A new genetic testing technique – called ANEVA-DOT (analysis of expression variation—dosage outlier test) – could provide hope for rooting out the underlying causes of rare genetic diseases.
An estimated one in twenty Indians suffer from illnesses that full under the classification of “rare diseases”. Fifty percent of these cases afflict children. Despite this, the illnesses remain neglected, both in terms of funding for research, as well as public awareness. Rare diseases — despite the infrequency that the name infers — cumulatively affect around 350 million people worldwide. This figure includes roughly seventy million Indians.
Despite recent policies aiming to address the conditions, progress is slow — many conditions receive no help at all. According to a government policy document, there are currently around 7,000 to 8,000 rare diseases that fall under the classification. Of these, fewer than 300 have therapies available to treat them. About 95 percent of rare diseases have no approved treatment and fewer than one in ten patients receive disease specific treatment.
The new technology for diagnostics may prove to be helpful in addressing the untold millions that suffer from rare diseases — not just in India, but globally. Researchers, including those from Scripps Research Institute in the US, have capitalised on the fact that each person inherits a gene — or allele — from both parents. This has allowed for a more accurate means of study of single allele conditions than comparisons of genomes of different people.
The new method — the results of which were described in the journal Science — detected the activity levels of maternal and paternal alleles across the genome, allowing the researchers to determine when the activity of an allele was outside the normal range.
The researchers noted that many rare diseases are not detected by standard methods, with many only analysed if a genetic basis is obvious, such as a missing or severely truncated protein. Many rare diseases are caused by a single allele, making their detection by current methods difficult if protein expression is not significantly altered.
“It might tell you there are ten or twenty genes with allele activity levels that are way off, and you can then follow up to determine which of those is causing the disease—but compared with other methods, it cuts down dramatically the number of genes you have to analyse in that way,” said study first author Pejman Mohammadi.
Improving diagnostic techniques could at the very least allow many in India to be aware of the conditions they are affected by. However, with few avenues into research of many of the conditions, the benefits to the diagnosis could be minor in many cases.