A neomycin resistance cassette replaced exon 4 sequence downstream of nucleotide 583 (serine 195). Full length protein was not detected in brain homogenates from homozygous mice. A truncated form of the protein that is 162 bps shorter and lacks 54 residues within the N-terminal region of the VPS10p domain is detected at low levels in brain lysates from homozygous and heterozygous mice.