Homeobox genes seem to
play critical
roles in regulating
morphogenesis, patterning,
organogenesis, and differentiation. They have the
conserved sequence that
codes the
DNA-binding domain called homeodomain. The expression and cellular
localization of rPsx
mRNA in
rat placenta during
placental development were examined by
in situ hybridization histochemistry at different embryonic stages (Embryonic days 7.5~16.5). rPsx
mRNA was first detected in chorionic
ectoderm of
placenta at E 10.5. This transcript was localized in
labyrinth trophoblast and
trophoblast giant cells at E 11.5. Hybridization signals were observed in
labyrinth trophoblast, spongiotrophoblast, and
trophoblast giant cells at E 12.5, E 13.5, and E 14.5. At E 15.5, hybridization signal was detected in
labyrinth trophoblast and spongiotrophoblast but not in
trophoblast giant cells. Hybridization signal was only detected in
labyrinth trophoblast at E 16.5. rPsx
mRNA was not detected in
decidua and any
tissues of the
embryo from E 7.5 to E 9.5 of gestations. From these results, a new rPsx
homeobox gene is first expressed at E 10.5 and detected in chorionic
ectoderm,
labyrinth trophblast, spongiotrophoblast and
trophoblast giant cells of the
placenta. This
gene may
play a critical
role in differentiation and development of
trophoblast cells.