Richard W. Padgett
Department of Molecular Biology & Biochemistry
Piscataway, NJ 08855-0759
Signal transduction, trafficking of TGFß, microRNAs in cancer, developmental biology, C. elegans and Drosophila, signal transduction, cell biology, stem cells, molecular genetics, signaling pathways, cancer biology
My laboratory is interested in understanding the molecular mechanisms of growth control. Our primary focus is on the transforming growth factor-β-like pathways (TGFβ) in C. elegans and Drosophila.
TGFβ signaling pathways
Members of the TGFβ growth factor family are conserved in all animal phyla (from sponges to humans) and are expressed in essentially all vertebrate tissues, where they are involved in regulating cellular growth, patterning, and cell fate. As expected from their potent growth-regulatory properties, mutations in signaling components of these pathways are often associated with several diseases and cancers. Because of the powerful experimental techniques available in C. elegans and Drosophila, and that fact that these pathways are conserved, we are using nematodes and flies as model systems to dissect this signal transduction pathway. In both organisms, we have executed genetic screens to identify new aspects of TGFβ signaling and, as a complement to our genetic screens, we have generated microarray data in both organisms to identify downstream targets of these pathways as an aid to understand how they regulate growth.
Trafficking and Regulation of TGFβ pathways
Mutations from our genetic screens have identified a number of essential signaling components for TGFβ. These include the ligand, the two receptors, the Smads, and schnurri, which is a downstream transcription factor. In addition, we have identified a conserved co-receptor, which intersects with the trafficking of TGFβ. Another gene from our screen appears to be involved with degradation/trafficking of the receptors. Recent evidence suggests that signaling pathway strength is intimately associated with endocytosis, and these two genes from our screen offer new avenues to explore the trafficking, signaling, and degradation of the TGFβ pathway in C. elegans and Drosophila.
Development of a co-CRISPR technique in Drosophila
Genome editing using CRISPR has become a valuable tool in research, but identifying modifications can be time consuming and labor intensive. We developed a co-CRISPR strategy in Drosophila to simultaneously target a gene of interest and a marker gene, ebony, which is a recessive gene that produces dark body color. We found that Drosophila broods containing higher numbers of CRISPR-induced ebony mutations (“jackpot” lines) are significantly enriched for indel events in a separate gene of interest, while broods with few or no ebony offspring showed few mutations in the gene of interest. This co-CRISPR technique significantly improves the screening efficiency in identification of genome editing events in Drosophila.
microRNAs in developmental pathways
microRNAs are small RNAs (~21-23 nucleotides) that regulate gene expression by attenuating the translation of mRNAs in animal cells. We have shown that bantam, a conserved microRNA, regulates TGFβ signaling in Drosophila, and that TGFβ signaling induces the expression of bantam, thereby forming a regulatory loop. Current studies focus on understanding how bantam regulates TGFβ in the wing and the brain.