# Deciphering how a human mutation in leiomodin-3 leads to muscle disease

> **NIH NIH F31** · UNIVERSITY OF ARIZONA · 2020 · $37,964

## Abstract

PROJECT SUMMARY
 Striated muscle cell contraction is dependent on the proper overlap of myosin (thick) filaments and actin
(thin) filaments. Leiomodin (Lmod) and tropomodulin (Tmod) are proteins that bind to the pointed end of thin
filaments in order to fine-tune their lengths. Tmod1 and Lmod2 are the major isoforms in cardiac muscle. Lmod3
is the major skeletal isoform, however it is also expressed in cardiac muscle. Mutations in Tmod and Lmod have
been shown to result in dysregulated thin filament lengths and lead to the development of myopathies. The goal
of this proposal is to identify molecular mechanisms for how Tmod and Lmod proteins regulate thin filament
assembly. We plan to create a novel model of disease by studying a mutation that has been identified in Lmod3
in patients with nemaline myopathy (a skeletal muscle disorder). We hypothesize that introducing this mutation
in Tmod and Lmod will result in altered thin filament lengths and perturbed actin assembly, leading to disease
development. We have obtained a Lmod3 knockout mouse model, which will serve as an important tool for this
study. We propose the following aims: Aim 1 is to examine the role of Lmod3 in striated muscle by utilizing a
Lmod3 knockout (KO) mouse line. Immunofluorescence deconvolution microscopy will be used to assess overall
sarcomere structure and changes in thin filament lengths in these KO mice. Contractile force of individual skeletal
and cardiac myocytes will be measured. We will attempt to prevent skeletal and cardiac defects in these mice
by introducing Lmod3 via adeno-associated virus. Aim 2 will determine the effect of a nemaline myopathy-linked
mutation on thin filament lengths and actin dynamics. Mutated Lmod and Tmod proteins will be expressed in
both skeletal and cardiac myocytes via adenovirus. Thin filaments will be visualized and measured using
immunofluorescence microscopy, while fluorescence recovery after photobleaching will test mutated Lmod and
Tmod's ability to assemble to the pointed ends. Aim 3 is to determine how a nemaline myopathy-linked mutation
affects structure and function of Lmod/Tmod. Circular dichroism will be used to investigate the ability of mutated
Lmod and Tmod to fold properly, and nuclear magnetic resonance will be used to determine how structural
alterations could potentially affect mutated Tmod and Lmod's binding interfaces with other proteins, such as actin
and tropomyosin. We will assess functional changes in mutated Lmod and Tmod by performing pyrene-actin
polymerization assays and co-sedimentation assays. The long-term goal of this multidisciplinary project, that
spans from single molecule to whole animal studies, is to determine how perturbation of actin-thin filament
lengths leads to muscle disease. This is significant because actin is the most abundant protein in most cell types
and is involved in numerous essential cellular processes. The results obtained in this project will allow us to
decipher the connection bet...

## Key facts

- **NIH application ID:** 10000762
- **Project number:** 5F31AR076209-02
- **Recipient organization:** UNIVERSITY OF ARIZONA
- **Principal Investigator:** Lauren Elisa Schultz
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $37,964
- **Award type:** 5
- **Project period:** 2019-08-21 → 2022-08-20

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10000762

## Citation

> US National Institutes of Health, RePORTER application 10000762, Deciphering how a human mutation in leiomodin-3 leads to muscle disease (5F31AR076209-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10000762. Licensed CC0.

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