[
Proc Natl Acad Sci U S A,
2003]
The discovery of transgene silencing in plants and double-stranded RNA (dsRNA) interference in the worm Caenorhabditis elegans has led to the latest revolution in molecular biology, RNA interference (RNAi). Over 10 years ago it was noted that several transgenic plant lines each containing the same ectopic transgene not only failed to be expressed but also inhibited the expression of the endogenous gene. Similarly, a determined Craig Mello and Andy Fire, attempting to reduce gene function using using antisense RNA in the worm, discovered a minor contaminant in their antisense RNA preparation effectively and repeatedly reduced expression of the endogenous gene. In both cases, dsRNA homologous to the gene of interest was responsible for these observations. In the last 4 years, these discoveries have been extended to include protozoa,
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Dev Cell,
2002]
Presenilins mediate they-secretase cleavage of Notch transmembrane receptors as well as the transmembrane P-amyloid precursor protein (PAPP), but they are not thought to accomplish this alone. Recent genetic screens in C. elegans, presented in this issue of Developmental Cell, identify two genes that are essential to gamma-secretase activity and may interact with presenilins.
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J Cell Biol,
2007]
Cells must break symmetry to acquire polarity. Microtubules have been implicated in the induction of asymmetry in several cell types, but their role in the Caenorhabditis elegans zygote, a classic polarity model, has remained uncertain. One study (see Tsai and Ahringer on p. 397 of this issue) brings new light to this problem by demonstrating that severe loss of microtubules impairs polarity onset in C. elegans.