protein was experimentally shown to be an integral membrane protein. It has a type II conformation with its N-terminus facing the cytoplasm and the C-terminus facing the extracellular space.
Protein is first observed in the golgi basal to the nuclei in embryonic cycle 13. At cellularization the protein becomes concentrated at the apical invaginating membrane and later is detected in the lateral membrane.
protein accumulates in the membranes of neurons and their progeny. Extensive protein accumulation is observed in the CNS between embryonic stages 12 and 16. Analysis of serial sections shows strong accumulation of Nrt
protein in growing axon tracts but not in motor axons exiting the CNS. Some heterogeneity in the distribution in the cell cortex is seen. It is unclear if Nrt
protein accumulates in the growth cones because of the widespread accumulation in cell bodies. In the embryonic PNS, Nrt
protein is detected only in the polyinnervated sensory organs. In the pupal PNS, it is expressed by ocellar pioneer neurons but not by the neurons of neighboring bristles. It is also expressed by photoreceptors and some sensory neur ns in the wing.
protein was experimentally shown to be a transmembrane protein. It is expressed preferentially at the junctions between cells.
protein is detected in all developmental stages by Western blots with peaks in embryos and early pupae. Nrt
protein is first detected by immunolocalization in two regions of stage 5 embryos. By gastrulation, it extends throughout the embryo except at the pole cells. High levels persist in mesoderm and mesectoderm through stages 9-10. A new wave of expression appears in the visceral mesoderm during stage 13. Other mesodermal derivatives that express Nrt
protein are the fat body and dorsal vessel. Strong expression is seen in the proliferating CNS in stages 10 and 11 in both neuroblasts and their progeny. Protein accumulates preferentially in neuroblast surfaces in contact with other neural cells rather than epidermis. High levels continue during cytodifferentiation and persist until the 1st larval instar. In stage 13, the early uniform staining in the ectoderm is replaced by staining in some PNS structures. These are the head sensory organs, the spiracle sensory organ in the tail region, and a single cell cluster per segment in the trunk. By stage 16, weak staining in other sensory organs in the thoracic and abdominal segments is seen. Staining is also observed in the amnioserosa from early on. Nrt
protein decays after larval hatching but reappears in the CNS. It is found in the optic centers and in the ventral cord. It persists in imaginal neurons in the first half of the pupal period and then disappears gradually. Nrt
protein is also detected in the eye disc and the wing disc. In the eye disc, it is found in photoreceptor cells. In the wing disc, it is present at high levels in cells that will give rise to the wing margin and is also detected in cells that will give rise to intervein regions.