These mutant mice contain a loxP-flanked transcriptional blocker cassette inserted between exon 3 and 4 of the Htr2c gene. The floxed-transcriptional blocker cassette abolishes gene function. When these mutant mice are bred to mice that express Cre recombinase, the resulting offspring will have the floxed-transcriptional blocker cassette removed, resulting in rescued Htr2c gene function. These mice may be useful for studying serotonin induced appetite suppression in obesity and diabetes.
Joel K Elmquist, UT Southwestern Med Center at Dallas
loxTB 5-Ht2CR mice contain a loxP-flanked transcriptional blocker cassette inserted between exons 3 and 4 of the 5-hydroxytryptamine (serotonin) receptor 2C (Htr2c) gene. The floxed-transcriptional blocker cassette abolishes gene function. Homozygous females and hemizygous males are fertile and normal in size. Hemizygous males have a high mortality rate due to seizures. Htr2c, an X-linked gene, is a serotonin receptor expressed in pro-opiomelanocortin neurons and plays a crucial role in the regulation of energy homeostasis and appetite suppression. Serotonin activates this receptor and suppresses appetite. These mice lack Htr2c expression in the cerebral cortex, hypothalamus, arcuate nucleus of hypothalamus, and the brainstem. They are hyperphagic, exhibiting a 50% increase in weekly food intake compared to wild-type littermates. They also develop late-onset hyperleptinemia, leptin insensitivity, and obesity which is accelerated on a high fat diet. These loxTB 5-Ht2CR mice display an increase in fat mass and a decrease in lean mass. When these mutant mice are bred to mice that express Cre recombinase, the resulting offspring will have the floxed-transcriptional blocker cassette removed, resulting in rescued Htr2c gene function. These mice may be useful for studying serotonin induced appetite suppression in obesity and diabetes.
A targeting vector was designed to insert a loxP-flanked transcriptional blocker cassette, containing a simian virus 40 (SV40) promoter, a neomycin (neo) resistance gene, and the polyadenylation sequence, between exon 3 and 4 of the 5-hydroxytryptamine (serotonin) receptor 2C (Htr2c) gene. The construct was electroporated into 129-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and the resulting chimeric males were bred to C57BL/6J females to generate a colony of loxTB 5-Ht2CR mice. The donating investigator reported that these mice were backcrossed for at least 9 generations to C57BL/6J background (see SNP note below). Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the colony.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. While most of the 27 markers throughout the genome suggested a C57BL/6 genetic background, markers on Chromosomes 6, 11, and 15 were found to be segregating. Also, 2 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed genetic background.
|Allele Name||targeted mutation 1, Joel K Elmquist|
|Allele Type||Targeted (Conditional ready (e.g. floxed), Null/Knockout)|
|Allele Synonym(s)||2C null; loxTB 5-HT2CR|
|Gene Symbol and Name||Htr2c, 5-hydroxytryptamine (serotonin) receptor 2C|
|Promoter||Htr2c, 5-hydroxytryptamine (serotonin) receptor 2C, mouse, laboratory|
|Strain of Origin||129|
|Molecular Note||A floxed transcription blocker cassette (loxTB) was inserted between exons 3 and 4. Expression is disrupted unless reactivated by cre mediated recombination. The absence of transcript expression was confirmed by RT-PCR on cerebral cortex, whole hypothalamus, arcuate nucleus of the hypothalamus, and brainstem extracts.|
|Mutations Made By|| |
Joel Elmquist, UT Southwestern Med Center at Dallas
The flox-STOP mutation is on the X chromosome. When maintaining a live colony, homozygous females may be bred to wildtype males or to C57BL/6J (Stock No. 000664) inbred males. The donating investigator reports that hemizygous males have decreased survival due to seizures.
When using the B6.129-Htr2ctm1Jke/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #015821 in your Materials and Methods section.