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G Struhl

Publications and source records attributed to G Struhl.

63 records · Page 4Linked to original sources
PubMed1982

Genes controlling segmental specification in the Drosophila thorax.

The roles of three homeotic genes, Ubx+, Scr+, and Antp+, in the Drosophila thorax have been studied by determining the cellular phenotypes of mutations resulting in loss of gene function. The principal results are: (i) The Scr+ and Ubx+ genes are required in the prothorax and metathorax, respectively; in the absence of these genes, both segments develop like the mesothorax. (ii) The Antp+ gene is required in all three thoracic segments: in its absence, parts of the mesothorax are transformed into corresponding parts of the antenna, and similar transformations to antenna are found in the prothorax and metathorax if the Scr+ and Ubx+ genes also are absent. (iii) Loss of the Ubx+ gene early in embryogenesis, but not later, leads to the inappropriate activity of the Scr+ gene in the meso- and metathorax. Results i and ii argue strongly that segmental determination is specified in a combinatorial fashion in the head and thorax by the selective activities of the Scr+, Ubx+, Antp+, and putative head-determining genes. Result iii suggests that a product of the Ubx+ gene also plays an early, regulatory role in ensuring the correct spatial expression of the Scr+ gene during subsequent development.

Animals↗
PubMed1982

Spineless-aristapedia: a homeotic gene that does not control the development of specific compartments in Drosophila.

A two-step screen for isolating null mutations of the spineless-aristapedia locus has been performed, and several amorphic mutations, as well as a small deficiency, have been obtained. With the exception of the deficiency, which deletes genes required for viability on either side of the spineless-aristapedia locus, these mutations result in a transformation of only the distal antenna into distal leg, thereby indicating that the spineless-aristapedia gene is required for specifying antennal as opposed to leg development in only the distal portion of the antenna. Because this distal region does not appear to be a developmental compartment, it is probable that the spineless-aristapedia gene, unlike several other homeotic genes, is required for maintaining the correct determined state in a population of cells defined by their relative position, not by their ancestry.

Alleles↗
PubMed1981

A gene product required for correct initiation of segmental determination in Drosophila.

The properties of mutations of the homoeotic gene extra sex combs (esc) indicate that the product of this gene is required early in development for correctly initiating segmental determination. Specifically, the esc+ gene product appears to be a necessary component of the process by which other homoeotic genes, such as those of the bithorax complex, are selectively turned one, or off, in particular segmental primordia. The resulting combinations of active and inactive genes established at this time then maintain the specific pathways of development followed subsequently by the different segments.

Drosophila↗
PubMed1979

Bristle patterns and compartment boundaries in the tarsi of Drosophila.

We describe cell lineage of the tarsus of wild-type Drosophila. Large Minute+ clones were made to map the position of the antero-posterior compartment boundary in all three tarsi. The tarsus is mirror symmetric, but the compartment boundary does not coincide with the mirror plane. This boundary runs along the dorsal and the ventral rows of bristles which are immediately posterior to the mirror plane; elements in these rows being made by both anterior and posterior polyclones. The provenance of bristles and bracts suggests that the bristle cells move into their final positions. The homoeotic mutation engrailed affects only the posterior compartments of all three tarsi. The mutations bithorax and postbithorax affect only the anterior and posterior compartments of the third legs, respectively, transforming them into homologous compartments of the second leg. These results support the selector gene model of development (Garcia-Bellido, 1975) and emphasize that collaboration between polyclones is important in pattern formation.

Animals↗
PubMedDate not supplied

Near-reciprocal phenotypes caused by inactivation or indiscriminate expression of the Drosophila segmentation gene ftz.

Early in development, Drosophila embryos express the segmentation gene fushi tarazu (ftz) in a 'zebra' pattern of active and inactive stripes, each about the width of a segment primordium. If the ftz gene is prevented from functioning, alternating portions of the body normally derived from the active stripes fail to develop, resulting in larvae which lack the denticle bands normally formed by the mesothorax and odd-numbered abdominal segments (that is, thoracic segment T2 and abdominal segments A1, A3, A5 and A7). Here, using the Drosophila heat shock protein 70 (hsp70) gene promoter to drive widespread expression of ftz transcripts on heat shock, I find that unrestricted ftz activity can cause a reciprocal 'pair-rule' phenotype--that is, the absence of the denticle bands which are normally derived from segments T1, T3, A2, A4, A6 and A8. These results show that both the 'on' and 'off' states of ftz gene expression have instructive roles in the development of alternating regions of the body, and hence suggest that the ftz gene acts combinatorially with other pair-rule genes (for example, even-skipped, odd-skipped, paired) to establish the metameric pattern of the body.

Animals↗
PubMedDate not supplied

A molecular gradient in early Drosophila embryos and its role in specifying the body pattern.

After fertilization, the protein products of the Drosophila homeobox gene caudal (cad) accumulate in a concentration gradient spanning the anteroposterior axis of the developing embryo. Mutations in the cad gene that reduce or eliminate the gradient cause abnormal zygotic expression of at least one segmentation gene (fushi tarazu) and alter the global body pattern.

Animals↗
PubMedDate not supplied

Borders of parasegments in Drosophila embryos are delimited by the fushi tarazu and even-skipped genes.

One of the earliest molecular signs of segmentation in Drosophila embryos is the striped expression of some pair-rule genes during the blastoderm stage. Two of these genes, fushi-tarazu (ftz) and even-skipped (eve) are expressed during this stage in complementary patterns of seven stripes which develop and disappear in concert. Here, we map the cells expressing each of these two pair-rule genes with respect to the 14 stripes of cells expressing the engrailed gene. We find that both ftz and eve generate stripes which have sharp boundaries at the anterior margin, but fade away posteriorly. The anterior boundaries correspond cell by cell with the anterior boundaries of expression of the engrailed gene. We therefore suggest that a key function of early ftz and eve gene activity is the formation of a sharp stable boundary at the anterior margin of each stripe. These boundary lines, rather than the narrowing zonal stripes, would delimit the anterior boundaries of engrailed and other homoeotic genes and thereby subdivide the embryo into parasegments.

Animals↗