Marsupial oocytes, fertilization and embryonic development can provide useful tools to study developmental mechanisms

Abstract

SummaryAn analysis of several features of marsupial oocytes and developmental stages from the zygote to the neonate shows the advantages of studying these to answer questions about mammalian development in general. Marsupials make good model systems providing that species have well established breeding and husbandry protocols, a detailed time table of embryonic development associated with appropriate monitoring to collect desired stages and an induced ovulation protocol to allow collection of normal oocytes and developmental stages. One of the specific features of marsupial development that would provide further insight into problems in mammalian development is distinct oocyte and/or zygote polarity. Additionally, because the conceptus is transparent, cell-cell associations can be studied until well after the hypoblast is formed. These combined features mean that lineage allocation and axis formation can be more easily studied and related to oocyte/ zygote polarity and the order of cell division in these conceptuses. Another feature is the ability to collect normal unattached embryonic and fetal stages in some species and to culture conceptuses from the primitive streak stage to within a few hours of birth. This ability means that stages of organogenesis in most organ systems are readily accessible without the complications of implantation.

Transcriptomic changes in the pre-implantation uterus highlight histotrophic nutrition of the developing marsupial embryo

“…In contrast, pre-implantation marsupial pregnancy has received much less attention, particularly from genetic studies, which have focused on the immunological changes in the uterus 15 , 18 . Understanding the complete physiology of pre-implantation marsupial pregnancy is important, because this period represents the majority of gestation, when the embryo is growing and undergoing early organogenesis 19 . The physiology of this period of mammalian pregnancy is an important area of medical research e.g.…”

Mammalian Reproduction Overview

“…Fertilization and embryonic development in marsupials show many differences from the same processes in the eutherian mammals; the main points of these differences are well summarized in two excellent reviews (Baggott, 1992;Selwood, 2007). Marsupial oocytes are much larger (150-200 mm diameter) than those of the eutherians (typically about 100 mm diameter), and after fertilization the zygotes exhibit visible polarity as an early indication of embryonic cell commitment.…”