CLONING THE GENE FOR CHILDHOOD-ONSET SMA

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Spinal muscular atrophy (SMA) is a progressive neurodegenerative disease with three different clinical manifestations: type I (Wernig-Hoffmann), type II (intermediate), and type III (Kugelberg-Welander). The SMA gene has recently been localized to chromosome 5q11.2-13.3 in this CIDA program sponsor Dr. Gilliam's laboratory. Recent progress in this laboratory has refined the SMA gene locus to a smaller region (approximately 2-5 cM) with several polymorphic flanking makers. A research project is proposed here to clone the disease gene region and to characterize the gene mutation. The specific aims of this project are: (1) to construct a long-range restriction map across the SMA locus to identify the restriction fragments and "CpG islands" within the two closest flanking markers; (2) to construct overlapping yeast artificial chromosome (YAC) and cosmid clones across the SMA locus by screening both YAC and cosmid libraries using the "chromosomal walk" techniques; (3) to identify gene-coding segments within the "minimal genetic region: by searching for conserved sequences, by identifying CpG islands, and by screening cDNA libraries constructed from normal and SMA tissues including brain, spinal cord, and muscle; (4) to identify the SMA disease gene mutation by detecting linkage disequilibrium, by screening for the pattern of RNA expression from the normal and SMA alleles, by direct sequencing and PCR amplification of the candidate gene to construct allele specific oligomers (ASOs) to assay large number of SMA and normal DNA samples; (5) to characterize the disease gene mutation in a large set of affected individuals and detect the correlation between the patterns of mutation and their phenotypic manifestations such as disease severity, age of onset, and pattern of inheritance. Innovative molecular genetic technology and strategy will be developed to achieve the above goals.