Normal and ectopic domains of the homeotic gene Sex combs reduced of Drosophila

Development ◽  
1993 ◽  
Vol 117 (3) ◽  
pp. 917-923 ◽  
Author(s):  
S. Pelaz ◽  
N. Urquia ◽  
G. Morata
Keyword(s):  
Ectopic Expression ◽  
Secondary Wave ◽  
Homeotic Gene ◽  
Bithorax Complex ◽  
Germ Band ◽  
Sex Combs Reduced ◽  
Normal Functions ◽  
Sex Combs ◽  
Normal Expression ◽  
Thoracic And Abdominal

The normal expression of the homeotic gene Sex combs reduced (Scr) is initially restricted to parasegment 2, later extends to 3, and by germ band retraction extends further to part of parasegment 4 (T1p). We find that in the absence of the bithorax complex (BX-C) genes there is Scr expression in the epidermis of the posterior compartments of the thoracic and abdominal parasegments. This ectopic expression appears at the same time as the normal one in T1p and requires the normal functions of the genes Antennapedia (Antp) and engrailed (en). In particular, en appears to play an important role in the activation of Scr because the expansion of en expression in naked mutants produces a corresponding expansion of the ectopic Scr stripes. We also find that in the epidermis Antp can have opposite effects on Scr expression; moderate levels of Antp product enhance Scr expression, whereas high levels suppress it. We propose the existence of a secondary wave of Scr activation, which takes place during germ band retraction, is triggered by en and requires Antp expression. It is repressed by the BX-C genes in the meso-, metathoracic and the abdominal segments.

Ectopic expression of homeotic genes caused by the elimination of the Polycomb gene in Drosophila imaginal epidermis

Development ◽  
1988 ◽  
Vol 104 (4) ◽  
pp. 713-720 ◽  
Author(s):  
A. Busturia ◽  
G. Morata
Keyword(s):  
Ectopic Expression ◽  
Homeotic Genes ◽  
Sex Combs Reduced ◽  
Hierarchical Order ◽  
Sex Combs ◽  
Morphological Patterns

The morphological patterns in the adult cuticle of Drosophila are determined principally by the homeotic genes of the bithorax and Antennapedia complexes. We find that many of these genes become indiscriminately active in the adult epidermis when the Pc gene is eliminated. By using the Pc3 mutation and various BX-C mutant combinations, we have generated clones of imaginal cells possessing different combinations of active homeotic genes. We find that, in the absence of BX-C genes, Pc- clones develop prothoracic patterns; this is probably due to the activity of Sex combs reduced which overrules Antennapedia. Adding contributions of Ultrabithorax, abdominal-A and Abdominal-B results in thoracic or abdominal patterns. We have established a hierarchical order among these genes: Antp less than Scr less than Ubx less than abd-A less than Abd-B. In addition, we show that the engrailed gene is ectopically active in Pc- imaginal cells.

scholarly journals The ash-1, ash-2 and trithorax genes of Drosophila melanogaster are functionally related.

Genetics ◽  
1989 ◽  
Vol 121 (3) ◽  
pp. 517-525 ◽  
Author(s):  
A Shearn
Keyword(s):  
Drosophila Melanogaster ◽  
Null Allele ◽  
Homeotic Gene ◽  
Bithorax Complex ◽  
Substantial Evidence ◽  
Genetic Tests ◽  
Recessive Lethal ◽  
The Third ◽  
Sex Combs

Abstract Mutations in the ash-1 and ash-2 genes of Drosophila melanogaster cause a wide variety of homeotic transformations that are similar to the transformations caused by mutations in the trithorax gene. Based on this similar variety of transformations, it was hypothesized that these genes are members of a functionally related set. Three genetic tests were employed here to evaluate that hypothesis. The first test was to examine interactions of ash-1, ash-2 and trithorax mutations with each other. Double and triple heterozygotes of recessive lethal alleles express characteristic homeotic transformations. For example, double heterozygotes of a null allele of ash-1 and a deletion of trithorax have partial transformations of their first and third legs to second legs and of their halteres to wings. The penetrance of these transformations is reduced by a duplication of the bithorax complex. The second test was to examine interactions with a mutation in the female sterile (1) homeotic gene. The penetrance of the homeotic phenotype in progeny from mutant mothers is increased by heterozygosis for alleles of ash-1 or ash-2 as well as for trithorax alleles. The third test was to examine the interaction with a mutation of the Polycomb gene. The extra sex combs phenotype caused by heterozygosis for a deletion of Polycomb is suppressed by heterozygosis for ash-1, ash-2 or trithorax alleles. The fact that mutations in each of the three genes gave rise to similar results in all three tests represents substantial evidence that ash-1, ash-2 and trithorax are members of a functionally related set of genes.

scholarly journals Needs and Targets for the multi sex combs Gene Product in Drosophila melanogaster

Genetics ◽  
1998 ◽  
Vol 149 (4) ◽  
pp. 1823-1838 ◽  
Author(s):  
Olivier Saget ◽  
Françoise Forquignon ◽  
Pedro Santamaria ◽  
Neel B Randsholt
Keyword(s):  
Drosophila Melanogaster ◽  
Ectopic Expression ◽  
Polycomb Group ◽  
Homeotic Genes ◽  
Maternal Control ◽  
Gap Gene ◽  
Sex Combs ◽  
Normal Expression ◽  
Selector Genes ◽  
Mutant Phenotypes

Abstract We have analyzed the requirements for the multi sex combs (mxc) gene during development to gain further insight into the mechanisms and developmental processes that depend on the important trans-regulators forming the Polycomb group (PcG) in Drosophila melanogaster. mxc is allelic with the tumor suppressor locus lethal (1) malignant blood neoplasm (l(1)mbn). We show that the mxc product is dramatically needed in most tissues because its loss leads to cell death after a few divisions. mxc has also a strong maternal effect. We find that hypomorphic mxc mutations enhance other PcG gene mutant phenotypes and cause ectopic expression of homeotic genes, confirming that PcG products are cooperatively involved in repression of selector genes outside their normal expression domains. We also demonstrate that the mxc product is needed for imaginal head specification, through regulation of the ANT-C gene Deformed. Our analysis reveals that mxc is involved in the maternal control of early zygotic gap gene expression previously reported for some PcG genes and suggests that the mechanism of this early PcG function could be different from the PcG-mediated regulation of homeotic selector genes later in development. We discuss these data in view of the numerous functions of PcG genes during development.

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.

scholarly journals Novel regulation of the homeotic gene Scr associated with a crustacean leg-to-maxilliped appendage transformation

Development ◽  
1999 ◽  
Vol 126 (6) ◽  
pp. 1121-1128 ◽  
Author(s):  
A. Abzhanov ◽  
T.C. Kaufman
Keyword(s):  
Expression Patterns ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Porcellio Scaber ◽  
Sex Combs Reduced ◽  
Early Embryos ◽  
Sex Combs ◽  
Thoracic Legs ◽  
Post Transcriptional Regulation ◽  
Late Stages

Homeotic genes are known to be involved in patterning morphological structures along the antero-posterior axis of insects and vertebrates. Because of their important roles in development, changes in the function and expression patterns of homeotic genes may have played a major role in the evolution of different body plans. For example, it has been proposed that during the evolution of several crustacean lineages, changes in the expression patterns of the homeotic genes Ultrabithorax and abdominal-A have played a role in transformation of the anterior thoracic appendages into mouthparts termed maxillipeds. This homeotic-like transformation is recapitulated at the late stages of the direct embryonic development of the crustacean Porcellio scaber (Oniscidea, Isopoda). Interestingly, this morphological change is associated with apparent novelties both in the transcriptional and post-transcriptional regulation of the Porcellio scaber ortholog of the Drosophila homeotic gene, Sex combs reduced (Scr). Specifically, we find that Scr mRNA is present in the second maxillary segment and the first pair of thoracic legs (T1) in early embryos, whereas protein accumulates only in the second maxillae. In later stages, however, high levels of SCR appear in the T1 legs, which correlates temporally with the transformation of these appendages into maxillipeds. Our observations provide further insight into the process of the homeotic leg-to-maxilliped transformation in the evolution of crustaceans and suggest a novel regulatory mechanism for this process in this group of arthropods.

scholarly journals Role of the esc+ gene product in ensuring the selective expression of segment-specific homeotic genes in Drosophila

Development ◽  
1983 ◽  
Vol 76 (1) ◽  
pp. 297-331
Author(s):  
Gary Struhl
Keyword(s):  
Gene Product ◽  
The Body ◽  
Homeotic Genes ◽  
Bithorax Complex ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Correct Determination ◽  
Correct Expression

The product of the extra sex combs+ (esc+) gene is required during embryogenesis for the correct determination of segments in Drosophila. If this product is absent, most segments develop like the normal eighth abdominal segment. Here, I extend previous results (Struhl, 1981a) showing that this phenotype results in large part from indiscriminate expression of the bithorax-complex genes which are normally active only in particular segments of the thorax and abdomen. In addition, I test whether the esc+ gene product is required for the correct expression of other homeotic genes. First, I have examined two genes of the Antennapedia-complex (Sex combs reduced+ and Antennapedia+): I find that both genes are normally required in only some of the body segments, but that in the absence of the esc+ gene product, both appear to function adventitiously in other segments. Second, comparing esc+ and esc− embryos lacking both these genes as well as the bithorax-complex, I find that additional homeotic genes (possibly those normally involved in specifying head segments) appear to be expressed indiscriminately when the esc+ gene product is absent. Finally, I present evidence that the products of the esc+ gene and the Polycomb+ gene (a second gene required for the correct regulation of the bithorax-complex) act independently. On the basis of these results, I propose a tentative outline of the roles and realms of action of all of these genes.

Trithorax regulates multiple homeotic genes in the bithorax and Antennapedia complexes and exerts different tissue-specific, parasegment-specific and promoter-specific effects on each

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 119-134 ◽  
Author(s):  
T.R. Breen ◽  
P.J. Harte
Keyword(s):  
Gene Expression ◽  
Expression Patterns ◽  
The Body ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Sex Combs Reduced ◽  
Tissue Specific ◽  
Specific Effects ◽  
Normal Expression ◽  
Homeotic Gene Expression

The trithorax (trx) gene is required for normal development of the body plan in Drosophila embryos and adults. Mutations in trx cause homeotic transformations throughout the body. Genetic studies suggest that trx encodes a positive regulatory factor required throughout development for normal expression of multiple homeotic genes of the bithorax and Antennapedia complexes (BX-C and ANT-C). To determine how trx influences homeotic gene expression, we examined the expression of the BX-C genes Ultrabithorax, abdominal-A, Abdominal-B and the ANT-C genes Antennapedia, Sex combs reduced and Deformed in trx embryos. We show that trx does indeed exert its effects by positively regulating homeotic gene expression and that its effects on expression of individual homeotic genes are complex: each of the BX-C and ANT-C genes examined exhibits different tissue-specific, parasegment-specific and promoter-specific reductions in their expression. This implies that each of these genes have different requirements for trx in different spatial contexts in order to achieve normal expression levels, presumably depending on the promoters involved and the other regulatory factors bound at each of their multiple tissue- and parasegment-specific cis-regulatory sites in different regions of the embryo. These results also imply that those components of homeotic gene expression patterns for which trx is dispensable, require other factors, possibly those encoded by other trithorax-like genes.

Blocking cell division does not remove the requirement for Polycomb function in Drosophila embryogenesis

Development ◽  
1990 ◽  
Vol 110 (4) ◽  
pp. 1319-1325 ◽  
Author(s):  
A.P. Gould ◽  
R.Y. Lai ◽  
M.J. Green ◽  
R.A. White
Keyword(s):  
Gene Expression ◽  
Cell Division ◽  
Dna Replication ◽  
Ectopic Expression ◽  
Homeotic Gene ◽  
Germ Band ◽  
Drosophila Embryogenesis ◽  
Stable Transmission ◽  
Homeotic Gene Expression

The Polycomb (Pc) gene is required from the extended germ band stage onwards, to maintain spatially restricted patterns of homeotic gene expression. It has been thought to be involved in the ‘stable inheritance of the determined state’. In this paper, we have tested the notion that the Pc gene is required specifically during or after DNA replication to enable the stable transmission of states of gene activity. We found that arresting cell division using the string mutation or blocking DNA replication with aphidicolin failed to prevent ectopic expression of the homeotic gene Ultrabithorax in Pc mutants. Thus, even in the absence of DNA replication, Pc is required to maintain spatially restricted patterns of homeotic gene expression. The role of the Pc gene product in the stable repression of homeotic gene transcription is discussed.

Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products

Development ◽  
1992 ◽  
Vol 114 (2) ◽  
pp. 493-505 ◽  
Author(s):  
J. Simon ◽  
A. Chiang ◽  
W. Bender
Keyword(s):  
Expression Patterns ◽  
Ectopic Expression ◽  
Specific Pattern ◽  
Polycomb Group ◽  
Polycomb Group Genes ◽  
Sex Combs ◽  
Normal Expression ◽  
Sex Comb ◽  
Regulatory Dna ◽  
Pair Rule

Mutations in genes of the Polycomb (Pc) group cause abnormal segmental development due to ectopic expression of the homeotic products of the Antennapedia and bithorax complexes. Here the requirements for Pc group genes in controlling the abdA and AbdB products of the bithorax complex are described. Embryos containing mutations in the genes Polycomb (Pc), extra sex combs (esc), Enhancer of zeste [E(z)], polyhomeotic (ph), Sex comb on midleg (Scm), Polycomb-like (Pcl), Sex comb extra (Sce), Additional sex combs (Asx), Posterior sex combs (Psc) and pleiohomeotic (pho) were examined. In every case, both abdA and AbdB are expressed outside of their normal domains along the anterior-posterior (A-P) axis, consistent with these Pc group products acting in a single pathway or molecular complex. The earliest detectable ectopic expression is highest in the parasegments immediately adjacent to the normal expression boundary. Surprisingly, in the most severe Pc group mutants, the earliest ectopic AbdB is distributed in a pair-rule pattern. At all stages, ectopic abdA in the epidermis is highest along the anterior edges of the parasegments, in a pattern that mimics the normal abdA cell-specific pattern. These examples of highly patterned mis-expression show that Pc group mutations do not cause indiscriminate activation of homeotic products. We suggest that the ectopic expression patterns result from factors that normally activate abdA and AbdB only in certain parasegments, but that in Pc group mutants these factors gain access to regulatory DNA in all parasegments.

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