Reference no: EM133354154

Question: FGF4 signaling in the inner cell mass (ICM) of the mouse blastocyst is essential for primitive endoderm (PE) specification and determination, and for the segregation of PE and epiblast (EPI) cells. But FGF4 is expressed throughout the ICM rather than being regionalized, and PE and EPI precursor cells are intermixed and distributed in a salt-and-pepper fashion. It is now known that an early stage in the ICM, EPI precursor cells express the gene encoding FGF4 but do not express the fgfr2 gene, whereas PE precursor cells express the gene for the receptor FGFR2, but not fgf4. This leads to the question of the mechanism by which inner cell mass cells are specified to express these genes differentially at an early stage so that some later will become PE cells and others will become EPI cells.

(A) Based on results and conclusions of experiments in the literature, propose a hypothesis involving molecular and cellular mechanism(s) that could explain how some inner cell mass cells are specified to become PE cells and others to become EPI cells.

(1) By what mechanism could FGF4 and FGFR2 expression be specified in different cells?

(2) How could regulation of FGF4 secretion and signaling lead to formation of two different cell types that are intermixed and closely packed within the ICM?

(B) Propose experiments to test your hypothesis. Please cite references to show the source of ideas and results and explain how they support your hypothesis.