Scientists have reconstructed the complete genome of a real person, with full sets of chromosomes from each parent, a breakthrough expected to advance research, improve the diagnosis of genetic diseases and make personalized genomics routine in medical care.
The work from the Telomere-to-Telomere (T2T) Consortium, led by researchers at Johns Hopkins University, the National Human Genome Research Institute (NHGRI), and the National Institute of Standards and Technology (NIST), establishes the most complete and highest quality human genome sequence ever constructed, filling critical gaps. The new approach allows any individual’s unique genome to be fully analyzed at much higher accuracy than the current standard, which excludes sequences that are different or missing from the historical reference genome.
“It will soon become commonplace to sequence an individual’s entire genome. What will that enable? And what does the future of medicine look like when you can generate someone’s complete genome at birth, attach it to their medical record, and then use that to inform precision medicine throughout their life,” said senior author Adam Phillippy , a Johns Hopkins research professor of computer science, biomedical engineering and genetic medicine. “Complete, personalized genomes are now possible for anyone.”
The work is published today as part of a 12-paper package of genomic advances in Cell and Cell Genomics , including papers that feature genome sequencing and analysis for eight additional vertebrate species including macaque, marmoset, and zebra finch.
These findings build on the groundbreaking 2022 completion of the first complete human genome by the T2T Consortium. That work filled in the last 8% of a single genome, but these new studies go much further by reconstructing complete “diploid” genomes, meaning each genome contains two slightly different copies of every chromosome, with one copy inherited from each parent.
“The first T2T project was like assembling a huge jigsaw puzzle. This time, we had pieces from two similar puzzles, one from mom and one from dad, all thrown into the same box,” Phillippy said. “So, it’s a harder computational challenge, but we’ve figured it out.”
The team sequenced the HG002 human genome, a sample from a living donor that is widely used as a reference material by the DNA sequencing and diagnostics industries. With near perfect accuracy, each chromosome spans from “telomere to telomere” and reveals 15% more of the genome, including previously inaccessible portions that are relevant to cancer and neurological disorders. The team added more than 900 million DNA letters that were absent from the prior benchmarks, including both sex chromosomes and areas with genes known to affect disease risk.
“Our complete reconstruction of the genetic makeup of the first reference material genome was the culmination of years of advances in technologies and analysis methods,” said NIST scientist and co-senior author Justin Zook. “The achievement gives technology developers the standard they need to measure and improve accuracy across the most complex regions of the human genome.”
At Hopkins, computational biologist Steven Salzberg and his team, including PhD student Hyun Joo “Hayden” Ji, led the effort to identify all of the genes on each chromosome copy, and computational biologist Michael Schatz ’s lab participated in what Phillippy called a “crowdsourcing” effort to extensively validate the accuracy of the work.
The achievement, along with the technological advances that made it possible, sets the stage for “personalized genomics,” where everyone’s complete genome sequence could serve as their own unique reference for medical care.
“This represents a paradigm shift from trying to find the differences between your genome and a reference to actually reconstructing your complete, unique genome,” Phillippy said. “This ensures that no regions of the genome are missed, and that the quality of the analysis does not depend on how similar you are to the reference genome.”
The total cost of the Human Genome Project, which concluded in 2003, was about $5 billion in today’s dollars. A more complete and accurate result can now be had for about $5,000, a million-fold reduction, Phillippy said.
The ability to quickly and affordably survey a patient’s entire genome is expected to greatly improve the ability to diagnose rare genetic diseases, especially in children.
“These types of genetic analyses happen today, but at a lower accuracy—in over half of the cases, doctors may not be able to determine the genetic cause,” Phillippy said. “We hope that these complete genomes will close the gap in rare disease diagnostics and give families the answers the need.”
Longer-term, the team expects the new benchmark will make it easier for doctors to predict any patient’s disease risk. Doctors already use mutations of the BRCA1 and BRCA2 genes to predict the risk of breast cancer, but complete genomes could improve risk prediction for other cancers and complex traits such as heart disease, immune disorders, and neuropsychiatric conditions, Phillippy said.
“We expect to discover new genomic variants that are associated with known diseases,” he said. “That, combined with the genomes of many non-human species, will allow us to train AI-based models of the genome to more accurately diagnose rare genetic disease and inform personalized medical care.”
The ability of this technology to reconstruct the complete or near-complete genome of any vertebrate species is highlighted by companion papers featuring macaque, marmoset, zebra finch, rat, vole, horse, donkey, and giraffe. These animal reference genomes are enabling research in evolution, biodiversity, and agriculture, such as how primates evolved, how birds learn to sing, and how livestock digest vegetation. Comparing the differences between these genomes helps researchers understand how they work and what makes humans unique.
The research involved dozens of scientists from institutions worldwide and was supported by the Intramural Research Program of the U.S. National Human Genome Research Institute, National Institutes of Health, National Institute of Standards and Technology, United States Department of Agriculture, and other funding agencies.
Cell