C57BL C57BL/6NJ Black 6N B6N https://www.jax.org/strain/005304 Sirarat Sarntivijai This is an NIH subline of C57BL/6. It was separated from C57BL/6J in 1951. 5 SNP differences have been identified that distinguish C57BL/6J from C57BL/6ByJ and C57BL/6NJ. Both C57BL/6ByJ and C57BL/6NJ type as follows: 08-015199792-M (rs3709624) is C; 11-004367508-M (rs3659787) is A; 13-041017317-M (rs3722313) is C; 15-057561875-M (rs3702158) is G; 19-049914266-M (rs3724876) is T. C57BL/6J types as follows: 08-015199792-M is T; 11-004367508-M is G; 13-041017317-M is T; 15-057561875-M is A; 19-049914266-M is G (Petkov and Wiles 2005.) This strain does not have the deletion in the Nnt gene that has been found in the C57BL/6J strain (Stock No. 000664). C57BL/6NJ mice are homozygous for Cyfip2M1N, a spontaneous mutation in the cytoplasmic FMR1 interacting protein 2 that results in an amino acid substitution of phenylalanine for serine at position 968 (S968F). The mutation is found in all C57BL/6N substrains but is not present in the C57BL/6J strain or substrains. The mutation results in 45% lower acute response to cocaine as measured by locomotor hyperactivity.