Feb. 25 (UPI) -- Researchers in China have identified two genes potentially involved in the development of Alzheimer's disease, they said Thursday.
The genes, which were found in the brains of people with the disease, are among roughly two dozen that may contribute to the cognitive decline associated with the common type of dementia, the researchers said in a study published by the journal PLOS Genetics.
It is unclear what role the two newly identified genes, PTPN9 and PCDHA4, play in the disease, which affects more than 5 million people in the United States, they said.
However, their discovery could help inform efforts to develop drugs to prevent and treat the disease, according to the researchers, from Tianjin Medical University in China.
"This study identifies genes whose expression in hippocampal tissue is associated with Alzheimer's disease and establishes the pathways from hippocampal gene expression to hippocampal volume to Alzheimer's disease," the researchers wrote.
The genes' activity in the hippocampus, the area of the brain that is believed to govern emotion and memory, could also be used to diagnose Alzheimer's disease with imaging methods such as MRI, they said.
Alzheimer's disease is a neurodegenerative disorder that causes worsening dementia and the formation of protein plaques and tangles in the brain -- and the hippocampus is one of the first regions to sustain damage.
For this study, the researchers identified genes expressed at higher or lower levels in the hippocampus of 111 people with Alzheimer's disease compared to those with healthy brains.
They focused on genes that are turned on and off in the brain region of people who have the disease, finding 24 Alzheimer's-related genes that appear to have an effect through the hippocampus, according to the researchers.
Many of the genes were already known to contribute to the disease but two had been previously unknown -- PTPN9 and PCDHA4.
The presence of the two genes is related to the size of the hippocampus and a diagnosis of Alzheimer's disease, they said.
In Alzheimer's disease, damage and loss of neurons causes the hippocampus to shrink, which can be measured through medical imaging, according to the researchers.
"The study identifies two novel genes associated with Alzheimer's disease in the context of hippocampal tissue and reveals candidate hippocampus-mediated neurobiological pathways from gene expression to Alzheimer's disease," they wrote.
