Figure 1.

Transcription factors involved in A–P patterning. TFs involved in A–P patterning function in a hierarchical network to subdivide the embryo into 14 segments. The early maternal factors are expressed in broad gradients, with subsequent TF groups expressed in patterns that are increasingly refined. TFs involved in early segmentation or expressed in early patterns that were characterized in this study are grouped according to their initial stage of expression and they are color-coded to indicate the type of DNA-binding domain [Cys₂His₂ zinc fingers = blue, homeodomains = green, bHLH = gray, bZip = red, winged helix = pink, nuclear hormone receptor = orange, POU motif = light blue, paired motif = yellow, and HMG = lavender. Runt is black and was characterized as an alpha fusion (37)].