All mouse procedures were performed in accordance with McGill University guidelines, which are set by the Canadian Council on Animal Care. Genomic DNA was isolated from tail biopsies and analyzed by Southern blotting and genomic PCR analysis. The DNA fragment utilized as the probe for the Southern blotting analysis was amplified with the following two oligonucleotides (5′-AAG CCT TTA CTG GTT GTG T-3′) and (5′-CTT GAA ACG CAC CGT AGG CT-3′). The wild-type sam68 allele was identified by genomic PCR using the following oligonucleotides 5′-AAA TCC TAA CCC TCC TCA GTC AG-3′ and 5′-GAT ATG ATG GAT GAT ATC TGT CAG-3′. The sam68-targeted allele was identified by genomic PCR using the following oligonucleotides 5′-CTT GGG TGG AGA GGC TAT TCG-3′ and 5′-GTC GGG CAT GCG CGC CTT GAG C-3′.