PCMT1 is a protein repair methyltransferase that initiates the conversion of L-isoaspartyl residues to normal L-aspartyl residues. Homozygous deficiency of this isoaspartyl repair methyl-transferase may be useful in studying isoaspartyl accumulation in seizure disorders, cellular-damage induced neurogenesis, aging, the PI3K/Akt signal transduction pathway, the insulin signaling pathway and autophagy/protein turnover.
Steven G Clarke, University of California Los Angeles (UCLA)
Heterozygous (Pcmt+/-) mice are viable and fertile. Homozygous (Pcmt-/-) mice have significantly increased isoaspartyl residues in intracellular proteins (deficits in the repair of isoaspartyl protein damage), with alterations in the insulin-like growth factor-I pathway and insulin receptor pathway in the brain. Homozygous mice exhibit reduced overall body size, progressive brain enlargement, increased neuronal cell proliferation, and death at approximately 45 days of age from tonic-clonic seizures. The brain enlargement is attributed to aberrantly increased insulin signaling in neuronal tissues. Homozygous Pcmt1-deficiency also increases the ratio of S-adenosylmethionine to S-adenosylhomocysteine by ~2.3-fold in brain tissue at 40 days of age, which likely affects the activity of many of the other cellular methyltransferases. Pcmt-/- mice also have a mild impairment in glucose tolerance (higher peak levels of blood glucose), but no significant differences in plasma insulin levels, during glucose tolerance tests.
The Pcmt1 knockout allele (Pcmt-) was designed by Dr. Stephen G. Young (University of California Los Angeles) with a neomycin-resistance cassette inserted into exon 1 (after the sequence encoding the first six amino acids) of the protein carboxyl methyltransferase gene (Pcmt1). The targeting vector was electroporated into 129S4/SvJae-derived RF8 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. Chimeric mice were bred with C57BL/6 mice to establish the colony. Heterozygous mice (Pcmt+/-) were bred together for more than fifteen years (genetic background approximately 50% 129/SvJae and 50% C57BL/6) prior to sending males to The Jackson Laboratory Repository in 2013. Upon arrival, males were used to cryopreserve sperm. To establish our living Pcmt- mouse colony, an aliquot of the frozen sperm was used to fertilize oocytes from C57BL/6J inbred females (Stock No. 000664).
|Allele Name||targeted mutation 1, Steven Clarke|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||Pcmt1-; PIMT-|
|Gene Symbol and Name||Pcmt1, protein-L-isoaspartate (D-aspartate) O-methyltransferase 1|
|Strain of Origin||129S4/SvJae|
|Molecular Note||Exon 1 was replaced with a neomycin selection cassette after sequence encoding the first 6 amino acids. Western blot analysis of various tissues and assays of brain, heart, liver, and red blood cells showed that the absence of protein and methyltransferase activity in homozygous mutant mice.|
Homozygous mice die at approximately 45 days of age from tonic-clonic seizures. When maintaining a live colony, heterozygous mice may be bred together or with wildtype mice from the colony.
When using the Pcmt1- mouse strain in a publication, please cite the originating article(s) and include JAX stock #023343 in your Materials and Methods section.