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Updated: Jun 27, 2026
The Olfactory System as a Model to Study Axonal Growth Patterns and Morphology In Vivo
Published on: October 30, 2014
MicroRNA processing pathway regulates olfactory neuron morphogenesis
Daniela Berdnik1, Audrey P Fan, Christopher J Potter
1Howard Hughes Medical Institute, Department of Biology, Stanford University, Stanford, CA 94305, USA.
Abstract:
The microRNA (miRNA) processing pathway produces miRNAs as posttranscriptional regulators of gene expression. The nuclear RNase III Drosha catalyzes the first processing step together with the dsRNA binding protein DGCR8/Pasha generating pre-miRNAs [1, 2]. The next cleavage employs the cytoplasmic RNase III Dicer producing miRNA duplexes [3, 4]. Finally, Argonautes are recruited with miRNAs into an RNA-induced silencing complex for mRNA recognition (Figure 1A). Here, we identify two members of the miRNA pathway, Pasha and Dicer-1, in a forward genetic screen for mutations that disrupt wiring specificity of Drosophila olfactory projection neurons (PNs). The olfactory system is built as discrete map of highly stereotyped neuronal connections [5, 6]. Each PN targets dendrites to a specific glomerulus in the antennal lobe and projects axons stereotypically into higher brain centers [7-9]. In selected PN classes, pasha and Dicer-1 mutants cause specific PN dendrite mistargeting in the antennal lobe and altered axonal terminations in higher brain centers. Furthermore, Pasha and Dicer-1 act cell autonomously in postmitotic neurons to regulate dendrite and axon targeting during development. However, Argonaute-1 and Argonaute-2 are dispensable for PN morphogenesis. Our findings suggest a role for the miRNA processing pathway in establishing wiring specificity in the nervous system.
Insights
The microRNA (miRNA) processing pathway, involving Pasha and Dicer-1, is crucial for wiring specificity in Drosophila olfactory neurons. Mutations disrupt neuronal connections, highlighting miRNA
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- MicroRNAs (miRNAs) are key posttranscriptional regulators of gene expression.
- The miRNA processing pathway involves sequential enzymatic steps including Drosha, Dicer, and Argonautes.
- Neuronal wiring specificity in the olfactory system relies on precise targeting of dendrites and axons.
Purpose of the Study:
- To identify genetic factors involved in the wiring specificity of Drosophila olfactory projection neurons (PNs).
- To investigate the role of the miRNA processing pathway in neuronal development and connectivity.
Main Methods:
- Conducted a forward genetic screen to identify mutations affecting PN wiring.
- Analyzed the function of identified genes, Pasha and Dicer-1, in Drosophila olfactory system development.
- Utilized genetic mutations and observed effects on dendrite and axon targeting in postmitotic neurons.
Main Results:
- Identified mutations in Pasha and Dicer-1, components of the miRNA pathway, disrupt PN wiring specificity.
- pasha and Dicer-1 mutants exhibit specific defects in PN dendrite targeting and axonal termination.
- Pasha and Dicer-1 function cell-autonomously in postmitotic neurons to regulate neuronal morphogenesis, while Argonaute proteins are not essential.
Conclusions:
- The miRNA processing pathway, specifically Pasha and Dicer-1, plays a critical role in establishing wiring specificity in the nervous system.
- These findings reveal a novel function for miRNA biogenesis components in neuronal development beyond gene regulation.
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