# Functional interrogation of putative osteoarthritis causal variants

> **NIH NIH R21** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2024 · $205,260

## Abstract

PROJECT SUMMARY
 A key priority for the NIH is to limit disability caused by osteoarthritis (OA) and other chronic diseases
that emerge with age. Our long-term goal is to catalyze effective strategies for early intervention by establishing
the mechanisms that lead to OA. Through genome-wide association studies (GWAS), it is clear that the genetic
risk for OA is driven primarily by a large number of non-coding single nucleotide variants (SNVs) that alter the
regulation of gene expression in chondrocytes and other cell types of the joint. Our overall hypothesis is that
testing the effect of OA GWAS SNVs on enhancer strength will identify the most likely causal variants, and that
analyzing transcription factor binding at these variants will provide insight into the mechanisms of genetic risk in
OA.
 We work with cadaveric chondrocytes from donors with no history of joint disease to provide a regulatory
environment that represents cartilage homeostasis. In addition to this baseline state, we also stimulate cells with
bioactive matrix fragments to initiate gene expression and chromatin accessibility changes that mimic the cellular
state during OA. The first aim is to identify expression modulating variants (emVars) in primary human
chondrocytes at baseline and in response to an OA-relevant stimulus. We will use massively parallel reporter
assays (MPRAs) to assess allele-specific activity of the 1259 variants that reside within 104 known OA GWAS
loci. The results from MPRAs and expression quantitative trait loci (eQTL) studies in other cell types and diseases
give us the expectation that we will identify 1-3 emVars for each of 10-30 loci and that some of these will be
specific to either baseline or stimulus conditions. The second aim is to computationally determine the
transcription factors that differentially bind to emVars. We expect to find that emVars preferentially reside in
regions that have accessible chromatin (as determined by ATAC-seq) and contain histone marks present in
enhancers (as determined by Cut & Run for H3K27ac). Further, we expect that emVars will alter transcription
factor binding strength and that stimulus-specific emVars will disrupt the binding sites of transcription factors that
we have shown coordinate gene expression changes in response to this stimulus.
 This proposal is innovative, as it represents the first MPRA in primary human chondrocytes and one of
the first “response MPRAs” to test the effect of cell state on allele-specific enhancer function for any disease.
These results will have a substantial effect on the field by providing some of the first examples of how specific
non-coding variants alter transcription factor binding to mediate the genetic risk of OA.

## Key facts

- **NIH application ID:** 10868846
- **Project number:** 1R21AR084104-01
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** Brian O Diekman
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $205,260
- **Award type:** 1
- **Project period:** 2024-04-01 → 2026-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10868846

## Citation

> US National Institutes of Health, RePORTER application 10868846, Functional interrogation of putative osteoarthritis causal variants (1R21AR084104-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10868846. Licensed CC0.

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