transcript is expressed in a quadrant pattern in the wing pouch (excluded from the D/V and A/P compartment boundaries), and in the presumptive mesonotum and notum. In the haltere disc, Egfr
is expressed in the prsumptive mesonotum, and in a small region surrounding the D/V compartment boundary.
Transcript is detected in a subset of the longitudinal glia in the ventral midline.
transcripts are distributed uniformly in the undifferentiated part of the eye-antennal disc from the antennal disc to in or slightly ahead of the morphogenetic furrow. They are also detected in the larval optic lobe in a pattern similar to the protein distribution.
transcripts are first observed in the late syncytial blastoderm embryo and increase substantially during cellularization. In gastrulating embryos, signal is higher in the ectoderm than in the endoderm or mesoderm and the strongest expression is seen in the cephalic furrow. During germ band extension, Egfr
transcripts continue to be detected in the ectoderm and in the mesoderm. As the neuroblasts segregate, expression is missing in the neuroblast layer but is seen as two stripes along the germ band in the ectoderm and in the meso erm. In the later part of germ band extension, expression is detected in the stomodeum, the clypeo-labrum, and in the gnathal segments. Egfr
is therefore found in all primordial tissues of the mouthparts and foregut. At stage 14, expression is observed in the region where the posterior spiracles and the telson will form. From stage 14 on, expression is observed in the ventral midline of the CNS. In stages 15 and 16, expression is observed along the entire periphery of the midgut. At stage 17, the most prominent regions of expression include the internal part of the proventriculus, the epit elium of the pharynx, and the fat body. In third instar larvae, expression is observed in imaginal discs. Expression is not evenly distributed among the discs or in a single disc. For example, in the eye disc, expression is abundant and uniform anterior to the morphogenetic furrow but posterior to the furrow is only found in the basal portion of the disc. Expression in the discs is observed in the epithelium but not in the adepithelium. Egfr
is also expressed unevenly in developing ovaries and is detected in restricted regions of the CNS. Expression is observed in the inner and outer proli eration centers and in cells of the developing optic lamina. In addition, expression is found in a subset of polytene larval tissues including the valvular epithelium of the proventriculus and the fat body. Low levels of expression are seen in the salivary glands and in a subset of cells in the Malphigian tubules. The larval pattern of expression continues into prepupae. In early pupae, expression continues in the disc epithelia, the optic lamina, and fat body. Weak expression is also observed around each ovarian egg chamber. Later in the pupal period, expression declines in the midgut epith lium and is observed in the fore- and hindguts. Egfr
expression in adults is mainly restricted to three types of tissues; imaginal fat body, valvular epithelium of the proventriculus, and the follicular epithelium of the ovary.
transcripts are observed in the periphery of cellular blastoderm embryos and persist at least until ventral furrow formation. In larvae, transcripts are observed in all imaginal discs and in subsets of cells within the cortex of the brain but not in the salivary glands. The expressing cells in the brain are thought to correspond to the proliferative centers. This pattern is consisten with Egfr
expression preferentially in mitotically active cells. In ovaries, expression is observed in the vitellogenic follicle cells in young egg chambers. Follicle cells surrounding more mature oocytes no longer have higher levels of Egfr
than the surrounding cells. Some transcript is also found in nurse cells and in the oocyte. In adults, some Egfr
transcript is observed in males and females in tissues other than the ovary showing that some Egfr
is expressed in nonproliferating cells in adults.
transcripts were found to be uniformly distributed in 10-14hr embryos and in 24hr embryos. In larvae, transcripts are uniformly distributed in the brain cortex, the anlagen of the ovaries and testes and in imaginal discs including the eye-antennal, wing, and genital discs. In adults, transcripts are localized in the cortex of the brain and in the thoracic and abdominal ganglia.
transcripts are detected at all stages of development tested. They are expressed at high levels in embryos and at reduced levels in larvae and pupae. In adults the 7.6kb transcript is much less abundant than the 7.1kb transcript.