scholarly journals A genetic analysis of deltex and its interaction with the Notch locus in Drosophila melanogaster.

Genetics ◽  
1992 ◽  
Vol 131 (1) ◽  
pp. 99-112 ◽  
Author(s):  
M J Gorman ◽  
J R Girton
Keyword(s):  
Cell Fate ◽  
Developmental Pathways ◽  
Phenotypic Characterization ◽  
Loss Of Function ◽  
Cell Fates ◽  
Cone Cells ◽  
Notch Gene ◽  
Notch Locus ◽  
Fate Decision

Abstract During Drosophila development networks of genes control the developmental pathways that specify cell fates. The Notch gene is a well characterized member of some cell fate pathways, and several other genes belonging to these same pathways have been identified because they share a neurogenic null phenotype with Notch. However, it is unlikely that the neurogenic genes represent all of the genes in these pathways. The goal of this research was to use a genetic approach to identify and characterize one of the other genes that acts with Notch to specify cell fate. Mutant alleles of genes in the same pathway should have phenotypes similar to Notch alleles and should show phenotypic interactions with Notch alleles. With this approach we identified the deltex gene as a potential cell fate gene. An extensive phenotypic characterization of loss-of-function deltex phenotypes showed abnormalities (such as thick wing veins, double bristles and extra cone cells) that suggest that deltex is involved in cell fate decision processes. Phenotypic interactions between deltex and Notch as seen in double mutants showed that Notch and deltex do not code for duplicate functions and that the two genes function together in many different developing tissues. The results of these investigations lead to the conclusion that the deltex gene functions with the Notch gene in one or more developmental pathways to specify cell fate.

Suppressors of a lin-12 hypomorph define genes that interact with both lin-12 and glp-1 in Caenorhabditis elegans.

Genetics ◽  
1993 ◽  
Vol 135 (3) ◽  
pp. 765-783 ◽  
Author(s):  
M Sundaram ◽  
I Greenwald
Keyword(s):  
Caenorhabditis Elegans ◽  
Cell Fate ◽  
Gene Dosage ◽  
Egg Laying ◽  
Loss Of Function ◽  
Cell Fate Decision ◽  
Cell Fates ◽  
Cell Fate Decisions ◽  
Suppressor Mutations ◽  
Fate Decision

Abstract The lin-12 gene of Caenorhabditis elegans is thought to encode a receptor which mediates cell-cell interactions required to specify certain cell fates. Reversion of the egg-laying defective phenotype caused by a hypomorphic lin-12 allele identified rare extragenic suppressor mutations in five genes, sel-1, sel-9, sel-10, sel-11 and sel(ar40) (sel = suppressor and/or enhancer of lin-12). Mutations in each of these sel genes suppress defects associated with reduced lin-12 activity, and enhance at least one defect associated with elevated lin-12 activity. None of the sel mutations cause any obvious phenotype in a wild-type background. Gene dosage experiments suggest that sel-1 and sel(ar40) mutations are reduction-of-function mutations, while sel-9 and sel-11 mutations are gain-of-function mutations. sel-1, sel-9, sel-11 and sel(ar40) mutations do not suppress amorphic lin-12 alleles, while sel-10 mutations are able to bypass partially the requirement for lin-12 activity in at least one cell fate decision. sel-1, sel-9, sel-10, sel-11 and sel(ar40) mutations are also able to suppress the maternal-effect lethality caused by a partial loss-of-function allele of glp-1, a gene that is both structurally and functionally related to lin-12. These sel genes may therefore function in both lin-12 and glp-1 mediated cell fate decisions.

The Drosophila orphan nuclear receptor seven-up requires the Ras pathway for its function in photoreceptor determination

Development ◽  
1995 ◽  
Vol 121 (1) ◽  
pp. 225-235 ◽  
Author(s):  
G. Begemann ◽  
A.M. Michon ◽  
L. vd Voorn ◽  
R. Wepf ◽  
M. Mlodzik
Keyword(s):  
Cell Fate ◽  
Nuclear Receptor ◽  
Egf Receptor ◽  
Cell Transformation ◽  
Orphan Nuclear Receptor ◽  
Loss Of Function ◽  
Cone Cell ◽  
Ras Pathway ◽  
Protein Levels ◽  
Cone Cells

The Drosophila seven-up (svp) gene specifies outer photoreceptor cell fate in eye development and encodes an orphan nuclear receptor with two isoforms. Transient expression under the sevenless enhancer of either svp isoform leads to a dosage-dependent transformation of cone cells into R7 photoreceptors, and at a lower frequency, R7 cells into outer photoreceptors. To investigate the cellular pathways involved, we have taken advantage of the dosage sensitivity and screened for genes that modify this svp-induced phenotype. We show that an active Ras pathway is essential for the function of both Svp isoforms. Loss-of-function mutations in components of the Ras signal transduction cascade act as dominant suppressors of the cone cell transformation, whilst loss-of-function mutations in negative regulators of Ras-activity act as dominant enhancers. Furthermore, Svp-mediated transformation of cone cells to outer photoreceptors, reminiscent of its wild-type function in specifying R3/4 and R1/6 identity, requires an activated Ras pathway in the same cells, or alternatively dramatic increase in ectopic Svp protein levels. Our results indicate that svp is only fully functional in conjunction with activated Ras. Since we find that mutations in the Egf-receptor are also among the strongest suppressors of svp-mediated cone cell transformation, we propose that the Ras activity in cone cells is due to low level Egfr signaling. Several models that could account for the observed svp regulation by the Ras pathway are discussed.

Genetic analysis of laminin A reveals diverse functions during morphogenesis in Drosophila

Development ◽  
1993 ◽  
Vol 118 (2) ◽  
pp. 325-337 ◽  
Author(s):  
C. Henchcliffe ◽  
L. Garcia-Alonso ◽  
J. Tang ◽  
C.S. Goodman
Keyword(s):  
Cell Fate ◽  
Genetic Characterization ◽  
Complete Loss ◽  
Loss Of Function ◽  
Partial Loss ◽  
Multidomain Structure ◽  
A Subunit ◽  
Wing Structure

In order to dissect the functions of laminin A in vivo, we have undertaken a molecular and genetic characterization of the laminin A subunit (lamA) gene in Drosophila. Sequence analysis predicts a multidomain structure similar to mammalian homologs. We generated a series of complete and partial loss-of-function mutant alleles of the lamA gene; complete loss-of-function mutations lead to late embryonic lethality. Certain combinations of partial loss-of-function lamA alleles give rise to escaper adults, which have rough eyes associated with changes in cell fate and pattern, misshapen legs and defects in wing structure. These phenotypes suggest that laminin A has diverse functions during morphogenesis in Drosophila.

scholarly journals Tau affects P53 function and cell fate during the DNA damage response

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Martina Sola ◽  
Claudia Magrin ◽  
Giona Pedrioli ◽  
Sandra Pinton ◽  
Agnese Salvadè ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Fate ◽  
Neurodegenerative Disorder ◽  
Neuroblastoma Cells ◽  
Molecular Response ◽  
Loss Of Function ◽  
Protein Deposition ◽  
Medical Need ◽  
Damage Response ◽  
Fate Decision

Abstract Cells are constantly exposed to DNA damaging insults. To protect the organism, cells developed a complex molecular response coordinated by P53, the master regulator of DNA repair, cell division and cell fate. DNA damage accumulation and abnormal cell fate decision may represent a pathomechanism shared by aging-associated disorders such as cancer and neurodegeneration. Here, we examined this hypothesis in the context of tauopathies, a neurodegenerative disorder group characterized by Tau protein deposition. For this, the response to an acute DNA damage was studied in neuroblastoma cells with depleted Tau, as a model of loss-of-function. Under these conditions, altered P53 stability and activity result in reduced cell death and increased cell senescence. This newly discovered function of Tau involves abnormal modification of P53 and its E3 ubiquitin ligase MDM2. Considering the medical need with vast social implications caused by neurodegeneration and cancer, our study may reform our approach to disease-modifying therapies.

scholarly journals Molecular Characterization of eutF Mutants ofSalmonella typhimurium LT2 Identifies eutFLesions as Partial-Loss-of-Function tonB Alleles

1999 ◽  
Vol 181 (2) ◽  
pp. 368-374 ◽  
Author(s):  
Michael G. Thomas ◽  
George A. O’Toole ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Amino Acid ◽  
Molecular Characterization ◽  
Immunoblot Analysis ◽  
Phenotypic Characterization ◽  
Loss Of Function ◽  
Wild Type ◽  
Partial Loss ◽  
Acid Addition ◽  
Fusion Site

ABSTRACT The eutF locus of Salmonella typhimuriumLT2 was identified as a locus necessary for the utilization of ethanolamine as a sole carbon source. Initial models suggested that EutF was involved in either ethanolamine transport or was a transcriptional regulator of an ethanolamine transporter. Phenotypic characterization of eutF mutants suggested EutF was somehow involved in 1,2-propanediol, propionate, and succinate utilization. Here we provide evidence that two alleles defining the eutFlocus, Δ903 and eutF1115, are partial-loss-of-function tonB alleles. Both mutations were complemented by plasmids containing a wild-type allele of theEscherichia coli tonB gene. Immunoblot analysis using TonB monoclonal antibodies detected a TonB fusion protein in strains carrying eutF alleles. Molecular analysis of the Δ903 allele identified a deletion that resulted in the fusion of the 3′ end of tonB with the 3′ end oftrpA. In-frame translation of the tonB-trpAfusion resulted in the final 9 amino acids of TonB being replaced by a 45-amino-acid addition. We isolated a derivative of a strain carrying allele Δ903 that regained the ability to grow on ethanolamine as a carbon and energy source. The molecular characterization of the mutation that corrected the Eut−phenotype caused by allele Δ903 showed that the new mutation was a deletion of two nucleotides at the tonB-trpAfusion site. This deletion resulted in a frameshift that replaced the 45-amino-acid addition with a 5-amino-acid addition. This change resulted in a TonB protein with sufficient activity to restore growth on ethanolamine and eut operon expression to nearly wild-type levels. It was concluded that the observed EutF phenotypes were due to the partial loss of TonB function, which is proposed to result in reduced cobalamin and ferric siderophore transport in an aerobic environment; thus, the eutF locus does not exist.

The Notch locus of Drosophila is required in epidermal cells for epidermal development

Development ◽  
1990 ◽  
Vol 109 (4) ◽  
pp. 875-885 ◽  
Author(s):  
P.E. Hoppe ◽  
R.J. Greenspan
Keyword(s):  
Cell Surface ◽  
Cell Fate ◽  
Mitotic Recombination ◽  
Epidermal Cells ◽  
Cell Fate Decisions ◽  
Notch Protein ◽  
Notch Gene ◽  
Cell Surface Interactions ◽  
Notch Locus ◽  
Type Gene

The Notch locus of Drosophila plays an important role in cell fate decisions within the neurogenic ectoderm, a role thought to involve interactions at the cell surface. We have assayed the requirement for Notch gene expression in epidermal cells by two kinds of genetic mosaics. First, with gynandromorphs, we removed the wild-type gene long before the critical developmental events to produce large mutant clones. The genotype of cells in large clones was scored by means of an antibody to the Notch protein. Second, using mitotic recombination, we removed the gene at successively later times after completion of the mitotically active early cleavage stages, to produce small clones. These clones were detected by means of a linked mutation of cuticle pattern, armadillo. The results of both experiments demonstrate a requirement for Notch expression by epidermal cells, and thus argue against the model that the Notch product acts as a signal required only in the neuroblast to influence neighboring epidermal cells. The mitotic recombination experiment revealed that Notch product is required by epidermal cells subsequent to neuroblast delamination. This result implies that the Notch gene functions to maintain the determined state of epidermal cells, possibly by mediating cell surface interactions within the epidermis.

scholarly journals Nine Novel PAX9 Mutations and a Distinct Tooth Agenesis Genotype-Phenotype

2017 ◽  
Vol 97 (2) ◽  
pp. 155-162 ◽  
Author(s):  
S.-W. Wong ◽  
D. Han ◽  
H. Zhang ◽  
Y. Liu ◽  
X. Zhang ◽  
...  
Keyword(s):  
Dna Analysis ◽  
Direct Sequencing ◽  
Taste Perception ◽  
Phenotypic Characterization ◽  
Tooth Agenesis ◽  
Reaction Products ◽  
Loss Of Function ◽  
Second Molar ◽  
Functional Studies

Tooth agenesis is one of the most common developmental anomalies affecting function and esthetics. The paired-domain transcription factor, Pax9, is critical for patterning and morphogenesis of tooth and taste buds. Mutations of PAX9 have been identified in patients with tooth agenesis. Despite significant progress in the genetics of tooth agenesis, many gaps in knowledge exist in refining the genotype-phenotype correlation between PAX9 and tooth agenesis. In the present study, we complete genetic and phenotypic characterization of multiplex Chinese families with nonsyndromic (NS) tooth agenesis. Direct sequencing of polymerase chain reaction products revealed 9 novel (c.140G>C, c.167T>A, c.332G>C, c.194C>A, c.271A>T, c.146delC, c.185_189dup, c.256_262dup, and c.592delG) and 2 known heterozygous mutations in the PAX9 gene among 120 probands. Subsequently, pedigrees were extended, and we confirmed that the mutations co-segregated with the tooth agenesis phenotype (with exception of families in which DNA analysis was not available). In 1 family ( n = 6), 2 individuals harbored both the PAX9 c.592delG mutation and a heterozygous missense mutation (c.739C>T) in the MSX1 gene. Clinical characterization of families segregating a PAX9 mutation reveal that all affected individuals were missing the mandibular second molar and their maxillary central incisors are most susceptible to microdontia. A significant reduction of bitter taste perception was documented in individuals harboring PAX9 mutations ( n = 3). Functional studies revealed that PAX9 haploinsufficiency or a loss of function of the PAX9 protein underlies tooth agenesis.

scholarly journals Expression of constitutively active Notch arrests follicle cells at a precursor stage during Drosophila oogenesis and disrupts the anterior-posterior axis of the oocyte

Development ◽  
1996 ◽  
Vol 122 (11) ◽  
pp. 3639-3650 ◽  
Author(s):  
M.K. Larkin ◽  
K. Holder ◽  
C. Yost ◽  
E. Giniger ◽  
H. Ruohola-Baker
Keyword(s):  
Cell Fate ◽  
Ovarian Follicle ◽  
Follicle Cells ◽  
Cell Fates ◽  
Drosophila Oogenesis ◽  
Cell Fate Decisions ◽  
Notch Gene ◽  
Anterior Posterior ◽  
Anterior Posterior Axis ◽  
Constitutively Active

During early development, there are numerous instances where a bipotent progenitor divides to give rise to two progeny cells with different fates. The Notch gene of Drosophila and its homologues in other metazoans have been implicated in many of these cell fate decisions. It has been argued that the role of Notch in such instances may be to maintain cells in a precursor state susceptible to specific differentiating signals. This has been difficult to prove, however, due to a lack of definitive markers for precursor identity. We here perform molecular and morphological analyses of the roles of Notch in ovarian follicle cells during Drosophila oogenesis. These studies show directly that constitutively active Notch arrests cells at a precursor stage, while the loss of Notch function eliminates this stage. Expression of moderate levels of activated Notch leads to partial transformation of cell fates, as found in other systems, and we show that this milder phenotype correlates with a prolonged, but still transient, precursor stage. We also find that expression of constitutively active Notch in follicle cells at later stages leads to a defect in the anterior-posterior axis of the oocyte.

scholarly journals High-throughput generation and phenotypic characterization of zebrafish CRISPR mutants of DNA repair genes

2020 ◽  
Author(s):  
Unbeom Shin ◽  
Khriezhanuo Nakhro ◽  
Chang-Kyu Oh ◽  
Blake Carrington ◽  
Hayne Song ◽  
...  
Keyword(s):  
Dna Repair ◽  
High Throughput ◽  
Phenotypic Characterization ◽  
Normal Brain ◽  
Dna Repair Genes ◽  
Loss Of Function ◽  
Repair Genes ◽  
Six Genes ◽  
Mutant Collection

ABSTRACTA systematic knowledge of the roles of DNA repair genes at the level of the organism has been limited due to the lack of appropriate experimental techniques. Here, we generated zebrafish loss-of-function mutants for 32 DNA repair and replication genes through multiplexed CRISPR/Cas9-mediated mutagenesis. High-throughput phenotypic characterization of our mutant collection revealed that three genes (atad5a, ddb1, pcna) are essential for proper embryonic development and hematopoiesis; seven genes (apex1, atrip, ino80, mre11a, shfm1, telo2, wrn) are required for growth and development during juvenile stage and six genes (blm, brca2, fanci, rad51, rad54l, rtel1) play critical roles in sex development. Furthermore, mutation in six genes (atad5a, brca2, polk, rad51, shfm1, xrcc1) displayed hypersensitivity to DNA damage agents. Further characterization of atad5a−/− mutants demonstrate that Atad5a is required for normal brain development and hematopoiesis. Our zebrafish mutant collection provides a unique resource for understanding of the roles of DNA repair genes at the organismal level.

scholarly journals Epistatic, Synthetic, and Balancing Interactions among Tubulin Missense Mutations Affecting Neurite Growth in Caenorhabditis elegans

2020 ◽  
pp. mbc.E20-07-0492
Author(s):  
Ho Ming Terence Lee ◽  
Natalie Yvonne Sayegh ◽  
A. Sophia Gayek ◽  
Susan Laura Javier Jao ◽  
Martin Chalfie ◽  
...  
Keyword(s):  
Genetic Interaction ◽  
Neurite Growth ◽  
Phenotypic Characterization ◽  
Missense Mutations ◽  
Loss Of Function ◽  
C Elegans ◽  
Touch Receptor Neurons ◽  
Receptor Neurons ◽  
Tubulin Mutations

Mutations in tubulins affect microtubule (MT) dynamics and functions during neuronal differentiation and their genetic interaction provides insights into the regulation of MT functions. We previously used C. elegans touch receptor neurons to analyze the cellular impact of tubulin mutations and reported the phenotypes of 67 tubulin missense mutations, categorized into three classes: loss-of-function ( lf), antimorphic ( anti), and neomorphic ( neo) alleles. In this study, we isolated 54 additional tubulin alleles through suppressor screens in sensitized backgrounds that caused excessive neurite growth. These alleles included 32 missense mutations not analyzed before, bringing the total number of mutations in our collection to 99. Phenotypic characterization of these newly isolated mutations identified three new types of alleles: partial lf and weak neo alleles of mec-7/β-tubulin that had subtle effects and strong anti alleles of mec-12/α-tubulin. We also discovered complex genetic interactions among the tubulin mutations, including the suppression of neo mutations by intragenic lf and anti alleles, additive and synthetic effects between mec-7 neo alleles, and unexpected epistasis, in which weaker neo alleles masked the effects of stronger neo alleles in inducing ectopic neurite growth. We also observed balancing between neo and anti alleles, whose respective MT-hyperstablizing and -destabilizing effects neutralized each other.

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