Is Whole Genome Sequencing a Better Method for HCM Genetic Testing?

According to this study published recently in the Journal of the American College of Cardiology, whole genome testing may sometimes be used to identify the gene(s) responsible for HCM when targeted genetic testing (the type used in the clinical setting) has been inconclusive.

In particular, the study found the responsible gene(s) in 9 of 26 families (20%) in whom targeted testing had previously been inconclusive.

When used as the initial form of genetic testing, whole genome sequencing identified the responsible HCM gene in 5 of 12 families, or 42%.

According to this article in Wired U.K., a whole genome sequencing test costs about $600 and takes just a few weeks to complete.  On the other had, the cost of data storage necessary to store such a large amount of collective data is, according to this article, prohibitively high.

If not for everyone, perhaps whole genome sequencing could be used in families where traditional genetic testing has proven inconclusive.  Time will tell.

Is Direct-to-Consumer Genetic Testing Helpful or Harmful to HCM Families?

This recent article published in Nature discusses several real-life scenarios in which patients were mistakenly diagnosed with serious genetic cardiac conditions, including HCM, as a result of erroneous direct-to-consumer genetic testing.

These misdiagnoses directly resulted from misinterpretation of raw data by third party interpretation services that were working with raw data provided to them by direct-to-consumer genetic testing companies.

After medical testing, none of the patients discussed in the highlighted cases were ultimately found to have disease or be in need of medical intervention, though all underwent unnecessary medical testing and/or invasive procedures. Some even made radical lifestyle changes as a result of the erroneous genetic information.

This article demonstrates the unreliability of direct-to-consumer genetic testing, which has the potential to cause great upheaval to both patients and the medical system.

As always, patients seeking genetic testing should do their homework. Genetic testing for heart conditions is best when done by the experts – cardiac genetic counselors!

Do HCM Family Screening Protocols Need Adjustment?

A recent editorial published in Circulation: Genomic and Precision Medicine suggests that current HCM screening protocols may need adjustment to account for recent findings by a study by researchers in the Netherlands.  The Dutch study, published in the same journal, found that of 620 relatives of HCM patients who underwent genetic testing, 43% were found to be genetically positive for HCM, while 30% were diagnosed with HCM at the initial screening. 16% more went on to develop HCM during 7 years of repeated cardiac evaluation.

On the other hand, the 57% of relatives found to be genotype-negative were released from clinical HCM follow-up.

The Australian authors of the editorial, Semsarian and Ingles, note that current screening protocols would have failed to identify the 6 children (15%) who were diagnosed under the age of 12, half of which had a particularly malignant family history.

Additionally, few teens were diagnosed with HCM, which stands in contrast to current opinion that HCM is most likely to develop during adolescence. Indeed, most newly diagnosed family members were older than the age of 36, with 44% being over the age of 50.

Lastly, Semsarian and Ingles note their concern with general utilization of the Dutch practice of releasing a gene negative family member from serial follow up since the impact of all genes which have a role in causing HCM is not yet known while new genes which may cause HCM are still being identified. 

Semsarian and Ingles also note that the Dutch patient sample differs from more typical patient populations found in the U.S. and Australia where causes of HCM are more diverse and cannot be easily tied to a specific gene.

Continuing Genetic Counseling Helpful for Silent HCM Gene Carriers

An article entitled Psychosocial Impact of a Positive Gene Result for Asymptomatic Relatives at Risk of Hypertrophic Cardiomyopathy was published in this week’s Journal for Genetic Counseling.

The article focuses on the motivation for and the impact of HCM genetic testing on family members.  The 32 participants in the study all encouraged family members to undergo genetic testing with the hope that the knowledge gained would benefit family members down the line.  However, the study found that the psychological impact of a positive result, in the absence of overt disease, was highly variable. Some gene positive individuals perceived that they had an absolute risk of developing HCM, with substantial detriment to their lifestyle choices, while others were not at all affected by the result and made no lifestyle changes.

Continue reading “Continuing Genetic Counseling Helpful for Silent HCM Gene Carriers”

Are HCM Kids With MYH7 Gene at Increased Risk?

A recent Canadian study found that children with HCM who carry a single mutation in the MYH7 gene or who have multiple HCM-causative genetic mutations are at increased risk of major adverse cardiac events when compared to children who carry a single mutation in another gene.

Of the 98 gene positive children in this study, those with a MYH7 mutation or those with multiple mutations were more likely to need a myectomy or an ICD or to experience a sudden cardiac arrest or a heart transplant when compared to children with other HCM causative mutations.

The article also suggests that current screening protocols which recommend clinical and genetic screening for HCM beginning at age 12 may be insufficient.

Greater Certainty in Genetic Testing Results at HCM Specialty Centers

A recent study published by members of the SHaRe Cardiomyopathy Registry found that genetic test results for HCM are more definitive and helpful to patients when testing has been carried out at a high volume HCM center – especially a center that shares genetic data with other HCM centers. 

Continue reading “Greater Certainty in Genetic Testing Results at HCM Specialty Centers”

Multiple Mutations in HCM

A recent paper by researchers in Australia, published this week in Circulation: Cardiovascular Genetics, found more than one rare HCM gene in 4% of patients in a 758 patient sample group.

The researchers found that those patients with multiple rare HCM genes tended to present with HCM at a younger age, were more likely to experience cardiac arrest or death from other causes, and were more likely to require a heart transplant.

In general, few patients have multiples of mutations commonly associated with HCM.  See this Canadian study from April of this year which found that multiple mutations were less prevalent and harmful than previously thought.

CRISPR Eliminates HCM Gene !

Scientists, in a follow up to three earlier, less successful, Chinese experiments, have for the first time used a recently developed gene editing process known as “CRISPR” to remove a genetic defect from a human embryo.  The specific defect that the scientists targeted was a mutation in MYBPC3, a common genetic cause of hypertrophic cardiomyopathy (HCM).

What Happened in the Study?

The study authors consisted of a multi-national team of geneticists, cardiologists, fertility experts and embryologists.  Led by Dr. Shoukhrat Mitalipov of Oregon Health Sciences University, in collaboration with researchers at the Salk Institute in La Jolla, CA, China and South Korea, the researchers were able to largely remove the HCM gene MYBPC3 from very early stage human embryos.

Their research involved using eggs from 12 healthy female donors, and sperm from a male HCM patient with the MYBPC3 gene.  When gene-editing components were introduced to the egg along with the sperm, prior to fertilization of the egg, approximately 3/4 of the embryos repaired themselves using the DNA blueprint provided by the normal, non-mutated copy of the gene from the unaffected female.  This was somewhat surprising to researchers, who had theorized that cells would replicate using a blueprint from the repaired paternal gene – not the healthy gene of the mother.

Ultimately, genes were corrected in 42 of 58 embryos, constituting 72.4% of the total, a higher proportion than expected, and far more than any correction shown in previous experiments.

Implications for the Future

This technique is still far from general usage and will require further study and refinement.  And, currently it is not legal in the United States since the Food & Drug Administration currently prohibits medical gene editing which would impact future generations.

However, it would be possible for this technique to be used alongside current technology to assist families with genetic diseases like HCM.  If used in conjunction with pre-implantation genetic testing and in-vitro fertilization (PGD), the technique could repair the large proportion of embryos (roughly 50%) which must be discarded due to genetic defectiveness.

While there are critics who say that this technology will lead to “designer babies” and that it creates troubling ethical issues for society, most HCM patients believe that it provides a ray of hope, so that hopefully one day, in the not-too-distant-future, our children and grandchildren will be free of the affliction that has permeated our lives, as well as the lives of our siblings, our parents, our aunts and uncles, our cousins, our grandparents, and our great-grandparents.

Story Links:

As this story was reported by all major news sources, links to many of the articles can be found below.

Nature

The Atlantic

New York Times

Washington Post.

NPR

LA Times

Los Angeles Times – Q&A video clip with lead study author Shourkhrat Mitalipov

The Guardian

USA Today

MIT Technology Review

Gizmodo

Boston Herald

LA Times article regarding ethics -response to first article

NOTE THAT APPROXIMATELY A MONTH AFTER THE PUBLICATION OF THIS ARTICLE, THE RESULTS HAVE BEEN CALLED INTO QUESTION BY OTHER SCIENTISTS.

See this article in MIT Technology Review, this article in Science Magazinethis article in Nature, and this article in The Scientist, all of which cite this article in BioRxiv which poses alternative theories for the results claimed by the original paper.

Unwitting Geneticist Discovers Her Own Cardiomyopathy Gene: Heidi Rehm’s Story

Dr. Heidi Rehm is a human geneticist and clinical laboratory director at Harvard Medical School who has spent much of her career studying the genetics of cardiomyopathy.

Imagine her surprise when she found out that she, her mother and her daughter all have a mutation in the MYH7 gene which has been associated with dilated cardiomyopathy!

The unexpected revelation came as an indirect result of a visit to her daughter’s orthodontist.  When one of her daughter’s teeth was delayed coming in, the orthodontist suggested that there might be a genetic cause for the late tooth.  This provided the idea behind her high school daughter’s summer biology research project: 2 weeks in her mom’s lab sequencing her exome, looking for a genetic cause for her delayed tooth.

Though the mouth genetics turned out to be normal and the tooth eventually arrived, an totally unexpected incidental finding turned up instead:  a variation in the MYH7 gene which has been associated with dilated cardiomyopathy.

Continue reading “Unwitting Geneticist Discovers Her Own Cardiomyopathy Gene: Heidi Rehm’s Story”

Could a Tarantula Help to Unravel the Mysteries of HCM?

Researchers from around the globe have joined together to study an unlikely subject in order to understand the genetics of HCM according to a paper published today in the journal  eLIFE.

Dr. Christine Seidman, a cardiologist from Harvard Medical School, Dr. James Ware  a geneticist from the MRC London Institute of Medical Sciences at Imperial College London, and Dr. Raúl Padrón, a structural biologist at the Venezuelan Institute for Scientific Research, have joined forces in order to study the tarantula.

The reason for their focus on the tarantula is because the proteins comprising the muscles inside the furry spider are actually very similar to proteins inside the human heart.

Dr. Seidman, who had taken note of Dr. Padrón’s work with spiders, sought him out at a meeting to discuss the similarity of heart proteins to those in tarantula muscles and asked him whether they might collaborate.

By studying the way that the spider proteins interact with one another, the scientists hope that they will gain further insight into whether and how certain genes cause different types of hereditary cardiomyopathy, including hypertrophic and dilated.

I hope that they find the answers soon, before any tarantulas escape from their lab!

EEEEEEEKKKK!