| Summary: | In bovine, early embryonic mortality (EEM) results in low reproductive
efficiency, the major cause for which is believed to be impaired development of the
embryo, but mechanisms involved therein remain poorly understood. A lack of
progesterone support from the corpus luteum (CL) also contributes to EEM. Recent
studies demonstrate that regulated expression of distinct cadherins that mediate Ca²⁺ -
dependent cell-cell adhesion and ADAMTS (a disintegrin and metalloproteinase with
thrombospondin motifs) subtypes involved in cell-matrix interactions, and steroid
receptors mediate important cellular events underlying the formation and organization of
tissues, however, their role in preimplantation embryogenesis is poorly characterized.
Understanding genes involved in the blastocyst and CL formation provides interesting
possibilities in improving embryo viability. To address these issues, investigations into
the expression of cadherins, ADAMTS, estrogen and progesterone receptor isoforms
during the preimplantation embryogenesis in bovine embryos at timed stages of
development has been undertaken, using reverse transcription-polymerase chain reaction
(RT-PCR) or immunohistochemistry strategies. In addition, expression of ADAMTS
subtypes in ovarian follicles and CL has also been characterized. These studies indicate
that multiple cadherins, both type 1 (E-, N - and P-Cad) and type 2 (cad-8, -10 and -11),
with their specific localizations, at least in part, provide the molecular basis for the
formation and organization of the inner cell mass and the trophectoderm. The differential
mRNA and protein expression of steroid receptor isoforms (ERα, ERβ, PRA and PRB)
suggests distinct role(s) during early embryogenesis and provides evidence for direct
effect of steroids on the embryo. The regulated but complex expression of ADAMTS
subtypes both in the embryo (ADAMTS-1, -4, -5, -6, -8, -9, -10, but not ADAMTS-2, -3,
-7 or -12) and the ovary (ADAMTS-1, -2, -3, -4, -5, -7, -8, -9, but not ADAMTS-6, -10
or -12) suggests that these proteinases could be involved in cell-matrix interactions and
contributing towards important cellular events like cell migration, differentiation and
remodeling of the extracellular matrix. Though, the biological significance of these
molecules remains unclear, these studies demonstrate that novel cellular molecules
involved in cell-cell, cell-matrix and steroid interactions could be playing a key role
during developmental processes like embryogenesis and/or CL formation. === Land and Food Systems, Faculty of === Graduate
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