Mice homozygous for the Ap3b1tm1.1Sms knock-out exhibit reduced levels of the adaptor protein complex delta-3 subunit in brain tissue, and in the kidney mu-3 and delta-3 subunit proteins levels are greatly reduced. Melanosomes and lysosomes are abnormal in these mice.
Margit Burmeister, University of Michigan
Ap3b1 encodes the beta-3A subunit of the adaptor protein complex 3 (AP-3). Mice that are homozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. No Ap3b1 mRNA is detected by Northern blot analysis of spleen and kidney tissue, and beta-3A immunoreactivity is absent in monocytes from homozygous mice. In brain tissue from homozygous mutants, expression levels of the AP-3 beta-3B (beta-NAP), mu-3 and sigma-3 subunit proteins are normal, but expression of the delta-3 subunit protein is reduced. In kidney, no sigma-3 protein is detected, and mu-3 and delta-3 subunit proteins levels are greatly reduced.
Homozygotes have a diluted coat color (light gray), which is lighter than the coats of homozygotes carrying the allelic pearl (Ap3b1pe) spontaneous mutation. Cultured melanocytes from homozygous mutant mice have very few pigment granules. Lysosomal-associated membrane proteins and tyrosinase are mislocalized in cultured fibroblasts and melanocytes. Vesicular zinc in embryonic fibroblasts from homozygotes is either greatly reduced or absent, and histochemically reactive synaptic vesicle zinc and zinc-uptake transmembrane proteins are increased in brain sections. Homozygotes also exhibit prolonged bleeding times. This mutant mouse strain may be useful in studies of intracellular membrane protein trafficking, intracellular organelle formation and Hermansky-Pudlak syndrome.
A targeting vector containing a loxP site flanked neomycin resistance and phosphoglycerate kinase selection cassette and IRES-lacZ was used to disrupt the coding exon. The construct was electroporated into 129-derived R1-45 embryonic stem (ES) cells. Correctly targeted ES cells were co-cultured with C57BL/6 morulae. The resulting male chimeric animals were crossed to C57BL/6 mice. The mice were crossed to transgenic CMV-Cre (on a mixed background) to remove the PGK-neo selection cassette. Mice were then backcrossed to C57BL/6 for 5 generations (while selecting against the Cre-expressing transgene) prior to arrival at The Jackson Laboratory.
|Allele Name||targeted mutation 1.1, Suzanne L Mansour|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Ap3b1, adaptor-related protein complex 3, beta 1 subunit|
|Strain of Origin||(129X1/SvJ x 129S1/Sv)F1-Kitl+|
|Molecular Note||An IRES-lacZ and a floxed PGKneomycin selection cassette was inserted into the coding region of the gene. Subsequent transient transcription of Cre recombinase removed the neomycin selection cassette. Northern blot analysis on RNA derived from spleen and kidney of homozygous mice confirmed that no detectable transcript was expressed from this allele.|
|Mutations Made By|| |
Suzanne Mansour, University of Utah
When maintaining a live colony, these mice are bred as homozygotes.
When using the Ap3b1LN mouse strain in a publication, please cite the originating article(s) and include JAX stock #006253 in your Materials and Methods section.