The migration of cranial neural crest (CNC) cells is controlled by proteins that regulate gene expression, cell proliferation, cell signaling and cell adhesion. Among these proteins the ADAM cell surface metalloproteases can regulate both cell signaling and cell adhesion. They do so by cleaving signaling and adhesion molecules from the cell surface. There is a fundamental gap in understanding how ADAM proteins control cell migration in general and CNC migration in particular. Our long-term goal is to understand how CNC migration is controlled in a developing embryo. The objective of this application is to determine how ADAM metalloproteases control CNC migration. The central hypothesis of this proposal, based on extensive preliminary data, is that ADAM metalloproteases control cell migration both by shedding cell adhesion molecules from the plasma membrane and by the independent activity of their cytoplasmic domains inside of the nucleus.
Aim 1 : To identify how ADAM cleavage of Cadherin-11 controls CNC migration. We have shown that Cad-11 is cleaved by ADAM13 during CNC migration and that the Cad-11 extracellular fragment containing the adhesive site is shed and can rescue migration in embryos lacking ADAM13 or overexpressing Cad-11. Our hypothesis is that this fragment binds to the surface of CNC via a receptor and promotes migration. We propose to determine how the extracellular fragment of Cad-11 promotes migration. We will determine, 1) what are the consequences of not cleaving Cad-11 on CNC specification and migration, 2) if the Cad-11 extracellular fragment stimulates directed cell migration and/or interfere with contact mediated inhibition, and 3) What are the signaling pathways involved in this process.
Aim 2 : To identify the mechanism by which the ADAM cytoplasmic domain controls CNC migration. We have shown that the ADAM13 cytoplasmic domain (C13) is cleaved and translocates into the nucleus. We showed that this is critical for gene expression and CNC migration in vivo. We also showed that one gene regulated by C13, Calpain8 is essential for CNC migration. Our hypothesis is that the ADAM13 cytoplasmic domain controls gene expression by modifying the function of a transcription factor to promote CNC migration. We will determine 1) the amino acid sequence(s) in C13 that are responsible for the control of gene expression and cell migration, and 2) the mechanism by which C13 regulates the expression of Calpain8. The approach is innovative, because it shows for the first time in any system that ADAM cytoplasmic domains function in the nucleus to regulate specific gene expression and cell migration. The proposed research is significant, because it is expected to vertically advance the field by identifying evolutionary conserved motifs in ADAM cytoplasmic domain that control the activity of transcription factors (e.g. FoxD3). In addition, the Cad-11 extracellular domain has been shown to increase cancer cell invasion, thus our results will shed the light on the mechanism by which this domain operates.
The proposed project is relevant to public health because it increases our knowledge of craniofacial development in a vertebrate model organism amenable to experimental studies. The understanding of ADAM control of cell migration is also relevant as these proteins are often up-regulated and associated with invasion of cancer cells. The current study also shows that ADAM cytoplasmic domains control the expression of genes that are relevant to multiple human diseases.
Showing the most recent 10 out of 33 publications
