# Functional analyses of EPAS1 alleles from populations adapted to high altitude

> **NIH NIH F31** · UNIVERSITY OF CHICAGO · 2020 · $21,512

## Abstract

PROJECT SUMMARY
 For over 10,000 years Tibetan populations have lived at altitudes above 3500m resulting in a modern
population of over 3 million indigenous people adapted to thrive in an environment with just 60% the sea level
oxygen concentration. This environment parallels the hypoxia that characterizes or complicates many
cardiovascular and hematopoietic disorders. Tibetans display many unique phenotypes, including unelevated
hemoglobin levels. Despite the low hemoglobin levels, Tibetans do not have higher oxygen saturation than
lowlanders at the same altitude and are therefore severely hypoxemic. Intriguingly, they also experience better
reproductive outcomes, and protection against hypoxic pulmonary hypertension and chronic mountain sickness
compared to lowlanders at high altitude. Population genetic studies have repeatedly shown strong signals of
positive selection and association with unelevated hemoglobin levels in the endothelial PAS domain 1 (EPAS1)
gene, whose protein product, Hif-2α, is a central regulator of the hypoxia inducible factors (HIF) pathway. The
Di Rienzo lab has conducted a genome-wide association study for hemoglobin levels in Tibetans that allowed
narrowing down the region of association to a 17kb segment containing epigenetic signatures of active
enhancer elements in endothelial cells, a cell type which has been implicated in both normal hypoxic response
and in diseases characterized by hypoxic tissues and HIF pathway dysfunction, such as asthma and pulmonary
hypertension.
 This project seeks to comprehensively examine the effects of these genetic variants on endothelial
function and how these genetic effects translate into physiological adaptations to hypoxia. To achieve this goal,
in Aim 1, I will examine the changes in chromatin architecture in endothelial cells cultured in normoxia and
hypoxia using capture HiC and ATAC-seq. These results will not only help inform my expectations for the
EPAS1 locus, but will also provide an invaluable dataset on the impacts of hypoxia on endothelial chromatin
architecture. In Aim 2, I will focus on identifying causal SNPs in EPAS1 by using reporter gene assays and
CRISPR-cas9 gene editing technology followed by functional and molecular assays of cellular phenotypes.
This will allow me to both identify causal SNPs at the EPAS1 locus, and definitively connect them to EPAS1
expression and physiological outcomes in an endothelial context. In Aim 3, having validated causal alleles with
differential enhancer activity, I will examine their effect in vivo by performing transient LacZ transgenic assays
in mice. This will broaden the scope of our understanding of the adaptive alleles by indicating their spatial
distribution and the sufficiency of high and low-altitude alleles to drive expression in the endothelium.

## Key facts

- **NIH application ID:** 9949773
- **Project number:** 5F31HL142146-03
- **Recipient organization:** UNIVERSITY OF CHICAGO
- **Principal Investigator:** Olivia Anne Gray
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $21,512
- **Award type:** 5
- **Project period:** 2018-07-01 → 2020-10-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9949773

## Citation

> US National Institutes of Health, RePORTER application 9949773, Functional analyses of EPAS1 alleles from populations adapted to high altitude (5F31HL142146-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9949773. Licensed CC0.

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