scholarly journals Effect of abx, bx and pbx mutations on expression of homeotic genes in Drosophila larvae.

Genetics ◽  
1990 ◽  
Vol 124 (4) ◽  
pp. 899-908 ◽  
Author(s):  
J W Little ◽  
C A Byrd ◽  
D L Brower
Keyword(s):  
Ectopic Expression ◽  
Wing Disc ◽  
Homeotic Genes ◽  
Wild Type ◽  
Posterior Compartment ◽  
Altered Expression ◽  
Anterior Compartment ◽  
Regulatory Domains ◽  
Wild Type Phenotype ◽  
Drosophila Larvae

Abstract We have examined the patterns of expression of the homeotic gene Ubx in imaginal discs of Drosophila larvae carrying mutations in the abx, bx and pbx regulatory domains. In haltere discs, all five bx insertion mutations examined led to a general reduction in Ubx expression in the anterior compartment; for a given allele, the strength of the adult cuticle phenotype correlated with the degree of Ubx reduction. Deletions mapping near or overlapping the sites of bx insertions, including three abx alleles and the bx34e-prv(bx-prv) allele, showed greatly reduced Ubx expression in parts of the anterior compartment of the haltere disc; however, anterior patches of strong Ubx expression often remained, in highly variable patterns. As expected, the pbx1 mutation led to reduced Ubx expression in the posterior compartment of the haltere disc; surprisingly, pbx1 also led to altered expression of the en protein near the compartment border in the central region of the disc. In the metathoracic leg, all the bx alleles caused extreme reduction in Ubx expression in the anterior regions, with no allele-specific differences. In contrast, abx and bx-prv alleles resulted in patchy anterior reductions in third leg discs. In the larval central nervous system, abx but not bx alleles affected Ubx expression; the bx-prv deletion gave a wild-type phenotype, but it could not fully complement abx mutations. In the posterior wing disc, the bx-prv allele, and to a much lesser extent the bx34e chromosome from which it arose, led to ectopic expression of Ubx. Unlike other grain-of-function mutations in the BX-C, this phenotype appeared to be partially recessive to wild type. Finally, we asked whether the ppx transformation, which results from early lack of Ubx+ function in the mesothorax and is seen in abx animals, is due to ectopic Scr expression. Some mesothoracic leg and wing discs from abx2 larvae displayed ectopic expression of Scr, which was variable in extent but always confined to the posterior compartment.

Positional signaling by hedgehog in Drosophila imaginal disc development

Development ◽  
1995 ◽  
Vol 121 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A.L. Felsenfeld ◽  
J.A. Kennison
Keyword(s):  
Hedgehog Signaling ◽  
Imaginal Disc ◽  
Ectopic Expression ◽  
Posterior Compartment ◽  
Anterior Compartment ◽  
Segment Polarity ◽  
Wing Structures ◽  
Wing Discs ◽  
Segment Polarity Gene ◽  
Polarity Gene

We describe a dominant gain-of-function allele of the segment polarity gene hedgehog. This mutation causes ectopic expression of hedgehog mRNA in the anterior compartment of wing discs, leading to overgrowth of tissue in the anterior of the wing and partial duplication of distal wing structures. The posterior compartment of the wing is unaffected. Other imaginal derivatives are affected, resulting in duplications of legs and antennae and malformations of eyes. In mutant imaginal wing discs, expression of the decapentaplegic gene, which is implicated in the hedgehog signaling pathway, is also perturbed. The results suggest that hedgehog protein acts in the wing as a signal to instruct neighboring cells to adopt fates appropriate to the region of the wing just anterior to the compartmental boundary.

Dorsotonals/homothorax, the Drosophila homologue of meis1, interacts with extradenticle in patterning of the embryonic PNS

Development ◽  
1998 ◽  
Vol 125 (6) ◽  
pp. 1037-1048 ◽  
Author(s):  
E. Kurant ◽  
C.Y. Pai ◽  
R. Sharf ◽  
N. Halachmi ◽  
Y.H. Sun ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Molecular Mechanisms ◽  
Normal Development ◽  
Protein A ◽  
Ectopic Expression ◽  
Homeotic Genes ◽  
Wild Type ◽  
Protein Activity ◽  
Low Levels ◽  
Restricted Pattern

The homeotic genes of the bithorax complex are required, among other things, for establishing the patterns of sensory organs in the embryonic peripheral nervous system (PNS). However, the molecular mechanisms by which these genes affect pattern formation in the PNS are not understood and other genes that function in this pathway are not characterized. Here we report the phenotypic and molecular analysis of one such gene, homothorax (hth; also named dorsotonals). Mutations in the hth gene seem to alter the identity of the abdominal chordotonal neurons, which depend on Abd-A for their normal development. However, these mutations do not alter the expression of the abd-A gene, suggesting that hth may be involved in modulating abd-A activity. We have generated multiple mutations in the hth locus and cloned the hth gene. hth encodes a homeodomain-containing protein that is most similar to the murine proto-oncogene meis1. The hth gene is expressed throughout embryonic development in a spatially restricted pattern, which is modulated in abdominal segments by abd-A and Ubx. The spatial distribution of the HTH protein during embryonic development is very similar to the distribution of the Extradenticle (EXD) protein, a known modulator of homeotic gene activity. Here we show that the PNS phenotype of exd mutant embryos is virtually indistinguishable from that of hth mutant embryos and does not simply follow the homeotic transformations observed in the epidermis. We also show that the HTH protein is present in extremely low levels in embryos lacking exd activity as compared to wild-type embryos. In contrast, the EXD protein is present in fairly normal levels in hth mutant embryos, but fails to accumulate in nuclei and remains cytoplasmic. Ectopic expression of hth can drive ectopic nuclear localization of EXD. Based on our observations we propose that the genetic interactions between hth and exd serve as a novel mechanism for regulating homeotic protein activity in embryonic PNS development.

scholarly journals The function of engrailed and the specification of Drosophila wing pattern

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3447-3456 ◽  
Author(s):  
I. Guillen ◽  
J.L. Mullor ◽  
J. Capdevila ◽  
E. Sanchez-Herrero ◽  
G. Morata ◽  
...  
Keyword(s):  
Wing Disc ◽  
Gene Products ◽  
Wing Pattern ◽  
Related Gene ◽  
Posterior Compartment ◽  
Anterior Compartment ◽  
Drosophila Wing ◽  
Partial Inactivation ◽  
Autoregulatory Mechanism ◽  
Adult Drosophila

The adult Drosophila wing (as the other appendages) is subdivided into anterior and posterior compartments that exhibit characteristic patterns. The engrailed (en) gene has been proposed to be paramount in the specification of the posterior compartment identity. Here, we explore the adult en function by targeting its expression in different regions of the wing disc. In the anterior compartment, ectopic en expression gives rise to the substitution of anterior structures by posterior ones, thus demonstrating its role in specification of posterior patterns. The en-expressing cells in the anterior compartment also induce high levels of the hedgehog (hh) and decapentaplegic (dpp) gene products, which results in local duplications of anterior patterns. Besides, hh is able to activate en and the engrailed-related gene invected (inv) in this compartment. In the posterior compartment we find that elevated levels of en product result in partial inactivation of the endogenous en and inv genes, indicating the existence of a negative autoregulatory mechanism. We propose that en has a dual role: a general one for patterning of the appendage, achieved through the activation of secreted proteins like hh and dpp, and a more specific one, determining posterior identity, in which the inv gene may be implicated.

scholarly journals Control of cell fate and polarity in the adult abdominal segments of Drosophila by optomotor-blind

Development ◽  
1997 ◽  
Vol 124 (19) ◽  
pp. 3715-3726 ◽  
Author(s):  
A. Kopp ◽  
I. Duncan
Keyword(s):  
Cell Fate ◽  
Anterior Part ◽  
Ectopic Expression ◽  
Mirror Image ◽  
Posterior Compartment ◽  
Anterior Portion ◽  
Posterior Portion ◽  
Anterior Compartment ◽  
Compartment Boundary ◽  
Hh Signaling

In an accompanying report (Kopp, A., Muskavitch, M. A. T. and Duncan, I. (1997) Development 124, 3703–3714), we show that Hh protein secreted by posterior compartment cells patterns the posterior portion of the anterior compartment in adult abdominal segments. Here we show that this function of hh is mediated by optomotor-blind (omb). omb- mutants mimic the effects of loss-of-function alleles of hh: structures from the posterior of the anterior compartment are lost, and often this region develops as a mirror image of the anterior portion. Structures from the anterior part of the posterior compartment are also lost. In the pupa, omb expression in abdominal histoblasts is highest at or near the compartment boundary, and decreases in a shallow gradient toward the anterior. This gradient is due to activation of omb by Hh secreted by posterior compartment cells. In contrast to imaginal discs, this Hh signaling is not mediated by dpp or wg. We describe several gain-of-function alleles that cause ectopic expression of omb in the anterior of the segment. Most of these cause the anterior region to develop with posterior characteristics without affecting polarity. However, an allele that drives high level ubiquitous expression of omb (QdFab) causes the anterior tergite to develop as a mirror-image duplication of the posterior tergite, a pattern opposite to that seen in omb- mutants. Ubiquitous expression of hh causes similar double-posterior patterning. We find that omb- alleles suppress this effect of ectopic hh expression and that posterior patterning becomes independent of hh in the QdFab mutant. These observations indicate that omb is the primary target of hh signaling in the adult abdomen. However, it is clear that other targets exist. One of these is likely Scruffy, a novel gene that we describe, which acts in parallel to omb. To explain the effects of omb alleles, we propose that both anterior and posterior compartments in the abdomen are polarized by underlying symmetric gradients of unknown origin. We suggest that omb has two functions. First, it specifies the development of appropriate structures both anterior and posterior to the compartment boundary. Second, it causes cells to reverse their interpretation of polarity specified by the underlying symmetric gradients.

The roles of hedgehog and engrailed in patterning adult abdominal segments of Drosophila

Development ◽  
1997 ◽  
Vol 124 (19) ◽  
pp. 3703-3714 ◽  
Author(s):  
A. Kopp ◽  
M.A. Muskavitch ◽  
I. Duncan
Keyword(s):  
Ectopic Expression ◽  
Restrictive Temperature ◽  
Primary Role ◽  
Loss Of Function ◽  
Posterior Compartment ◽  
Anterior Portion ◽  
Posterior Portion ◽  
Anterior Compartment ◽  
Present Evidence ◽  
Anterior Patterning

We present evidence that hedgehog (hh) protein secreted by posterior compartment cells plays a key role in patterning the posterior portion of the anterior compartment in adult abdominal segments. Loss of function of hh in the hh(ts2) mutant causes the loss of posterior tergite characteristics in the anterior compartment, whereas ectopic expression driven by hs-hh or the gain-of-function allele hh(Mir) causes transformation of anterior structures toward the posterior. FLP-out hh-expressing clones in the anterior compartment induce surrounding wild-type cells to produce posterior tergite structures, establishing that hh functions nonautonomously. The effects of pulses of ectopic expression driven by hs-hh indicate that bristle type and pigmentation are patterned by hh at widely different times in pupal development. We also present evidence that the primary polarization of abdominal segments is symmetric. This symmetry is strikingly revealed by ectopic expression of engrailed (en). As expected, this transforms anterior compartment cells to posterior compartment identity. In addition, however, ectopic en expression causes an autonomous reversal of polarity in the anterior portion of the anterior compartment, but not the posterior portion. By determining the position of polarity reversal within en-expressing clones, we were able to define a cryptic line of symmetry that lies within the pigment band of the normal tergite. This line appears to be retained in hh(ts2) mutants raised at the restrictive temperature, suggesting it is not established by hh signaling. We argue that the primary role of hh in controlling polarity is to cause anterior compartment cells to reverse their interpretation of an underlying symmetric polarization. Consistent with this, we find that strong ectopic expression of hh causes mirror-symmetric double posterior patterning, whereas hh loss of function can cause mirror-symmetric double anterior patterning.

scholarly journals The Neuron-Enriched Splicing Pattern ofDrosophila erect wing Is Dependent on the Presence of ELAV Protein

2000 ◽  
Vol 20 (5) ◽  
pp. 1836-1845 ◽  
Author(s):  
Sandhya P. Koushika ◽  
Matthias Soller ◽  
Kalpana White
Keyword(s):  
Protein Expression ◽  
Posttranscriptional Regulation ◽  
Rna Binding ◽  
Ectopic Expression ◽  
Imaginal Discs ◽  
Wing Disc ◽  
Wild Type ◽  
Splice Isoforms ◽  
Posttranscriptional Control ◽  
Splice Forms

ABSTRACT Although the Drosophila melanogaster erect wing(ewg) gene is broadly transcribed in adults, an unusual posttranscriptional regulation involving alternative and inefficient splicing generates a 116-kDa EWG protein in neurons, while protein expression elsewhere or of other isoforms is below detection at this stage. This posttranscriptional control is important, as broad expression of EWG can be lethal. In this paper, we show that ELAV, a neuron-specific RNA binding protein, is necessary to regulate EWG protein expression in ELAV-null eye imaginal disc clones and that ELAV is sufficient for EWG expression in wing disc imaginal tissue after ectopic expression. Further, analysis of EWG expression elicited from intron-containing genomic transgenes and cDNA minitransgenes in ELAV-deficient eye discs shows that this regulation is dependent on the presence of ewg introns. Analyses of the ewg splicing patterns in wild-type and ELAV-deficient eye imaginal discs and in wild-type and ectopic ELAV-expressing wing imaginal discs, show that certain neuronal splice isoforms correspond to ELAV levels. The data presented in this paper are consistent with a mechanism in which ELAV increases the splicing efficiency ofewg transcripts in alternatively spliced regions rather than with a mechanism in which stability of specific splice forms is enhanced by ELAV. Additionally, we report that ELAV promotes a neuron-enriched splice isoform of Drosophila armadillotranscript. ELAV, however, is not involved in all neuron-enriched splice events.

Analysis of vestigialW (νgW): a mutation causing homoeosis of haltere to wing and posterior wing duplications in Drosophila melanogaster

Development ◽  
1981 ◽  
Vol 65 (Supplement) ◽  
pp. 49-76
Author(s):  
Mary Bownes ◽  
Sarah Roberts
Keyword(s):  
Cell Death ◽  
Wing Disc ◽  
Chromosome 2 ◽  
Wing Morphology ◽  
Wild Type ◽  
Heterozygous Condition ◽  
Anterior Compartment ◽  
Chromosome Substitutions ◽  
Different Temperatures ◽  
The Right

νgW is a homozygous lethal mutation killing embryos prior to formation of the syncitial blastoderm. In heterozygous condition it causes duplications of the posterior wing, ranging from very small duplications of the axillary cord and alar lobe to large duplications including much of the wing blade and the posterior row of bristles. No anterior margin structures are ever observed. The thorax is sometimes slightly abnormal, but rarely shows large duplications. The size of the wing is related to the number of pattern elements deleted or duplicated. Heterozygous νgW flies also show homoeosis of the haltere to wing. This occurs in the capitellum, where wing blade is observed, but no wing margin structures are found. As with the bithorax (bx) mutation which transforms anterior haltere to anterior wing this aspect of the phenotype is repressed by the Contrabithorax (Cbx) mutation. The transformed haltere discs show more growth than wild-type haltere discs. Flies heterozygous for νgW also show a high frequency of pupal lethality, those forming pharate adults generally show the most extreme νgW phenotype. No cell death has been observed in the imaginal discs of third instar larvae, suggesting that if the wing defects result from cell death this must occur early in development. The homoeosis in the haltere discs and duplications of the wing disc are reflected by the altered morphology and growth of these discs. There are some minor differences in the expressivity of the phenotype when flies are reared at different temperatures. Chromosome substitutions suggested that all aspects of the phenotype related to the νgW mutation and that other mutations had not occurred in the stock. Cytological analysis indicated that νgW is a deletion or inversion on the right arm of chromosome 2 from 47F/48A to 49C. Complementation studies with various mutants thought to be located within the deletion, or inversion and which affect wing morphology have been undertaken. Cbx causes transformations of wing to haltere; this occurs in the posterior compartment far more frequently than in the anterior compartment. Cbx; νgW flies have wings where one of the duplicates is no longer present, presumably transformed to haltere, though this is difficult to identify. One copy of the axillary cord, alar lobe etc, the structures commonly duplicated in νgW, are present, but they are the anterior duplicate rather than the original posterior copy of these structures. Thus Cbx acts upon genuine posterior structures but not those posterior structures in νgW which form in anterior wing locations, suggesting that although these structures differentiate into posterior wing, to the Cbx gene product the cells are still ‘anterior’.

The Drosophila segment polarity gene patched is involved in a position-signalling mechanism in imaginal discs

Development ◽  
1990 ◽  
Vol 110 (1) ◽  
pp. 105-114 ◽  
Author(s):  
R.G. Phillips ◽  
I.J. Roberts ◽  
P.W. Ingham ◽  
J.R. Whittle
Keyword(s):  
Cell Loss ◽  
Wing Disc ◽  
Mirror Image ◽  
Double Labelling ◽  
Wild Type ◽  
Anterior Compartment ◽  
Vein Formation ◽  
Segment Polarity ◽  
Segment Polarity Gene ◽  
Polarity Gene

We demonstrate the role of the segment polarity gene patched (ptc) in patterning in the cuticle of the adult fly. Genetic mosaics of a lethal allele of patched show that the contribution of patched varies in a position-specific manner, defining three regions in the wing where ptc clones, respectively, behave as wild-type cells, affect vein formation, or are rarely recovered. Analysis of twin clones demonstrates that the reduced clone frequency results from a proliferation failure or cell loss. In the region where clones upset venation, they autonomously fail to form veins and also non-autonomously induce ectopic veins in adjacent wild-type cells. In heteroallelic combinations with lethal alleles, two viable alleles produce distinct phenotypes: (1) loss of structures and mirror-image duplications in the region where patched clones fail to proliferate; (2) vein abnormalities in the anterior compartment. We propose that these differences reflect independently mutable functions within the gene. We show the pattern of patched transcription in the developing imaginal wing disc in relation to the expression of certain other reporter genes using a novel double-labelling method combining non-radioactive detection of in situ hybridization with beta-galactosidase detection. The patched transcript is present throughout the anterior compartment, with a stripe of maximal intensity along the A/P compartment border extending into the posterior compartment. We propose that the patched product is a component of a cell-to-cell position-signalling mechanism, a proposal consistent with the predicted structure of the patched protein.

Ectopic expression of UBX and ABD-B proteins during Drosophila embryogenesis: competition, not a functional hierarchy, explains phenotypic suppression

Development ◽  
1992 ◽  
Vol 116 (4) ◽  
pp. 841-854 ◽  
Author(s):  
M.L. Lamka ◽  
A.M. Boulet ◽  
S. Sakonju
Keyword(s):  
Ectopic Expression ◽  
Homeotic Genes ◽  
Wild Type ◽  
Homeodomain Proteins ◽  
Regulatory Interactions ◽  
M Proteins ◽  
Dose Dependent Fashion ◽  
Functional Hierarchy ◽  
Dose Dependent ◽  
Similar Stage

The Abdominal-B (Abd-B) gene, a member of the bithorax complex (BX-C), specifies the identities of parasegments (PS) 10–14 in Drosophila. Abd-B codes for two structurally related homeodomain proteins, ABD-B m and ABD-B r, that are expressed in PS10-13 and PS14-15, respectively. Although ABD-B m and r proteins have distinct developmental functions, ectopic expression of either protein during embryogenesis induces the development of filzkorper and associated spiracular hairs, structures normally located in PS13, at ectopic sites in the larval thorax and abdomen. These results suggest that other parasegmental differences contribute to the phenotype specified by ABD-B r activity in PS14. Both ABD-B m and r repress the expression of other homeotic genes, such as Ubx and abd-A, in PS10-14. However, the importance of these and other cross-regulatory interactions among homeotic genes has been questioned. Since ectopic UBX protein apparently failed to transform abdominal segments, Gonzalez-Reyes et al. (Gonzalez-Reyes, A., Urquia, N., Gehring, W.J., Struhl, G. and Morata, G. (1990). Nature 344, 78–80) proposed a functional hierarchy in which ABD-A and ABD-B activities override UBX activity. We tested this model by expressing UBX and ABD-B m proteins ectopically in wild-type and BX-C-deficient embryos. Ectopic ABD-B m does not prevent transformations induced by ectopic UBX. Instead, ectopic UBX and ABD-B m proteins compete for the specification of segmental identities in a dose-dependent fashion. Our results support a quantitative competition among the homeotic proteins rather than the existence of a strict functional hierarchy. Therefore, we suggest that cross-regulatory interactions are not irrelevant but are important for repressing the expression of competing homeotic proteins. To explain the apparent failure of ectopic UBX to transform the abdominal segments, we expressed UBX at different times during embryonic development. Our results show that ectopic UBX affects abdominal cuticular identities if expressed during early stages of embryogenesis. In later embryonic stages, abdominal segments become resistant to transformation by ectopic UBX while thoracic segments remain susceptible. Head segments also show a similar stage-dependent susceptibility to transformation by ectopic UBX in early embryogenesis but become resistant in later stages. These results suggest that abdominal and head identities are determined earlier than are thoracic identities.

scholarly journals Dosage requirements of Ultrabithorax and bithoraxoid in the determination of segment identity in Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 124 (2) ◽  
pp. 357-366 ◽  
Author(s):  
S M Smolik-Utlaut
Keyword(s):  
Drosophila Embryo ◽  
Bithorax Complex ◽  
Wild Type ◽  
Posterior Compartment ◽  
Anterior Compartment ◽  
First Instar ◽  
Multiple Copies ◽  
Cellular Identity ◽  
Segmental Identity

Abstract The wild-type Ultrabithorax (Ubx) and bithoraxoid (bxd) functions are primarily responsible for establishing the identity of parasegment 6 (PS6) in the Drosophila embryo and thus the identity of the posterior compartment of the third thoracic segment (pT3) and the anterior compartment of the first abdominal segment (aA1) in the adult. The experiments described were designed to test the ability of an increased dosage of Ubx+ and bxd+ to affect the transformation of PS5 toward PS6. The results are consistent with the ideas that (1) multiple copies of Ubx+ and bxd+ cause some cells within PS5 to take on the characteristics of PS6 cells but do not cause an overall parasegmental transformation of PS5 toward PS6, (2) cellular identity depends not only on the activity of Ubx+ but on its concentration as well, and (3) that an interaction between Ubx+ and the wild-type Antennapedia (Antp) gene establishes segmental identity in pT2. In the first instar larvae carrying eight copies of Ubx+ and bxd+ the fine hairs of the T3 setal belt are transformed toward the hook-like structures of the A1 setal belt. Other structures within this segment are unaffected. In the adult, the haltere is reduced in size. The transformation of pT2 cells (wing) toward pT3 cells (haltere) is seen in adults carrying eight doses of wild type Ubx and bxd by decreasing the amount of the bithorax complex (BX-C) regulator Polycomb (Pc). However, the transformation of the T3 setal belt is not enhanced in the larvae of these animals. The interaction between the genes of the Antennapedia complex (ANT-C) and the Ubx+ and bxd+ functions in pT2 is dosage sensitive only when the animals carry one copy of Pc. In these animals, the transformation of wing toward haltere is significantly enhanced.

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