# Genetic study of gap junction formation and regulation in C. elegans neurons

> **NIH NIH R01** · DUKE UNIVERSITY · 2020 · $350,000

## Abstract

Gap junctions play essential roles in many biological processes, such as embryo development, cell
differentiation, cell growth, metabolic coordination of avascular organs, and neural development, and
misregulation of gap junctions has been linked to many diseases. However, the molecular mechanisms
underlying gap junction formation and regulation are still largely unknown. Using C. elegans PLM neurons as a
model, we found that functional GFP-tagged innexins form plaque structures that represent the location of gap
junctions in vivo. We then carried out an unbiased genetic screen using transgenes expressing GFP-tagged
innexins and uncovered 12 mutants with 3 types of defects in gap junctions. Based on mutants isolated from
this genetic screen, we outline 3 aims in this proposal to study mechanisms for gap junction formation,
turnover, and elimination. In the preliminary studies we discovered the previously unknown function of CED-
10/Rac and MEC-15/ F-box/WD repeat-containing protein in regulating gap junction formation, and in Specific
Aim 1 we outline a plan to investigate the function and regulation of CED-10 and MEC-15 in gap junction
formation. Regulation of gap junction turnover plays an important role in gap junction functions. In our previous
study, we revealed that the C. elegans ankyrin protein UNC-44 and CRMP UNC-33 regulate gap junction
turnover. However, neither unc-44 nor unc-33 mutants have completely penetrant phenotypes, suggesting that
other pathways are involved in regulating gap junction turnover. In this proposal we present evidence to show
that the C. elegans titin UNC-22 functions in parallel with the UNC-44/UNC-33 pathway and is likely regulated
by microtubules to modulate gap junction turnover. In Aim 2 we propose to study the regulatory mechanisms of
UNC-22/titin and microtubules and their crosstalk with the UNC-44/UNC-33 pathway in gap junction turnover.
During neuronal development gap junction channels are expressed on the membrane before gap junction
formation, and little is known about the distribution and function of gap junction channels at this stage. We
show that UNC-9/innexin forms puncta along the axon in PLM neurons before the formation of gap junctions,
and these transient clusters of gap junction channels are eliminated by the autophagy pathway when neurons
form gap junctions. In Aim 3 we outline a plan to address the function of these transient clusters of gap junction
channels and the autophagy pathway in regulating neuronal development. Completion of this proposal will lead
to the discovery of novel mechanisms of gap junction formation and regulation, the establishment of C. elegans
PLM neurons as a powerful model to study gap junctions, and the generation of new tools for further studies.
Given that many neural disorders are associated with defects in gap junctions, this project will likely aid in the
understanding of brain development and functions in both physiological and pathological conditions.

## Key facts

- **NIH application ID:** 9957134
- **Project number:** 5R01NS105638-03
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** Dong Yan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $350,000
- **Award type:** 5
- **Project period:** 2018-09-30 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9957134

## Citation

> US National Institutes of Health, RePORTER application 9957134, Genetic study of gap junction formation and regulation in C. elegans neurons (5R01NS105638-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9957134. Licensed CC0.

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