The gene responsible for spinocerebellar ataxia type1 (SCA1) has been localized to a 6.7-cM region between the centromeric marker D6S109 and the telomeric marker D6S89. We screened two yeast artificial chromosome (YAC) libraries using sequence-tagged sites at D6S89 and at newly identified markers in 6p22-p23. Fifty YAC clones were identified and 34 insert termini were isolated from some of these YACs for detailed overlap mapping and long-range restriction analysis. A large YAC contig estimated to span 2.5 Mb was developed and genetic analysis in five large SCA1 kindreds using highly informative dinucleotide repeat polymorphisms mapped to this contig allowed the identification of D6S274 as the closest centromeric flanking marker for SCA1. Long-range restriction analysis determined the size for the critical SCA1 region, as defined by the two flanking markers D6S274 and D6S89, to be 1.2 Mb. This region is spanned by a minimum set of four nonchimeric YAC clones. The development of a 2.5-Mb YAC contig in 6p22-p23 provides valuable reagents for characterization of this genomic region and for the cloning of the SCA1 gene.
Bibliographical noteFunding Information:
We are grateful to E. Brundage and A. Jayakumar of the Baylor Cloning Core for their efforts in YAC isolation and to the staff of Baylor Nucleic Acids Core (R. Gibbs, director) for their sequencing and oligonucleotidc synthesis efforts. We thank Catherine Tasnier for careful preparation of the manuscript. This work was supported by Grants NS27699 (H.Y.Z.) and NS22920 (H.T.O.) from the National Institutes of Health, by the Mental Retardation Research Center, by a Human Genome Center grant (HGO0210), by funds from the Muscular Dystrophy Association (H.T.O., L.P.W.R., and H.Y.Z.), and by the National Ataxia Foundation. S.B. was supported by a fellowship from Seconda Clinica Neurologica, II Facolt~ di Medicina e Chirurgia, Uni-versit~ di Napoli, Naples, Italy.