- Combining stem cell and gene editing
technologies can help in accurately predicting heart disease-causing
potential of specific gene variants
- Not all gene variants cause or
increase risk of heart disease; knowing the disease-causing
potential of a given gene variant helps to avoid unnecessary tests and
treatment in persons who carry only a "benign" (non-disease causing)
- Gene variant refers to slight
variations in the DNA sequences of the same gene among different
sequencing of lab engineered cell lines from healthy persons using stem cell
and gene editing techniques can help predict whether a given gene variant increases the risk of developing
heart disease or not. The study was conducted by a team of scientists including
the study's senior author Joseph
C. Wu, M.D., Ph.D., director of the Stanford Cardiovascular Institute and Simon
H. Stertzer, M.D. Endowed Professor in the Department of Medicine (Cardiology)
and Department of Radiology at the Stanford University School of Medicine in
findings of the study appear in the American Heart Association's journal Circulation.
Aim of Study
advances in genome and DNA sequencing, several gene variants have been
discovered to be associated
certain disease conditions. However one cannot be sure whether these gene
variants actually lead to disease or not.
‘Knowing whether a specific gene variant present in a person can cause heart disease will help clinicians to optimize therapy to suit the patient.’
goal of the study is to be able to characterize
a given gene variant's disease-causing potential or
This would help in further evaluating and treating those persons actually at
risk and avoiding unnecessary treatments
and undue stress to persons who may be only carrying a "benign
Details of Study
study demonstrates for the first time, the potential benefits of combining stem
cell technology to create induced pluripotent stem cells and
CRISPR/Cas9-mediated genome editing technology for use as a customized risk-assessment platform to measure the disease-causing
potential of a yet uncharacterized genetic variants
, referred to as a
"variants of uncertain significance" or VUS.
scientists analyzed gene variants
associated with hypertrophic
cardiomyopathy, a disease marked by thickening of heart
muscle and known to cause sudden cardiac death in athletes and young
team obtained DNA from 54 "healthy" persons without heart
disease, and sequenced their DNA
with a known DNA panel of 135 genes causing cardiomyopathy and
congenital heart disease, associated with sudden cardiac death.
of the participants chosen had family members over several generations
MYL3 gene variant, which is
associated with hypertrophic cardiomyopathy.
blood mononuclear cells of the participants were isolated and these cells
were engineered in the lab to form induced pluripotent stem cells
(iPSCs). These were then genome edited using the CRISPR/Cas9 gene editing
technology to create cells with identical genetics (isogenic iPSC lines).
analysis of DNA sequence was conducted on the engineered cell lines to determine whether a given MYL3 gene
variant could lead to disease.
DNA sequencing results unearthed 592
unique genetic variants, of which 78 percent of genetic variants were
characterized as "benign," "likely benign," or a
"variant of uncertain significance." However, 17 gene variants were characterized as
"possibly pathogenic" or disease-causing.
the study results demonstrate the
importance of characterizing a given gene variant as pathogenic
out of 592 in this case) to avoid unnecessary testing and anxiety among many
patients who carry harmless variants
genetic testing will create a lot of stress for a healthy individual who may be
getting echocardiograms, MRIs or medications that they may not need," Wu
said. "Results from this study will help improve the interpretation and
diagnostic accuracy of gene variants, especially in the era of personalized
medicine and precision health. The goal is to optimize the decision making of
clinicians in their choices of therapy by providing a much clearer result for
the 'variant of uncertain significance' carriers."
Standard Treatment of
symptomatic patients with hypertrophic cardiomyopathy are treated based on
severity of those symptoms. Asymptomatic persons are usually not treated.
Treatment options include lifestyle and dietary changes, treating underlying
causes that might aggravate the condition, drugs for hypertrophic
cardiomyopathy, and sometimes surgery in severe cases.
this new technology,
preventive interventions can be introduced in apparently healthy individuals
gene variant for more favorable patient outcome in the long term.
Overview of Induced Pluripotent Stem Cells and Gene Editing
pluripotent stem cells
are increasingly being to investigate
molecular and cellular changes occurring in several inherited disorders.
However, one of the biggest challenges in
iPSC-based research of inherited diseases hinge on discriminating between
the impact of a specific mutation and the genetic background of these cells. To
overcome this, scientists use the CRISPR/Cas9 gene editing technology
which enables modifications of genes with a high degree of accuracy. This technique
therefore enables the creation of isogenic (identical genetics) cell lines in
order to focus on the disease causing ability of a specific mutation
would be apt to conclude with the remarks of Circulation
editor, Joseph A. Hill, M.D., Ph.D., chief of cardiology at UT Southwestern
Medical Center in Dallas, who says, "This study combined two new powerful
technologies, induced pluripotent stem cells and CRISPR-Cas9 gene editing, to
model a patient's heart in a dish and to test whether those heart cells
manifested signs of disease. This approach heralds a new era of in vitro
disease modeling and drug testing as pivotal elements of precision
- Ning Ma, Joe Zhang, Ilanit Itzhaki, Sophia L. Zhang et al., "Determining the Pathogenicity of a Genomic Variant of Uncertain Significance Using CRISPR/Cas9 and Human-Induced Pluripotent Stem Cells" Circulation (2018) https://doi.org/10.1161/CIRCULATIONAHA.117.032273
- D. G. MacArthur, T. A. Manolio, D. P. Dimmock, H. L. Rehm, et al., "Guidelines for investigating causality of sequence variants in human disease" PMC (2014) doi: 10.1038/nature13127