Required for normal tracheal development and maintenance of the trans-epithelial diffusion barrier. Functions as a homophilic cell-adhesion molecule. May play a role in early neuronal differentiation and axon outgrowth. Located at the extracellular face of the membrane and becomes associated with septate junctions. Expressed on differentiating neuronal cells from the onset of neurogenesis in both the central and peripheral nervous systems. First detected in the cellularized blastoderm, apart from in the ventral side. Expression persists uniformly in the early ectoderm until the end of gastrulation. From stage 10, expressed in an alternating strong/weak pattern in each segment until stage 15 when it disappears. From stage 11, expressed in subsets of neurons and later subsets of glial cells. From early stage 13, strongly expressed in trachea, hindgut, foregut and the nervous system. Expressed in embryos. Flies exhibit more sinuous tracheal branches and uneven lumen with numerous breaks in the dorsal and lateral branches. Probable cloning artifact.