDNA variants in humans or in animal models of mtDNA‐linked diseases. We present compelling evidence for the existence of sequencing errors on the current mouse mtDNA reference sequence. This includes the deletion of a full codon in two genes, the substitution of one amino acid on five occasions and also the involvement of tRNA and rRNA genes. The conclusions are supported by: (i) the re‐sequencing of the original cell line used by Bibb and Clayton, the LA9 cell line, (ii) the sequencing of a second L‐derivative clone (L929), and (iii) the comparison with 12 other mtDNA sequences from live mice, 10 of them maternally related with the mouse from which the L cells were generated. Two of the latest sequences are reported for the first time in this study (Balb/cJ and C57BL/6J). In addition, we found that both the LA9 and L929 mtDNAs also contain private clone polymorphic variants that, at least in the case of L929, promote functional impairment of the oxidative phosphorylation system. Conse quently, the mtDNA of the strain used for the mouse genome project (C57BL/6J) is proposed as the new standard for the mouse mtDNA sequence.