87Preventive Genetics by Early Diagnosis
of Mitochondrial Diseases
Diseases resulting from mutations in mitochondrial DNA are common in both
adults and children. Most mitochondrial disease may go undiagnosed because a
primary care physician does not suspect the disease or because the causative muta-
tion is missed by current routine diagnostic methods. MitoDx™ (MEDomics Inc) is
an innovative test for early diagnosis of mitochondrial diseases using next genera-
tion sequencing technology (SOLiD from Life Technologies) to detect all mutations
in any of the 37 mitochondrial DNA genes. Because cells contain hundreds of
mtDNA molecules, any particular tissue may contain mtDNA molecules that are all
identical, or there may be a fraction that differs. When both normal and mutant
molecules exist, the mitochondria are said to be heteroplasmic. The heteroplasmic
fraction of mutations can differ substantially among tissues. Low levels of hetero-
plasmy in blood are generally not detected by standard methods, but are detected by
the MitoDx™ test even at levels as low as 1 %. Diagnosis of mitochondrial disease
can enable life-saving therapy decisions and accurate family risk counseling. This
is guided by experts and is different from personal genetic service offered by vari-
ous companies shown in the following section.
Direct-to-Consumer Genetic Services
A large number of companies offers test to screen for diseases with a genetic compo-
nent or to identify those at risk of developing a certain disease. Some of the compa-
nies developing genetic tests are mentioned in other categories such as those involved
in prenatal and cancer diagnostics. Commercialization of genetic technologies is
expanding the horizons for the marketing and sales of direct-to- consumer (DTC)
genetic tests. Several companies are involved in this activity. Some companies have
made available DTC “personal genome services” that rely on the same arrays of
500,000 to 1 million SNPs used in genome wide association studies. Essentially, a
client sends a DNA sample to one of these companies, which analyzes the sample by
means of SNP array; the data are stored in an online private account, the results are
compared with allele-phenotype databases maintained and updated by the company,
and the customer receives readout of his or her levels of risk for specifi c conditions.
Future of Molecular Diagnostics in Personalized Medicine
Most cells are healthy, but they can become cancerous, get infected by viruses, and
undergo cycles as well as aging. Single cell analysis will be important for develop-
ment of personalized treatments that target disease at the cellular level. Trend in
Future of Molecular Diagnostics in Personalized Medicine