scholarly journals Systematic functional analysis of Rab GTPases reveals limits of neuronal robustness in Drosophila

2020 ◽  
Author(s):  
Friederike E. Kohrs ◽  
Ilsa-Maria Daumann ◽  
Bojana Pavlović ◽  
Eugene Jennifer Jin ◽  
Shih-Ching Lin ◽  
...  
Keyword(s):  
Nervous System ◽  
Synaptic Vesicle ◽  
Membrane Trafficking ◽  
Synaptic Function ◽  
Rab Gtpases ◽  
Continuous Stimulation ◽  
Different Temperatures ◽  
Morphological Defects ◽  
And Function

SummaryRab GTPases are molecular switches that regulate membrane trafficking in all cells. Neurons have particular demands on membrane trafficking and express numerous Rab GTPases of unknown function. Here we report the generation and characterization of molecularly defined null mutants for all 26 rab genes in Drosophila. In addition, we created a transgenic fly collection for the acute, synchronous release system RUSH for all 26 Rabs. In flies, all rab genes are expressed in the nervous system where at least half exhibit particularly high levels compared to other tissues. Surprisingly, loss of any of these 13 nervous-system enriched Rabs yields viable and fertile flies without obvious morphological defects. However, 9 of these 13 affect either developmental timing when challenged with different temperatures, or neuronal function when challenged with continuous stimulation. These defects are non-lethal under laboratory conditions, but represent sensitized genetic backgrounds that reveal limits of developmental and functional robustness to environmental challenges. Interestingly, the neuronal rab26 was previously proposed to function in synaptic maintenance by linking autophagy and synaptic vesicle recycling and we identified rab26 as one of six rab mutants with reduced synaptic function under continuous stimulation conditions. However, we found no changes to autophagy or synaptic vesicle markers in the rab26 mutant, but instead a cell-specific role in membrane receptor turnover associated with cholinergic synapses in the fly visual system. Our systematic functional analyses suggest that several Rabs ensure robust development and function under varying environmental conditions. The mutant and transgenic fly collections generated in this study provide a basis for further studies of Rabs during development and homeostasis in vivo.

scholarly journals Systematic functional analysis of rab GTPases reveals limits of neuronal robustness to environmental challenges in flies

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Friederike E Kohrs ◽  
Ilsa-Maria Daumann ◽  
Bojana Pavlovic ◽  
Eugene Jennifer Jin ◽  
F Ridvan Kiral ◽  
...  
Keyword(s):  
Nervous System ◽  
Membrane Trafficking ◽  
Rab Gtpases ◽  
Continuous Stimulation ◽  
Different Temperatures ◽  
Morphological Defects ◽  
And Function

Rab GTPases are molecular switches that regulate membrane trafficking in all cells. Neurons have particular demands on membrane trafficking and express numerous Rab GTPases of unknown function. Here, we report the generation and characterization of molecularly defined null mutants for all 26 rab genes in Drosophila. In flies, all rab genes are expressed in the nervous system where at least half exhibit particularly high levels compared to other tissues. Surprisingly, loss of any of these 13 nervous system-enriched Rabs yielded viable and fertile flies without obvious morphological defects. However, all 13 mutants differentially affected development when challenged with different temperatures, or neuronal function when challenged with continuous stimulation. We identified a synaptic maintenance defect following continuous stimulation for six mutants, including an autophagy-independent role of rab26. The complete mutant collection generated in this study provides a basis for further comprehensive studies of Rab GTPases during development and function in vivo.

scholarly journals Rabs in Signaling and Embryonic Development

2020 ◽  
Vol 21 (3) ◽  
pp. 1064 ◽  
Author(s):  
Sonya Nassari ◽  
Tomas Del Olmo ◽  
Steve Jean
Keyword(s):  
Embryonic Development ◽  
Membrane Trafficking ◽  
Intracellular Signaling ◽  
Rab Proteins ◽  
Rab Gtpases ◽  
Cellular Processes ◽  
Complex Process ◽  
Signaling Events ◽  
And Function

Rab GTPases play key roles in various cellular processes. They are essential, among other roles, to membrane trafficking and intracellular signaling events. Both trafficking and signaling events are crucial for proper embryonic development. Indeed, embryogenesis is a complex process in which cells respond to various signals and undergo dramatic changes in their shape, position, and function. Over the last few decades, cellular studies have highlighted the novel signaling roles played by Rab GTPases, while numerous studies have shed light on the important requirements of Rab proteins at various steps of embryonic development. In this review, we aimed to generate an overview of Rab contributions during animal embryogenesis. We first briefly summarize the involvement of Rabs in signaling events. We then extensively highlight the contribution of Rabs in shaping metazoan development and conclude with new approaches that will allow investigation of Rab functions in vivo.

scholarly journals CSPα reduces aggregates and rescues striatal dopamine release in αsynuclein transgenic mice

2020 ◽  
Author(s):  
L Caló ◽  
E Hidari ◽  
M Wegrzynowicz ◽  
JW Dalley ◽  
BL Schneider ◽  
...  
Keyword(s):  
Dopamine Release ◽  
Early Stage ◽  
Synaptic Function ◽  
Snare Complex ◽  
Early Event ◽  
Vesicle Recycling ◽  
Cysteine String Protein ◽  
And Function

AbstractαSynuclein aggregation at the synapse is an early event in Parkinson’s disease and is associated with impaired striatal synaptic function and dopaminergic neuronal death. The cysteine string protein (CSPα) and αsynuclein have partially overlapping roles in maintaining synaptic function and mutations in each cause neurodegenerative diseases. CSPα is a member of the DNAJ/HSP40 family of co-chaperones and like αsynuclein, chaperones the SNARE complex assembly and neurotransmitter release. αSynuclein can rescue neurodegeneration in CSPαKO mice. However, whether αsynuclein aggregation alters CSPα expression and function is unknown. Here we show that αsynuclein aggregation at the synapse induces a decrease in synaptic CSPα and a reduction in the complexes that CSPα forms with HSC70 and STGa. We further show that viral delivery of CSPα rescues in vitro the impaired vesicle recycling in PC12 cells with αsynuclein aggregates and in vivo reduces synaptic αsynuclein aggregates restoring normal dopamine release in 1-120hαsyn mice. These novel findings reveal a mechanism by which αsynuclein aggregation alters CSPα at the synapse, and show that CSPα rescues αsynuclein aggregation-related phenotype in 1-120hαsyn mice similar to the effect of αsynuclein in CSPαKO mice. These results implicate CSPα as a potential therapeutic target for the treatment of early-stage PD.

scholarly journals Dihydroceramide desaturase directs the switch between exosome production and autophagy for neuronal maintenance

2020 ◽  
Author(s):  
Chen-Yi Wu ◽  
Jhih-Gang Jhang ◽  
Chih-Wei Lin ◽  
Han-Chen Ho ◽  
Chih-Chiang Chan ◽  
...  
Keyword(s):  
Nervous System ◽  
Desaturase Gene ◽  
Dihydroceramide Desaturase ◽  
Autophagic Degradation ◽  
Photoreceptor Neurons ◽  
And Function ◽  
Neuronal Maintenance ◽  
Autophagy Inhibition

ABSTRACTExosomes play important roles in the nervous system. Mutations in the human dihydroceramide desaturase gene, DEGS1, are recently linked to severe neurological disorders, but the cause remains unknown. Here, we show that Ifc is required for the morphology and function of Drosophila photoreceptor neurons and not in the surrounding glia, but the degeneration of ifc-KO eyes can be rescued by glial expression of ifc, possibly mediated by exosomes. We develop an in vivo assay using Drosophila eye imaginal discs and show that the level and activity of Ifc correlates with the detection of exosome-like vesicles. While ifc overexpression and autophagy inhibition both enhances exosome production, combining the two had no additive effect. Moreover, ifc-KO reduces the density of the exosome precursor intraluminal vesicles (ILVs) in vivo, and DEGS1 promotes ILV formation in vitro. In conclusion, dihydroceramide desaturase promotes exosome formation and prevents its autophagic degradation in the nervous system.

scholarly journals Two New Early Bacteriophage T4 Genes,repEA and repEB, That Are Important for DNA Replication Initiated from Origin E

1999 ◽  
Vol 181 (22) ◽  
pp. 7115-7125 ◽  
Author(s):  
Rita Vaiskunaite ◽  
Andrew Miller ◽  
Laura Davenport ◽  
Gisela Mosig
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Bacteriophage T4 ◽  
Direct Synthesis ◽  
Growth Conditions ◽  
Dna Strands ◽  
Different Temperatures ◽  
And Function ◽  
Different Origins

ABSTRACT Two new, small, early bacteriophage T4 genes, repEA andrepEB, located within the origin E (oriE) region of T4 DNA replication, affect functioning of this origin. An important and unusual property of the oriE region is that it is transcribed at early and late periods after infection, but in opposite directions (from complementary DNA strands). The early transcripts are mRNAs for RepEA and RepEB proteins, and they can serve as primers for leading-strand DNA synthesis. The late transcripts, which are genuine antisense RNAs for the early transcripts, direct synthesis of virion components. Because the T4 genome contains several origins, and because recombination can bypass a primase requirement for retrograde synthesis, neither defects in a single origin nor primase deficiencies are lethal in T4 (Mosig et al., FEMS Microbiol. Rev. 17:83–98, 1995). Therefore, repEA and repEBwere expected and found to be important for T4 DNA replication only when activities of other origins were reduced. To investigate the in vivo roles of the two repE genes, we constructed nonsense mutations in each of them and combined them with the motAmutation sip1 that greatly reduces initiation from other origins. As expected, T4 DNA synthesis and progeny production were severely reduced in the double mutants as compared with the singlemotA mutant, but early transcription of oriEwas reduced neither in the motA nor in the repEmutants. Moreover, residual DNA replication and growth of the double mutants were different at different temperatures, suggesting different functions for repEA and repEB. We surmise that the different structures and protein requirements for functioning of the different origins enhance the flexibility of T4 to adapt to varied growth conditions, and we expect that different origins in other organisms with multiorigin chromosomes might differ in structure and function for similar reasons.

Axonal Regulation of Central Nervous System Myelination: Structure and Function

2017 ◽  
Vol 24 (1) ◽  
pp. 7-21 ◽  
Author(s):  
Anna Klingseisen ◽  
David A. Lyons
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Adult Life ◽  
Structure And Function ◽  
Myelinated Axons ◽  
Cross Sectional ◽  
Recent Advances ◽  
Cross Sectional Size ◽  
And Function

Approximately half of the human brain consists of myelinated axons. Central nervous system (CNS) myelin is made by oligodendrocytes and is essential for nervous system formation, health, and function. Once thought simply as a static insulator that facilitated rapid impulse conduction, myelin is now known to be made and remodeled in to adult life. Oligodendrocytes have a remarkable capacity to differentiate by default, but many aspects of their development can be influenced by axons. However, how axons and oligodendrocytes interact and cooperate to regulate myelination in the CNS remains unclear. Here, we review recent advances in our understanding of how such interactions generate the complexity of myelination known to exist in vivo. We highlight intriguing results that indicate that the cross-sectional size of an axon alone may regulate myelination to a surprising degree. We also review new studies, which have highlighted diversity in the myelination of axons of different neuronal subtypes and circuits, and structure-function relationships, which suggest that myelinated axons can be exquisitely fine-tuned to mediate precise conduction needs. We also discuss recent advances in our understanding of how neuronal activity regulates CNS myelination, and aim to provide an integrated overview of how axon-oligodendrocyte interactions sculpt neuronal circuit structure and function.

scholarly journals Late onset of Syt2a expression at synapses relevant to social behavior

2020 ◽  
Author(s):  
Collette Goode ◽  
Mae Voeun ◽  
Denver Ncube ◽  
Judith Eisen ◽  
Philip Washbourne ◽  
...  
Keyword(s):  
Nervous System ◽  
Social Behavior ◽  
Tyrosine Hydroxylase ◽  
Synaptic Vesicle ◽  
Larval Development ◽  
Late Onset ◽  
Synaptic Function ◽  
Biosynthetic Enzyme ◽  
Expression Levels ◽  
Socially Relevant

AbstractAs they form, synapses go through various stages of maturation and refinement. These steps are linked to significant changes in synaptic function, potentially resulting in changes in behavior. Here, we examined the distribution of the synaptic vesicle protein Synaptotagmin 2a (Syt2a) during development of the zebrafish nervous system. Syt2a is widely distributed throughout the midbrain and hindbrain early during larval development but very weakly expressed in the forebrain. Later in development, Syt2a expression levels increase, particularly in regions associated with social behavior, and most intriguingly, around the time social behavior becomes apparent. We provide evidence that Syt2a localizes to synapses on socially-relevant neurons in the ventral forebrain, co-localizing with tyrosine hydroxylase, a biosynthetic enzyme in the dopamine pathway. Our results suggest a maturation step for synapses in the forebrain that are spatiotemporally related to social behavior.

In vivo imaging of synaptic function in the central nervous system

2009 ◽  
Vol 204 (1) ◽  
pp. 1-31 ◽  
Author(s):  
Susanne Nikolaus ◽  
Christina Antke ◽  
Hans-Wilhelm Müller
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
In Vivo Imaging ◽  
Synaptic Function ◽  
The Central Nervous System

scholarly journals Cofilin recruitment and function during actin-mediated endocytosis dictated by actin nucleotide state

2007 ◽  
Vol 178 (7) ◽  
pp. 1251-1264 ◽  
Author(s):  
Voytek Okreglak ◽  
David G. Drubin
Keyword(s):  
Actin Filament ◽  
Membrane Trafficking ◽  
Adenosine Diphosphate ◽  
Living Cells ◽  
Actin Assembly ◽  
Actin Networks ◽  
Actin Turnover ◽  
And Function

Cofilin is the major mediator of actin filament turnover in vivo. However, the molecular mechanism of cofilin recruitment to actin networks during dynamic actin-mediated processes in living cells and cofilin's precise in vivo functions have not been determined. In this study, we analyzed the dynamics of fluorescently tagged cofilin and the role of cofilin-mediated actin turnover during endocytosis in Saccharomyces cerevisiae. In living cells, cofilin is not necessary for actin assembly on endocytic membranes but is recruited to molecularly aged adenosine diphosphate actin filaments and is necessary for their rapid disassembly. Defects in cofilin function alter the morphology of actin networks in vivo and reduce the rate of actin flux through actin networks. The consequences of decreasing actin flux are manifested by decreased but not blocked endocytic internalization at the plasma membrane and defects in late steps of membrane trafficking to the vacuole. These results suggest that cofilin-mediated actin filament flux is required for the multiple steps of endocytic trafficking.

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