Generation of GAL4-responsive muscleblind constructs

The muscleblind (mbl) gene encodes protein isoforms Mbl A to Mbl D, which arise by alternative splicing from a common primary transcript. Mbl A, B, and C contain two Zn-finger domains of the type Cys3His, while Mbl D contains only one complete Zn finger. Loss of function mutations in the gene reveal that mbl is involved in both terminal photoreceptor and muscle differentiation in Drosophila. During retina development mbl is essential for rhabdomere differentiation in photoreceptor neuron. Clones homozygous null for mbl completely lack these lightharvesting structures (Begemann et al., 1997). Similarly, the terminal differentiation of the larval body wall muscles is compromised in mbl mutant…