A molecular basis for transdetermination in Drosophila imaginal discs: interactions between wingless and decapentaplegic signaling

We are investigating how Drosophila imaginal disc cells establish and maintain their appendage-specific determined states. We have previously shown that ectopic expression of wingless (wg) induces leg disc cells to activate expression of the wing marker Vestigial (Vg) and transdetermine to wing cells. Here we show that ectopic wg expression non-cell-autonomously induces Vg expression in leg discs and that activated Armadillo, a cytosolic transducer of the Wg signal, cell-autonomously induces Vg expression in leg discs, indicating that this Vg expression is directly activated by Wg signaling. We find that ubiquitous expression of wg in leg discs can induce only dorsal leg disc cells to express Vg and transdetermine to wing. Dorsal leg disc cells normally express high levels of decapentaplegic (dpp) and its downstream target, optomotor-blind (omb). We find that high levels of dpp expression, which are both necessary and sufficient for dorsal leg development, are required for wg-induced transdetermination. We show that dorsalization of ventral leg disc cells, through targeted expression of either dpp or omb, is sufficient to allow wg to induce Vg expression and wing fate. Thus, dpp and omb promote both dorsal leg cell fate as well as transdetermination-competent leg disc cells. Taken together, our results show that the Wg and Dpp signaling pathways cooperate to induce Vg expression and leg-towing transdetermination. We also show that a specific vg regulatory element, the vg boundary enhancer, is required for transdetermination. We propose that an interaction between Wg and Dpp signaling can explain why leg disc cells transdetermine to wing and that our results have implications for normal leg and wing development.

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Lhx2, a vertebrate homologue of apterous, regulates vertebrate limb outgrowth

Development ◽

10.1242/dev.125.20.3925 ◽

1998 ◽

Vol 125 (20) ◽

pp. 3925-3934 ◽

Cited By ~ 3

Author(s):

C. Rodriguez-Esteban ◽

J.W. Schwabe ◽

J.D. Pena ◽

D.E. Rincon-Limas ◽

J. Magallon ◽

...

Keyword(s):

Cell Fate ◽

Wing Development ◽

Dorsoventral Axis ◽

Drosophila Wing ◽

Vertebrate Limb ◽

Limb Outgrowth ◽

Necessary And Sufficient ◽

Dorsal Cell Fate

apterous specifies dorsal cell fate and directs outgrowth of the wing during Drosophila wing development. Here we show that, in vertebrates, these functions appear to be performed by two separate proteins. Lmx-1 is necessary and sufficient to specify dorsal identity and Lhx2 regulates limb outgrowth. Our results suggest that Lhx2 is closer to apterous than Lmx-1, yet, in vertebrates, Lhx2 does not specify dorsal cell fate. This implies that in vertebrates, unlike Drosophila, limb outgrowth can be dissociated from the establishment of the dorsoventral axis.

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dachshund encodes a nuclear protein required for normal eye and leg development in Drosophila

Development ◽

10.1242/dev.120.12.3473 ◽

1994 ◽

Vol 120 (12) ◽

pp. 3473-3486 ◽

Cited By ~ 42

Author(s):

G. Mardon ◽

N.M. Solomon ◽

G.M. Rubin

Keyword(s):

Cell Fate ◽

Posterior Margin ◽

Imaginal Disc ◽

Nuclear Protein ◽

Eye Disc ◽

Leg Development ◽

Disc Cells ◽

Neural Specification ◽

Eye Imaginal Disc

Neural specification and differentiation in the Drosophila eye sweep across the unpatterned epithelial monolayer of the eye imaginal disc following a developmental wave termed the morphogenetic furrow. The furrow begins at the posterior margin of the eye imaginal disc and moves anteriorly as a linear front. Progression of the furrow requires the function of hedgehog, which encodes a secreted signaling protein. We characterize mutations in dachshund, a gene that encodes a novel nuclear protein required for normal cell-fate determination of imaginal disc cells. In the absence of dachshund function, cells at the posterior margin of the eye disc fail to follow a retinal differentiation pathway and appear to adopt a cuticle fate instead. These cells are therefore unable to respond to pattern propagation signals such as hedgehog and furrow initiation does not occur. In contrast, cells in more anterior portions of the eye disc are able to differentiate as retinal cells in the absence of dachshund activity and respond normally to patterning signals. These results suggest that posterior margin cells are distinct from other cells of the eye imaginal disc by early stages of development. dachshund is also necessary for proper differentiation of a subset of segments in the developing leg. Null mutations in dachshund result in flies with no eyes and shortened legs.

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Undulated short-tail Deletion Mutation in the Mouse Ablates Pax1 and Leads to Ectopic Activation of Neighboring Nkx2-2 in Domains That Normally Express Pax1

Genetics ◽

10.1093/genetics/165.1.299 ◽

2003 ◽

Vol 165 (1) ◽

pp. 299-307

Author(s):

Chikara Kokubu ◽

Bettina Wilm ◽

Tomoko Kokubu ◽

Matthias Wahl ◽

Isabel Rodrigo ◽

...

Keyword(s):

Molecular Basis ◽

Ectopic Expression ◽

Deletion Mutation ◽

Loss Of Function ◽

Downstream Target ◽

Short Tail ◽

Ectopic Activation ◽

Or Genes ◽

Null Mutants ◽

Antisense Genes

Abstract Previous studies have indicated that the Undulated short-tail deletion mutation in mouse Pax1 (Pax1Un-s) not only ablates Pax1, but also disturbs a gene or genes nearby Pax1. However, which gene(s) is involved and how the Pax1Un-s phenotype is confined to the Pax1-positive tissues remain unknown. In the present study, we determined the Pax1Un-s deletion interval to be 125 kb and characterized genes around Pax1. We show that the Pax1Un-s mutation affects four physically linked genes within or near the deletion, including Pax1, Nkx2-2, and their potential antisense genes. Remarkably, Nkx2-2 is ectopically activated in the sclerotome and limb buds of Pax1Un-s embryos, both of which normally express Pax1. This result suggests that the Pax1Un-s deletion leads to an illegitimate interaction between remotely located Pax1 enhancers and the Nkx2-2 promoter by disrupting an insulation mechanism between Pax1 and Nkx2-2. Furthermore, we show that expression of Bapx1, a downstream target of Pax1, is more strongly affected in Pax1Un-s mutants than in Pax1-null mutants, suggesting that the ectopic expression of Nkx2-2 interferes with the Pax1-Bapx1 pathway. Taken together, we propose that a combination of a loss-of-function mutation of Pax1 and a gain-of-function mutation of Nkx2-2 is the molecular basis of the Pax1Un-s mutation.

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The Basic Helix-Loop-Helix Transcription Factor Cph2 Regulates Hyphal Development in CandidaalbicansPartly via Tec1

Molecular and Cellular Biology ◽

10.1128/mcb.21.19.6418-6428.2001 ◽

2001 ◽

Vol 21 (19) ◽

pp. 6418-6428 ◽

Cited By ~ 83

Author(s):

Shelley Lane ◽

Song Zhou ◽

Ting Pan ◽

Qian Dai ◽

Haoping Liu

Keyword(s):

Transcription Factor ◽

Protein Kinase ◽

Binding Sites ◽

Regulatory Element ◽

Ectopic Expression ◽

Mitogen Activated Protein Kinase ◽

Northern Analysis ◽

Hyphal Development ◽

Basic Helix Loop Helix ◽

Helix Loop Helix

ABSTRACT Candida albicans undergoes a morphogenetic switch from budding yeast to hyphal growth form in response to a variety of stimuli and growth conditions. Multiple signaling pathways, including a Cph1-mediated mitogen-activated protein kinase pathway and an Efg1-mediated cyclic AMP/protein kinase A pathway, regulate the transition. Here we report the identification of a basic helix-loop-helix transcription factor of the Myc subfamily (Cph2) by its ability to promote pseudohyphal growth inSaccharomyces cerevisiae. Like sterol response element binding protein 1, Cph2 has a Tyr instead of a conserved Arg in the basic DNA binding region. Cph2 regulates hyphal development in C. albicans, ascph2/cph2 mutant strains show medium-specific impairment in hyphal development and in the induction of hypha-specific genes. However, many hypha-specific genes do not have potential Cph2 binding sites in their upstream regions. Interestingly, upstream sequences of all known hypha-specific genes are found to contain potential binding sites for Tec1, a regulator of hyphal development. Northern analysis shows that TEC1 transcription is highest in the medium in which cph2/cph2 displays a defect in hyphal development, and Cph2 is necessary for this transcriptional induction of TEC1. In vitro gel mobility shift experiments show that Cph2 directly binds to the two sterol regulatory element 1-like elements upstream of TEC1. Furthermore, the ectopic expression of TEC1 suppresses the defect ofcph2/cph2 in hyphal development. Therefore, the function of Cph2 in hyphal transcription is mediated, in part, through Tec1. We further show that this function of Cph2 is independent of the Cph1- and Efg1-mediated pathways.

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Cancer cells activate p53 in response to 10-formyltetrahydrofolate dehydrogenase expression

Biochemical Journal ◽

10.1042/bj20050533 ◽

2005 ◽

Vol 391 (3) ◽

pp. 503-511 ◽

Cited By ~ 27

Author(s):

Natalia V. Oleinik ◽

Natalia I. Krupenko ◽

David G. Priest ◽

Sergey A. Krupenko

Keyword(s):

Cancer Cells ◽

Ectopic Expression ◽

A549 Cells ◽

Dominant Negative ◽

G1 Arrest ◽

Transactivation Domain ◽

Downstream Target ◽

Formyltetrahydrofolate Dehydrogenase ◽

Induced Apoptosis ◽

Hct116 Cells

A folate enzyme, FDH (10-formyltetrahydrofolate dehydrogenase; EC 1.5.1.6), is not a typical tumour suppressor, but it has two basic characteristics of one, i.e. it is down-regulated in tumours and its expression is selectively cytotoxic to cancer cells. We have recently shown that ectopic expression of FDH in A549 lung cancer cells induces G1 arrest and apoptosis that was accompanied by elevation of p53 and its downstream target, p21. It was not known, however, whether FDH-induced apoptosis is p53-dependent or not. In the present study, we report that FDH-induced suppressor effects are strictly p53-dependent in A549 cells. Both knockdown of p53 using an RNAi (RNA interference) approach and disabling of p53 function by dominant-negative inhibition with R175H mutant p53 prevented FDH-induced cytotoxicity in these cells. Ablation of the FDH-suppressor effect is associated with an inability to activate apoptosis in the absence of functional p53. We have also shown that FDH elevation results in p53 phosphorylation at Ser-6 and Ser-20 in the p53 transactivation domain, and Ser-392 in the C-terminal domain, but only Ser-6 is strictly required to mediate FDH effects. Also, translocation of p53 to the nuclei and expression of the pro-apoptotic protein PUMA (Bcl2 binding component 3) was observed after induction of FDH expression. Elevation of FDH in p53 functional HCT116 cells induced strong growth inhibition, while growth of p53-deficient HCT116 cells was unaffected. This implies that activation of p53-dependent pathways is a general downstream mechanism in response to induction of FDH expression in p53 functional cancer cells.

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hlh-12, a gene that is necessary and sufficient to promote migration of gonadal regulatory cells in C. elegans, evolved within the Caenorhabditis clade

Genetics ◽

10.1093/genetics/iyab127 ◽

2021 ◽

Author(s):

Hana E Littleford ◽

Karin Kiontke ◽

David H A Fitch ◽

Iva Greenwald

Keyword(s):

Ectopic Expression ◽

Morphological Diversity ◽

Nematode Species ◽

Bhlh Protein ◽

Vulval Development ◽

C Elegans ◽

Form And Function ◽

Somatic Gonad ◽

And Function ◽

Necessary And Sufficient

Abstract Specialized cells of the somatic gonad primordium of nematodes play important roles in the final form and function of the mature gonad. C. elegans hermaphrodites are somatic females that have a two-armed, U-shaped gonad that connects to the vulva at the midbody. The outgrowth of each gonad arm from the somatic gonad primordium is led by two female Distal Tip Cells (fDTC), while the Anchor Cell (AC) remains stationary and central to coordinate uterine and vulval development. The bHLH protein HLH-2 and its dimerization partners LIN-32 and HLH-12 had previously been shown to be required for fDTC specification. Here, we show that ectopic expression of both HLH-12 and LIN-32 in cells with AC potential transiently transforms them into fDTC-like cells. Furthermore, hlh-12 was known to be required for the fDTCs to sustain gonad arm outgrowth. Here, we show that ectopic expression of HLH-12 in the normally stationary AC causes displacement from its normal position, and that displacement likely results from activation of the leader program of fDTCs because it requires genes necessary for gonad arm outgrowth. Thus, HLH-12 is both necessary and sufficient to promote gonadal regulatory cell migration. As differences in female gonadal morphology of different nematode species reflect differences in the fate or migratory properties of the fDTCs or of the AC, we hypothesized that evolutionary changes in the expression of hlh-12 may underlie evolution of such morphological diversity. However, we were unable to identify an hlh-12 ortholog outside of Caenorhabditis. Instead, by performing a comprehensive phylogenetic analysis of all Class II bHLH proteins in multiple nematode species, we found that HLH-12 evolved within the Caenorhabditis clade, possibly by duplicative transposition of hlh-10. Our analysis suggests that control of gene regulatory hierarchies for gonadogenesis can be remarkably plastic during evolution without adverse phenotypic consequence.

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Requirements of Lim1, a Drosophila LIM-homeobox gene, for normal leg and antennal development

Development ◽

10.1242/dev.127.20.4315 ◽

2000 ◽

Vol 127 (20) ◽

pp. 4315-4323 ◽

Cited By ~ 3

Author(s):

T. Tsuji ◽

A. Sato ◽

I. Hiratani ◽

M. Taira ◽

K. Saigo ◽

...

Keyword(s):

Ectopic Expression ◽

Homeobox Genes ◽

Homeobox Gene ◽

Homeodomain Protein ◽

Border Cells ◽

Null Mutant ◽

Tarsal Segment ◽

Segment Boundary ◽

Leg Development ◽

Antagonistic Interactions

During Drosophila leg development, the distal-most compartment (pretarsus) and its immediate neighbour (tarsal segment 5) are specified by a pretarsus-specific homeobox gene, aristaless, and tarsal-segment-specific Bar homeobox genes, respectively; the pretarsus/tarsal-segment boundary is formed by antagonistic interactions between Bar and pretarsus-specific genes that include aristaless (Kojima, T., Sato, M. and Saigo, K. (2000) Development 127, 769–778). Here, we show that Drosophila Lim1, a homologue of vertebrate Lim1 encoding a LIM-homeodomain protein, is involved in pretarsus specification and boundary formation through its activation of aristaless. Ectopic expression of Lim1 caused aristaless misexpression, while aristaless expression was significantly reduced in Lim1-null mutant clones. Pretarsus Lim1 expression was negatively regulated by Bar and abolished in leg discs lacking aristaless activity, which was associated with strong Bar misexpression in the presumptive pretarsus. No Lim1 misexpression occurred upon aristaless misexpression. The concerted function of Lim1 and aristaless was required to maintain Fasciclin 2 expression in border cells and form a smooth pretarsus/tarsal-segment boundary. Lim1 was also required for femur, coxa and antennal development.

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fringeandNotchspecify polar cell fate duringDrosophilaoogenesis

Development ◽

10.1242/dev.128.12.2243 ◽

2001 ◽

Vol 128 (12) ◽

pp. 2243-2253 ◽

Cited By ~ 11

Author(s):

Muriel Grammont ◽

Kenneth D. Irvine

Keyword(s):

Cell Fate ◽

Null Allele ◽

Somatic Cells ◽

Ectopic Expression ◽

Notch Receptor ◽

Drosophila Oogenesis ◽

Early Stages ◽

Polar Cell ◽

Hypomorphic Alleles ◽

Notch Activation

fringe encodes a glycosyltransferase that modulates the ability of the Notch receptor to be activated by its ligands. We describe studies of fringe function during early stages of Drosophila oogenesis. Animals mutant for hypomorphic alleles of fringe contain follicles with an incorrect number of germline cells, which are separated by abnormally long and disorganized stalks. Analysis of clones of somatic cells mutant for a null allele of fringe localizes the requirement for fringe in follicle formation to the polar cells, and demonstrates that fringe is required for polar cell fate. Clones of cells mutant for Notch also lack polar cells and the requirement for Notch in follicle formation appears to map to the polar cells. Ectopic expression of fringe or of an activated form of Notch can generate an extra polar cell. Our results indicate that fringe plays a key role in positioning Notch activation during early oogenesis, and establish a function for the polar cells in separating germline cysts into individual follicles.

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Only two of the five zinc fingers of the eukaryotic transcriptional repressor PRDI-BF1 are required for sequence-specific DNA binding

Molecular and Cellular Biology ◽

10.1128/mcb.12.5.1940-1949.1992 ◽

1992 ◽

Vol 12 (5) ◽

pp. 1940-1949

Author(s):

A D Keller ◽

T Maniatis

Keyword(s):

Dna Binding ◽

Zinc Finger ◽

Specific Binding ◽

Regulatory Element ◽

Zinc Fingers ◽

Transcriptional Repressor ◽

Gene Promoter ◽

Binding Activity ◽

Necessary And Sufficient ◽

Sequence Requirements

The eukaryotic transcriptional repressor PRDI-BF1 contains five zinc fingers of the C2H2 type, and the protein binds specifically to PRDI, a 14-bp regulatory element of the beta interferon gene promoter. We have investigated the amino acid sequence requirements for specific binding to PRDI and found that the five zinc fingers and a short stretch of amino acids N terminal to the first finger are necessary and sufficient for PRDI-specific binding. The contribution of individual zinc fingers to DNA binding was investigated by inserting them in various combinations into another zinc finger-containing DNA-binding protein whose own fingers had been removed. We found that insertion of PRDI-BF1 zinc fingers 1 and 2 confer PRDI-binding activity on the recipient protein. In contrast, the insertion of PRDI-BF1 zinc fingers 2 through 5, the insertion of zinc finger 1 or 2 alone, and the insertion of zinc fingers 1 and 2 in reverse order did not confer PRDI-binding activity. We conclude that the first two PRDI-BF1 zinc fingers together are sufficient for the sequence-specific recognition of PRDI.

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