He moved to the United States in 1999, where he began working at the Mayo Clinic in Jacksonville, Florida studying the genetic basis of Parkinson's disease, ataxia, and dystonia.

He moved to the National Institutes of Health in 2001 to head the newly formed Molecular Genetics unit within the Laboratory of Neurogenetics.

In 2006 he took over as Chief of the Laboratory of Neurogenetics and became an NIH Distinguished Investigator in the intramural program at the National Institute on Aging (NIA) in 2017.

In 2020 he stepped down as the Chief of the Laboratory of Neurogenetics and became the Acting Director of the newly formed Center for Alzheimer's and Related Dementias at the NIA (CARD https://card.nih.gov/).

His first well-known work described the discovery of a triplication mutation of the alpha-synuclein gene that causes a severe, early-onset form of Parkinson's disease.