Departmental Seminar: Dr. Kevin Janes

Event Date: 12.9.2013 Day: Monday Time: 12:00 pm Location: 700 Fairchild Event Type: Departmental

Abstract

Regulated changes in gene expression underlie many biological processes, but globally profiling cell-to-cell variations in transcriptional regulation is problematic when measuring single cells.  We have developed an approach, called stochastic profiling, that applies probability theory to transcriptome-wide measurements of small pools of cells to identify single-cell regulatory heterogeneities.  In the first half of the talk, I will discuss a two-state regulatory circuit that was identified by stochastic profiling (Nat Methods 7:311-7 [2010]).  The circuit involves TGFb-family signaling and the junD transcription factor, which are asynchronously activated in 3D breast epithelial cultures to coordinate normal morphogenesis.  The circuit also appears to be re-initiated during the early stages of basal-like breast cancer, contributing to the mosaicked expression patterns observed clinically by histology.

            In the second half of the talk, I will talk about work in progress that applies stochastic profiling as a tool for uncovering the mechanistic basis of phenotypes that are incompletely penetrant.  In a 3D in vitro culture model of breast epithelial-acinar morphogenesis, inducible activation of the receptor tyrosine kinase ErbB2 causes hyperproliferative multi-acinar structures that in many ways are reminiscent of early-stage breast tumors (Nat Cell Biol 3:785 [2001]).  Importantly, the penetrance of the phenotype is incomplete-only a random fraction of cultured acini exhibit the morphogenetic defect when ErbB2 is activated.  How this fraction is specified and the mechanism by which a multi-acinus initiates are unknown.  We have used stochastic profiling to identify the very-small number of the transcripts that 1) become heterogeneously regulated specifically upon ErbB2 activation and 2) are stochastically upregulated at a frequency consistent with the number of multi-acini that will eventually form.  This subset of transcripts yielded a remarkable group of candidate regulators with strong ties to phosphoinositide signaling, small nucleolar RNAs, and the microtubule cytoskeleton.  Ongoing work seeks to perturb these candidates individually and in combination to converge upon the regulatory circuit linking ErbB2 signaling to multi-acinus formation.