These mice were a gift from Dr. Hector Molina. Insertion of a neomycin resistance cassette in exon 5 resulted in mice deficient in <i>Crry</i>. Heterozygous mice, obtained from gene targeting in embryonic stem cells and blastocyst injection, were crossed with C3<sup>-/-</sup> mice and subsequently intercrossed to generate Crry<sup>-/-</sup>C3<sup>-/-</sup> mice. Crry and C3 are absent from platelets.