Question

Transitions between epithelia and mesenchyme are essential for various developmental processes and can occur in either direction: from mesenchyme to epithelium (MET) or from epithelium to mesenchyme (EMT). Briefly, describe an example of an MET during somitogensies, how it contributes to somite formation, and the roles of the Mesp transcription factor and the Rho GTPase, Cdc42, in this process.

Answer 1

---- Meslunchymal epithelial transition - Mesenchymal cells from an emosyonic Connectile tissue with a disorganised cellular orgnization can undergo transition: Uto an epithelial e olganization: clorganised cellulas layer) as la developmental process and are said to have 'undergone a Mesenchymal to epithelial tkasestion.(MET) O this morphological change appears to be the opposite process. tol that seen in epithelial mesenclymal transition. Meschymal cells. connective tissue-like that have undergone. this process may at a later time. and under specific signaling. Cand undergo the opposite process. Mesenchymal to epithelial in development, this process can be repeted several times during tissue. differentiation: o

Somitogenesis - During early somite formations the mesenchymal pasarial mesoderm: undergoes a MET to form the initial segment of the somite ball this ball Cof mesoderm has an epithelial couler layer and a -core of mesenchyme. the early somite -also contain a space the somitoceol. that is lost as the mesoderm proliferates to form a solid ball. the somite epithelial layer then breaks down as the somite dispress to form the siderotone and demomyo tome: the ceremony.tome initaly semains. as an epeilhelial layer that also is lost as the 'dermatome and mayotome praliferate. and migrates

Role of Rho. cde42 Treatmet of Msc with TGF B resulted in increased phosphorylation of Smade and the Rho GT pase downstream effectors MLC2C in particular Rhoa but also ract and calcu2) suggesting that The ß introduces Rho GT pase activation in parallel with canonical The B singiling u Kinetic analysis indicated a high and significat activation of smada. JPKAL and paku after 24 h. and of M2C2 after 2 h. and the-induced Rho GTpase singling in the Taf o induced miyofibroblasto u diffrentiation of MSC, We estesblised MISC lines lacking Rhoa, Raci, or cdc42 by CRISPR casero Imediatel genome CRISTAL editing

somite formations Anterior - Resegmentatos T T DOODOKCIEL Boundry het formatróis Segneel determinais Determinatsis front candal PSM A Taulbut paranial mesoderm Preduction Axis elongations -pasterior