# Patterning Mechanisms for Ventricular Septation and Congenital Heart Disease

> **NIH NIH R56** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2024 · $605,275

## Abstract

PROJECT SUMMARY
The most common congenital heart disease (CHD) in children involves incomplete formation of the
interventricular septum (IVS), which occurs in isolation or as part of more complex CHD lesions. Myocardial fiber
orientation, lineage tracing and asymmetric gene expression together suggest distinct L-R patterning of the IVS.
However, there exists a gap in the understanding of the developmental mechanisms of IVS patterning and VSD
etiologies. This hinders improvements to CHD prenatal screening, prognosis and evaluation of extra-cardiac
anomalies, as well as efforts to engineer tissue patches for heart repair. The overall objective of this proposal
is to delineate how L-R IVS patterning is controlled, and how perturbations lead to VSDs. We have preliminary
data that suggests the secreted guidance cues Ntn1 and Slit2 control boundary regulation for L-R patterning of
the IVS. Both genes were dysregulated in a genetic pathway dependent on the CHD-linked transcription factor,
Tbx5. We found that homozygous loss of function (LOF) of Ntn1 or Slit2 resulted in membranous or muscular
VSDs and a trabecular-like IVS. Ntn1 LOF led to displacement of the IVS boundary toward the LV, suggesting
that Ntn1 may be a key regulator of boundary positioning. Conversely, Slit2 LOF disrupted boundary integrity,
leading to mixing of RV and LV lineages, suggesting Slit2 regulation of boundary maintenance. Based on these
preliminary data, we hypothesize that NTN1 and SLIT2 control complementary aspects of boundary regulation
to segregate LV and RV lineages at the IVS for L-R patterning and ventricular septation. To discover how these
developmental cues direct ventricular septation, we propose the following three Specific Aims: (1) test the
hypothesis that NTN1 from the left side of the IVS determines boundary positioning for L-R IVS patterning by
chemorepulsion, (2) test the hypothesis that a SLIT2 signal from the RV and LV maintains boundary integrity to
preserve cell segregation for L-R IVS patterning by chemorepulsion of IVS cells, and (3) test the hypothesis that
boundary perturbations of L-R IVS patterning cause cell signature disturbances of misplaced cells and adjacent
tissue microenvironments. Successful completion of this project will provide insights into the regulation of L-R
IVS patterning and the origins of human CHDs. By expanding our comprehension of the basis of CHDs, we will
take an important step towards our long-term goal to improve the natural history of CHDs.

## Key facts

- **NIH application ID:** 11175773
- **Project number:** 1R56HL166894-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Irfan S Kathiriya
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $605,275
- **Award type:** 1
- **Project period:** 2024-09-19 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11175773

## Citation

> US National Institutes of Health, RePORTER application 11175773, Patterning Mechanisms for Ventricular Septation and Congenital Heart Disease (1R56HL166894-01A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/11175773. Licensed CC0.

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