# Genetic Studies of Sarcomere-based Cardiac Diseases

> **NIH NIH R01** · MAYO CLINIC ROCHESTER · 2022 · $566,562

## Abstract

Project Summary
 TITIN (TTN) truncating variants (TTNtvs) have been found to be the most common genetic factor for
dilated cardiomyopathy (DCM). However, allelic heterogeneity (AH) of TTNtv DCM, i.e. TTNtvs are also found
in reference populations, significantly confound diagnosis and therapeutic development of these patients.
Pathogenic TTNtvs are mainly found in the C-terminal A-band region (TTNtv-As) but less in the N-terminal Z-
disc region (TTNtv-Zs). Moreover, pathological signaling pathways for TTNtv DCM remain largely unknown.
Here, we aim to leverage unique research opportunities enabled by zebrafish genetics to decipher underlying
mechanisms of AH, discover pathological signaling pathways, and develop effective therapeutic avenues. Our
preliminary studies showed that AH of TTNtv DCM can be recapitulated in both embryonic and adult zebrafish,
opening the door for mechanistic studies of AH in vivo. From our screen of known cardiomyopathy signaling
pathways, we identified mTOR, autophagy, MAPK and PDE1 as candidate signaling pathways that could be
leveraged for therapeutic benefits. We also established a F0-based genetic assay using the Microhomology-
mediated end joining (MMEJ) genome editing technology that enables us to rapidly discover new signaling
pathways. Based on these preliminary studies, we proposed to leverage unique genetic and chemical genetic
tools in zebrafish to prove that zebrafish is the first in vivo animal model for allelic heterogeneity of TTNtv DCM,
which can be used to decipher primary damages incurred by TTNtvs, to discover sequential pathological
signaling pathways, and to develop mechanism-based therapies. The proposal is organized into the 3 specific
aims. In Specific Aim 1, we will decipher allelic heterogeneity of ttntv DCM via studying a panel of ttntv mutants
and ttn null mutants. In Specific Aim 2, we propose to elucidate molecular basis of autophagy dysregulation in
ttntv DCM and develop an autophagy-based therapy. In Specific Aim 3, we will confirm MAPK and PDE1 as
candidate signalings and discover additional new genes and signaling pathways by carrying MMEJ-based F0
screens. Upon completion of the proposal, we anticipate the following deliverables: 1) provide in vivo evidence
to clarify why TTNtv-As are more likely to cause DCM phenotypes than TTNtv-Zs; 2) obtain insights on
autophagy, MAPK and PDE signaling pathways in ttntv DCM, and identify mechanism-based therapeutic
avenues for ttntv DCM; 3) establish a F0-based genetic screening approach that is capable of systematically
discovering new genes for ttntv DCM, opening an unprecedented opportunity for mechanistic studies of an
inherited cardiomyopathy.

## Key facts

- **NIH application ID:** 10516335
- **Project number:** 2R01HL081753-15A1
- **Recipient organization:** MAYO CLINIC ROCHESTER
- **Principal Investigator:** Xiaolei Xu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $566,562
- **Award type:** 2
- **Project period:** 2005-08-01 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10516335

## Citation

> US National Institutes of Health, RePORTER application 10516335, Genetic Studies of Sarcomere-based Cardiac Diseases (2R01HL081753-15A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10516335. Licensed CC0.

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