A neomycin cassette replaced a genomic fragment that contains three coding exons of the gene corresponding to amino acids 62-194. Northern analysis of total RNA extracted from homozygous tissue showed the absence of full length message, and a presence of a truncated mRNA that should not yield a functional protein. Immunohistochemical analysis did not detect any protein produced from this allele in tissue sections derived from from homozygous embryos. (J:33712)