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A neomycin resistance cassette was inserted into exon 2 of the gene. Northern blots of brain, kidney, and lung tissues from homozygous mutant mice showed no detectable full-length wild-type mRNA. Two smaller bands were detectable by Northern blot. The authors attributed these bands to transcription through the inserted neomycin cassette and beyond. Further analysis by Western blot of brain extracts from homozygous mutant mice showed no full-length wild-type protein. Again, two bands, which the authors attributed to carboxy-terminal breakdown products of the shortened protein, were seen. The resulting proteins were determined to lack amino acids 20 - 75. (J:21937)