Required for apical extracellular matrix organization and epithelial junction maintenance. In the excretory canal cell at the 1.5-fold embryonic stage, localized uniformly at the cell membrane. In L1 larvae, expressed in a subset of epithelial cells including epidermal, vulval and rectal cells and the excretory duct and pore. Absent from internal epithelia such as the gut and pharyngeal tubes. Transiently expressed in the excretory canal cell at the 1.5-fold embryonic stage but no longer visible in this cell at hatching. Expression begins around the ventral closure stage of embryogenesis, continues throughout larval development and decreases in adulthood. Highly lethal at L1 larval stage due to excretory defects. A small percentage of mutants die as embryos and a very small number survive to adulthood and are fertile but have defects in locomotion and egg-laying. There is no maternal effect on lethality.