BUTTONHEAD AND D-SP1 - A NOVEL DROSOPHILA GENE PAIR

The Drosophila gene buttonhead (btd) is a gap-like head segmentation g ene which encodes a triple zinc finger protein structurally and functi onally related to the human transcription factor Sp1. Here we report t he pattern of btd expression during embryogenesis. btd is not only exp ressed and required in the blastoderm anlagen of the antennal, interca lary and mandibular segments as reported previously, but both expressi on and requirement extend into the anlage of the maxillary segment, Fr om gastrulation onwards, bid is expressed in distinct spatial and temp oral patterns, suggesting that btd might be required for a number of d evelopmental processes beyond head segmentation. In fact, analysis of btd mutant embryos revealed that btd participates in the formation of the peripheral nervous system. However, no other morphologically appar ent phenotype was observed. We identified a btd-related gene, termed D -Sp1, which is expressed in temporal and spatial patterns similar to b td during postblastodermal development. No localized expression domain s of D-Sp1, which is located in the same X-chromosomal band as btd, we re seen during the blastoderm stage. The results suggest that D-Sp1 an d btd represent a novel gene pair with partially redundant functions a fter the blastoderm stage.