Codons 466-529 in exon 10, including the catalytic phosphorylation site (aspartic acid 475), were replaced with a neomycin resistance gene. Northern blot indicated no difference in levels of mRNA between wild-type and heterozygous mice. RT-PCR confirmed that the exon 9 was spliced to exon 11, producing the transcript of the expected length. (J:91844)