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Composition of marsupial zona pellucida: a molecular and phylogenetic approach.
The zona pellucida (ZP) is an extracellular matrix that surrounds mammalian oocytes. In eutherians, it is formed from three or four proteins (ZP1, ZP2, ZP3, ZP4). In the few marsupials that have been studied, however, only three of these have been characterised (ZP2, ZP3, ZP4). Nevertheless, the composition in marsupials may be more complex, since recently a duplication of the ZP3 gene was described in one species. The aim of this work was to elucidate the ZP composition in marsupials and relate it to the evolution of the ZP gene family. For that, an in silico and/or molecular analysis was undertaken, focusing on two South American species (gray short-tailed opossum and common opossum), and four Australian species (brushtail possum, koala, Bennett’s wallaby, Tammar wallaby and Tasmanian devil). This analysis identified the presence of ZP1 mRNA and mRNA from two or three paralogs of ZP3 in marsupials. Furthermore, evidence for ZP1 and ZP4 pseudogenes in the South American subfamily Didelphinae, and for ZP3 pseudogenes in two marsupials, is provided. In conclusion, two different composition models are proposed for marsupials: a model with four proteins (ZP1, ZP2 and ZP3 (two copies)) for the South American species and a model with six proteins (ZP1, ZP2, ZP3 (three copies) and ZP4) for the Australasian species.
RD16519 Accepted 20 September 2017
© CSIRO 2017