A 7.8kb genomic fragment from the sim locus that includes a set of regulatory elements is fused upstream of the lacZ coding sequence. The sim fragment includes part of the sim coding sequence and thus expression is predicted to result in a fusion protein that contains the N-terminal 482 amino acids of sim fused to lacZ starting at amino acid 7. The sim coding sequence also includes a nuclear localisation signal.
At stage 15, expression observed in midline glia and in some midline neurons; at this stage, wild-type sim expressed in glia only.
Construct has a weak sim rescuing activity.