(a) Schematic representation of the Itgb1 floxed allele. To monitor Cre mediated deletion, a promoterless LacZ gene was inserted downstream of the 3′ loxP site, resulting in LacZ expression driven by the endogenous Itgb1 promoter only after deletion; (b) First round mating using Itgb1 flox/flox with Sycp1-Cre +/+ females or Zp3-Cre +/+ males to obtain double heterozygous Sycp1-Cre +/− Itgb1 flox/- or Zp3-Cre +/− Itgb1 flox/− that (c) we mated, respectively, with Itgb1 flox/flox males or females. These crosses made it possible to obtain (left) the males of interest (Sycp1-Cre +/− Itgb1 flox/flo, KD) and their controls (Cre −/− Itgb1 flox/flox) and (right) the females of interest (Zp3-Cre +/− Itgb1 flox/flox, KO) and their controls (Zp3-Cre −/− Itgb1 flox/flox); (d) By way of example, the two gels show the presence of Cre whether it is under the control of the Zp3 promoter or that of Sycp1 promoter and the presence of the Lox sites on one or two alleles.