Experimental and Bioinformatic upgrade for genome-wide mapping of nucleosomes in Trypanosoma cruzi

We adapted the widely used digestion of chromatin with micrococcal nuclease (MNase) followed by deep sequencing to the parasite Trypanosoma cruzi, which presents numerous singularities. In this work, we use the hybrid CL Brener strain carrying two set of chromosomes from two substantially different parental strains. The hybrid strain CL Brener is composed of the Esmeraldo-like and non Esmeraldo-like haplotypes. Additionally, part of the genome was not assembled into any of the haplotypes. Sometimes the community working in the field uses just one haplotype as reference genome for simplicity. In this work, we emphasize the importance of using its whole genome as a reference. Moreover, we extended our analysis to a clonal strain, Sylvio-X10. Overall design: We mapped nucleosomes genome wide from exponentially growing epimastigotes of the Cl Brener and Sylvio-X10 strains. An exhaustive and thorough computational workflow was developed for data analysis, highlighting the relevance of using its whole genome as a reference instead of the commonly used Esmeraldo-like haplotype. Moreover, the performance of two aligners, Bowtie2 and HISAT2 was tested to find the most appropriate tool to map any genomic read to reference genomes bearing this complexity.