The roles of the homeobox genes aristaless and Distal-less in patterning the legs and wings of Drosophila

Development ◽  
1998 ◽  
Vol 125 (22) ◽  
pp. 4483-4493 ◽  
Author(s):  
G. Campbell ◽  
A. Tomlinson
Keyword(s):  
Null Allele ◽  
Normal Development ◽  
Distal Tibia ◽  
Homeobox Genes ◽  
Clonal Analysis ◽  
Loss Of Function ◽  
Wild Type ◽  
Adhesive Properties ◽  
Wing Imaginal Discs ◽  
Mutant Cells

In the leg and wing imaginal discs of Drosophila, the expression domains of the homeobox genes aristaless (al) and Distal-less (Dll) are defined by the secreted signaling molecules Wingless (Wg) and Decapentaplegic (Dpp). Here, the roles played by al and Dll in patterning the legs and wings have been investigated through loss of function studies. In the developing leg, al is expressed at the presumptive tip and a molecularly defined null allele of al reveals that its only function in patterning the leg appears to be to direct the growth and differentiation of the structures at the tip. In contrast, Dll has previously been shown to be required for the development of all of the leg more distal than the coxa. Dll protein can be detected in a central domain in leg discs throughout most of larval development, and in mature discs this domain corresponds to the distal-most region of the leg, the tarsus and the distal tibia. Clonal analysis reveals that late in development these are the only regions in which Dll function is required. However, earlier in development Dll is required in more proximal regions of the leg suggesting it is expressed at high levels in these cells early in development but not later. This reveals a correlation between a temporal requirement for Dll and position along the proximodistal axis; how this may relate to the generation of the P/D axis is discussed. Dll is required in the distal regions of the leg for the expression of tarsal-specific genes including al and bric-a-brac. Dll mutant cells in the leg sort out from wild-type cells suggesting one function of Dll here is to control adhesive properties of cells. Dll is also required for the normal development of the wing, primarily for the differentiation of the wing margin.

Different roles for Pax6 in the optic vesicle and facial epithelium mediate early morphogenesis of the murine eye

Development ◽  
2000 ◽  
Vol 127 (5) ◽  
pp. 945-956 ◽  
Author(s):  
J.M. Collinson ◽  
R.E. Hill ◽  
J.D. West
Keyword(s):  
Histological Analysis ◽  
Eye Development ◽  
Wild Type Mouse ◽  
Lens Epithelium ◽  
Optic Vesicle ◽  
Wild Type ◽  
Adhesive Properties ◽  
Optic Vesicles ◽  
Lens Placode ◽  
Mutant Cells

Chimaeric mice were made by aggregating Pax6(−/−) and wild-type mouse embryos, in order to study the interaction between the optic vesicle and the prospective lens epithelium during early stages of eye development. Histological analysis of the distribution of homozygous mutant cells in the chimaeras showed that the cell-autonomous removal of Pax6(−/−) cells from the lens, shown previously at E12.5, is nearly complete by E9.5. Most mutant cells are eliminated from an area of facial epithelium wider than, but including, the developing lens placode. This result suggests a role for Pax6 in maintaining a region of the facial epithelium that has the tissue competence to undergo lens differentiation. Segregation of wild-type and Pax6(−/−) cells occurs in the optic vesicle at E9.5 and is most likely a result of different adhesive properties of wild-type and mutant cells. Also, proximo-distal specification of the optic vesicle (as assayed by the elimination of Pax6(−/−) cells distally), is disrupted in the presence of a high proportion of mutant cells. This suggests that Pax6 operates during the establishment of patterning along the proximo-distal axis of the vesicle. Examination of chimaeras with a high proportion of mutant cells showed that Pax6 is required in the optic vesicle for maintenance of contact with the overlying lens epithelium. This may explain why Pax6(−/−) optic vesicles are inefficient at inducing a lens placode. Contact is preferentially maintained when the lens epithelium is also wild-type. Together, these results demonstrate requirements for functional Pax6 in both the optic vesicle and surface epithelia in order to mediate the interactions between the two tissues during the earliest stages of eye development.

scholarly journals Integrated K+ channel and K+-Cl− cotransporter functions regulate fin proportionality in zebrafish

2019 ◽  
Author(s):  
Jennifer S. Lanni ◽  
David Peal ◽  
Laura Ekstrom ◽  
Haining Chen ◽  
Caroline Stanclift ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Missense Mutation ◽  
Signaling Pathway ◽  
Normal Development ◽  
Growth Restriction ◽  
K Channel ◽  
Loss Of Function ◽  
Wild Type ◽  
Original Size ◽  
Dose Dependent

SummaryThe coordination of growth during development establishes proportionality within and among the different anatomic structures of organisms. Innate memory of this proportionality is preserved, as shown in the ability of regenerating structures to return to their original size. Although the regulation of this coordination is incompletely understood, mutant analyses of zebrafish with long-finned phenotypes have uncovered important roles for bioelectric signaling in modulating growth and size of the fins and barbs. To date, long-finned mutants identified are caused by hypermorphic mutations, leaving unresolved whether such signaling is required for normal development. We isolated a new zebrafish mutant, schleier, with proportional overgrowth phenotypes caused by a missense mutation and loss of function in the K+-Cl− cotransporter Kcc4a. Genetic depletion of Kcc4a in wild-type fish leads to a dose-dependent loss of growth restriction in fins and barbs, supporting a requirement for Kcc4a in regulation of proportion. Epistasis experiments suggest that Kcc4a and the two-pore potassium channel Kcnk5b both contribute to a common bioelectrical signaling response in the fin. These data suggest that an integrated bioelectric signaling pathway is required for the coordination of size and proportion during development.Graphical Abstract

scholarly journals A non-canonical role for p27Kip1 in restricting proliferation of corneal endothelial cells during development

2019 ◽  
Author(s):  
Dennis M. Defoe ◽  
Huiying Rao ◽  
David J. Harris ◽  
Preston D. Moore ◽  
Jan Brocher ◽  
...  
Keyword(s):  
Protein Function ◽  
Corneal Endothelium ◽  
Clustering Algorithm ◽  
Critical Factor ◽  
Cell Number ◽  
Loss Of Function ◽  
Wild Type ◽  
Tissue Organization ◽  
Density Based Clustering ◽  
Mutant Cells

AbstractThe cell cycle regulator p27Kip1 is a critical factor controlling cell number in many lineages. While its anti-proliferative effects are well-established, the extent to which this is a result of its function as a cyclin-dependent kinase (CDK) inhibitor or through other known molecular interactions is not clear. To genetically dissect its role in the developing corneal endothelium, we examined mice harboring two loss-of-function alleles, a null allele (p27−) that abrogates all protein function and a knockin allele (p27CK−) that targets only its interaction with cyclins and CDKs. Whole-animal mutants, in which all cells are either homozygous knockout or knockin, exhibit identical proliferative increases (∼0.6-fold) compared with wild-type tissues. On the other hand, use of mosaic analysis with double markers (MADM) to produce infrequently-occurring clones of wild-type and mutant cells within the same tissue environment uncovers a roughly three- and six-fold expansion of individual p27CK−/CK− and p27−/− cells, respectively. Mosaicism also reveals distinct migration phenotypes, with p27−/− cells being highly restricted to their site of production and p27CK−/CK− cells more widely scattered within the endothelium. Using a density-based clustering algorithm to quantify dispersal of MADM-generated clones, a four-fold difference in aggregation is seen between the two types of mutant cells. Overall, our analysis reveals that, in developing mouse corneal endothelium, p27 regulates cell number by acting cell autonomously, both through its interactions with cyclins and CDKs and through a cyclin-CDK-independent mechanism(s). Combined with its parallel influence on cell motility, it constitutes a potent multi-functional effector mechanism with major impact on tissue organization.

scholarly journals Role of SpoVG in Asymmetric Septation inBacillus subtilis

1999 ◽  
Vol 181 (11) ◽  
pp. 3392-3401 ◽  
Author(s):  
Kiyoshi Matsuno ◽  
Abraham L. Sonenshein
Keyword(s):  
Cell Division ◽  
Signal Transduction Pathway ◽  
Negative Regulator ◽  
Stage I ◽  
Loss Of Function ◽  
Wild Type ◽  
Gene Coding ◽  
Additional Defect ◽  
Cell Division Inhibitor ◽  
Mutant Cells

ABSTRACT Deletion of the citC gene, coding for isocitrate dehydrogenase, arrests sporulation of Bacillus subtilis at stage I after bipolar localization of the cell division protein FtsZ but before formation of the asymmetric septum. A spontaneous extragenic suppressor mutation that overcame the stage I block was found to map within the spoVG gene. The suppressing mutation and otherspoVG loss-of-function mutations enabled citCmutant cells to form asymmetric septa and to activate the forespore-specific sigma factor ςF. However, little induction of mother cell-specific, ςE-dependent sporulation genes was observed in a citC spoVG double mutant, indicating that there is an additional defect(s) in compartmentalized gene expression in the citC mutant. These other defects could be partially overcome by reducing the synthesis of citrate, by buffering the medium, or by adding excess MnCl2. Overexpression of the spoVG gene in wild-type cells significantly delayed ςF activation. Increased expression and stability of SpoVG in citC mutant cells may contribute to the citC mutant phenotype. Inactivation of the spoVG gene caused a population of otherwise wild-type cells to produce a small number of minicells during growth and caused sporulating cells to complete asymmetric septation more rapidly than normal. Unlike the case for inactivation of the cell division inhibitor gene minD, many of these minicells contained DNA and appeared only when the primary sporulation signal transduction pathway, the Spo0A phosphorelay, was active. These results suggest that SpoVG interferes with or is a negative regulator of the pathway leading to asymmetric septation.

Mutations in sfdA and sfdB Suppress Multiple Developmental Mutations in Aspergillus nidulans

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 159-168
Author(s):  
Ellen M Kellner ◽  
Thomas H Adams
Keyword(s):  
Aspergillus Nidulans ◽  
Null Allele ◽  
Hyphal Growth ◽  
Loss Of Function ◽  
Wild Type ◽  
Regulatory Pathway ◽  
Submerged Cultures ◽  
Developmental Defects ◽  
Suppressor Mutations ◽  
Its Gene

Abstract Conidiophore morphogenesis in Aspergillus nidulans occurs in response to developmental signals that result in the activation of brlA, a well-characterized gene that encodes a transcription factor that is central to asexual development. Loss-of-function mutations in flbD and other fluffy loci have previously been shown to result in delayed development and reduced expression of brlA. flbD message is detectable during both hyphal growth and conidiation, and its gene product is similar to the Myb family of transcription factors. To further understand the regulatory pathway to brlA activation and conidiation, we isolated suppressor mutations that rescued development in strains with a flbD null allele. We describe here two new loci, designated sfdA and sfdB for suppressors of flbD, that bypass the requirement of flbD for development. sfd mutant alleles were found to restore developmental timing and brlA expression to strains with flbD deletions. In addition, sfd mutations suppress the developmental defects in strains harboring loss-of-function mutations in fluG, flbA, flbB, flbC, and flbE. All alleles of sfdA and sfdB that we have isolated are recessive to their wild-type alleles in diploids. Strains with mutant sfd alleles in otherwise developmentally wild-type backgrounds have reduced growth phenotypes and develop conidiophores in submerged cultures.

A unique mutation in the Enhancer of split gene complex affects the fates of the mystery cells in the developing Drosophila eye

Development ◽  
1992 ◽  
Vol 115 (1) ◽  
pp. 89-101 ◽  
Author(s):  
J.A. Fischer-Vize ◽  
P.D. Vize ◽  
G.M. Rubin
Keyword(s):  
Compound Eye ◽  
Photoreceptor Cells ◽  
Neural Cells ◽  
Loss Of Function ◽  
Wild Type ◽  
Partial Loss ◽  
Eye Disc ◽  
Mutant Cells ◽  
Enhancer Of Split

An unusual recessive allele of the Drosophila groucho gene, which encodes a transducin-like protein, affects the fates of specific cells in the eye disc. groucho is one of several transcription units in the Enhancer of split complex. Most groucho mutations are zygotic lethal due to the proliferation of embryonic neural cells at the expense of epidermal cells. In contrast, flies homozygous for the mutant allele described here, groBFP2, are viable but have abnormal eyes. The Drosophila compound eye is composed of several hundred identical facets, or ommatidia, each of which contains eight photoreceptor cells, R1-R8. In groBFP2 mutant retinas, most of the facets contain eight normally determined photoreceptor cells and one or two additional R-cells of the R3/4 subtype. The extra photoreceptors appear to arise from the mystery cells, which are part of the precluster that initiates the ommatidium, but do not normally become neurons. groBFP2 behaves as a partial loss-of-function mutant. Analysis of ommatidia mosaic for wild-type and groBFP2 mutant cells suggests that the focus of action of the groBFP2 mutation is outside of the photoreceptor cells. These results imply that one function of groucho is in a pathway whereby neuralization of the mystery cells is inhibited by other non-neural cells in the eye disc. In addition, determination of R3/4 photoreceptors usually requires contact with R2 and R5. Specification of the mystery cells as ectopic R3/4 subtype photoreceptors in groBFP2 mutant eye discs implies that induction by R2 or R5 is not absolutely necessary for R3/4 cell determination.

scholarly journals Reduced function of the glutathione S-transferase S1 suppresses behavioral hyperexcitability in Drosophila expressing a mutant voltage-gated sodium channel

2020 ◽  
Author(s):  
Hung-Lin Chen ◽  
Junko Kasuya ◽  
Patrick Lansdon ◽  
Garrett Kaas ◽  
Hanxi Tang ◽  
...  
Keyword(s):  
Action Potentials ◽  
Null Allele ◽  
Single Gene ◽  
Loss Of Function ◽  
Wild Type ◽  
Bioactive Lipids ◽  
Glutathione S Transferase ◽  
Excitable Cells ◽  
Voltage Gated ◽  
Prostaglandin D Synthase

ABSTRACTVoltage-gated sodium (Nav) channels play a central role in the generation and propagation of action potentials in excitable cells such as neurons and muscles. To determine how the phenotypes of Nav-channel mutants are affected by other genes, we performed a forward genetic screen for dominant modifiers of the seizure-prone, gain-of-function Drosophila melanogaster Nav-channel mutant, paraShu. Our analyses using chromosome deficiencies, gene-specific RNA interference, and single-gene mutants revealed that a null allele of glutathione S-transferase S1 (GstS1) dominantly suppresses paraShu phenotypes. Reduced GstS1 function also suppressed phenotypes of other seizure-prone Nav-channel mutants, paraGEFS+ and parabss. Notably, paraShu mutants expressed 50% less GstS1 than wild-type flies, further supporting the notion that paraShu and GstS1 interact functionally. Introduction of a loss-of-function GstS1 mutation into a paraShu background led to up- and down-regulation of various genes, with those encoding cytochrome P450 (CYP) enzymes most significantly over-represented in this group. Because GstS1 is a fly ortholog of mammalian hematopoietic prostaglandin D synthase, and in mammals CYPs are involved in the oxygenation of polyunsaturated fatty acids including prostaglandins, our results raise the intriguing possibility that bioactive lipids play a role in GstS1-mediated suppression of paraShu phenotypes.

scholarly journals Superficial Dsg2 Expression Limits Epidermal Blister Formation Mediated by Pemphigus Foliaceus Antibodies and Exfoliative Toxins

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Donna Brennan ◽  
Ying Hu ◽  
Walid Medhat ◽  
Alicia Dowling ◽  
Mỹ G. Mahoney
Keyword(s):  
Cell Adhesion ◽  
Ectopic Expression ◽  
Pemphigus Foliaceus ◽  
Loss Of Function ◽  
Wild Type ◽  
Adhesive Properties ◽  
Epidermal Structure ◽  
Blister Formation ◽  
And Function ◽  
Cell Cell

Cell-cell adhesion mediated by desmosomes is crucial for maintaining proper epidermal structure and function, as evidenced by several severe and potentially fatal skin disorders involving impairment of desmosomal proteins. Pemphigus foliaceus (PF) and staphylococcal scalded skin syndrome (SSSS) are subcorneal blistering diseases resulting from loss of function of the desmosomal cadherin, desmoglein 1 (Dsg1). To further study the pathomechanism of these diseases and to assess the adhesive properties of Dsg2, we employed a recently established transgenic (Tg) mouse model expressing Dsg2 in the superficial epidermis. Neonatal Tg and wild type (WT) mice were injected with purified ETA or PF Ig. We showed that ectopic expression of Dsg2 reduced the extent of blister formation in response to both ETA and PF Ig. In response to PF Ig, we observed either a dramatic loss or a reorganization of Dsg1-α, Dsg1-β, and, to a lesser extent, Dsg1-γ, in WT mice. The Inv-Dsg2 Tg mice showed enhanced retention of Dsg1 at the cell-cell border. Collectively, our data support the role for Dsg2 in cell adhesion and suggest that ectopic superficial expression of Dsg2 can increase membrane preservation of Dsg1 and limit epidermal blister formation mediated by PF antibodies and exfoliative toxins.

scholarly journals Lethal (2) giant discs (Lgd)/CC2D1 is required for the full activity of the ESCRT machinery

BMC Biology ◽  
2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Miriam Baeumers ◽  
Kristina Ruhnau ◽  
Thomas Breuer ◽  
Hendrik Pannen ◽  
Bastian Goerlich ◽  
...  
Keyword(s):  
Transmembrane Proteins ◽  
Loss Of Function ◽  
Wild Type ◽  
Endosomal Sorting ◽  
Full Activity ◽  
Complete Degradation ◽  
Escrt Machinery ◽  
Intracellular Domains ◽  
Mutant Cells ◽  
Reduced Activity

Abstract Background A major task of the endosomal sorting complex required for transport (ESCRT) machinery is the pinching off of cargo-loaded intraluminal vesicles (ILVs) into the lumen of maturing endosomes (MEs), which is essential for the complete degradation of transmembrane proteins in the lysosome. The ESCRT machinery is also required for the termination of signalling through activated signalling receptors, as it separates their intracellular domains from the cytosol. At the heart of the machinery lies the ESCRT-III complex, which is required for an increasing number of processes where membrane regions are abscised away from the cytosol. The core of ESCRT-III, comprising four members of the CHMP protein family, organises the assembly of a homopolymer of CHMP4, Shrub in Drosophila, that is essential for abscission. We and others identified the tumour-suppressor lethal (2) giant discs (Lgd)/CC2D1 as a physical interactor of Shrub/CHMP4 in Drosophila and mammals, respectively. Results Here, we show that the loss of function of lgd constitutes a state of reduced activity of Shrub/CHMP4/ESCRT-III. This hypomorphic shrub mutant situation causes a slight decrease in the rate of ILV formation that appears to result in incomplete incorporation of Notch into ILVs. We found that the forced incorporation in ILVs of lgd mutant MEs suppresses the uncontrolled and ligand-independent activation of Notch. Moreover, the analysis of Su(dx) lgd double mutants clarifies their relationship and suggests that they are not operating in a linear pathway. We could show that, despite prolonged lifetime, the MEs of lgd mutants have a similar ILV density as wild-type but less than rab7 mutant MEs, suggesting the rate in lgd mutants is slightly reduced. The analysis of the MEs of wild-type and mutant cells in the electron microscope revealed that the ESCRT-containing electron-dense microdomains of ILV formation at the limiting membrane are elongated, indicating a change in ESCRT activity. Since lgd mutants can be rescued to normal adult flies if extra copies of shrub (or its mammalian ortholog CHMP4B) are added into the genome, we conclude that the net activity of Shrub is reduced upon loss of lgd function. Finally, we show that, in solution, CHMP4B/Shrub exists in two conformations. LGD1/Lgd binding does not affect the conformational state of Shrub, suggesting that Lgd is not a chaperone for Shrub/CHMP4B. Conclusion Our results suggest that Lgd is required for the full activity of Shrub/ESCRT-III. In its absence, the activity of the ESCRT machinery is reduced. This reduction causes the escape of a fraction of cargo, among it Notch, from incorporation into ILVs, which in turn leads to an activation of this fraction of Notch after fusion of the ME with the lysosome. Our results highlight the importance of the incorporation of Notch into ILV not only to assure complete degradation, but also to avoid uncontrolled activation of the pathway.

Ultrastructure and Morphology of the Neurospora Crassa Cell Wall Mutants, Slime And Slime X, Using Tem and Sem

1976 ◽  
Vol 34 ◽  
pp. 54-55
Author(s):  
Karen S. Howard ◽  
H. D. Braymer ◽  
M. D. Socolofsky ◽  
S. A. Milligan
Keyword(s):  
Cell Wall ◽  
Neurospora Crassa ◽  
Wild Type ◽  
Morphological Comparison ◽  
Small Areas ◽  
Solid Media ◽  
Thin Sectioning ◽  
X Cells ◽  
Mutant Cells ◽  
Isolated Cell

The recently isolated cell wall mutant slime X of Neurospora crassa was prepared for ultrastructural and morphological comparison with the cell wall mutant slime. The purpose of this article is to discuss the methods of preparation for TEM and SEM observations, as well as to make a preliminary comparison of the two mutants.TEM: Cells of the slime mutant were prepared for thin sectioning by the method of Bigger, et al. Slime X cells were prepared in the same manner with the following two exceptions: the cells were embedded in 3% agar prior to fixation and the buffered solutions contained 5% sucrose throughout the procedure.SEM: Two methods were used to prepare mutant and wild type Neurospora for the SEM. First, single colonies of mutant cells and small areas of wild type hyphae were cut from solid media and fixed with OSO4 vapors similar to the procedure used by Harris, et al. with one alteration. The cell-containing agar blocks were dehydrated by immersion in 2,2-dimethoxypropane (DMP).

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