We present a genetic model of selective nigral neuron death without Lewy body formation--autosomal recessive juvenile parkinsonism (AR-JP). Mapping of AR-JP gene to a single recessive locus on chromosome 6q25.2-27 is a strong indication of the idea that a loss-of-function mutation of a single gene is sufficient to cause selective nigral neuron death. The absence of Lewy body formation in AR-JP is important, because most cases of neuron death caused by loss-of-function mechanism are not accompanied by inclusion body. Our findings clearly indicate that nigral cells are critically dependent for their survival on the function of AR-JP protein. This raises an important question of whether or not AR-JP protein contributes to the downstream pathway of cell death in Parkinson's disease.