An integral component of the septate junction. May play a role in cell-cell interactions that are necessary for proper development. Vital for embryonic development. Septate junction in the apical-lateral domain of epithelial cells during embryonic and imaginal disk development. At onset of germ band retraction, expression is seen in epidermis, hindgut and foregut. During retraction, expression extends to tracheal branches and salivary glands. Expressed weakly in 4-8 hours embryos, more abundant expression in 8-12 hours and remains throughout later embryonic and larval stages.