Analysis of an SMN gene-like DNA fragment.

Part of a survival motor neuron (SMN) gene-like DNA fragment has been identified. This DNA fragment was accidentally isolated from cDNA by RT-PCR using primers specific for the region between exon 3 and 6 of the SMN gene. This fragment was used as a probe to hybridize the mRNA from several tissues, but we have been unable to detect any transcript of this SMN-like gene in these tissues. Thus, we have inferred this SMN gene-like fragment was a genomic product contaminant that was amplified in the reaction. Sequencing analysis of this fragment, which contains several stop codons, revealed a 74.6% nucleotide homology with the SMN gene. From these results, we believe that this DNA fragment is not a mutated form of SMN gene. Rather, it is an SMN-like pseudogene, which is variably present even in normal individuals.