Generation of C1galt1 conditional knockout mice. (A) Schematic showing the mucin-type O-glycan biosynthetic pathway and relevant glycosyltransferases. (B) Targeting strategy for conditional deletion of the C1galt1 gene. The targeting construct contains the second and third exons of C1galt1 and the PGK-neo cassette (Neo) flanked by three loxP sites and Neo flanked by FRT sites. Neo was removed by crossing with mice expressing FLPe under control of the human β-actin promoter. C1galt1 exons were deleted by mating C1galt1^flox/+ mice with Ayu1-Cre mice, which ubiquitously express the cre recombinase. The position of the Southern hybridization probe is indicated by the bold line. Arrows, F1, R1, and R2 indicate the position of primers for genotyping. PCR performed on genomic DNA extracted from (C) tails and (D) bone marrow of WT and Mx1-cre::C1galt1^flox/− mice injected with pIpC.