Practice question

BMP receptors are serine/threonine kinase family phosphorylating receptor-regulated Smads Smad1,5,8 upon BMP2/4 binding to ALK2/3/6 type I and BMPR2 type II. Phosphorylated Smad1/5/8 complexes with Co-Smad Smad4, translocates to nucleus via importin beta binding MH2 domain to activate Id1-3, Msx1/2 transcription factors patterning ventral mesoderm and inhibiting neurogenesis by repressing Sox2. STAT proteins transduce JAK cytokine signaling via tyrosine phosphorylation and dimerization, JAK is cytoplasmic tyrosine kinase, beta-catenin transduces Wnt via TCF/LEF. Thus Smad proteins canonical intracellular transducers distinguishing TGF-beta/BMP pathway from RTK and GPCR signaling logic for dorsoventral patterning.