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Growing dendrites and axons differ in their reliance on the secretory pathway.

ABSTRACT: Little is known about how the distinct architectures of dendrites and axons are established. From a genetic screen, we isolated dendritic arbor reduction (dar) mutants with reduced dendritic arbors but normal axons of Drosophila neurons. We identified dar2, dar3, and dar6 genes as the homologs of Sec23, Sar1, and Rab1 of the secretory pathway. In both Drosophila and rodent neurons, defects in Sar1 expression preferentially affected dendritic growth, revealing evolutionarily conserved difference between dendritic and axonal development in the sensitivity to limiting membrane supply from the secretory pathway. Whereas limiting ER-to-Golgi transport resulted in decreased membrane supply from soma to dendrites, membrane supply to axons remained sustained. We also show that dendritic growth is contributed by Golgi outposts, which are found predominantly in dendrites. The distinct dependence between dendritic and axonal growth on the secretory pathway helps to establish different morphology of dendrites and axons.

SUBMITTER: Ye B

PROVIDER: S-EPMC2020851 | biostudies-literature | 2007 Aug

REPOSITORIES: biostudies-literature

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Growing dendrites and axons differ in their reliance on the secretory pathway.

Ye Bing B Zhang Ye Y Song Wei W Younger Susan H SH Jan Lily Yeh LY Jan Yuh Nung YN

Cell 20070801 4

Little is known about how the distinct architectures of dendrites and axons are established. From a genetic screen, we isolated dendritic arbor reduction (dar) mutants with reduced dendritic arbors but normal axons of Drosophila neurons. We identified dar2, dar3, and dar6 genes as the homologs of Sec23, Sar1, and Rab1 of the secretory pathway. In both Drosophila and rodent neurons, defects in Sar1 expression preferentially affected dendritic growth, revealing evolutionarily conserved difference ...[more]

PMID: 17719548

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Project description:BackgroundDendrites differ from axons in patterns of growth and development, as well as in morphology. Given that microtubules are key structural elements in cells, we assessed patterns of microtubule stability and polymerization during hippocampal neuron development in vitro to determine if these aspects of microtubule organization could distinguish axons from dendrites.ResultsQuantitative ratiometric immunocytochemistry identified significant differences in microtubule stability between axons and dendrites. Most notably, regardless of developmental stage, there were high levels of dynamic microtubules throughout the dendritic arbor, whereas dynamic microtubules were predominantly concentrated in the distal end of axons. Analysis of microtubule polymerization using green fluorescent protein-tagged EB1 showed both developmental and regional differences in microtubule polymerization between axons and dendrites. Early in development (for example, 1 to 2 days in vitro), polymerization events were distributed equally in both the anterograde and retrograde directions throughout the length of both axons and dendrites. As development progressed, however, polymerization became biased, with a greater number of polymerization events in distal than in proximal and middle regions. While polymerization occurred almost exclusively in the anterograde direction for axons, both anterograde and retrograde polymerization was observed in dendrites. This is in agreement with predicted differences in microtubule polarity within these compartments, although fewer retrograde events were observed in dendrites than expected.ConclusionBoth immunocytochemical and live imaging analyses showed that newly formed microtubules predominated at the distal end of axons and dendrites, suggesting a common mechanism that incorporates increased microtubule polymerization at growing process tips. Dendrites had more immature, dynamic microtubules throughout the entire arbor than did axons, however. Identifying these differences in microtubule stability and polymerization is a necessary first step toward understanding how they are developmentally regulated, and may reveal novel mechanisms underlying neuron maturation and dendritic plasticity that extend beyond the initial specification of polarity.

Dataset Information

Growing dendrites and axons differ in their reliance on the secretory pathway.

Publications

Growing dendrites and axons differ in their reliance on the secretory pathway.

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