Corporate Banner
Satellite Banner
Scientific Communities
Become a Member | Sign in
Home>News>This Article

A Cautionary Tale on Genome-Sequencing Diagnostics for Rare Diseases

Published: Tuesday, May 14, 2013
Last Updated: Tuesday, May 14, 2013
Bookmark and Share
Studies in several children have raising new questions about inheritance, genomic sequencing, and diagnostic.

Children born with rare, inherited conditions known as Congenital Disorders of Glycosylation, or CDG, have mutations in one of the many enzymes the body uses to decorate its proteins and cells with sugars. Properly diagnosing a child with CDG and pinpointing the exact sugar gene that's mutated can be a huge relief for parents—they better understand what they're dealing with and doctors can sometimes use that information to develop a therapeutic approach. Whole-exome sequencing, an abbreviated form of whole-genome sequencing, is increasingly used as a diagnostic for CDG.

But researchers at Sanford-Burnham Medical Research Institute (Sanford-Burnham) recently discovered three children with CDG who are mosaics—only some cells in some tissues have the mutation. For that reason, standard exome sequencing initially missed their mutations, highlighting the technique's diagnostic limitations in some rare cases. These findings were published April 4 in the American Journal of Human Genetics.

"This study was one surprise after another," said Hudson Freeze, Ph.D., director of Sanford-Burnham's Genetic Disease Program and senior author of the study. "What we learned is that you have to be careful—you can't simply trust that you'll get all the answers from gene sequencing alone."

Searching for a rare disease mutation

Complicated arrangements of sugar molecules decorate almost every protein and cell in the body. These sugars are crucial for cellular growth, communication, and many other processes. As a result of a mutation in an enzyme that assembles these sugars, children with CDG experience a wide variety of symptoms, including intellectual disability, digestive problems, seizures, and low blood sugar.

To diagnose CDG, researchers will test the sugar arrangements on a common protein called transferrin. Increasingly, they'll also look for known CDG-related mutations by whole-exome sequencing, a technique that sequences only the small portion of the genome that encodes proteins. The patients are typically three to five years old.

A cautionary tale for genomic diagnostics

In this study, the researchers observed different proportions and representations of sugar arrangements depending on which tissues were examined. In other words, these children have the first demonstrated cases of CDG "mosaicism"—their mutations only appear in some cell types throughout the body, not all. As a result, the usual diagnostic tests, like whole-exome sequencing, missed the mutations. It was only when Freeze's team took a closer look, examining proteins by hand using biochemical methods, did they identify the CDG mutations in these three children.

The team then went back to the three original children and examined their transferrin again. Surprisingly, these readings, which had previously shown abnormalities, had become normal. Freeze and his team believe this is because mutated cells in the children's livers died and were replaced by normal cells over time.

"If the transferrin test hadn't been performed early on for these children, we never would've picked up these cases of CDG. We got lucky in this case, but it just shows that we can't rely on any one test by itself in isolation," Freeze said.

Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,800+ scientific posters on ePosters
  • More Than 4,000+ scientific videos on LabTube
  • 35 community eNewsletters

Sign In

Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Sanford-Burnham to Partner with Pfizer
The collaboration will see the organisations identify new therapeutic targets for preventing and treating complications of obesity and diabetes.
Tuesday, August 20, 2013
“Junk DNA” Drives Embryonic Development
An embryo is an amazing thing. From just one initial cell, an entire living, breathing body emerges, full of working cells and organs.
Thursday, December 06, 2012
Scientific News
High Throughput Mass Spectrometry-Based Screening Assay Trends
Dr John Comley provides an insight into HT MS-based screening with a focus on future user requirements and preferences.
Promising Drug Combination for Advanced Prostate Cancer
A new drug combination may be effective in treating men with metastatic prostate cancer. Preliminary results of this new approach are encouraging and have led to an ongoing international study being conducted in 196 hospitals worldwide.
A Cellular Symphony Responsible for Autoimmune Disease
Broad Institute researchers have used a novel approach to increase our understanding of the immune system as a whole.
When it Comes to Breast Cancer, Common Pigeon is No Bird Brain
If pigeons went to medical school and specialized in pathology or radiology, they’d be pretty good at distinguishing digitized microscope slides and mammograms of normal vs. cancerous breast tissue, a new study has found.
Editing of LIMS Data Made Faster and More Efficient in Matrix Gemini
The latest version of the Matrix Gemini LIMS (Laboratory Information Management System) from Autoscribe Informatics now provides faster and more efficient editing of LIMS data by eliminating the need for a second editing screen.
How a Genetic Locus Protects Adult Blood-Forming Stem Cells
Mammalian imprinted Gtl2 protects adult hematopoietic stem cells by restricting metabolic activity in the cells' mitochondria.
Genetic Basis of Fatal Flu Side Effect Discovered
A group of people with fatal H1N1 flu died after their viral infections triggered a deadly hyperinflammatory disorder in susceptible individuals with gene mutations linked to the overactive immune response, according to a recent study.
New Tech Vastly Improves CRISPR/Cas9 Accuracy
A new CRISPR/Cas9 technology developed by scientists at UMass Medical School is precise enough to surgically edit DNA at nearly any genomic location, while avoiding potentially harmful off-target changes typically seen in standard CRISPR gene editing techniques.
The MaxSignal Colistin ELISA Test Kit from Bioo Scientific
Kit can help prevent the antibiotic apocalypse by keeping last resort drugs out of the food supply.
"Good" Mozzie Virus Might Hold Key to Fighting Human Disease
Australian scientists have discovered a new virus carried by one of the country’s most common pest mosquitoes.
Scroll Up
Scroll Down
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,800+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
4,000+ scientific videos