vvl trasnscript is expressed at early stage 10 in the tracheal placodes, and in homologous cells in segments that will not form trachea. At stage 11, vvl is also expressed in 10 dorsal epithelial patches in each trunk segment, which are displaced with respect to the tracheal primoridia. By stage 15, vvl transcript is expressed in most of the embryonic trunk epithelium

Expression assayed at stages 9, 11, 13, and 17. Expression may be continuous between assayed stages in some tissues.

vvl is expressed in the ectoderm of the anterior hindgut at embryonic stage 14.

vvl transcripts first appear at 5-6hr of development, show a peak of expression between 10hr and 13hr and decline substantially by the end of embryogenesis.

vvl transcripts are first detected in 3-6 hr embryos, are at a maximum level in 6-12 hr embryos and persist throughout development. They are first detected in the tracheal placodes of germ band extended embryos. They are later observed in cells surrounding the tracheal pits that may be chordotonal organs and in a group of cells on the roof of the stomodeal invagination. A complex pattern of expression is observed in the PNS and CNS.

vvl transcripts are initially detected in 3-6 hr embryos, progressively increase to maximum levels in late embryos, and decline thereafter. Transcripts are initially detected in the ectoderm of stage 10 embyros at regular, repeating intervals. This correlates with sites of the invaginations that are the origins of the tracheal placodes. Transcripts are also found along the midline of the CNS. vvl transcripts are found in a subset of neurons in the CNS that substantially overlap those that express acj6 transcripts.

vvl transcript is detected in oocytes and early embryos.

Expression of vvl protein is observed in a subset of ventral motor neurons which exit the ventral nerve cord via the ISNb nerve branch. There is co-expression with Oli protein.

vvl protein is expressed in the differentiated neurons of the the outermost domain of the medulla anlage from third instar larvae and in pupa until 12h APF, distal to the domain of run. Thereafter and in adults, vvl protein is found in layers 8 to 10 of the medulla. It is also observed in the adult neurons of the lobula and lobula plate and in non-neuronal cells of the lamina.

vvl is expressed in many tissues in larvae and adults including fat body, oenocytes, epidermis, tracha, proventriculus, midgut, hindgut, salivary gland, and Malpighian tubule as well as in the larval brain, some imaginal discs, gastric caecum, ring gland, and ejaculatory duct. It was not detected in the lymph gland or hemocytes, in the accessory glands, seminal vesicle, or testis, or in any part of the female reproductive tract.

vvl is first detected in a few neuroblasts of the eveloping brain anlage at embryonic stage 11. By stage 13, it is abundant in neuroblasts and their progeny in each brain neuromere. By stage 15, vvl is observed in specific clusters within all brain neuromeres. A prominent expression domain is observed in the developing tritocerebrum. The majority of cells expressing vvl in the tritocerebrum overlap the lab expression domain.

vvl protein expression is first apparent in early stage 10 in two rows of 10-cell patches corresponding to the developing tracheal placodes. vvl expression serves as a marker for the tracheal pits as they undergo extensive morphogenetic movements in stages 10-13. Epidermal vvl expression becomes prominant from stages 13-16/17 and masks the tracheal expression at these stages. During this period, strong staining is seen in the seven laterally symmetrical oenocyte clusters in segments A1-A7. vvl is also expressed in the hindgut in stages 13-15. vvl expression is observed in the developing head region in stage 10/11 embryos in tissues of the procephalon, clypeolabrum, and labium. The most prominant labeling is seen in laterally symmetrical placodes of cells located on both the dorsal and ventral sides of the stomodeal opening. This corresponds to regions containing sensory progenitor cells derived from the clypeolabrum and labrum. Expression is seen in the cells of the mesectoderm in stages 10-12. Mesectoderm expression extends beyond stage 12 in the middle pair of midline glia (MGM). In later stages, vvl is expressed in a uniform repeated pattern of ~25 nuclei per neuromere grouped into 5 distinctive clusters: 1) a midline cluster of four nuclei containing the MGM and a pair of RP motoneurons, 2) two symmetrical mediolateral clusters that contain the paired serotonergic neurons, and 3) two symmetrical lateral clusters.