Thousands of genomes reveal human genetic differences around the world

Researchers have gained new insights into genetic variation among people living around the world after sequencing the genomes of more than 2,500 people from across Asia, Europe, Africa and the Americas.

The report, published today in Nature, details the final set of findings from the 1000 Genomes Project, which was launched in 2008.

Jan Korbel, from European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, who’s team was involved in the study, noted that as expected genetic commonalities were found across geographic regions. But he was astonished by results that found other variations formed by new mutation processes that would require further research to explore.

Paul Flicek, who is in charge of the public repository of data at the EMBL outstation in Hinxton, UK, says he hopes many studies will make use of the data, which is openly available for use in research.

Thousands of genes

The human genome consists of approximately three billion DNA base pairs and carries an estimated 20,000 genes, which are the building blocks of life.

By studying the genomes of multiple individuals, we can gain an insight into the genetic differences between them and how they are associated with different traits, like eye colour, or diseases.

While there have been many human genome studies, the 1000 Genome Project has created the world’s largest catalogue of genomic differences among humans, and is making all its data publicly available.

Timothy Smith, the Scientific Programs Manager for the Human Variome Project based at the University of Melbourne, says the 1000 Genome Project is the “most comprehensive human study to date” and is pleased the researchers allow for data sharing.

“In a research context like this, a lot of people are concerned that making data available cuts off future publishing opportunities, but if you don’t make underlying data available it’s hard to justify findings.”

Missing a gene?

A related study published in the same edition of Nature found more than 200 genes, any of which can be entirely missing in any one individual.

Such a discovery could assist with future investigations into how humans have evolved to discard genes that are no longer necessary for survival.

Professor Andrew Sinclair, the Deputy Director of the Murdoch Children’s Research Institute in Melbourne, says this study drills down into the structural changes in the genome to show it on finer scale than ever before.

He points out that the researchers found 18 million base pairs of structural variants across all populations, which is “a larger proportion of the genome than previously thought”. In many instances he says there are “hotspots” in the human genome that are prone to such structural changes.

These can include things such as deletions, insertions, duplications and inversions, where one or more copies of a gene are deleted, moved around or altered in some way.

“The researchers identified 200 instances where both copies of a gene were deleted, suggesting that these genes were non-essential in those individuals.”

Sinclair says “most of the genes that were deleted were associated the immune system and probably reflect individual differences in disease susceptibility”.

Clara Gaff, the Executive Director of the Melbourne Genomics Health Alliance, says while previous studies in medical and clinical trials focused mostly on the genome sequence, this work develops our understanding of the human genome further.

“Genetic structural variation is an important aspect of human disease and so it’s important to develop a better understanding of how genomes affect human health,” she said.