In this era of fast-moving genome research, it seems that new genes are discovered every month for common diseases like Crohn’s disease, prostate cancer, or type 2 diabetes. However, Alzheimer’s disease has stubbornly resisted giving up any more secrets to researchers – until now.
For 15 years, only one gene, APOE, has been unambiguously associated with Alzheimer’s disease, yet scientists knew that the risk variant of APOE explained only a small amount of the genetic risk for Alzheimer’s. Now, a new study by an international team of researchers has revealed a mutation, in a newly discovered gene, that can double the risk of Alzheimer’s disease.
The researchers cracked this piece of Alzheimer’s code by turning to bioinformatics. They used the power of sophisticated math and computing to screen for genes that are expressed in certain regions of the brain and found on chromosome regions that had previously been suspected in Alzheimer’s.
The gene they found, which they call CALHM1, appears to carry the code for building a calcium channel in the brain. Calcium is an important part of brain function, and problems in calcium transport had already been linked to Alzheimer’s disease, although scientists don’t yet know exactly how.
The researchers compared five groups of Alzheimer’s patients with five groups of healthy people. People who inherited one copy of the risky gene variant of CALHM1 were 37 percent more likely to develop Alzheimer’s. People who inherited two copies – one from each parent – were twice (or 200 percent) as likely to develop Alzheimer’s. The risky gene variant is fairly common, and was carried by 22 percent of healthy people in the study.
The effect of this variant is small compared with the long-established APOE variants, which can increase a person’s risk by 20-fold, or 2000 percent, if they inherit the most risky version. But CALHM1’s risk is still significant, especially given how much we have to learn about Alzheimer’s.
This gene discovery doesn’t settle the biggest debate in Alzheimer’s genetics: Is individual risk worth finding out? But the researchers behind CALHM1 hope that their findings can eventually help answer that question by pointing other scientists towards developing new treatments or Alzheimer’s preventions.
At Navigenics, we’ve given careful consideration to Alzheimer’s gene testing, and decided that the insights it yields can be a part of good preventive health care. As a result, we’ll be taking a close look at this research, to decide whether to add this new gene variant to the Alzheimer’s information we already provide.