TGFB1 and systemic sclerosis: Growth differentiation factor-6 (GDF6), a member of the TGF-ß superfamily that is also regulated by both TGF-β and Egr-1, was up-regulated in the basal epidermis, dermal fibroblasts and in vascular cells in SSc skin biopsies compared to control biopsies (Fig. 5C).