Figure 7.

Model for MADF-BESS function in the wing-hinge. (A) The GRN for wing-hinge development includes wg, tsh, hth, and exd as major patterning genes. In the hng1 loss of function, our data indicate an increase in activity of Tsh/Hth/Exd. hng1 appears to negatively regulate the Wg/Hth-positive autoregulatory loop. hng1 also negatively regulates tsh, possibly acting downstream of jing. (B) The three hng genes along with stwl appear to be functionally equivalent and are part of the GRN that patterns the wing hinge. Five additional genes retain, at least partially, functions of the hng family of genes and can replace, to an extent, hng function. The four hinge genes code for proteins (blue circles), which we hypothesize may be part of a dimer/tetramer that is the active transcriptional regulator. Function could be regulated by increasing/decreasing the concentration of the Hng proteins, with the concentration of the functional polymer dependent on spatiotemporal expression and also the levels of the hng genes.