An international team of researchers said on Friday they had uncovered another link between faulty genes and the most common form of Alzheimer's disease.
A variant of a gene called CALHM1, located on Chromosome 10, plays a role in late-onset Alzheimer's, which accounts for the majority of cases of this disease.
Alzheimer's is a degenerative disorder of the brain characterised by forgetfulness and dementia. It is caused by a massive loss of cells in several regions of the brain, driven by a buildup of plaques of amyloid protein.
CALHM1, whose initials stand for calcium homeostasis modulator 1, acts as a channel for controlling the entrance of calcium into neurons, according to the new study.
The culprit variant increases levels of peptides, or building blocks, for amyloid plaques by interfering with calcium flows into these cells.
People with a single copy of the CALHM1 variant in their pairs of genes increase the likelihood of late-onset Alzheimer's disease by 44 percent, and for those with both copies of the variant, the risk could be even higher.
The findings are important because they open up potential avenues for drugs that will interfere with the molecular cascade that produces the toxic plaques.
There is also a rare form of Alzheimer's called early onset, for which a clear picture is emerging that a few dominant genetic mutations are to blame.
Late-onset Alzheimer's, though, is more complex, with suspected causes that are both genetic and environmental. Until now, the only other gene clearly associated with it was a variant of a gene called APOE, on Chromosome 19.
The number of people worldwide with Alzheimer's is set to rise from 24 million people today to 42 million in 2020 and 81 million in 2040, according to some estimates.