New York, April 2 : Researchers have identified 13 new rare genomic variants associated with Alzheimer's disease in a first-of-its-kind human genome study. The lesser-known gene mutations may hold critical information about the biology of the disease and can lead to the development of new drugs for the devastating neurological condition, according to researchers from the Massachusetts General Hospital (MGH) in the US. The new gene variants are linked with the functioning of synapses -- the junctions that transmit information between neurons -- development of neurons and neuroplasticity -- the ability of neurons to reorganise the brain's neural network. "This paper brings us to the next stage of disease-gene discovery by allowing us to look at the entire sequence of the human genome and assess the rare genomic variants, which we couldn't do before," said lead author Dmitry Prokopenko from MGH's McCance Center for Brain Health. The results are published in the Alzheimer's & Dementia: The Journal of the Alzheimer's Association. "Rare gene variants are the dark matter of the human genome," said Rudolph Tanzi, director of the hospital's Genetics and Ageing Research Unit. Of the three billion pairs of nucleotide bases that form a complete set of DNA, each person has 50 to 60 million gene variants -- and 77 per cent are rare, he added. For the study, the researchers performed whole genome sequencing on the genomes of 2,247 individuals from 605 families that include multiple members who have been diagnosed with AD. They also analysed genome sequencing datasets on 1,669 unrelated individuals. /IANS