buttonhead and D-Spl: a novel Drosophila gene pair

Abstract

The Drosophila gene buttonhead (btd) is a gap-like head segmentation gene which encodes a triple zinc finger protein structurally and functionally related to the human transcription factor Spl. Here we report the pattern of btd expression during embryogenesis. btd is not only expressed and required in the blastoderm anlagen of the antennal, intercalary and mandibular segments as reported previously, but both expression and requirement extend into the anlage of the maxillary segment. From gastrulation onwards, btd is expressed in distinct spatial and temporal patterns, suggesting that btd might be required for a number of developmental 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 apparent phenotype was observed. We identified a btd-related gene, termed D-Sp1, which is expressed in temporal and spatial patterns similar to btd during postblastodermal development. No localized expression domains of D-Sp1, which is located in the same X-chromosomal band as btd, were seen during the blastoderm stage. The results suggest that D-Sp1 and btd represent a novel gene pair with partially redundant functions after the blastoderm stage.

The role ofbuttonheadandSp1in the development of the ventral imaginal discs ofDrosophila

“…btd and Sp1 expression domains in the thoracic segments The expression patterns of btd and of Sp1 during embryogenesis have already been described (Wimmer et al, 1993;Wimmer et al, 1996). In early embryos btd is expressed in the head region, but by the extended germ band stage the expression domain has expanded to the ventral region of cephalic, thoracic and abdominal segments.…”

“…It is located 753 bp 5′ of the btd gene (FlyBase). We note that the related gene Sp1, the Drosophila homologue of the human SP1 (Wimmer et al, 1993;Wimmer et al, 1996) is immediately adjacent (FlyBase). It is likely that btd and Sp1 have originated by a tandem duplication of a primordial btdlike gene.…”

“…For double fluorescent in situ/antibody label we followed the method as described by (Knirr et al, 1999). For the in situ label we used a btd RNA probe reported previously (Wimmer et al, 1996) and provided by Herbert Jackle. As probe for Sp1 we used an RNA transcribed from a cloned 2 kb DNA fragment obtained by PCR using primers from the 5′ and 3′ UTR.…”

“…It turned out to be buttonhead (btd), which encodes a zinc-finger transcription factor (Wimmer et al, 1993) and is known to be required for the formation of the intercalary, antennal and mandibular head segments (Cohen and Jürgens, 1990). A related adjacent gene, termed Sp1 (previously known as D-Sp1), has been previously characterised (Wimmer et al, 1996), the function of which is partially redundant with that of btd (Schock et al, 1999). We find that in addition to their role in head development btd and Sp1 are involved in the development of the ventral imaginal discs.…”

Novel Sp Family-like Transcription Factors Are Present in Adult Insect Cells and Are Involved in Transcription from the Polyhedrin Gene Initiator Promoter

“…Other proteins that belong to the Sp superfamily include the Krü ppel-like factors, including BKLF, EKLF, IKLF, etc. (15, 16); the BTEB proteins (BTEB1 and 2); CPBP proteins (CPBP, Zf9, UKLF); TIEG (TIEG 1 and 2) proteins (15,16); and the protein products of the huckebein (hkb) (44), buttonhead (bth) (45), and D-Sp1 (46) genes that are expressed in Drosophila embryos only during the blastoderm stage. There are no reports, however, of such factors being present in adult insect tissue (20,47,48).…”