Role of the Primary Cilium in the Transcriptional and Chemotactic Response to Shh

Sonic Hedgehog (Shh) is a signaling molecule that is required for proper neural tube development in vertebrates. A well-described function of Shh is the induction of genes involved in the differentiation of ventral cell types in the developing neural tube. The primary cilium, a microtubule-based cellular appendage present in most cells, plays a critical role in the transcriptional Shh response. Shh not only induces changes in gene expression, but several cell lines migrate towards sources of Shh (chemotaxis), using a mechanism that does not require transcription and translation. Preliminary results show that for this Shh response, the primary cilium is dispensable. Based on these findings it is hypothesized that, in the presence of Shh in the cellular environment, the presence of the primary cilium is central in a cell’s transcriptional response, but not its chemotactic response. I plan to assess the roles of proteins involved in the formation and maintenance of the primary cilium, as well as molecules involved in the delivery of cargo to the primary cilium, in the distinction between the two different Shh responses. I generated a panel of miRNA constructs and will assess if 1) they affect the presence, length or shape of primary cilia, 2) if they affect the ability of a cell to respond to Shh transcriptionally and 3) if they affect the ability of a cell to migrate towards sources of Shh. These results should help in our understanding of what cilial functions are required for the transcriptional or chemotactic response to Shh.