scholarly journals Genetic analysis of embryonic cis-acting regulatory elements of the Drosophila homeotic gene sex combs reduced.

Genetics ◽  
1995 ◽  
Vol 140 (2) ◽  
pp. 557-572 ◽  
Author(s):  
M J Gorman ◽  
T C Kaufman
Keyword(s):  
Expression Pattern ◽  
Chromosomal Rearrangements ◽  
Regulatory Elements ◽  
Homeotic Gene ◽  
Sex Combs Reduced ◽  
Cis Acting ◽  
Transcriptional Regulatory Elements ◽  
Visceral Mesoderm ◽  
Posterior Midgut ◽  
Sex Combs

Abstract The homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster is expressed in the labial and prothoracic segments of the ectoderm, in parasegments two and three of the CNS, and in the visceral mesoderm of the anterior and posterior midgut. The mutationally defined function of Scr is to specify the identity of the labial and prothoracic segments and to control the development of the gastric caeca. The Scr locus occupies a chromosomal region of approximately 80 kb within the Antennapedia complex (ANT-C). To understand how Scr's spatiotemporal expression pattern is generated in the embryo, we have mapped its transcriptional regulatory elements using three approaches. First, we examined the expression pattern of Scr in embryos containing chromosomal rearrangements that remove potential Scr regulatory elements. Second, we made and analyzed a set of Scr minigene transformants. Third, we analyzed a set of Scr-lacZ enhancer tester constructs. Using more sensitive anti-SCR antisera, we discovered that Scr is expressed in tissues that were not previously thought to accumulate SCR: a stripe of ectodermal cells in the parasegment 2 region of stage 5 embryos, the embryonic salivary glands, and the dorsal ridge. Four DNA fragments that had previously been shown in an analysis of Scr-lacZ reporter constructs to contain putative Scr enhancer elements were found to have functional enhancers; similarly, another Scr fragment was found to contain a functional repressor. Our results suggest that regulation of Scr in the labial segment and the CNS requires the apparently synergistic action of multiple, widely spaced enhancer elements. Regulation in the prothorax also appears to be controlled by multiple enhancers:one complete pattern element and one subpattern element. In contrast, Scr regulation in the visceral mesoderm is controlled by an enhancer(s) located in only one DNA fragment.

scholarly journals Characterization of the cis-regulatory region of the Drosophila homeotic gene Sex combs reduced.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 781-795
Author(s):  
J G Gindhart ◽  
A N King ◽  
T C Kaufman
Keyword(s):  
Gene Expression ◽  
Reporter Gene ◽  
Regulatory Region ◽  
Reporter Gene Expression ◽  
Homeotic Gene ◽  
Regulatory Sequences ◽  
Dna Fragments ◽  
Sex Combs Reduced ◽  
Posterior Midgut ◽  
Sex Combs

Abstract The Drosophila homeotic gene Sex combs reduced (Scr) controls the segmental identity of the labial and prothoracic segments in the embryo and adult. It encodes a sequence-specific transcription factor that controls, in concert with other gene products, differentiative pathways of tissues in which Scr is expressed. During embryogenesis, Scr accumulation is observed in a discrete spatiotemporal pattern that includes the labial and prothoracic ectoderm, the subesophageal ganglion of the ventral nerve cord and the visceral mesoderm of the anterior and posterior midgut. Previous analyses have demonstrated that breakpoint mutations located in a 75-kb interval, including the Scr transcription unit and 50 kb of upstream DNA, cause Scr misexpression during development, presumably because these mutations remove Scr cis-regulatory sequences from the proximity of the Scr promoter. To gain a better understanding of the regulatory interactions necessary for the control of Scr transcription during embryogenesis, we have begun a molecular analysis of the Scr regulatory interval. DNA fragments from this 75-kb region were subcloned into P-element vectors containing either an Scr-lacZ or hsp70-lacZ fusion gene, and patterns of reporter gene expression were assayed in transgenic embryos. Several fragments appear to contain Scr regulatory sequences, as they direct reporter gene expression in patterns similar to those normally observed for Scr, whereas other DNA fragments direct Scr reporter gene expression in developmentally interesting but non-Scr-like patterns during embryogenesis. Scr expression in some tissues appears to be controlled by multiple regulatory elements that are separated, in some cases, by more than 20 kb of intervening DNA. Interestingly, regulatory sequences that direct reporter gene expression in an Scr-like pattern in the anterior and posterior midgut are imbedded in the regulatory region of the segmentation gene fushi tarazu (ftz), which is normally located between 10 and 20 kb 5' of the Scr transcription start site. This analysis provides an entry point for the study of how Scr transcription is regulated at the molecular level.

Transvection and Silencing of the Scr Homeotic Gene of Drosophila melanogaster

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 733-746
Author(s):  
Jeffrey W Southworth ◽  
James A Kennison
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosomal Aberrations ◽  
Regulatory Element ◽  
Regulatory Elements ◽  
Anomalous Behavior ◽  
Polycomb Group ◽  
Homeotic Gene ◽  
Polycomb Group Proteins ◽  
Sex Combs Reduced ◽  
In Cis

Abstract The Sex combs reduced (Scr) gene specifies the identities of the labial and first thoracic segments in Drosophila melanogaster. In imaginal cells, some Scr mutations allow cis-regulatory elements on one chromosome to stimulate expression of the promoter on the homolog, a phenomenon that was named transvection by Ed Lewis in 1954. Transvection at the Scr gene is blocked by rearrangements that disrupt pairing, but is zeste independent. Silencing of the Scr gene in the second and third thoracic segments, which requires the Polycomb group proteins, is disrupted by most chromosomal aberrations within the Scr gene. Some chromosomal aberrations completely derepress Scr even in the presence of normal levels of all Polycomb group proteins. On the basis of the pattern of chromosomal aberrations that disrupt Scr gene silencing, we propose a model in which two cis-regulatory elements interact to stabilize silencing of any promoter or cis-regulatory element physically between them. This model also explains the anomalous behavior of the Scx allele of the flanking homeotic gene, Antennapedia. This allele, which is associated with an insertion near the Antennapedia P1 promoter, inactivates the Antennapedia P1 and P2 promoters in cis and derepresses the Scr promoters both in cis and on the homologous chromosome.

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.

The large upstream control region of the Drosophila homeotic gene Ultrabithorax

Development ◽  
1991 ◽  
Vol 111 (2) ◽  
pp. 407-424 ◽  
Author(s):  
K.D. Irvine ◽  
S.L. Helfand ◽  
D.S. Hogness
Keyword(s):  
Expression Pattern ◽  
Control Region ◽  
Homeotic Gene ◽  
Visceral Mesoderm ◽  
Initial Activation ◽  
Chromosome Breakpoint ◽  
Sequence Requirements ◽  
Upstream Control ◽  
Beta Galactosidase ◽  
Pair Rule

Ultrabithorax (Ubx) is a Drosophila homeotic gene that determines the segmental identities of parts of the thorax and abdomen. Appropriate Ubx transcription requires a long upstream control region (UCR) that is defined genetically by the bithoraxoid (bxd) and postbithorax (pbx) subfunction mutations. We have directly analyzed UCR functions by the examination of beta-galactosidase expression in flies containing Ubx-lacZ fusion genes. 35 kb of UCR DNA confers upon beta-galactosidase an expression pattern that closely parallels normal Ubx expression throughout development. In contrast, 22 kb of UCR DNA confers fewer features of normal Ubx expression, and with 5 kb of UCR DNA the expression pattern has no resemblance to Ubx expression except in the visceral mesoderm. We have also shown that bxd chromosome breakpoint mutants form a comparable 5′ deletion series in which the severity of the effect on Ubx expression correlates with the amount of upstream DNA remaining in the mutant. In Ubx-lacZ fusions containing 22 kb of UCR DNA, and in comparable bxd mutants, there is a persistent pair-rule pattern of metameric expression in early development, demonstrating that there are distinct mechanisms with different sequence requirements for the initial activation of Ubx in different metameres. The correction of this pair-rule pattern later in embryogenesis shows that there are also distinct mechanisms for the activation of Ubx at different times during development.

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.

Rescue and regulation of proboscipedia: a homeotic gene of the Antennapedia Complex

Development ◽  
1991 ◽  
Vol 113 (1) ◽  
pp. 257-271 ◽  
Author(s):  
F.M. Randazzo ◽  
D.L. Cribbs ◽  
T.C. Kaufman
Keyword(s):  
Biological Significance ◽  
Regulatory Elements ◽  
P Element ◽  
Homeotic Gene ◽  
Its Sequence ◽  
Drosophila Genome ◽  
Homeotic Genes ◽  
Cis Acting ◽  
Positional Conservation ◽  
Hox Clusters

The extraordinary positional conservation of the homeotic genes within the Antennapedia and the Bithorax Complexes (ANT-C and BX-C) in Drosophila melanogaster and the murine Hox and human HOX clusters of genes can be interpreted as a reflection of functional necessity. The homeotic gene proboscipedia (pb) resides within the ANT-C, and its sequence is related to that of Hox-1.5. We show that two independent pb minigene P-element insertion lines completely rescue the labial palp-to-first leg homeotic transformation caused by pb null mutations; thus, a homeotic gene of the ANT-C can properly carry out its homeotic function outside of the complex. Despite the complete rescue of the null, the minigene expresses pb protein in only a subset of pb's normal domains of expression. Therefore, the biological significance of the excluded expression pattern elements remains unclear except to note they appear unnecessary for specifying normal labial identity. Additionally, by using reporter gene constructs inserted into the Drosophila genome and by comparing pb-associated genomic sequences from two divergent species, we have located cis-acting regulatory elements required for pb expression in embryos and larvae.

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

Identification of Polycomb and trithorax group responsive elements in the regulatory region of the Drosophila homeotic gene Sex combs reduced.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 797-814 ◽  
Author(s):  
J G Gindhart ◽  
T C Kaufman
Keyword(s):  
Regulatory Region ◽  
Polycomb Group ◽  
Homeotic Gene ◽  
Regulatory Sequences ◽  
Dependent Manner ◽  
Gene Products ◽  
Dna Fragments ◽  
Sex Combs Reduced ◽  
Trithorax Group ◽  
Sex Combs

Abstract The Drosophila homeotic gene Sex combs reduced (Scr) is necessary for the establishment and maintenance of the morphological identity of the labial and prothoracic segments. In the early embryo, its expression pattern is established through the activity of several gap and segmentation gene products, as well as other transcription factors. Once established, the Polycomb group (Pc-G) and trithorax group (trx-G) gene products maintain the spatial pattern of Scr expression for the remainder of development. We report the identification of DNA fragments in the Scr regulatory region that may be important for its regulation by Polycomb and trithorax group gene products. When DNA fragments containing these regulatory sequences are subcloned into P-element vectors containing a white minigene, transformants containing these constructs exhibit mosaic patterns of pigmentation in the adult eye, indicating that white minigene expression is repressed in a clonally heritable manner. The size of pigmented and nonpigmented clones in the adult eye suggests that the event determining whether a cell in the eye anlagen will express white occurs at least as early as the first larval instar. The amount of white minigene repression is reduced in some Polycomb group mutants, whereas repression is enhanced in flies mutant for a subset of trithorax group loci. The repressor activity of one fragment, normally located in Scr Intron 2, is increased when it is able to homologously pair, a property consistent with genetic data suggesting that Scr exhibits transvection. Another Scr regulatory fragment, normally located 40 kb upstream of the Scr promoter, silences ectopic expression of an Scr-lacZ fusion gene in the embryo and does so in a Polycomb-dependent manner. We propose that the regulatory sequences located within these DNA fragments may normally mediate the regulation of Scr by proteins encoded by members of the Polycomb and trithorax group loci.

Sign in / Sign up

Export Citation Format

Share Document