Male C57BL/6 mice were treated with multidose N-ethyl-N-nitrosourea (ENU) and then bred to C3H/He females. The resulting male pups were then bred to C3H/He females to obtain second generation mice. The resulting female offspring were subsequently bred back to their parental line to obtain third generation mice. A mutagenesis screen was then performed to select mice with mutations effecting neural development. A family of mice, line 811, exhibiting craniorachischisis was identified. A forward-genetic screen approach found mutations in the Sec24 related gene family, member B (Sec24b) gene. Sequencing of this gene identified two transcripts each with a T to A transversion in exon 9 resulting in a premature stop codon (Y613X and Y579X). Craniorachischisis was confirmed in mice harboring the Y613X mutation. These mice were backcrossed to C3H/He mice (see SNP note below). Upon arrival at The Jackson Laboratory, mice were bred to C3H/HeJ (Stock No. 000659) for at least one generation to establish the colony.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. The 27 markers throughout the genome were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed genetic background.
