E6-AP mutant mice carry a paternally imprinted Ube3a (ubiquitin protein ligase E3A) knock-out mutation and may be useful in studies of Angelman syndrome (AS).
Genetic background-dependent differences in the behavioral, EEG activity and seizure phenotypes are observed - see C57BL/6 Ube3a maternal deletion mice ("B6 AS" ; Stock No. 016590) and 129 Ube3a maternal deletion mice ("129 AS" ; Stock No. 004477).
Dr. Arthur Beaudet, Baylor College of Medicine
Mice that are heterozygous for the targeted mutation are viable and fertile. Due to imprinting, with preferential expression of the maternal allele, heterozygous mice with a maternal deficiency display the phenotype while heterozygous mice with a paternal deficiency do not. There is a slightly reduced viability prior to weaning for homozygous offspring from heterozygous parents for mice on the hybrid B6;129 background. Surviving homozygous mice can display delayed growth and motor dysfunctions and have reduced fertility. No gene product (mRNA) is detected by Northern blot analysis in homozygous ES cells. Heterozygous mice that inherit the deficient allele maternally exhibit a 64-73% reduction in protein levels in heart, liver, and kidney tissues. In situ hybridization reveals no detectable expression in hippocampal neurons and Purkinje cells of heterozygotes with a maternal deficiency. Heterozygous mice with the maternal deficiency develop fewer dopaminergic neurons in the substantia nigra, display reduced motor coordination (tremor, ataxia), impaired long-term potentiation, defective neocortical plasticity, fluid consumption defects (abnormal licking behavior), and context-dependent learning abnormalities. Homozygous mice and heterozygous mice with a maternal deficiency have increased Purkinje cell cytoplasmic levels of TRP53 (transformation related protein 53), elevated levels of PML (promyelocytic leukemia tumor suppressor) protein in multiple tissues and an increased susceptibility to tonic clonic seizures induced by handling.
Mice with this Ube3a knock-out mutation are available on different genetic backgrounds - either C57BL/6 (Stock No. 016590) or 129 (Stock No. 004477). Born et al. 2017 Sci Rep. 7:8451 [PMID:28814801] describes genetic background differences in the behavioral, EEG activity and seizure phenotypes for these mutant mice. In summary, C57BL/6 Ube3a maternal deletion mice ("B6 AS") displayed robust behavioral impairments, spontaneous EEG polyspikes, and increased cortical and hippocampal power primarily driven by delta and theta frequencies. 129 Ube3a maternal deletion mice ("129 AS") demonstrated limited behavioral abnormalities, performed poorly on wire hang and contextual fear conditioning and exhibited a lower seizure threshold and altered spectral power. See that publication for more specific details.
A targeting vector containing neomycin resistance and herpes simplex virus thymidine kinase genes and a loxP site was used to disrupt a 3 kb sequence including exon 2. The construct was electroporated into 129S7/SvEvBrd-Hprtb-m2 derived AB2.2 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts.
The resulting chimeric animals were crossed to 129 mice. The mice were backcrossed to C57BL/6 for at least 5 generations and then backcrossed to C57BL/6J for 2 generations prior to transfer to the Repository.
Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.
|Allele Name||targeted mutation 1, Arthur L Beaudet|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||E6-AP-; E6AP-; Ube3A KO|
|Gene Symbol and Name||Ube3a, ubiquitin protein ligase E3A|
|Strain of Origin||129S7/SvEvBrd-Hprtb-m2|
|Molecular Note||A 3kb genomic region including exon 2 was replaced with a neo-loxP-hprt cassette via homologous recombination, resulting in deletion of 100 N-terminal amino acids in the encoded protein and a frameshift inactivating all putative protein isoforms. Homozygous mutant animals were identified by Southern blot and PCR genotype analysis.|
|Mutations Made By|| |
Dr. Arthur Beaudet, Baylor College of Medicine
Paternal imprinting silences the Ube3a gene in neurons.
For routine colony maintenance at The Jackson Laboratory Repository, wildtype females (or C57BL/6J inbred females) are bred with heterozygous males; this results in offspring with no abnormal neurological phenotype as the Ube3a mutation is silenced. These offspring are the "Heterozygous for Ube3atm1Alb, paternal transmission" genotype.
For researchers to obtain the "Ube3a-null" phenotype in neurons (both maternal and paternal Ube3a alleles are non-functional), heterozygous females are bred with wildtype males (or C57BL/6J inbred males); this results in maternal transmission of the Ube3a mutant allele and paternal transmission of the imprinted/silenced wildtype allele. These offspring are the "Heterozygous for Ube3atm1Alb, maternal transmission" genotype.
In addition, variable lethality and subfertility of homozygotes is observed.
When using the B6 E6-AP- mouse strain in a publication, please cite the originating article(s) and include JAX stock #016590 in your Materials and Methods section.