Didelphis albiventris: an overview of an unprecedented transcriptome sequencing of the white-eared opossum

Abstract

Background The white-eared opossum (Didelphis albiventris) is widely distributed throughout Brazil and South America. They have been used as animal models to study different aspects in science, from the restoration of degraded green areas to medical aspects of the Chagas disease, leishmaniasis and resistance against snake venom. As a marsupial, D. albiventris can also aid the comprehension of the molecular mechanisms that govern the different stages of organogenesis, as their joeys are born after only 13 days, depending on placentation, and the final stages of organogenesis occurs when the neonates are inside the pouch, depending on lactation. As the genome of this opossum species, and/or its transcriptome, had not been completely sequenced yet, the use of D. albiventris as an animal model is limited. In this work, we have sequenced the D. albiventris transcriptome, by RNA-seq, to obtain the first catalogue of differentially expressed genes (DE) and gene ontology (GO) annotation during the neonatal stages of the marsupial development. Results The D. albiventris transcriptome was obtained from whole neonates harvested at birth (P0), at five days old (P5) and ten days old (P10). The de novo assembly of these transcripts allowed us to obtain 85,338 transcripts. Only ~30% of these transcripts could be mapped against M. domestica genome, the closest phylogenetic relative with available nucleotide sequences. Among the expressed transcripts, 2,077 were found to be DE between P0 and P5, 13,780 between P0 and P10, and 1,453 between P5 and P10. Enriched GO terms were mainly related to immune system, blood tissue development and differentiation, vision, hearing, digestion, CNS and limb development. Conclusions The unveiling of opossum transcriptomes provides an out-group to better understand the distinct characteristics associated with the evolution of mammalian species. Nevertheless, this is the first transcriptome sequencing and available catalogue of genes of a marsupial species at different neonatal stages, allowing the study of mechanisms involved in the organogenesis.