skip to main content


Title: Conserved role for Ataxin‐2 in mediating endoplasmic reticulum dynamics
Abstract

Ataxin‐2, a conserved RNA‐binding protein, is implicated in the late‐onset neurodegenerative disease Spinocerebellar ataxia type‐2 (SCA2). SCA2 is characterized by shrunken dendritic arbors and torpedo‐like axons within the Purkinje neurons of the cerebellum. Torpedo‐like axons have been described to contain displaced endoplasmic reticulum (ER) in the periphery of the cell; however, the role of Ataxin‐2 in mediating ER function in SCA2 is unclear. We utilized theCaenorhabditis elegansandDrosophilahomologs of Ataxin‐2 (ATX‐2 and DAtx2, respectively) to determine the role of Ataxin‐2 in ER function and dynamics in embryos and neurons. Loss of ATX‐2 and DAtx2 resulted in collapse of the ER in dividing embryonic cells and germline, and ultrastructure analysis revealed unique spherical stacks of ER in mature oocytes and fragmented and truncated ER tubules in the embryo. ATX‐2 and DAtx2 reside in puncta adjacent to the ER in bothC. elegansandDrosophilaembryos. Lastly, depletion of DAtx2 in culturedDrosophilaneurons recapitulated the shrunken dendritic arbor phenotype of SCA2. ER morphology and dynamics were severely disrupted in these neurons. Taken together, we provide evidence that Ataxin‐2 plays an evolutionary conserved role in ER dynamics and morphology inC. elegansandDrosophilaembryos during development and in fly neurons, suggesting a possible SCA2 disease mechanism.

 
more » « less
Award ID(s):
1716298
NSF-PAR ID:
10460947
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Traffic
Volume:
20
Issue:
6
ISSN:
1398-9219
Page Range / eLocation ID:
p. 436-447
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Precise temporal control of neuro differentiation and post‐differentiation events are necessary for the creation of appropriate wiring diagram in the brain. To make advances in the treatment of neurodevelopmental and neurodegenerative disorders, and traumatic brain injury, it is important to understand these mechanisms.Caenorhabditis eleganshas emerged as a revolutionary tool for the study of neural circuits due to its genetic homology to vertebrates and ease of genetic manipulation. microRNA(miRNA), a ubiquitous class of small non‐codingRNA, that inhibits the expression of target genes, has emerged as an important timing control molecule through research conducted onC. elegans. This review will focus on the temporal control of neurodifferentiation and post‐differentiation events exerted by two conserved miRNAs,lin‐4andlet‐7. We summarize recent findings on the role oflin‐4as a timing regulator controlling transition of sequential events in neuronal pathfinding and synaptic remodeling, and the role oflet‐7as a timing regulator that limits the regeneration potential of post‐differentiatedAVMneurons as they age.

     
    more » « less
  2. Abstract Objective

    RNA-binding proteins (RBPs) are important regulators of gene expression that influence mRNA splicing, stability, localization, transport, and translational control. In particular, RBPs play an important role in neurons, which have a complex morphology. Previously, we showed that there are many RBPs that play a conserved role in dendrite development inDrosophiladendritic arborization neurons andCaenorhabditis elegans(C. elegans) PVD neurons including the cytoplasmic polyadenylation element binding proteins (CPEBs), Orb inDrosophilaand CPB-3 inC. elegans, and the DEAD box RNA helicases, Me31B inDrosophilaand CGH-1 inC. elegans. During these studies, we observed that fluorescently-labeled CPB-3 and CGH-1 localize to cytoplasmic particles that are motile, and our research aims to further characterize these RBP-containing particles in live neurons.

    Results

    Here we extend on previous work to show that CPB-3 and CGH-1 localize to motile particles within dendrites that move at a speed consistent with microtubule-based transport. This is consistent with a model in which CPB-3 and CGH-1 influence dendrite development through the transport and localization of their mRNA targets. Moreover, CPB-3 and CGH-1 rarely localize to the same particles suggesting that these RBPs function in discrete ribonucleoprotein particles (RNPs) that may regulate distinct mRNAs.

     
    more » « less
  3. Summary

    Faithful chromosome segregation is required for both mitotic and meiotic cell divisions and is regulated by multiple mechanisms including the anaphase‐promoting complex/cyclosome (APC/C), which is the largest known E3 ubiquitin‐ligase complex and has been implicated in regulating chromosome segregation in both mitosis and meiosis in animals. However, the role of theAPC/C during plant meiosis remains largely unknown. Here, we show that ArabidopsisAPC8is required for male meiosis.

    We used a combination of genetic analyses, cytology and immunolocalisation to define the function of AtAPC8 in male meiosis.

    Meiocytes fromapc8‐1plants exhibit several meiotic defects including improper alignment of bivalents at metaphase I, unequal chromosome segregation during anaphaseII, and subsequent formation of polyads. Immunolocalisation using an antitubulin antibody showed thatAPC8 is required for normal spindle morphology. We also observed mitotic defects inapc8‐1,including abnormal sister chromatid segregation and microtubule morphology.

    Our results demonstrate that ArabidopsisAPC/C is required for meiotic chromosome segregation and thatAPC/C‐mediated regulation of meiotic chromosome segregation is a conserved mechanism among eukaryotes.

     
    more » « less
  4. Background

    The mammalian guanine deaminase (GDA), called cypin, is important for proper neural development, by regulating dendritic arborization through modulation of microtubule (MT) dynamics. Additionally, cypin can promote MT assembly in vitro. However, it has never been tested whether cypin (or other GDA orthologs) binds to MTs or modulates MT dynamics. Here, we address these questions and characterizeXenopus laevisGDA (Gda) for the first time during embryonic development.

    Results

    We find that exogenously expressed human cypin and Gda both display a cytosolic distribution in primary embryonic cells. Furthermore, while expression of human cypin can promote MT polymerization,XenopusGda has no effect. Additionally, we find that the tubulin‐binding collapsin response mediator protein (CRMP) homology domain is only partially conserved between cypin and Gda. This likely explains the divergence in function, as we discovered that the cypin region containing the CRMP homology and PDZ‐binding domain is necessary for regulating MT dynamics. Finally, we observed thatgdais strongly expressed in the kidneys during late embryonic development, although it does not appear to be critical for kidney development.

    Conclusions

    Together, these results suggest that GDA has diverged in function between mammals and amphibians, and that mammalian GDA plays an indirect role in regulating MT dynamics. Developmental Dynamics 248:296–305, 2019. © 2019 Wiley Periodicals, Inc.

     
    more » « less
  5. Summary

    The GreenCut encompasses a suite of nucleus‐encoded proteins with orthologs among green lineage organisms (plants, green algae), but that are absent or poorly conserved in non‐photosynthetic/heterotrophic organisms. InChlamydomonas reinhardtii,CPLD49 (Conserved inPlantLineage andDiatoms49) is an uncharacterized GreenCut protein that is critical for maintaining normal photosynthetic function. We demonstrate that acpld49mutant has impaired photoautotrophic growth under high‐light conditions. The mutant exhibits a nearly 90% reduction in the level of the cytochromeb6fcomplex (Cytb6f), which impacts linear and cyclic electron transport, but does not compromise the ability of the strain to perform state transitions. Furthermore,CPLD49 strongly associates with thylakoid membranes where it may be part of a membrane protein complex with another GreenCut protein,CPLD38; a mutant null forCPLD38 also impacts Cytb6fcomplex accumulation. We investigated several potential functions ofCPLD49, with some suggested by protein homology. Our findings are congruent with the hypothesis thatCPLD38 andCPLD49 are part of a novel thylakoid membrane complex that primarily modulates accumulation, but also impacts the activity of the Cytb6fcomplex. Based on motifs ofCPLD49 and the activities of otherCPLD49‐like proteins, we suggest a role for this putative dehydrogenase in the synthesis of a lipophilic thylakoid membrane molecule or cofactor that influences the assembly and activity of Cytb6f.

     
    more » « less