# Regulation of the actin cytoskeleton by Abl2 and its role in dendritic spine stability

> **NIH NIH F31** · YALE UNIVERSITY · 2021 · $21,530

## Abstract

Project Summary
Disruption of dendritic spine stability is a hallmark of neurological and neurodegenerative disorders. Dendritic
spines are supported by an underlying actin framework consisting of at least two distinct actin pools, with stable
filaments concentrated in the spine core and dynamic branched filaments in the outer shell. How these distinct
populations are regulated to maintain spine stability while allowing ongoing structural plasticity is unclear. The
Abl2 nonreceptor tyrosine kinase is essential for dendritic spine stability. Previous work and my preliminary data
show that Abl2 binding to actin both regulates actin filament stability and promotes Arp2/3 complex-mediated
actin branching. These functions to not appear to require Abl2 kinase activity, suggesting that Abl2 modulates
the cytoskeleton via direct interactions with actin. In this proposal, I will test the hypothesis that direct interactions
of Abl2 with actin filaments, to control filament stability and actin branching, regulate dendritic spine morphology
and stability.
My first aim is to determine how Abl2 stabilizes filaments. In this aim, I will use single filament TIRF
microscopy (TIRFm) assays to determine the minimal fragment of Abl2 capable of stabilizing filaments. I will then
determine key features of Abl2 decoration of actin filaments required for stabilization using 2-color TIRFm with
Abl2-GFP and Rhodamine-actin. This will reveal if filament stabilization requires a threshold of global Abl2
decoration or local Abl2 binding at the site of depolymerization.
My second aim is to elucidate how Abl2 activates the Arp2/3 complex. It is not known what parts of Abl2
are required for Arp2/3 activation or which step of the Arp2/3 complex branching mechanism is impacted by
Abl2. I will use TIRFm actin-branching assays to determine the minimal fragment of Abl2 capable of promoting
actin branching. I will also use 2-color TIRFm to study the effects of Abl2 actin decoration on actin branching,
testing if branches form preferentially on Abl2 decorated regions of filament.
My third aim is to determine how Abl2 cytoskeletal regulation impacts dendritic spine stability and
morphology. Knockdown (KD) of Abl2 in primary cultured neurons destabilizes dendritic spines, and alters spine
shape, actin dynamics, and filamentous actin levels within the spines that remain. To test the functions of Abl2
required to restore these disruptions, I will rescue Abl2KD neurons with different mutants of Abl2 known to
possess specific actin-regulating functions, including any found in Aims 1 and 2. I will use fluorescence recovery
after photobleaching (FRAP) of GFP-actin and immunofluorescence to determine Abl2 functions sufficient to
restore proper spine actin dynamics and filamentous actin levels in spines. I will then identify which functions of
Abl2 are sufficient to support normal spine shape and long-term stability.

## Key facts

- **NIH application ID:** 10241272
- **Project number:** 5F31NS113511-03
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Josie Bircher
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $21,530
- **Award type:** 5
- **Project period:** 2019-09-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10241272

## Citation

> US National Institutes of Health, RePORTER application 10241272, Regulation of the actin cytoskeleton by Abl2 and its role in dendritic spine stability (5F31NS113511-03). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10241272. Licensed CC0.

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