MicroRNA functions in plant embryos

Plant miRNAs are short non-coding RNAs that mediate the repression of hundreds of genes. The basic plant body plan is established during early embryogenesis, and recent results have demonstrated that miRNAs play pivotal roles during both embryonic pattern formation and developmental timing. Multiple miRNAs appear to specifically repress transcription factor families during early embryogenesis. Therefore miRNAs probably have a large influence on the gene regulatory networks that contribute to the earliest cellular differentiation events in plants.

Expression of β-catenin is necessary for physiological growth of adult skeletal muscle

Expression of β-catenin is known to be important for developmental processes such as embryonic pattern formation and determination of cell fate. Inappropriate expression, however, has been linked to pathological states such as cancer. Here we report that expression of β-catenin is necessary for physiological growth of skeletal muscle in response to mechanical overload. Conditional inactivation of β-catenin was induced in control and overloaded muscle through intramuscular injection of adenovirus expressing Cre recombinase in β-catenin floxed mice. Individual muscle fiber analysis was performed to identify positively transfected/inactivated cells and determine fiber cross-sectional area. The results demonstrate that fiber growth is completely inhibited when the β-catenin expression is lost. This effect was cell autonomous, as fibers that did not exhibit recombination in the floxed mice grew to the same magnitude as infected/noninfected fibers from wild-type mice. These findings suggest that β-catenin may be a primary molecular site through which multiple signaling pathways converge in regulating physiological growth.