transcripts are first expressed in the cellular blastoderm embryos in what becomes the segmented portion of the embryo but not at the poles. During gastrulation, they are expressed throughout the ectoderm but not in the procephalon. Beginning in stage 11 embryos, expression is strong in the thoracic region but begins to decline in the abdominal region. Expression is also moderate in the mandible and maxilla but absent from the labium. hth
expression is also observed at this time in the visceral mesoderm and at a very high level in the clypeolabrum. In stages 13-14, expression appears in the developing Malpighian tubules and in the CNS. It remains high in the head and thorax and low in the abdomen. During stages 15-17, expression declines in the ectoderm and becomes more prominant in the CNS. The CNS expression is graded, higher in the anterior region and weak in the posterior regions.
transcripts are relatively abundant in 3-15hr embryos, 1st instar larvae, and pupae. They are less abundant in 2nd instar larvae and are at very low levels in early embryos, third instar larvae, and adults.
transcripts are expressed in the wing disc in the notum, winge hinge, and ventral pleura. In the leg discs, expression is in the periphery region corresponding to the proximal segments of the legs. In the antennal disc, the expression is in all but the arista region. In the eye disc, hth
expression is strong in the anterior region surrounding the eye field, including the regions corresponding to the ptilinum, ocellus, and head capsules, and weak in the posterior and lateral margins of the disc. hth
is also expressed in all cells of the peripodial membrane in the eye disc. Weak expression is observed in the posterior region composed of mature photoreceptors. This expression pattern generally coincides with that of exd
transcripts are first detected at 3hr of embryogenesis in a broad domain extending from 15-85% egg length. In later stages the pattern becomes very dynamic. The strongest expression is seen in the trunk region and portions of the head. Starting at stage 9, staining is stronger in the thorax than in the abdomen and this difference increases with time. By stage 14, expression is strong in the CNS, especially in the thorax. In the midgut, expression is strongest in the gastric caeca primordia and in a central broad domain in the endoderm. Expression is absent in the most anterior and posterior portions of the midgut endoderm. By stage 16, strong expression is seen in the Malpighian tubules. Expression in the endoderm begins posterior to the first midgut constriction and ends just anterior to the third midgut constriction. In leg and antennal discs, hth
is expressed in the peripheral cells of these discs.