Effects of Constitutive and Acute Connexin 36 Deficiency on Brain-Wide Susceptibility to PTZ-Induced Neuronal Hyperactivity

Connexins are transmembrane proteins that form hemichannels allowing the exchange of molecules between the extracellular space and the cell interior. Two hemichannels from adjacent cells dock and form a continuous gap junction pore, thereby permitting direct intercellular communication. Connexin 36 (Cx36), expressed primarily in neurons, is involved in the synchronous activity of neurons and may play a role in aberrant synchronous firing, as seen in seizures. To understand the reciprocal interactions between Cx36 and seizure-like neural activity, we examined three questions: (a) does Cx36 deficiency affect seizure susceptibility, (b) does seizure-like activity affect Cx36 expression patterns, and (c) does acute blockade of Cx36 conductance increase seizure susceptibility. We utilize the zebrafish pentylenetetrazol [PTZ; a GABA(A) receptor antagonist] induced seizure model, taking advantage of the compact size and optical translucency of the larval zebrafish brain to assess how PTZ affects brain-wide neuronal activity and Cx36 protein expression. We exposed wild-type and genetic Cx36-deficient (cx35.5-/-) zebrafish larvae to PTZ and subsequently mapped neuronal activity across the whole brain, using phosphorylated extracellular-signal-regulated kinase (pERK) as a proxy for neuronal activity. We found that cx35.5-/- fish exhibited region-specific susceptibility and resistance to PTZ-induced hyperactivity compared to wild-type controls, suggesting that genetic Cx36 deficiency may affect seizure susceptibility in a region-specific manner. Regions that showed increased PTZ sensitivity include the dorsal telencephalon, which is implicated in human epilepsy, and the lateral hypothalamus, which has been underexplored. We also found that PTZ-induced neuronal hyperactivity resulted in a rapid reduction of Cx36 protein levels within 30 min. This Cx36 reduction persists after 1-h of recovery but recovered after 3–6 h. This acute downregulation of Cx36 by PTZ is likely maladaptive, as acute pharmacological blockade of Cx36 by mefloquine results in increased susceptibility to PTZ-induced neuronal hyperactivity. Together, these results demonstrate a reciprocal relationship between Cx36 and seizure-associated neuronal hyperactivity: Cx36 deficiency contributes region-specific susceptibility to neuronal hyperactivity, while neuronal hyperactivity-induced downregulation of Cx36 may increase the risk of future epileptic events.

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Effects of constitutive and acute Connexin 36 deficiency on brain-wide susceptibility to PTZ-induced neuronal hyperactivity

10.1101/2020.07.27.223651 ◽

2020 ◽

Author(s):

Alyssa A. Brunal ◽

Kareem C. Clark ◽

Manxiu Ma ◽

Y. Albert Pan

Keyword(s):

Neuronal Activity ◽

Expression Patterns ◽

Reciprocal Relationship ◽

Seizure Susceptibility ◽

Wild Type ◽

Rapid Reduction ◽

Connexin 36 ◽

Human Epilepsy ◽

Compact Size ◽

Specific Susceptibility

ABSTRACTConnexins are transmembrane proteins that form hemichannels allowing the exchange of molecules between the extracellular space and cell interior. Two hemichannels from adjacent cells dock and form a continuous gap junction pore, thereby permitting direct intercellular communication. Connexin 36 (Cx36), expressed primarily in neurons, is involved in the synchronous activity of neurons and may play a role in aberrant synchronous firing, as seen in seizures. To understand the reciprocal interactions between Cx36 and seizure-like neural activity, we examined three questions: a) does Cx36 deficiency affect seizure susceptibility, b) does seizure-like activity affect Cx36 expression patterns, and c) does acute blockade of Cx36 conductance increase seizure susceptibility. We utilize the zebrafish pentylenetetrazol (PTZ; a GABA(A) receptor antagonist) induced seizure model, taking advantage of the compact size and optical translucency of the larval zebrafish brain to assess how PTZ affects brain-wide neuronal activity and Cx36 protein expression. We exposed wild-type and genetic Cx36-deficient (cx35.5- /-) zebrafish larvae to PTZ and subsequently mapped neuronal activity across the whole brain, using phosphorylated extracellular-signal-regulated kinase (pERK) as a proxy for neuronal activity. We found that cx35.5-/- fish exhibited region-specific susceptibility and resistance to PTZ-induced hyperactivity compared to wild-type controls, suggesting that genetic Cx36 deficiency may affect seizure susceptibility in a region-specific manner. Regions that showed increased PTZ sensitivity include the dorsal telencephalon, which is implicated in human epilepsy, and the lateral hypothalamus, which has been underexplored. We also found that PTZ-induced neuronal hyperactivity resulted in a rapid reduction of Cx36 protein levels. 30 minutes and one-hour exposure to 20 mM PTZ significantly reduced the expression of Cx36. This Cx36 reduction persists after one-hour of recovery but recovered after 3-6 hours. This acute downregulation of Cx36 by PTZ is likely maladaptive, as acute pharmacological blockade of Cx36 by mefloquine results in increased susceptibility to PTZ-induced neuronal hyperactivity. Together, these results demonstrate a reciprocal relationship between Cx36 and seizure-associated neuronal hyperactivity: Cx36 deficiency contributes region-specific susceptibility to neuronal hyperactivity, while neuronal hyperactivity-induced downregulation of Cx36 may increase the risk of future epileptic events.

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Analysis of maxillopedia Expression Pattern and Larval Cuticular Phenotype in Wild-Type and Mutant Tribolium

Genetics ◽

10.1093/genetics/155.2.721 ◽

2000 ◽

Vol 155 (2) ◽

pp. 721-731 ◽

Cited By ~ 7

Author(s):

Teresa D Shippy ◽

Jianhua Guo ◽

Susan J Brown ◽

Richard W Beeman ◽

Robin E Denell

Keyword(s):

Rna Interference ◽

Expression Pattern ◽

Tribolium Castaneum ◽

Expression Patterns ◽

Ectopic Expression ◽

Homeotic Gene ◽

Wild Type ◽

Double Stranded Rna ◽

Similar Expression ◽

Mutant Phenotypes

Abstract The Tribolium castaneum homeotic gene maxillopedia (mxp) is the ortholog of Drosophila proboscipedia (pb). Here we describe and classify available mxp alleles. Larvae lacking all mxp function die soon after hatching, exhibiting strong transformations of maxillary and labial palps to legs. Hypomorphic mxp alleles produce less severe transformations to leg. RNA interference with maxillopedia double-stranded RNA results in phenocopies of mxp mutant phenotypes ranging from partial to complete transformations. A number of gain-of-function (GOF) mxp alleles have been isolated based on transformations of adult antennae and/or legs toward palps. Finally, we have characterized the mxp expression pattern in wild-type and mutant embryos. In normal embryos, mxp is expressed in the maxillary and labial segments, whereas ectopic expression is observed in some GOF variants. Although mxp and Pb display very similar expression patterns, pb null embryos develop normally. The mxp mutant larval phenotype in Tribolium is consistent with the hypothesis that an ancestral pb-like gene had an embryonic function that was lost in the lineage leading to Drosophila.

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Apoptosis in late stage Drosophila nurse cells does not require genes within the H99 deficiency

Development ◽

10.1242/dev.125.6.1075 ◽

1998 ◽

Vol 125 (6) ◽

pp. 1075-1082 ◽

Cited By ~ 12

Author(s):

K. Foley ◽

L. Cooley

Keyword(s):

Dna Fragmentation ◽

Late Stage ◽

Expression Patterns ◽

Nuclear Material ◽

Nurse Cells ◽

Wild Type ◽

Negative Regulators ◽

Egg Chambers ◽

Positive Regulators ◽

Egg Chamber

We have determined that nurse cells are cleared from the Drosophila egg chamber by apoptosis. DNA fragmentation begins in nurse cells at stage 12, following the completion of cytoplasm transfer from the nurse cells to the oocyte. During stage 13, nurse cells increasingly contain highly fragmented DNA and disappear from the egg chamber concomitantly with the formation of apoptotic vesicles containing highly fragmented nuclear material. In dumpless mutant egg chambers that fail to complete cytoplasm transport from the nurse cells, DNA fragmentation is markedly delayed and begins during stage 13, when the majority of cytoplasm is lost from the nurse cells. These data suggest the presence of cytoplasmic factors in nurse cells that inhibit the initiation of DNA fragmentation. In addition, we have examined the ovarian expression patterns of regulatory genes implicated in Drosophila apoptosis. The positive regulators, reaper (rpr), head involution defective (hid) and grim, as well as the negative regulators, DIAP1 and DIAP2, are transcribed during oogenesis. However, germline clones homozygous for the deficiency Df(3)H99, which deletes rpr, hid and grim, undergo oogenesis in a manner morphologically indistinguishable from wild type, indicating that genes within this region are not necessary for apoptosis in nurse cells.

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Modifications of Seizure Susceptibility inDrosophila

Journal of Neurophysiology ◽

10.1152/jn.2000.83.2.998 ◽

2000 ◽

Vol 83 (2) ◽

pp. 998-1009 ◽

Cited By ~ 75

Author(s):

Daniel Kuebler ◽

Mark A. Tanouye

Keyword(s):

Idiopathic Epilepsy ◽

Seizure Susceptibility ◽

Wild Type ◽

Physiological Basis ◽

Seizure Disorders ◽

Spontaneous Seizures ◽

Wide Range ◽

Symptomatic Seizures ◽

Type Strains ◽

Over Time

In a given population, certain individuals are much more likely to have seizures than others. This increase in seizure susceptibility can lead to spontaneous seizures, such as seen in idiopathic epilepsy, or to symptomatic seizures that occur after insults to the nervous system. Despite the frequency of these seizure disorders in the human population, the genetic and physiological basis for these defects remains unclear. The present study makes use of Drosophila as a potentially powerful model for understanding seizure susceptibility in humans. In addition to the genetic and molecular advantages of using Drosophila, it has been found that seizures in Drosophila share much in common with seizures seen in humans. However, the most powerful aspect of this model lies in the ability to accurately measure seizure susceptibility across genotypes and over time. In the current study seizure susceptibility was quantified in a variety of mutant and wild-type strains, and it was found that genetic mutations can modulate susceptibility over an extremely wide range. This genetic modulation of seizure susceptibility apparently occurs without affecting the threshold of individual neurons. Seizure susceptibility also varied depending on the experience of the fly, decreasing immediately after a seizure and then gradually increasing over time. A novel phenomenon was also identified in which seizures are suppressed after certain high-intensity stimuli. These results demonstrate the utility of Drosophila as a model system for studying human seizure disorders and provide insights into the possible mechanisms by which seizure susceptibility is modified.

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Downregulation of CD40L–CD40 attenuates seizure susceptibility and severity of seizures

Scientific Reports ◽

10.1038/s41598-021-96760-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Esther Pototskiy ◽

Katherine Vinokuroff ◽

Andrew Ojeda ◽

C. Kendall Major ◽

Deepak Sharma ◽

...

Keyword(s):

Cortical Neurons ◽

Molecular Techniques ◽

Seizure Susceptibility ◽

Wild Type ◽

Upward Trend ◽

Seizure Severity ◽

Cd40 Expression ◽

Neuro Inflammation ◽

And Control ◽

Deficient Mice

AbstractUnregulated neuro-inflammation mediates seizures in temporal lobe epilepsy (TLE). Our aim was to determine the effect of CD40–CD40L activation in experimental seizures. CD40 deficient mice (CD40KO) and control mice (wild type, WT) received pentenyltetrazole (PTZ) or pilocarpine to evaluate seizures and status epilepticus (SE) respectively. In mice, anti-CD40L antibody was administered intranasally before PTZ. Brain samples from human TLE and post-seizure mice were processed to determine CD40–CD40L expression using histological and molecular techniques. CD40 expression was higher in hippocampus from human TLE and in cortical neurons and hippocampal neural terminals after experimental seizures. CD40–CD40L levels increased after seizures in the hippocampus and in the cortex. After SE, CD40L/CD40 levels increased in cortex and showed an upward trend in the hippocampus. CD40KO mice demonstrated reduction in seizure severity and in latency compared to WT mice. Anti-CD40L antibody limited seizure susceptibility and seizure severity. CD40L–CD40 interaction can serve as a target for an immuno-therapy for TLE.

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FGF-7 modulates ureteric bud growth and nephron number in the developing kidney

Development ◽

10.1242/dev.126.3.547 ◽

1999 ◽

Vol 126 (3) ◽

pp. 547-554 ◽

Cited By ~ 11

Author(s):

J. Qiao ◽

R. Uzzo ◽

T. Obara-Ishihara ◽

L. Degenstein ◽

E. Fuchs ◽

...

Keyword(s):

Expression Patterns ◽

Body Volume ◽

Metanephric Mesenchyme ◽

Nephron Number ◽

Wild Type ◽

Ureteric Bud ◽

Kidney Size ◽

Bud Growth ◽

Collecting System

The importance of proportioning kidney size to body volume was established by clinical studies which demonstrated that in-born defecits of nephron number predispose the kidney to disease. As the kidney develops, the expanding ureteric bud or renal collecting system induces surrounding metanephric mesenchyme to proliferate and differentiate into nephrons. Thus, it is likely that nephron number is related to ureteric bud growth. The expression patterns of mRNAs encoding Fibroblast Growth Factor-7 (FGF-7) and its high affinity receptor suggested that FGF-7 signaling may play a role in regulating ureteric bud growth. To test this hypothesis we examined kidneys from FGF-7-null and wild-type mice. Results of these studies demonstrate that the developing ureteric bud and mature collecting system of FGF-7-null kidneys is markedly smaller than wild type. Furthermore, morphometric analyses indicate that mature FGF-7-null kidneys have 30+/−6% fewer nephrons than wild-type kidneys. In vitro experiments demonstrate that elevated levels of FGF-7 augment ureteric bud growth and increase the number of nephrons that form in rodent metanephric kidney organ cultures. Collectively, these results demonstrate that FGF-7 levels modulate the extent of ureteric bud growth during development and the number of nephrons that eventually form in the kidney.

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Pax6 regulates specification of ventral neurone subtypes in the hindbrain by establishing progenitor domains

Development ◽

10.1242/dev.129.6.1327 ◽

2002 ◽

Vol 129 (6) ◽

pp. 1327-1338 ◽

Cited By ~ 1

Author(s):

Masanori Takahashi ◽

Noriko Osumi

Keyword(s):

Expression Patterns ◽

Domain Formation ◽

Wild Type ◽

Whole Embryo Culture ◽

Neuronal Markers ◽

Signalling Molecules ◽

Neuronal Progenitors ◽

In The Wild ◽

Mutant Rat

Recent studies have shown that generation of different kinds of neurones is controlled by combinatorial actions of homeodomain (HD) proteins expressed in the neuronal progenitors. Pax6 is a HD protein that has previously been shown to be involved in the differentiation of the hindbrain somatic (SM) motoneurones and V1 interneurones in the hindbrain and/or spinal cord. To investigate in greater depth the role of Pax6 in generation of the ventral neurones, we first examined the expression patterns of HD protein genes and subtype-specific neuronal markers in the hindbrain of the Pax6 homozygous mutant rat. We found that Islet2 (SM neurone marker) and En1 (V1 interneurone marker) were transiently expressed in a small number of cells, indicating that Pax6 is not directly required for specification of these neurones. We also observed that domains of all other HD protein genes (Nkx2.2, Nkx6.1, Irx3, Dbx2 and Dbx1) were shifted and their boundaries became blurred. Thus, Pax6 is required for establishment of the progenitor domains of the ventral neurones. Next, we performed Pax6 overexpression experiments by electroporating rat embryos in whole embryo culture. Pax6 overexpression in the wild type decreased expression of Nkx2.2, but ectopically increased expression of Irx3, Dbx1 and Dbx2. Moreover, electroporation of Pax6 into the Pax6 mutant hindbrain rescued the development of Islet2-positive and En1-positive neurones. To know reasons for perturbed progenitor domain formation in Pax6 mutant, we examined expression patterns of Shh signalling molecules and states of cell death and cell proliferation. Shh was similarly expressed in the floor plate of the mutant hindbrain, while the expressions of Ptc1, Gli1 and Gli2 were altered only in the progenitor domains for the motoneurones. The position and number of TUNEL-positive cells were unchanged in the Pax6 mutant. Although the proportion of cells that were BrdU-positive slightly increased in the mutant, there was no relationship with specific progenitor domains. Taken together, we conclude that Pax6 regulates specification of the ventral neurone subtypes by establishing the correct progenitor domains.

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Inhibition of Critical DNA Dioxygenase Activity in IDH1/2 Mutant Myeloid Neoplasms

Blood ◽

10.1182/blood-2020-143094 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 28-28

Author(s):

Simona Pagliuca ◽

Yihong Guan ◽

Anand D. Tiwari ◽

Dale Grabowski ◽

Carmelo Gurnari ◽

...

Keyword(s):

Cell Growth ◽

Cell Lines ◽

Synthetic Lethality ◽

Expression Patterns ◽

Inducible Promoter ◽

Loss Of Function ◽

Wild Type ◽

Private Company ◽

Myeloid Neoplasms ◽

Dioxygenase Activity

Neomorphic mutations in IDH1/2 producing R-2-Hydroxyglutrate (R-2HG), are common in myeloid malignancies and in various solid cancers. A diffuse hypermethylated status is the biological consequence of the R-2HG-mediated inhibition of several α-ketoglutarate (αKG)-dependent enzymes including DNA dioxygenases TET1, TET2 and TET3.1,2 Specifically, the inhibition of TET2, either induced by the interaction with R-2HG or by direct genomic silencing (as in case of TET2 loss of function mutations) is responsible for the block of the DNA cytosine demethylation pathway, inducing changes in expression patterns, (e.g. decreasing expression of tumor suppressor genes) and impairing execution of differentiation programs. Analysis of genomic data from a Cleveland Clinic (CCF) cohort of AML/MDS patients combined in a meta-analytic fashion with BeatAML3 and Tumor Cancer Genome Atlas (TCGA) cohorts (1119 profiled patients) showed that IDH1/2 mutations are mutually exclusive (only 3% [N=4/106] of AML IDH1/2 mutated cases had TET2 mutations, expected to be at a frequency of 18% [N=110/585] in IDH1/2 wild type cases, p=.000125). In this scenario we suggest that the loss of TET2 activity due to mutations prevents the expansion of IDH1/2 mutant myeloid neoplasms (MNs) because of phenotypic redundancies inducing synthetic lethality. With this premise we stipulated that a critical level of DNA dioxygenase activity exists and thus cells with low TET2 activity will not tolerate further inhibition by R-2HG. Here we propose to apply pharmacologic inhibition of TET2 to produce an additive effect on DNA dioxygenases to investigate whether this will result in a synthetic lethality of IDH1/2 mutant cells. Specifically we hypothesize that TET-dioxygenase inhibition may be implemented as a possible therapeutic strategy in neomorphic IDH1/2 mutant MNs. To explore this hypothesis we conducted a series of in vitro experiments in different isogenic cell lines expressing either mutant or wild type IDH1 or IDH2, that were simultaneously mutant, wild type (WT) or knock down (KD) for TET2 (TF1-IDH2R140Q, K562-IDH1R132C both WT for TET2 gene, and K18-IDH1R132CTET2KD and SIGM5-IDH1R132C TET2MT, both with a doxycycline inducible promoter for mutant IDH1). First we found that the doxycycline induction of ectopic IDH1R132C expression led to R-2HG increase (~10,000-fold over the baseline) and induced cell death in TET2-deficient cells (experiments conducted in SIGM5-IDH1R132C cells showing 70% of decrease in cell growth after five days of IDH induction with doxycycline), confirming the cytotoxic effect of cellular R-2HG. We then tested in IDH1/2MT cells sensitivity towards TETi76, a specific TET inhibitor designed on R-2HG scaffold (with more than 200 fold potency compared to R-2HG in cell-free assays of 5-hydroxy-methyl cytosine [5hMC] production).4 This compound showed particular selectivity towards inhibition of DNA dioxygenases when a set of 23 other dioxygenase inhibitors were screened. Most importantly, consistent with our hypothesis, TETi76 preferentially inhibited the proliferation of IDH1/2MT cells either following doxycycline-induction both in TET2WTand TET2 deficient models (K562 TET2WT, K18 TET2kD, SIGM-5 TET2MT cell lines), or in models not carrying the inducible promoter (TF1 TETWT) (Growth inhibition: 20-25% in IDHWT vs 70-80% in IDHMT cell lines after 72h of co-culture with TETi76 treatment for concentrations ranging between 1 and 5 µM. P-value range: 0.04-0.001 in pairwise comparisons with untreated controls). Overall, our findings are consistent with the idea that neomorphic IDH1/2MT phenocopies loss of function TET2MT, through R-2HG, down-modulating pathways fundamental for cell homeostasis, division and differentiation. If a residual TET-activity is needed for the function of IDH1/2MT cells, the complete block of the residual activity appears to inevitably disrupt this phenotype impairing cell growth and proliferation. This is also in agreement with the paucity of TET3 and TET1 mutation in the context of TET2MT carriers. In summary, results shown here represent an important proof of concept that the increased inhibition of DNA dioxygenase activity, instead of being more leukemogenic, can be synthetically lethal. Our observations may have implications with regard to the therapy of IDH1/2 mutated neoplasms including AML and MDS Disclosures Saunthararajah: EpiDestiny: Consultancy, Current equity holder in private company, Patents & Royalties: University of Illinois at Chicago. Maciejewski:Alexion, BMS: Speakers Bureau; Novartis, Roche: Consultancy, Honoraria.

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Mutant p53 Disrupts MCF-10A Cell Polarity in Three-dimensional Culture via Epithelial-to-mesenchymal Transitions

Journal of Biological Chemistry ◽

10.1074/jbc.m110.214585 ◽

2011 ◽

Vol 286 (18) ◽

pp. 16218-16228 ◽

Cited By ~ 60

Author(s):

Yanhong Zhang ◽

Wensheng Yan ◽

Xinbin Chen

Keyword(s):

Cell Polarity ◽

Expression Patterns ◽

Ectopic Expression ◽

Three Dimensional ◽

Mutant P53 ◽

Wild Type ◽

Gain Of Function ◽

Three Dimensional Culture ◽

Wild Type P53 ◽

E Cadherin

Mutant p53 is not only deficient in tumor suppression but also acquires additional activity, called gain of function. Mutant p53 gain of function is recapitulated in knock-in mice that carry one null allele and one mutant allele of the p53 gene. These knock-in mice develop aggressive tumors compared with p53-null mice. Recently, we and others showed that tumor cells carrying a mutant p53 are addicted to the mutant for cell survival and resistance to DNA damage. To further define mutant p53 gain of function, we used the MCF-10A three-dimensional model of mammary morphogenesis. MCF-10A cells in three-dimensional culture undergo a series of morphological changes and form polarized and growth-arrested spheroids with hollow lumen, which resembles normal glandular architectures in vivo. Here, we found that endogenous wild-type p53 in MCF-10A cells was not required for acinus formation, but knockdown of endogenous wild-type p53 (p53-KD) led to partial clearance of cells in the lumen due to decreased apoptosis. Consistent with this, p53-KD altered expression patterns of the cell adhesion molecule E-cadherin, the cytoskeletal marker β-catenin, and the extracellular matrix protein laminin V. We also found that ectopic expression of the mutant G245S led to a phenotype similar to p53-KD, whereas a combination of ectopic expression of siRNA-resistant G245S with p53-KD led to a less cleared lumen. In contrast, ectopic expression of mutant R248W, R175H, and R273H disrupted normal acinus architectures with filled lumen and led to formation of irregular and multiacinus structures regardless of p53-KD. In addition, these mutants altered normal expression patterns and/or levels of E-cadherin, β-catenin, laminin V, and tight junction marker ZO-1. Furthermore, epithelial-to-mesenchymal transitions (EMT) markers, Snail, Slug, and Twist, were highly induced by mutant p53 and/or p53-KD. Together, we postulate that EMT represents a mutant p53 gain of function and mutant p53 alters cell polarity via EMT.

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The Maize Clade A PP2C Phosphatases Play Critical Roles in Multiple Abiotic Stress Responses

International Journal of Molecular Sciences ◽

10.3390/ijms20143573 ◽

2019 ◽

Vol 20 (14) ◽

pp. 3573 ◽

Cited By ~ 8

Author(s):

Zhenghua He ◽

Jinfeng Wu ◽

Xiaopeng Sun ◽

Mingqiu Dai

Keyword(s):

Drought Tolerance ◽

Stress Responses ◽

Transgenic Arabidopsis ◽

Expression Patterns ◽

Survival Rates ◽

Wild Type ◽

Multiple Stresses ◽

Core Components ◽

Leaf Water Loss ◽

Natural Variations

As the core components of abscisic acid (ABA) signal pathway, Clade A PP2C (PP2C-A) phosphatases in ABA-dependent stress responses have been well studied in Arabidopsis. However, the roles and natural variations of maize PP2C-A in stress responses remain largely unknown. In this study, we investigated the expression patterns of ZmPP2C-As treated with multiple stresses and generated transgenic Arabidopsis plants overexpressing most of the ZmPP2C-A genes. The results showed that the expression of most ZmPP2C-As were dramatically induced by multiple stresses (drought, salt, and ABA), indicating that these genes may have important roles in response to these stresses. Compared with wild-type plants, ZmPP2C-A1, ZmPP2C-A2, and ZmPP2C-A6 overexpression plants had higher germination rates after ABA and NaCl treatments. ZmPP2C-A2 and ZmPP2C-A6 negatively regulated drought responses as the plants overexpressing these genes had lower survival rates, higher leaf water loss rates, and lower proline accumulation compared to wild type plants. The natural variations of ZmPP2C-As associated with drought tolerance were also analyzed and favorable alleles were detected. We widely studied the roles of ZmPP2C-A genes in stress responses and the natural variations detected in these genes have the potential to be used as molecular markers in genetic improvement of maize drought tolerance.

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