Mutation analysis of the parkin and PINK1 genes in American Caucasian early-onset Parkinson disease families

Mutations in the parkin gene and the PTEN-induced putative kinase 1 gene (PINK1) have been identified as the most common causes of autosomal recessive early-onset Parkinson disease (EOPD). To investigate the presence of the parkin and PINK1 gene mutation(s) and to explore genotype-phenotype correlations in American Caucasian families with EOPD from North American, we screened these two genes in probands of six families by direct sequencing, semi-quantitative PCR and RT PCR. No PINK1 gene mutation was found in any of the probands, but compound heterozygous mutations (EX 3 del and EX 3-4 del) in the parkin gene were identified in one family. Extended analysis of the parkin-positive family showed the phenotype of patients was that of classic autosomal recessive EOPD, characterized by early age at onset, slow progression, beneficial response to levodopa, and levodopa-related motor complications. Three heterozygous mutation carriers (EX 3 del or EX 3-4 del) were free of any neurological symptoms. None of 62 healthy controls harbored EX 3 del or EX 3-4 del mutation. Our data suggest that compound heterozygous mutations (EX 3 and EX 3-4 del) in the parkin gene were the cause of EOPD in one of six Caucasian families; heterozygous EX 3 del and heterozygous EX 3-4 del forms were insufficient to cause this disorder, consistent with a loss-of-function mechanism of the parkin mutations. The results may provide new insights into the cause and diagnosis of PD and have implications for genetic counseling. (c) 2007 Elsevier Ireland Ltd. All rights reserved.