In addition, in several animals (reviewed in [4]), Hox genes exhibit temporal colinearity, and the temporal order of initiation of expression reflects the order of Hox genes in the cluster (e. g., "anterior" genes are expressed earlier than genes with posterior expression domains).
It has been shown that knockdown of the posteriorly expressed Wnt8 in a spider perturbs the posterior expression of cad and Delta/Notch pathway components [ 24].
(A ) Alx4 was initially expressed throughout the fin buds at stage 25, but the posterior expression of Alx4 was reduced by stage 27.
As confirmation of this, our analyses of fixed embryos that develop either in vivo or in vitro indicate that the expression domains of Cerl and Lefty1 are coincident and lie opposite the posterior expression domain of Brachyury.
Mean posterior expression estimates for each gene were log2 transformed.
After metamorphosis, when distinct posterior expression boundaries appear, CapI-Antp also has a posterior expression boundary at the thoracic abdominal junction.
A more striking defect in Hb expression was the nearly complete loss of posterior expression.
As expression patterns mature during late larval and early juvenile stages, posterior expression boundaries appear anterior to the growth zone.
Posterior expression boundaries in Chaetopterus correlate with the boundary between regions A and B, posterior expression boundaries correlate with the thoracic abdominal transition in Capitella, and posterior expression boundaries correspond with the anterior boundary of the caudal ganglion in the leech.
In alligator, strong anterior and posterior expression in the mesopodial-zeugodial region of the forelimb persists into late stages (white arrows in Stages 14, 16 and 17).
In the transition to stage 8, a posterior expression boundary appears, and prominent expression becomes limited to the VNC of segments T5 T8 (Figure 9E and 9F).
