The map of the human genome. The result is online on the BioRxiv website, which welcomes the articles awaiting examination by the scientific community. The numerous authors of the research, who belong to the T2T (Telomere-to-Telomere) consortium, thus open the way to the possibility of knowing single chromosomes to a level of detail never before achieved, with repercussions in many fields of biomedicine, from diagnosis to innovative therapies.
The new map now includes 3.9 billion base pairs, up from 3.2 billion for the first human genome sequence obtained 20 years ago, and also includes 8% ‘missing’ DNA.
Several scientists call the result “very important”. Among them the Harvard biologist and sequencing pioneer George Church), but also Ewan Birney, European Molecular Biology Laboratory – Embl. For all, this is a step forward for future research. The consortium said it increased the number of DNA bases from 2.92 billion to 3.05 billion, an increase of 4.5%.
Cells of the uterus
The DNA sequence used did not come from a person, but from a mass of cells that forms in the uterus when an egg without a nucleus is fertilized. This meant that the cluster contained two copies of the same 23 chromosomes, instead of two different sets of chromosomes, like normal human cells. The researchers chose these cells, which had been stored in a laboratory, because that made the computational effort to create the DNA sequence easier. Some doubts concern some aspects relating to the cell line used. But Miga said cell line studies showed that it is similar to human cells and that the researchers used cells that were kept frozen, not propagated for many years.
If the result of the research were confirmed with the publication, the work would be configured as a won challenge. That missing 8% of the genome has in fact to do with ‘unmappable’ regions, full of repetitions.
The technologies used
One of the technologies used is able to pass a DNA molecule through a tiny hole, resulting in a very long sequence, the other uses lasers to repeatedly examine the same DNA sequence, creating a reading that can be extremely accurate. Beyond all, the significance of the enterprise is summed up by Michael Schatz, associate professor at Johns Hopkins University:
“Now we finally have the right data,” he said. “And the right technology”.
Hope for diagnoses and new treatments
From genomics studies come new hopes for diagnosis, but also for new therapeutic targets and opportunities for in-depth exploration of pathogenic mechanisms. But despite notable recent advances in large-scale whole genome sequencing technology, there are still few clinics around the world that routinely use it for patients.
The integration of genomics in the health system is a very difficult goal to achieve, despite the progressive decrease in costs of more than a million times, sequencing reaching today a few hundred euros.