Mitochondrial DNA Structure in Trypanosoma cruzi

Abstract

Kinetoplastids display a single, large mitochondrion per cell, with their mitochondrial DNA referred to as the kinetoplast. This kinetoplast is a network of concatenated circular molecules comprising a maxicircle (20-64 kb) and up to thousands of minicircles varying in size depending on the species (0.5-10 kb). In Trypanosoma cruzi, maxicircles contain typical mitochondrial genes found in other eukaryotes. They consist of coding and divergent/variable regions, complicating their assembly due to repetitive elements. However, next-generation sequencing (NGS) methods have resolved these issues, enabling the complete sequencing of maxicircles from different strains. Furthermore, several insertions and deletions in the maxicircle sequences have been identified among strains, affecting specific genes. Unique to kinetoplastids, minicircles play a crucial role in a particular U-insertion/deletion RNA editing system by encoding guide RNAs (gRNAs). These gRNAs are essential for editing and maturing maxicircle mRNAs. In Trypanosoma cruzi, although only a few studies have utilized NGS methods to date, the structure of these molecules suggests a classification into four main groups of minicircles. This classification is based on their size and the number of highly conserved regions (mHCRs) and hypervariable regions (mHVRs).

Keywords: Trypanosoma cruzi; kinetoplast; maxicircles; minicircles.

Figure 1

The architecture of the T. cruzi maxicircle. The coding region (CR), AT-rich, short-repeat region, and long-repeat region are shown, according to Berná et al., [33] as well as the genes of the CR: green for the ribosomal genes, blue for the genes in the negative strand, and brown for the genes in the positive strand.

Figure 2

Architecture of the minicircles of TcI and TcII strains of T. cruzi. Minicircle groups 1–4 of sizes are shown, along with their ranges, according to the data of Callejas-Hernández et al. [32] and Gómez-Palacio et al. [57]. mHCRs: highly conserved regions (green). mHVRs: hypervariable regions (grey). bp = base pairs.