Caenorhabditis elegansgenesart-3was first identified as the homolog of human SART3 (Squamous cell carcinomaAntigenRecognized byT-cells 3). In humans, expression of SART3 is associated with squamous cell carcinoma, thus most of the studies focus on its potential role as a target of cancer immunotherapy (Shichijo et al. 1998; Yang et al. 1999). Furthermore, SART3 is also known as Tip110 (Liu et al. 2002; Whitmill et al. 2016) in the context of HIV virus host activation pathway. Despite these disease related studies, the molecular function of this protein was not revealed until the yeast homolog was identified as spliceosome U4/U6 snRNP recycling factor (Bell et al. 2002). The function of SART3 in development, however, remains unknown. Here we report that theC. eleganssart-3mutant hermaphrodites exhibit a Mog (MasculinizationOf theGermline) phenotype in adulthood suggesting thatsart-3normally functions to regulate the switch from spermatogenic to oogenic gametic sex.