Based on the above figure, which one of the following assumptions is correct?
(1) The interplay between Cdx2 and Oct4 can influence the formation of ICM
(2) The ICM would form even if expression of Oct4 was inhibited.
(3) YAP and TEAD4 are upstream components of Cdx2 and can be inhibited by Nanog.
(4) The expression of Stat3 is optional for maintaining pluripotency of the ICM.

The fate determination that occurs early in mammalian development—whether a blastomere becomes trophoblast or inner cell mass (ICM)—is critically influenced by the expression and interaction of the transcription factors Cdx2 and Oct4. Both molecules are initially present in embryonic cells but become differentially restricted as development proceeds, shaping lineage specification.

Research details that Cdx2 and Oct4 act as mutual repressors: high Cdx2 levels inhibit Oct4 to promote trophoblast differentiation, while sustained Oct4 expression is vital for ICM formation and pluripotency. Their antagonistic regulatory relationship serves as an embryonic switch, guiding blastomeres toward their eventual fate based on internal and external molecular signals. Loss of Oct4 leads to failure in ICM formation, as cells default to trophoblast fate, underscoring the non-negotiable role of this factor in maintaining pluripotency. Conversely, Cdx2 ensures proper trophoblast lineage differentiation and represses Oct4 in these cells.

Assumptions that Oct4 is dispensable for ICM formation or that other molecules like Stat3 play merely optional roles in ICM pluripotency have been disproven by experimental evidence. While YAP and TEAD4 are upstream of Cdx2, there is no credible data supporting direct inhibition of these molecules by Nanog in the context of lineage segregation.

Therefore, the correct assumption is:

(1) The interplay between Cdx2 and Oct4 can influence the formation of ICM