scholarly journals Putting the model to the test: are APC proteins essential for neuronal polarity, axon outgrowth, and axon targeting?

2008 ◽  
Vol 183 (2) ◽  
pp. 203-212 ◽  
Author(s):  
Nasser M. Rusan ◽  
Kathryn Akong ◽  
Mark Peifer
Keyword(s):  
Cell Cycle Progression ◽  
Asymmetric Cell Division ◽  
Dominant Negative ◽  
Axon Outgrowth ◽  
Neuronal Polarity ◽  
Axon Pathfinding ◽  
Loss Of Function ◽  
Axon Targeting ◽  
Affect Cell Cycle Progression ◽  
Division Axis

The highly polarized architecture of neurons is important for their function. Experimental data based on dominant-negative approaches suggest that the tumor suppressor adenomatous polyposis coli (APC), a regulator of Wnt signaling and the cytoskeleton, regulates polarity of neuroectodermal precursors and neurons, helping specify one neurite as the axon, promoting its outgrowth, and guiding axon pathfinding. However, such dominant-negative approaches might affect processes in which APC is not essential. We completely removed both APCs from Drosophila melanogaster larval neural precursors and neurons, testing whether APCs play universal roles in neuronal polarity. Surprisingly, APCs are not essential for asymmetric cell division or the stereotyped division axis of central brain (CB) neuroblasts, although they do affect cell cycle progression and spindle architecture. Likewise, CB, lobular plug, and mushroom body neurons do not require APCs for polarization, axon outgrowth, or, in the latter two cases, axon targeting. These data suggest that proposed cytoskeletal roles for APCs in mammals should be reassessed using loss of function tools.

scholarly journals The Rap1–Rgl–Ral signaling network regulates neuroblast cortical polarity and spindle orientation

2011 ◽  
Vol 195 (4) ◽  
pp. 553-562 ◽  
Author(s):  
Ana Carmena ◽  
Aljona Makarova ◽  
Stephan Speicher
Keyword(s):  
Cell Fate ◽  
Asymmetric Cell Division ◽  
Signaling Network ◽  
Spindle Orientation ◽  
Nucleotide Exchange ◽  
Loss Of Function ◽  
Axis Orientation ◽  
Division Axis ◽  
Guanosine Triphosphatase

A crucial first step in asymmetric cell division is to establish an axis of cell polarity along which the mitotic spindle aligns. Drosophila melanogaster neural stem cells, called neuroblasts (NBs), divide asymmetrically through intrinsic polarity cues, which regulate spindle orientation and cortical polarity. In this paper, we show that the Ras-like small guanosine triphosphatase Rap1 signals through the Ral guanine nucleotide exchange factor Rgl and the PDZ protein Canoe (Cno; AF-6/Afadin in vertebrates) to modulate the NB division axis and its apicobasal cortical polarity. Rap1 is slightly enriched at the apical pole of metaphase/anaphase NBs and was found in a complex with atypical protein kinase C and Par6 in vivo. Loss of function and gain of function of Rap1, Rgl, and Ral proteins disrupt the mitotic axis orientation, the localization of Cno and Mushroom body defect, and the localization of cell fate determinants. We propose that the Rap1–Rgl–Ral signaling network is a novel mechanism that cooperates with other intrinsic polarity cues to modulate asymmetric NB division.

scholarly journals Hematopoietic Stem Cell Transplantation Resolves the Immune Deficit Associated with STAT3-Dominant-Negative Hyper-IgE Syndrome

2021 ◽  
Author(s):  
Stephanie C. Harrison ◽  
Christo Tsilifis ◽  
Mary A. Slatter ◽  
Zohreh Nademi ◽  
Austen Worth ◽  
...  
Keyword(s):  
Stem Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Stem Cell Transplantation ◽  
Cell Transplantation ◽  
Hematopoietic Stem Cell ◽  
Early Report ◽  
Dominant Negative ◽  
Loss Of Function ◽  
Hematopoietic Stem ◽  
Hyper Ige Syndrome

AbstractAutosomal dominant hyper-IgE syndrome caused by dominant-negative loss-of-function mutations in signal transducer and activator of transcription factor 3 (STAT3) (STAT3-HIES) is a rare primary immunodeficiency with multisystem pathology. The quality of life in patients with STAT3-HIES is determined by not only the progressive, life-limiting pulmonary disease, but also significant skin disease including recurrent infections and abscesses requiring surgery. Our early report indicated that hematopoietic stem cell transplantation might not be effective in patients with STAT3-HIES, although a few subsequent reports have reported successful outcomes. We update on progress of our patient now with over 18 years of follow-up and report on an additional seven cases, all of whom have survived despite demonstrating significant disease-related pathology prior to transplant. We conclude that effective cure of the immunological aspects of the disease and stabilization of even severe lung involvement may be achieved by allogeneic hematopoietic stem cell transplantation. Recurrent skin infections and abscesses may be abolished. Donor TH17 cells may produce comparable levels of IL17A to healthy controls. The future challenge will be to determine which patients should best be offered this treatment and at what point in their disease history.

scholarly journals Rgs4 is a regulator of mTOR activity required for motoneuron axon outgrowth and neuronal development in zebrafish

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aya Mikdache ◽  
Marie-José Boueid ◽  
Lorijn van der Spek ◽  
Emilie Lesport ◽  
Brigitte Delespierre ◽  
...  
Keyword(s):  
Nervous System ◽  
G Protein ◽  
Neural Development ◽  
Neuronal Development ◽  
Axon Outgrowth ◽  
Rgs Proteins ◽  
Protein Signaling ◽  
Loss Of Function ◽  
G Protein Coupled

AbstractThe Regulator of G protein signaling 4 (Rgs4) is a member of the RGS proteins superfamily that modulates the activity of G-protein coupled receptors. It is mainly expressed in the nervous system and is linked to several neuronal signaling pathways; however, its role in neural development in vivo remains inconclusive. Here, we generated and characterized a rgs4 loss of function model (MZrgs4) in zebrafish. MZrgs4 embryos showed motility defects and presented reduced head and eye sizes, reflecting defective motoneurons axon outgrowth and a significant decrease in the number of neurons in the central and peripheral nervous system. Forcing the expression of Rgs4 specifically within motoneurons rescued their early defective outgrowth in MZrgs4 embryos, indicating an autonomous role for Rgs4 in motoneurons. We also analyzed the role of Akt, Erk and mechanistic target of rapamycin (mTOR) signaling cascades and showed a requirement for these pathways in motoneurons axon outgrowth and neuronal development. Drawing on pharmacological and rescue experiments in MZrgs4, we provide evidence that Rgs4 facilitates signaling mediated by Akt, Erk and mTOR in order to drive axon outgrowth in motoneurons and regulate neuronal numbers.

scholarly journals A Modified Screening System for Loss-of-Function and Dominant Negative Alleles of Essential MCMV Genes

PLoS ONE ◽  
2014 ◽  
Vol 9 (4) ◽  
pp. e94918
Author(s):  
Madlen Pogoda ◽  
Jens B. Bosse ◽  
Karl-Klaus Conzelmann ◽  
Ulrich H. Koszinowski ◽  
Zsolt Ruzsics
Keyword(s):  
Dominant Negative ◽  
Screening System ◽  
Loss Of Function

scholarly journals The Paramyxovirus Simian Virus 5 V Protein Slows Progression of the Cell Cycle

2000 ◽  
Vol 74 (19) ◽  
pp. 9152-9166 ◽  
Author(s):  
Grace Y. Lin ◽  
Robert A. Lamb
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Simian Virus ◽  
S Phase ◽  
V Protein ◽  
Simian Virus 5 ◽  
C Terminus ◽  
M Phase ◽  
Infected Cells ◽  
Affect Cell Cycle Progression

ABSTRACT Infection of cells by many viruses affects the cell division cycle of the host cell to favor viral replication. We examined the ability of the paramyxovirus simian parainfluenza virus 5 (SV5) to affect cell cycle progression, and we found that SV5 slows the rate of proliferation of HeLa T4 cells. The SV5-infected cells had a delayed transition from G1 to S phase and prolonged progression through S phase, and some of the infected cells were arrested in G2 or M phase. The levels of p53 and p21CIP1were not increased in SV5-infected cells compared to mock-infected cells, suggesting that the changes in the cell cycle occur through a p53-independent mechanism. However, the phosphorylation of the retinoblastoma protein (pRB) was delayed and prolonged in SV5-infected cells. The changes in the cell cycle were also observed in cells expressing the SV5 V protein but not in the cells expressing the SV5 P protein or the V protein lacking its unique C terminus (VΔC). The unique C terminus of the V protein of SV5 was shown previously to interact with DDB1, which is the 127-kDa subunit of the multifunctional damage-specific DNA-binding protein (DDB) heterodimer. The coexpression of DDB1 with V can partially restore the changes in the cell cycle caused by expression of the V protein.

SCL-mediated regulation of the cell-cycle regulator p21 is critical for murine megakaryopoiesis

Blood ◽  
2011 ◽  
Vol 118 (3) ◽  
pp. 723-735 ◽  
Author(s):  
Hedia Chagraoui ◽  
Mira Kassouf ◽  
Sreemoti Banerjee ◽  
Nicolas Goardon ◽  
Kevin Clark ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcriptional Control ◽  
Cell Cycle Progression ◽  
Cellular Proliferation ◽  
Loss Of Function ◽  
Cycle Progression ◽  
Cell Cycle Regulator ◽  
Nuclear Changes ◽  
Cytoplasmic Maturation

Abstract Megakaryopoiesis is a complex process that involves major cellular and nuclear changes and relies on controlled coordination of cellular proliferation and differentiation. These mechanisms are orchestrated in part by transcriptional regulators. The key hematopoietic transcription factor stem cell leukemia (SCL)/TAL1 is required in early hematopoietic progenitors for specification of the megakaryocytic lineage. These early functions have, so far, prevented full investigation of its role in megakaryocyte development in loss-of-function studies. Here, we report that SCL critically controls terminal megakaryocyte maturation. In vivo deletion of Scl specifically in the megakaryocytic lineage affects all key attributes of megakaryocyte progenitors (MkPs), namely, proliferation, ploidization, cytoplasmic maturation, and platelet release. Genome-wide expression analysis reveals increased expression of the cell-cycle regulator p21 in Scl-deleted MkPs. Importantly, p21 knockdown-mediated rescue of Scl-mutant MkPs shows full restoration of cell-cycle progression and partial rescue of the nuclear and cytoplasmic maturation defects. Therefore, SCL-mediated transcriptional control of p21 is essential for terminal maturation of MkPs. Our study provides a mechanistic link between a major hematopoietic transcriptional regulator, cell-cycle progression, and megakaryocytic differentiation.

scholarly journals Defective Neuronal Positioning Correlates With Aberrant Motor Circuit Function in Zebrafish

2021 ◽  
Vol 15 ◽  
Author(s):  
Emilia Asante ◽  
Devynn Hummel ◽  
Suman Gurung ◽  
Yasmin M. Kassim ◽  
Noor Al-Shakarji ◽  
...  
Keyword(s):  
Neuromuscular Junctions ◽  
Larval Feeding ◽  
Normal Brain ◽  
Axon Pathfinding ◽  
Loss Of Function ◽  
Jaw Muscles ◽  
Normal Brain Function ◽  
Functional Consequences ◽  
And Migration ◽  
Circuit Function

Precise positioning of neurons resulting from cell division and migration during development is critical for normal brain function. Disruption of neuronal migration can cause a myriad of neurological disorders. To investigate the functional consequences of defective neuronal positioning on circuit function, we studied a zebrafish frizzled3a (fzd3a) loss-of-function mutant off-limits (olt) where the facial branchiomotor (FBM) neurons fail to migrate out of their birthplace. A jaw movement assay, which measures the opening of the zebrafish jaw (gape), showed that the frequency of gape events, but not their amplitude, was decreased in olt mutants. Consistent with this, a larval feeding assay revealed decreased food intake in olt mutants, indicating that the FBM circuit in mutants generates defective functional outputs. We tested various mechanisms that could generate defective functional outputs in mutants. While fzd3a is ubiquitously expressed in neural and non-neural tissues, jaw cartilage and muscle developed normally in olt mutants, and muscle function also appeared to be unaffected. Although FBM neurons were mispositioned in olt mutants, axon pathfinding to jaw muscles was unaffected. Moreover, neuromuscular junctions established by FBM neurons on jaw muscles were similar between wildtype siblings and olt mutants. Interestingly, motor axons innervating the interhyoideus jaw muscle were frequently defasciculated in olt mutants. Furthermore, GCaMP imaging revealed that mutant FBM neurons were less active than their wildtype counterparts. These data show that aberrant positioning of FBM neurons in olt mutants is correlated with subtle defects in fasciculation and neuronal activity, potentially generating defective functional outputs.

scholarly journals Rett-causing mutations reveal two domains critical for MeCP2 function and for toxicity in MECP2 duplication syndrome mice

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Laura Dean Heckman ◽  
Maria H Chahrour ◽  
Huda Y Zoghbi
Keyword(s):  
Transcriptional Repression ◽  
Neurological Disorder ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Loss Of Function ◽  
Gene Encoding ◽  
C Terminus ◽  
Mecp2 Duplication Syndrome ◽  
Negative Effect ◽  
Duplication Syndrome

Loss of function of the X-linked gene encoding methyl-CpG binding protein 2 (MeCP2) causes the progressive neurological disorder Rett syndrome (RTT). Conversely, duplication or triplication of Xq28 causes an equally wide-ranging progressive neurological disorder, MECP2 duplication syndrome, whose features overlap somewhat with RTT. To understand which MeCP2 functions cause toxicity in the duplication syndrome, we generated mouse models expressing endogenous Mecp2 along with a RTT-causing mutation in either the methyl-CpG binding domain (MBD) or the transcriptional repression domain (TRD). We determined that both the MBD and TRD must function for doubling MeCP2 to be toxic. Mutating the MBD reproduces the null phenotype and expressing the TRD mutant produces milder RTT phenotypes, yet both mutations are harmless when expressed with endogenous Mecp2. Surprisingly, mutating the TRD is more detrimental than deleting the entire C-terminus, indicating a dominant-negative effect on MeCP2 function, likely due to the disruption of a basic cluster.

scholarly journals Ras controls growth, survival and differentiation in the Drosophila eye by different thresholds of MAP kinase activity

Development ◽  
2001 ◽  
Vol 128 (9) ◽  
pp. 1687-1696 ◽  
Author(s):  
K. Halfar ◽  
C. Rommel ◽  
H. Stocker ◽  
E. Hafen
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Photoreceptor Cells ◽  
Loss Of Function ◽  
Cellular Functions ◽  
Partial Loss ◽  
Cycle Progression ◽  
Mapk Activity ◽  
Dividing Cells

Ras mediates a plethora of cellular functions during development. In the developing eye of Drosophila, Ras performs three temporally separate functions. In dividing cells, it is required for growth but is not essential for cell cycle progression. In postmitotic cells, it promotes survival and subsequent differentiation of ommatidial cells. In the present paper, we have analyzed the different roles of Ras during eye development by using molecularly defined complete and partial loss-of-function mutations of Ras. We show that the three different functions of Ras are mediated by distinct thresholds of MAPK activity. Low MAPK activity prolongs cell survival and permits differentiation of R8 photoreceptor cells while high or persistent MAPK activity is sufficient to precociously induce R1-R7 photoreceptor differentiation in dividing cells.

scholarly journals The RASSF6 Tumor Suppressor Protein Regulates Apoptosis and Cell Cycle Progression via Retinoblastoma Protein

2018 ◽  
Vol 38 (17) ◽  
Author(s):  
Shakhawoat Hossain ◽  
Hiroaki Iwasa ◽  
Aradhan Sarkar ◽  
Junichi Maruyama ◽  
Kyoko Arimoto-Matsuzaki ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Loss Of Function ◽  
Cycle Progression ◽  
P53 Expression ◽  
Cycle Arrest ◽  
Hct116 Cells

ABSTRACT RASSF6 is a member of the tumor suppressor Ras association domain family (RASSF) proteins. RASSF6 is frequently suppressed in human cancers, and its low expression level is associated with poor prognosis. RASSF6 regulates cell cycle arrest and apoptosis and plays a tumor suppressor role. Mechanistically, RASSF6 blocks MDM2-mediated p53 degradation and enhances p53 expression. However, RASSF6 also induces cell cycle arrest and apoptosis in a p53-negative background, which implies that the tumor suppressor function of RASSF6 does not depend solely on p53. In this study, we revealed that RASSF6 mediates cell cycle arrest and apoptosis via pRb. RASSF6 enhances the interaction between pRb and protein phosphatase. RASSF6 also enhances P16INK4A and P14ARF expression by suppressing BMI1. In this way, RASSF6 increases unphosphorylated pRb and augments the interaction between pRb and E2F1. Moreover, RASSF6 induces TP73 target genes via pRb and E2F1 in a p53-negative background. Finally, we confirmed that RASSF6 depletion induces polyploid cells in p53-negative HCT116 cells. In conclusion, RASSF6 behaves as a tumor suppressor in cancers with loss of function of p53, and pRb is implicated in this function of RASSF6.

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