B6J.129-Comt^tm1.1Tunb/J

Stock number: 032900
Product name: COMT-Met
Research areas: Neurobiology Research

Description

COMT-Met knock-in mice express COMT*L148M, which is analogous to the functional human polymorphism Val¹⁵⁸Met (COMT-Met, also called COMT*V158M or Met¹⁵⁸) that has been investigated in a wide range of neuropsychiatric phenotypes. COMT-Met knock-in mice are a highly specific mouse model of altered COMT activity, and may be useful for studying dopamine metabolism, including COMT inhibition in any psychiatric conditions for which prefrontal dopamine is implicated.

Detailed description

Catechol-O-methyltransferase (COMT) metabolizes dopamine, and genetic and pharmacological reductions in COMT activity increase prefrontal dopamine transmission. Human COMT mutations are associated with schizophrenia, anxiety, mood disorders, obsessive-compulsive disorder and attention deficit disorder. The human COMT gene population includes the Val¹⁵⁸ allele (COMT-Val) and a functional polymorphism Val¹⁵⁸Met allele (COMT-Met, also called COMT*V158M or Met¹⁵⁸), the latter of which has been investigated in a wide range of neuropsychiatric phenotypes. In human populations, COMT-Met homozygotes have ~40% lower COMT activity than COMT-Val homozygotes.

To simulate the human Val¹⁵⁸Met mutation, Stock No. 032900 has the mouse COMT-Met knock-in allele designed to have the relevant genomic sequence of mouse Comt exon 3 changed such that it encodes the leucine-to-methionine amino acid substitution (COMT*L148M) mutant protein. Mice homozygous for this COMT-Met knock-in allele exhibit ~40% reduced COMT abundance and activity (consistent with the human polymorphism) and selectively reduced dopamine metabolism, with no apparent alteration of other genes. Subtle changes in baseline performance of learning and memory tasks are observed, with no alterations in the anxiety-related behaviors examined. Pharmacological COMT inhibition reveals COMT-Met homozygotes demonstrate cortical function deficits compared to similarly treated wildtype mice (5-choice serial reaction time task [5CSRTT] following administration of the brain-penetrant COMT inhibitor tolcapone). The donating investigator also reports that homozygotes show changes in reward processing (December 2018; unpublished observations).

Mice homozygous for this COMT-Met knock-in allele are viable and fertile with normal breeding, and no reported spontaneous abnormalities other than those described above. Mice heterozygous for this COMT-Met knock-in allele are viable and fertile with normal breeding, and no reported gross phenotypic abnormalities.

In addition to Dr. Elizabeth M. Tunbridge's mouse COMT-Met knock-in allele expressing the mouse COMT*L148M mutant protein (Stock No. 032900), The Jackson Laboratory also has available Dr. Xianjin Zhou's mouse lines that express human COMT Met sequences (Stock Nos. 032383/027993) and human COMT Val sequences (Stock Nos. 032382/027990).

Development

The COMT-Met knock-in allele (COMT*L148M) was created in the laboratories of Dr. Jingshan Chen and Dr. Elizabeth M. Tunbridge (University of Oxford) to alter exon 3 of the mouse catechol-O-methyltransferase locus (Comt) on chromosome 16 by changing the DNA sequence of codon 148 from CTA to ATG - the result to encode a leucine-to-methionine amino acids substitution (L148M) that is analogous to the human Val¹⁵⁸Met mutation (COMT-Met, also called COMT*V158M or Met¹⁵⁸). The targeting vector (also designed to insert a loxP-flanked PGK-neo selection cassette in intron 3) was electroporated into 129/Sv-derived embryonic stem (ES) cells. Chimeric animals bred to C57BL/6J for germline transmission. Mice were backcrossed to C57BL/6J inbred mice for three generations, and were then bred to mice expressing Cre recombinase under the control of the protamine promoter (129S/Sv‐Tg(Prm‐cre)58Og/J ; Stock No. 003328) for permanent deletion of the PGK-neo cassette. The resulting COMT-Met (COMT*L148M) knock-in mice were then bred with C57BL/6J inbred mice for 11 generations (and the cre-expressing transgene was removed) prior to sending males (black coat color) to The Jackson Laboratory Repository in 2019. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Of note, it is not known if the Y chromosome has been fixed to the C57BL/6J background during backcrossing.

Allele

Symbol: Comt^tm1.1Tunb
Name: targeted mutation 1.1, Elizabeth Tunbridge
MGI accession ID: MGI:6274226
Generation method: Targeted
Attributes: Humanized sequence
Synonyms: COMT-Met
Marker symbol: Comt
Marker name: catechol-O-methyltransferase
Marker synonyms: Comt1; D16Wsu103e; D330014B15Rik; HEL-S-98n
Chromosome: 16
Strain of origin: 129
Molecular note: The targeting was designed to alter the DNA sequence of codon 148 in exon 3 from CTA to ATG creating a leucine-to-methionine amino acids substitution (L148M) and insert a loxP-flanked PGK-neo selection cassette in intron 3. The substitution is analogous to the human Val<158>Met mutation. Cre-mediated recombination removed the floxed neo cassette. Immunoblot analysis indicats that both soluble and membrane bound protein isoforms are reduced in all brain regions.