My lab is combining the generation and analysis of transgenic and orthotopic mouse models with biochemical and proteomics approaches to define the roles of chondroitin sulfate and the balance of chondroitin sulfation in growth factor signaling (including TGFb and Ha-Ras signaling), mammalian development, pediatric diseases like Costello syndrome, and cancer.

Chondroitin sulfate is a glycosaminoglycan (GAG) consisting of repeating disaccharide units, which are attached to proteins to form proteoglycans. The multi-step synthesis of GAG sugar chains is regulated by various enzymes, including specific sulfotransferases, which catalyze the transfer of sulfate groups to different specific positions of the sugar residues. The balance of sulfation of C4 residues (C4S) versus C6 residues (C6S) is tightly regulated during development and disease, suggesting important biological functions.

My previous work has shown that the chondroitin-4-sulfotransferase-1 (C4st-1) gene is a target gene of the transforming growth factor b (TGFb) signaling pathway. I demonstrated that loss-of-function of the C4st-1 gene in a mouse model leads to severe embryonic defects, including skeletal, cardiac, and cell type-specific proliferation abnormalities, and results in perinatal lethality. My work also showed that dysregulation of human C4ST-1 (also called CHST11) is involved in the mediation of the effects of activated Ha-Ras signaling in Costello syndrome, a pediatric disease phenotypically similar to the C4ST-1 mouse model.

These results demonstrate a crucial role for C4ST-1 during mammalian development, and place C4ST-1 and the balance of chondroitin sulfation downstream of both TGFb and Ha-Ras signaling, two pathways with important roles not only in development, but also in human tumorigenesis.

We will be utilizing 3D-tissue culture techniques as well as mouse orthotopic tumor models to understand the roles of chondroitin sulfotransferase genes during tumor progression, metastasis and growth factor signaling. Secondly, we will be generating transgenic mouse models to analyze the effects of tissue-specific loss-of-function and overexpression of chondroitin sulfotransferase genes, in order to better understand the role of the balance of chondroitin sulfation in development, tissue homeostasis, and disease, including cancer.

Thirdly, we will be analyzing the potential roles of chondroitin sulfate in the modulation of signaling pathways through biochemical and proteomics/glycomics approaches.   Lastly, we will continue to analyze the mechanisms by which both TGFb and Ras signaling pathways control and regulate the C4ST-1 gene, and how this regulation is affected in Costello syndrome.