Progress Report:
Characterization and Development of a New Mouse Model of
Niemann Pick Type C (NPC) Disease
Robert Burgess, Kevin Seburn, and Robert Maue
The Jackson Laboratories, Bar Harbor, Maine, and
Dartmouth Medical School, Hanover, NH
As part of a large-scale mouse mutagenesis project, a subline of mutant mice (NMF164) was
generated that was initially characterized as resembling the existing npc nih mouse model of NPC
disease. Bolstered by generous support from the APMRF, breeding colonies of NMF164 mice were
established at both Dartmouth Medical School and The Jackson Laboratories in order that a
comprehensive analysis of these mice could proceed as quickly as possible and a well-characterized,
advantageous reagent could be made rapidly available to the NPC research community. The
NMF164 mice have been characterized at the genetic, biochemical, histological, and phenotypic
levels and compared to the existing npcnih and SPM mouse models of NPC disease. The results of
these analyses, which are now being gathered for publication, are summarized below.
At the genetic level, DNA sequencing determined that the mutation in the NMF164 mice
occurred at a site corresponding to amino acid 1005 of the NPC1 protein, which is very close to the
common human allele of the disorder at 1007 and in the loop of the protein that is most commonly
altered in human mutations, suggesting this will be a highly relevant animal model of NPC disease.
The sequence information was then used to develop a rapid genotyping assay to reliably discriminate
between the mutant and wild-type genomic sequences and facilitate subsequent analyses. The
corresponding allele in the SPM mouse was also sequenced in order to identify that mutation and
further confirm that the NMF164 mutation is distinct from the mutations in the other existing mouse
models. Other results, including failure of the NMF164 mutant to complement the npc nih and SPM
alleles of NPC1 disease, the moderate fertility of homozygous NMF164 mutants, and data on the
NMF 164 allele as a compound heterozygote with npc nih-null alleles also indicate that the mutation in
the NMF164 mice is distinct from the other mutations. However, despite an otherwise milder
phenotype the NMF164 mice do resemble npcnih mice in that there is a lower than expected
frequency of homozygotes produced from heterozygote breeding pairs.
For biochemical and histological analyses, samples were collected from the brain (cortex,
cerebellum), liver, and spleen of 15, 30, 60, 90, 100, and 120 day-old mice, and in collaboration with
Dr. Marie Vanier in France and Dr. TY Chang at Dartmouth the cholesterol and lipid accumulation
and metabolism in these tissues is being evaluated. In addition, histological results from the spleen,
liver, and cerebellum of NMF164 mutant mice at 15, 30, 60, and 90 days of age provide additional
evidence of cholesterol accumulation in these tissues, and confirm that the progressive demise of the
cerebellar Purkinje cells in these mice occurs at later time points than in the original npcnih mouse
model. Further examination of tissues is now ongoing using the BC-theta reagent obtained from Dr.
Ohno-Iwashita in Japan through arrangements with the APMRF.
Phenotypically, the NMF164 mice appear to exhibit the same characteristics as the original
npcnih subline of mice, though at older ages. Gait analysis at 60-65 days of age, when the effect of the
mutation on the gait of npcnih mice is noticeable, failed to reveal ataxia or gait abnormalities in
NMF164 mice. The characteristic tremor associated with this disorder is noticeable by 80 to 90 days
of age, however, and NMF164 mice are currently being tested at later ages to confirm they eventually
do develop an ataxia. The growth of NMF164 mice has also been evaluated, and there appears to be
a later onset and slower rate of weight loss than in the npc nih mice, consistent with their less severe
phenotype. Concurrently, the NMF164 mice appear to have an extended lifespan and often live 90110 days, notably longer than the 65-75 day lifespan of npcnih mice. Overall, the analyses suggest
that NMF164 mice are a potentially advantageous experimental model of NPC disease and
representative of the majority of clinical cases of this disorder.