New Flexon-based reagents for tissue-specific Auxin-Inducible Degradation and for characterizing Cre and Flp drivers in .

A Flexon stop cassette interrupts translation of a coding region until it is excised by a recombinase to allow for gene expression. We have expanded options for Auxin-Inducible Degradation by generating Flexon-based transgenes for tissue-specific expression of the ubiquitin ligase substrate recognition component TIR1 or the variant TIR1(F79G) after excision of the Flexon by Cre recombinase. We also describe Flexon-based tester transgenes to facilitate gathering accurate information about the expression pattern of Cre and Flp recombinase drivers that can be used in conjunction with any conditional expression reagents that utilize these recombinases.

EGFR signal transduction is downregulated in C. elegans vulval precursor cells during dauer diapause.

Caenorhabditis elegans larvae display developmental plasticity in response to environmental conditions: in adverse conditions, second-stage larvae enter a reversible, long-lived dauer stage instead of proceeding to reproductive adulthood. Dauer entry interrupts vulval induction and is associated with a reprogramming-like event that preserves the multipotency of vulval precursor cells (VPCs), allowing vulval development to reinitiate if conditions improve. Vulval induction requires the LIN-3/EGF-like signal from the gonad, which activates EGFR-Ras-ERK signal transduction in the nearest VPC, P6.

Genetic analysis of DAF-18/PTEN missense mutants for the ability to maintain quiescence of the somatic gonad and germ line in Caenorhabditis elegans dauer larvae.

The mammalian tumor suppressor PTEN has well-established lipid phosphatase and protein phosphatase activities. DAF-18, the Caenorhabditis elegans ortholog of PTEN, has a high degree of conservation in the catalytic domain, and human PTEN complements a null allele of daf-18, suggesting conserved protein function. Insights gleaned from studies of mammalian PTEN have been applied to studies of DAF-18 in C.

SALSA, a genetically encoded biosensor for spatiotemporal quantification of Notch signal transduction in vivo.

Notch-mediated lateral specification is a fundamental mechanism to resolve stochastic cell fate choices by amplifying initial differences between equivalent cells. To study how stochastic events impact Notch activity, we developed a biosensor, SALSA (sensor able to detect lateral signaling activity), consisting of an amplifying "switch"-Notch tagged with TEV protease-and a "reporter"-GFP fused to a nuclearly localized red fluorescent protein, separated by a TEVp cut site. When ligand activates Notch, TEVp enters the nucleus and releases GFP from its nuclear tether, allowing Notch activation to be quantified based on the changes in GFP subcellular localization.

Evolutionary plasticity in the requirement for force exerted by ligand endocytosis to activate C. elegans Notch proteins.

The conserved transmembrane receptor Notch has diverse and profound roles in controlling cell fate during animal development. In the absence of ligand, a negative regulatory region (NRR) in the Notch ectodomain adopts an autoinhibited confirmation, masking an ADAM protease cleavage site; ligand binding induces cleavage of the NRR, leading to Notch ectodomain shedding as the first step of signal transduction. In Drosophila and vertebrates, recruitment of transmembrane Delta/Serrate/LAG-2 (DSL) ligands by the endocytic adaptor Epsin, and their subsequent internalization by Clathrin-mediated endocytosis, exerts a "pulling force" on Notch that is essential to expose the cleavage site in the NRR.