The following statements were made regarding cell fate specification of trophoblast and inner cell mass (ICM) during mammalian embryogenesis:
A. Oct4 represses Cdx2 expression, enabling some cells to become ICM.
B. Cdx2 synthesized by the trophoblast cells activates Oct4 and Nanog.
C. Expression of Nanog allows cells of the ICM to retain their pluripotency.
D. YAP binds to TEAD4 and represses Cdx2 in the trophoblast cells.
Which one of the following options correctly represents events that determine the fate of trophoblasts and ICM?

Correct option is D

Correct Answer:
(d) A and C
Explanation:
During early mammalian development, Oct4 promotes ICM fate by repressing Cdx2, which is required for trophoblast specification (A correct).
Nanog expression is essential for maintaining pluripotency of ICM cells (C correct).
In contrast, Cdx2 represses Oct4 and Nanog, not the other way around, and YAP–TEAD4 activates (not represses) Cdx2 in trophoblasts.
Information Booster :
· The first cell fate decision separates trophoblast from ICM.
· ICM fate is maintained by pluripotency factors Oct4, Sox2, and Nanog.
· Trophoblast fate depends on Cdx2 activation via Hippo signaling.
· Proper repression and activation of these factors ensure lineage segregation.
Additional Information (Incorrect Options):
Statement B: Incorrect—Cdx2 represses, rather than activates, Oct4 and Nanog.
Statement D: Incorrect—YAP binding to TEAD4 activates Cdx2, driving trophoblast fate.
Therefore, options including B or D are incorrect.