Malignant melanoma in non-Caucasians: experience from Hawaii.

Data from the Hawaii Tumor Registry suggest that the incidence of melanoma in the non-Caucasian population of Hawaii is not substantially different from that of the remainder of the United States. Our experience indicates that melanoma in this population, although unusual, is not rare. Although lesions on the palms and soles are more common. as are subungal melanomas, primary tumors on other skin sites account for the majority of patients with cutaneous melanoma in the non-Caucasian population. The substantial difference in primary tumor thickness suggests the reported poorer outcomes for non-Caucasian patients with cutaneous melanoma may be explained, at least in part, by a delay in diagnosis. Given the evidence that preventive measures and educational efforts have dramatically impacted the diagnosis and outcome of melanoma patients, it is critical to recognize that similar efforts should be directed at the non-Caucasian population.

Identification of Rho GTPases implicated in terminal differentiation of muscle cells in ascidia.

BACKGROUND INFORMATION: Members of the Rho GTPase family mediate changes in the actin cytoskeleton and are also implicated in developmental processes, including myogenesis. Nevertheless, a comprehensive analysis of these proteins during myofibrillogenesis has never been performed in any organism. RESULTS: Using the ascidian model to identify the role of Rho GTPases on myofibrillogenesis, we show that transcripts for all Rho GTPases are detected in muscle cells of the embryo. We find that activation of RhoA, TC10 and Cdc42 (cell division cycle 42) disturbs the polarity of muscle cells, whereas that of other Rho GTPases induced cell positioning defects. Moreover, dominant negative version of five Rho GTPases, RhoA, Rac2, RCL2 (Rac- and Cdc42-like 2), TC10 and WRCH (Wnt-1 responsive Cdc42 homologue), impaired the formation of mature myofibrils. CONCLUSIONS: Taken together, our results show that several Rho GTPase-dependent pathways are required to control the spatial localization of muscle cells in the embryo and to coordinate myofibril assembly. This stresses the importance of analysing the entire Rho family when studying a new biological process.