Mutations (arginine codon 34 (AGG) to alanine (GCG) (p.R34A) and lysine codon 38 (AAA) to alanine (GCA) (p.K38A)) were introduced into the N-terminal Cardin-Weintraub motif encode by exon 1 to reduce high-affinity Shh-proteoglycan interaction without altering Shh's affinity for its receptor. For targeting purposes, a floxed neomycin cassette was introduced into intron 1 and subsequently removed by transient expression of cre recombinase. Expression levels of the mutant protein in homozygotes was identical to wild-type as determined by immunoblot analysis of cerebellar extracts. (J:150524)