Ces1ce was discovered in a specific-locus mutation screen of progeny of triethylenemelamine (TEM) mutagenized male DBA/2J mice, but appears to have been a pre-existing, spontaneous mutation. Although the TEM-treated parent was unavailable for genotyping, three lines of evidence suggest he was a heterozygous carrier of the mutation: 7 of 13 (54%) of his immediate offspring were heterozygous for Ces1ce; he was mated within 2 weeks after TEM treatment, so these progeny were generated from sperm that were either sperm or late spermatids when exposed, ruling out a clustering effect due to mutagenesis at the spermatogonial stage; and the seven Ces1ce/+ offspring occurred among litters of three dams (Soares 1979).
Mice of a strain/stock bearing Ces1ce, called ES-IE, were imported from Dr. Soares, then at NIEH, by Dr. Eva Eicher. The original stock was maintained by sister-brother inbreeding. In 1982, Ces1ce/Ces1ce males of this stock were bred to C57BL/6J females to produce embryos for cryopreservation. These heterozygous embryos were assigned Stock No. 000785. In 1995, mice were recovered from the cryopreserved embryos to generate an F2 generation, from which mice homozygous for both Ces1ce and a (nonagouti) were selected and bred to generate embryos for cryopreservation. These embryos, which are segregating for Tyrp1b and Myo5ad, were designated STOCK a/a Ces1ce/Ces1ce and retained Stock No. 000785.
STOCK Ces1ce/Ces1ce Foxn1nu/+ (Stock No. 003118) was generated by mating a STOCK a/a Ces1ce/Ces1ce (Stock No. 00785) female to a C57BL/6J-Foxn1nu/Foxn1nu male, then selecting Ces1ce homozygotes from the F2 as colony founders. Embryos were generated for cryopreservation by crossing Foxn1nu/+ or Foxn1nu/Foxn1nu females to Foxn1nu/+ or Foxn1nu/Foxn1nu males at generation F4+.
