Of the original 26 NZM strains, many resemble NZBxNZWF1 in lifespan and pathology, some strains show an accelearation of disease onset while others have delayed onset or are symptom free. All strains are homozygous for the NZW haplotype H2z (Ku, Au, Sz, Dz ).
The NZM strains are part of an original set of 26 inbred strains. All the mice originated in NZB x NZW mice, either F2 or backcrosses to NZW, in the Wadsworth Center for Laboratories and Research, Albany, NY (WCLR). The stocks came from the University of Minnesota in 1973 and had been strictly inbred at WCLR. For 12-15 months the mice were pen-bred for coat color: chocolate brown, tan and grey. Inbreeding was started from single pairs in 1981 by CT Olsen. At F4-F5 AE Gabrielsen took over and abandoned the color criterion for the grey mice and selected for continuation lines-to-be in which lupus nephritis deaths had already been documented.
Currently there are no related genes or alleles for this strain.