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Transforming growth factor (TGF)-beta 3 is known to regulate the disappearance of murine medial edge epithelium (MEE) during palatal fusion. Our previous studies showed that SMAD2, a TGF-beta signaling mediator, was expressed and phosphorylated primarily in the MEE and that SMAD2 phosphorylation in the MEE was temporospatially regulated by TGF-beta 3. The goal of this study was to examine the requirement for SMAD2 to complete the developmental events necessary for palatal fusion. SMAD2 expression was inhibited with Smad2 siRNA transfection into palatal tissues in vitro. The results showed that Smad2 siRNA transfection resulted in the maintenance of MEE cells in the palatal midline. Western blot and immunofluorescence analyses confirmed that the endogenous SMAD2 and phospho-SMAD2 levels were reduced following siRNA transfection. The SMAD3 level was not altered by the Smad2 siRNA transfection. The persistence of the MEE and the decreased SMAD2/phospho-SMAD2 levels were coincident with increased MEE cell proliferation. Addition of exogenous TGF-beta 3 increased p-SMAD2 level but not the total SMAD2 level. Therefore, exogenous TGF-beta 3 was not able to induce p-SMAD2 enough to rescue the palatal phenotype in the Smad2 siRNA group. The results indicated that the endogenous SMAD2 level is crucial in the regulation of disappearance of MEE during palatal fusion., ((c) 2006 Wiley-Liss, Inc.)

A gene for ethionine resistance isolated from the yeast Saccharomyces cerevisiae DKD-5D-H conferred on the yeast cells resistance to seleno-L-methionine and capability to produce S-adenosyl-L-methionine in the cells. An enzymatic study of the L-methionine synthetic pathway of L-methionine proto- and auxotrophs and in dried yeast cells with or without the gene suggested that the cloned gene for ethionine resistance is responsible for the activity of S-adenosyl-L-methionine synthase. To produce S-adenosyl-L-methionine by yeast cells transformed with the ethionine resistance gene, some culturing conditions were determined.