Together with tsp-12, regulates cell fate specification in the postembryonic mesodermal M lineage, body size and male development, probably by positively modulating BMP-like Sma/Mab signaling (PubMed:25978409, PubMed:28068334). Together with tsp-12, probably acts by modulating the activation of glp-1, Notch-like receptor, to regulate germline maturation (PubMed:20220101). Viable and fertile (PubMed:28068334). No effect on sup-17 localization in embryos (PubMed:28068334). In a tsp-12 (ok236) mutant background, exhibits vulva morphogenesis defects, impaired egg-laying, smaller body size and reduced RAD-SMAD reporter expression, a reporter system for the sma-6/daf-4 BMP-like pathway (PubMed:28068334). Males have severe tail defects including crumpled spicules, fused and shortened sensory rays and smaller fans (PubMed:28068334). F1 progeny die at the late embryonic stage with defects in ventral enclosure (PubMed:28068334). In a sma-9 (cc604) and tsp-12 (ok236) mutant background, restores the production of the 2 M lineage-derived coelomocytes (PubMed:28068334). In a glp-1 (ar202) mutant background, partially restores normal fertility (PubMed:20220101). Belongs to the tetraspanin (TM4SF) family.