The placenta is a specialized temporary fetal organ that is
requisite for fetal growth and development in eutherian mammals
and is crucial for a successful pregnancy. Early in pregnancy the
placenta is responsible for implantation, anchoring of the embryo
into the uterine wall, and producing hormones that initiate
maternal recognition of pregnancy. Throughout gestation, placental
development proceeds via an elegantly orchestrated regulation of
trophoblast invasion, proliferation and differentiation, as well as,
vasculogenesis and angiogenesis to ensure adequate blood supply
to support placental and fetal growth. Thereafter, the placenta
provides the sole conduit for transferring maternally derived nutrients
and gasses to the ever-demanding fetus.
Disruptions to placental development in the first half of pregnancy
and/or insufficient adaptive changes in the placenta in
response to maternal environment during the latter half of pregnancy
have been associated with a number of pregnancy
complications and compromised fetal outcomes. In this context,
defining placenta specific gene expression can contribute to the
understanding of placenta development and function. Unlike
microarrays, which have been the primary tool to-date to study
placental gene expression [1e4], RNA-seq allows digital quantitation
of gene expression data and hence allows assessment of relative
abundance between genes within and between samples. Here,
we set out to identify genes that are specific to human placenta
using deep sequencing technology in order to increase general
understanding of placental function and development.