scholarly journals Autocatalysis and phenotypic expression of Drosophila homeotic gene Deformed: its dependence on polarity and homeotic gene function

Development ◽  
1992 ◽  
Vol 116 (4) ◽  
pp. 1059-1068 ◽  
Author(s):  
A. Gonzalez-Reyes ◽  
A. Macias ◽  
G. Morata
Keyword(s):  
Heat Shock ◽  
Gene Function ◽  
Phenotypic Expression ◽  
Normal Function ◽  
Homeotic Gene ◽  
Activation Process ◽  
Homeotic Genes ◽  
Embryonic Cells ◽  
Noticeable Effect ◽  
In Cells

Previously published experiments have shown that the endogenous Dfd gene can be ectopically activated by its own (heat-shock-driven) product in a subset of cells of different segments. This results in the differentiation of maxillary structures like cirri and mouth hooks in places where they normally do not appear, and represents a phenomenon of autocatalysis of homeotic gene function that differs from the normal activation process. We show that this out-of-context activation occurs in cells belonging to the anterior compartments of the three thoracic and the A1 to A8 abdominal segments and that it requires the normal function of the polarity genes wingless (wg) and engrailed (en). The wg product, in addition to that of Dfd, appears to be sufficient to activate the endogenous Dfd gene in many embryonic cells. We have studied the effect of several homeotic genes on Dfd activation and phenotypic expression: Scr, Antp, Ubx and Abd-B repress Dfd both transcriptionally and at the phenotypic level, if their products are in sufficient amounts. The endogenous abd-A gene does not have a noticeable effect, but when it is replaced by an hsp70-abd-A gene, which produces a high and uniform level of expression, the phenotypic expression of Dfd is suppressed. Our results also suggest that the differentiation of cirri is induced by Dfd-expressing cells in non-expressing neighboring cells, and that this interaction occurs across the parasegmental border.

The role of the teashirt gene in trunk segmental identity in Drosophila

Development ◽  
1992 ◽  
Vol 115 (4) ◽  
pp. 1017-1033 ◽  
Author(s):  
L. Roder ◽  
C. Vola ◽  
S. Kerridge
Keyword(s):  
Gene Function ◽  
Ground State ◽  
Normal Function ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Ventral Part ◽  
Regulatory Interactions ◽  
Insight Into ◽  
Segmental Identity

The phenotypes of different mutant combinations of teashirt (tsh) and homeotic genes together with their regulatory interactions are described in order to gain insight into tsh gene function. We show that when tsh, Scr, Antp and BX-C genes are missing, the ventral part of the trunk (or thorax and abdomen) is transformed to anterior head identity showing that tsh is a homeotic gene. These genes act synergistically to suppress the expression of the procephalic gene labial (lab) in subsets of cells in each segment of the trunk. Transcripts from the tsh gene always accumulate in segments destined to acquire trunk identities. tsh gene activity is required for the normal function of the Antp and BX-C genes, which modulate in part the expression of tsh. As a whole, our results suggest that tsh plays an essential dual role, during embryogenesis, for determining segmental identity of the trunk. First, tsh is required critically for the identity of the anterior prothorax. Second, tsh is required globally for segmental identity throughout the entire trunk whereas the “classical” homeotic genes have more specific roles. Our results are consistent with the idea that tsh is defining the ground state of the Drosophila trunk region seen in the absence of the Antp and BX-C genes.

scholarly journals Setting limits on homeotic gene function: restraint of Sex combs reduced activity by teashirt and other homeotic genes.

1994 ◽  
Vol 13 (5) ◽  
pp. 1132-1144 ◽  
Author(s):  
D.J. Andrew ◽  
M.A. Horner ◽  
M.G. Petitt ◽  
S.M. Smolik ◽  
M.P. Scott
Keyword(s):  
Gene Function ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Reduced Activity

Dissecting the temporal requirements for homeotic gene function

Development ◽  
1994 ◽  
Vol 120 (7) ◽  
pp. 1983-1995 ◽  
Author(s):  
J. Castelli-Gair ◽  
S. Greig ◽  
G. Micklem ◽  
M. Akam
Keyword(s):  
Gene Expression ◽  
Nervous System ◽  
Gene Function ◽  
Cell Types ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Bithorax Complex ◽  
Cell Type ◽  
Homeotic Gene Expression

Homeotic genes confer identity to the different segments of Drosophila. These genes are expressed in many cell types over long periods of time. To determine when the homeotic genes are required for specific developmental events we have expressed the Ultrabithorax, abdominal-A and Abdominal-Bm proteins at different times during development using the GAL4 targeting technique. We find that early transient homeotic gene expression has no lasting effects on the differentiation of the larval epidermis, but it switches the fate of other cell types irreversibly (e.g. the spiracle primordia). We describe one cell type in the peripheral nervous system that makes sequential, independent responses to homeotic gene expression. We also provide evidence that supports the hypothesis of in vivo competition between the bithorax complex proteins for the regulation of their down-stream targets.

Engrailed-mediated repression of Ultrabithorax is necessary for the parasegment 6 identity in Drosophila

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3205-3212 ◽  
Author(s):  
R.S. Mann
Keyword(s):  
Gene Expression ◽  
Heat Shock ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Posterior Compartment ◽  
Anterior Compartment ◽  
Heat Shock Promoter ◽  
Sensory Structures ◽  
Different Levels ◽  
Homeotic Gene Expression

The homeotic genes of Drosophila are expressed in overlapping domains along the anterior-to-posterior axis and specify the distinct morphological patterns of each parasegment. Within single parasegments, the levels of homeotic gene expression are often modulated, in part because of cross-regulation by other homeotic gene products. However, the functional significance of different levels of homeotic gene expression is unclear. Here modulations in Ultrabithorax (Ubx) expression within parasegment 6 are examined. Specifically, Ubx is shown to be down-regulated in the posterior compartment of this parasegment by engrailed (en). The significance of Ubx repression by en was demonstrated by characterizing the expression of the Ubx target gene, Distal-less (Dll). In the posterior compartment of parasegment 6, Dll is normally expressed in a small cluster of cells. If Ubx is expressed uniformly via a heat-shock promoter, Dll is inappropriately repressed in these posterior compartment cells. In the anterior compartment of parasegment 6, Dll is normally repressed by high levels of Ubx. However, if en is expressed uniformly via a heat-shock promoter, Ubx is repressed and Dll is derepressed. Because Dll is required for the development of larval sensory structures, these results demonstrate that en-mediated repression of Ubx in the posterior compartment is necessary for the morphology of parasegment 6. Thus, different levels of homeotic gene expression can be important for their segmental patterning functions.

Absence of temporal ordering of apoptotic features in heat-shock treated leukemia and lymphoma cell lines

1996 ◽  
Vol 54 ◽  
pp. 758-759
Author(s):  
D. W. Fairbain ◽  
M.D. Standing ◽  
K.L. O'Neill
Keyword(s):  
Heat Shock ◽  
Cell Lines ◽  
Chromatin Condensation ◽  
Membrane Integrity ◽  
Resistant Cell ◽  
Membrane Blebbing ◽  
Late Loss ◽  
Induced Apoptosis ◽  
Dying Cells ◽  
In Cells

Apoptosis is a genetically defined response to physiological stimuli that results in cellular suicide. Features common to apoptotic cells include chromatin condensation, oligonucleosomal DNA fragmentation, membrane blebbing, nuclear destruction, and late loss of ability to exclude vital dyes. These characteristics contrast markedly from pathological necrosis, in which membrane integrity loss is demonstrated early, and other features of apoptosis, which allow a non-inflammatory removal of dead and dying cells, are absent. Using heat shock-induced apoptosis as a model for examining stress response in cells, we undertook to categorize a variety of human leukemias and lymphomas with regard to their response to heat shock. We were also interested in determining whether a common temporal order was followed in cells dying by apoptosis. In addition, based on our previous results, we investigated whether increasing heat load resulted in increased apoptosis, with particular interest in relatively resistant cell lines, or whether the mode of death changed from apoptosis to necrosis.

Homeotic complex and teashirt genes co-operate to establish trunk segmental identities in Drosophila

Development ◽  
1994 ◽  
Vol 120 (8) ◽  
pp. 2287-2296 ◽  
Author(s):  
P. de Zulueta ◽  
E. Alexandre ◽  
B. Jacq ◽  
S. Kerridge
Keyword(s):  
Heat Shock ◽  
Target Genes ◽  
Homeotic Genes ◽  
Sex Combs Reduced ◽  
Downstream Target ◽  
Functional Aspects ◽  
Sex Combs ◽  
Head Segment ◽  
Posterior Trunk ◽  
Segmental Identity

Homeotic genes determine the identities of metameres in Drosophila. We have examined functional aspects of the homeotic gene teashirt by ectopically expressing its product under the control of a heat-shock promoter during embryogenesis. Our results confirm that the gene is critical for segmental identity of the larva. Under mild heat-shock conditions, the Teashirt protein induces an almost complete transformation of the labial to prothoracic segmental identity, when expressed before 8 hours of development. Positive autoregulation of the endogenous teashirt gene and the presence of Sex combs reduced protein in the labium explain this homeosis. Patterns in the maxillary and a more anterior head segment are partly replaced with trunk ones. Additional Teashirt protein has no effect on the identity of the trunk segments where the gene is normally expressed; teashirt function is overridden by some homeotic complex acting in the posterior trunk. Strong heat-shock regimes provoke novel defects: ectopic sense organs differentiate in posterior abdominal segments and trunk pattern elements differentiate in the ninth abdominal segment. Teashirt acts in a partially redundant way with certain homeotic complex proteins but co-operates with them for the establishment of specific segment types. We suggest that Teashirt and HOM-C proteins regulate common sets of downstream target genes.

Modifying expression of the engrailed gene of Drosophila melanogaster

Development ◽  
1988 ◽  
Vol 104 (Supplement) ◽  
pp. 85-93 ◽  
Author(s):  
Stephen J. Poole ◽  
Thomas B. Kornberg
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Heat Shock ◽  
P Element ◽  
Drosophila Embryo ◽  
Hsp70 Promoter ◽  
Normal Period ◽  
In Cells

The engrailed gene is required for segmentation of the Drosophila embryo and is expressed in cells constituting the posterior developmental compartments. In mutant embryos lacking engrailed function, portions of the cuticular pattern in each segment are deleted, resulting in fusion of adjacent denticle bands. Using P-element-mediated transposition, we generated flies that express the engrailed gene under the control of an hsp70 promoter, and found that ectopic, heat-shock-induced, engrailed expression caused pattern defects similar to those in embryos lacking engrailed function. Sensitivity to heat shock was only during the cellular blastoderm and early gastrulation periods. This window of sensitivity corresponds to the time when wildtype engrailed protein localizes into segmentally reiterated stripes and represents only a small portion of the normal period of engrailed gene expression.

Circus movements and blebbing locomotion in dissociated embryonic cells of an amphibian, Xenopus laevis

1976 ◽  
Vol 22 (3) ◽  
pp. 575-583
Author(s):  
K.E. Johnson
Keyword(s):  
Xenopus Laevis ◽  
Cell Contact ◽  
Embryonic Cells ◽  
Gastrula Stage ◽  
Isolated Cells ◽  
Daughter Cells ◽  
Cytoplasmic Protrusion ◽  
Endodermal Cells ◽  
In Cells

Circus movements, which involve the circumferential rotation of a hyaline cytoplasmic protrusion, occur in cells obtained by EDTA dissociation of gastrula-stage Xenopus laevis embryos. Only a few dissociated blastula-stage cells show circus movements, more early gastrula-stage cells show them, and nearly all late gastrula-stage cells show them. Circus movements cease in cells prior to mitosis and begin again in daughter cells after mitosis is completed. In early gastrulae, only 17% of prospective endodermal cells show circus movements while 79% of prospective mesodern, archenteric roof, and posterior neural ectoderm do so. Isolated cells as well as groups of cells in vitro are often propelled by circus movements. There is an obvious antagonism between cell contact and circus movements. The morphogenetic significance of circus movements and blebbing locomotion is discussed.

Evolution of the insect body plan as revealed by the Sex combs reduced expression pattern

Development ◽  
1997 ◽  
Vol 124 (1) ◽  
pp. 149-157 ◽  
Author(s):  
B.T. Rogers ◽  
M.D. Peterson ◽  
T.C. Kaufman
Keyword(s):  
Morphological Evolution ◽  
Expression Patterns ◽  
Morphological Characters ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Cell Fates ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Evolutionarily Conserved ◽  
Epidermal Expression

The products of the HOM/Hox homeotic genes form a set of evolutionarily conserved transcription factors that control elaborate developmental processes and specify cell fates in many metazoans. We examined the expression of the ortholog of the homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster in insects of three divergent orders: Hemiptera, Orthoptera and Thysanura. Our data reflect how the conservation and variation of Scr expression has affected the morphological evolution of insects. Whereas the anterior epidermal expression of Scr, in a small part of the posterior maxillary and all of the labial segment, is found to be in common among all four insect orders, the posterior (thoracic) expression domains vary. Unlike what is observed in flies, the Scr orthologs of other insects are not expressed broadly over the first thoracic segment, but are restricted to small patches. We show here that Scr is required for suppression of wings on the prothorax of Drosophila. Moreover, Scr expression at the dorsal base of the prothoracic limb in two other winged insects, crickets (Orthoptera) and milkweed bugs (Hemiptera), is consistent with Scr acting as a suppressor of prothoracic wings in these insects. Scr is also expressed in a small patch of cells near the basitarsal-tibial junction of milkweed bugs, precisely where a leg comb develops, suggesting that Scr promotes comb formation, as it does in Drosophila. Surprisingly, the dorsal prothoracic expression of Scr is also present in the primitively wingless firebrat (Thysanura) and the leg patch is seen in crickets, which have no comb. Mapping both gene expression patterns and morphological characters onto the insect phylogenetic tree demonstrates that in the cases of wing suppression and comb formation the appearance of expression of Scr in the prothorax apparently precedes these specific functions.

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