Novel insertions in the mitochondrial maxicircle of <i>Trypanosoma musculi</i>, a mouse trypanosome.

<i>Trypanosoma musculi</i> is a, globally distributed, mouse-specific haemoflagellate, of the family Trypanosomatidae, which shares similar characteristics in morphology with <i>Trypanosoma lewisi</i>. The kinetoplast (mitochondrial) DNA of Trypanosomatidae flagellates is comprised of catenated maxicircles and minicircles. However, genetic information on the <i>T. musculi</i> kinetoplast remains largely unknown. In this study, the <i>T. musculi</i> maxicircle genome was completely assembled, with PacBio and Illumina sequencing, and the size was confirmed at 34 606 bp. It consisted of 2 distinct parts: the coding region and the divergent regions (DRs, DRI and II). In comparison with other trypanosome maxicircles (<i>Trypanosoma brucei</i>, <i>Trypanosoma cruzi</i> and <i>T. lewisi</i>), the <i>T. musculi</i> maxicircle has a syntenic distribution of genes and shares 73.9, 78.0 and 92.7% sequence identity, respectively, over the whole coding region. Moreover, novel insertions in <i>MURF2</i> (630 bp) and in <i>ND5</i> (1278 bp) were found, respectively, which are homologous to minicircles. These findings support an evolutionary scenario similar to the one proposed for insertions in <i>Trypanosoma cruzi</i>, the pathogen of American trypanosomiasis. These novel insertions, together with a deletion (281 bp) in <i>ND4</i>, question the role of Complex I in <i>T. musculi</i>. A detailed analysis of DRII indicated that it contains numerous repeat motifs and palindromes, the latter of which are highly conservative and contain A₅C elements. The comprehensively annotated kinetoplast maxicircle of <i>T. musculi</i> reveals a high degree of similarity between this parasite and the maxicircle of <i>T. lewisi</i> and suggests that the DRII could be a valuable marker for distinguishing these evolutionarily related species.