The HD_N171(TT);HQ-021 targeted mutation was designed by Taconic Artemis to have the CMV early enhancer/chicken beta actin promoter sequence and the N171 HTT transgene all inserted into the mouse Gt(ROSA)26Sor locus on chromosome 6. The N171 HTT sequence has a human huntingtin [HTT] fragment encoding the first 171 amino acids (with 145 mixed CAA-CAG repeats [see polyQ assay note below]). Mice were sent to the CHDI Foundation colony as Stock No. 370308 [CHDI-81002021]. The colony is reported to be on the C57BL/6 genetic background. In 2015, animals were sent from the CHDI Foundation colony to The Jackson Laboratory Repository, from which B6.HD_N171(TT);HQ-021 heterozygotes are available as Stock No. 027426.
Important note on polyQ assay: over several generations, the polyQ repeat assay shows heterozygous mice have maintained a stable 141 polyQ repeat length.
In 2016, 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 first generation rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome were all found to be C57BL/6 allele-type, 3 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating in some mice (chromosomes 8 [~15.2 Mbp], 11 [~4.4 Mbp], 13 [~41.0 Mbp], 15 [~57.6 Mbp] and 19 [~49.9 Mbp]). These data suggest that the mice sent to The Jackson Laboratory Repository colony were on a mixed C57BL/6J;C57BL/6N genetic background.
