B6;129P2-Or8a1^{tm42(Mc4r)Mom}/MomJ

Stock number: 028199
Research areas: Cell Biology Research, Neurobiology Research, Research Tools, Sensorineural Research

Description

This allele replaces the coding sequence of the G-protein coupled olfactory receptor Or8a1 (formerly Olfr151) with the coding sequence of Mc4r, a G-protein coupled receptor not usually expressed in the main olfactory epithelium. MC4R binds GNAS and shares 14% amino acid identity with OR8A1. This substitution allele is useful for assessing the minimal sequence requirements for a G protein coupled receptor that is driven by the promoter of an olfactory sensory receptor to facilitate monoallelic expression of olfactory receptors, coalescence of olfactory glomeruli, and signal transduction via cAMP in olfactory sensory neurons.

Detailed description

This substitution allele is partially successful as a surrogate olfactory receptor, but not as good as the substitution of beta 2 adrenergic receptor (see Stock# 006734). Consistent with normal allelic exclusion of olfactory receptors, olfactory sensory neurons that express this GFP tagged MC4R substitution allele do not express any other olfactory receptor, proving this sequence adequate for monoallelic expression. However, the level of expression and number of olfactory neurons expressing this substitution allele are reduced compared with that of endogenous OR8A1 (formerly called OLFR151) on non-mutant olfactory sensory neurons. Subcellular localization of this MC4R on olfactory sensory neurons is highly concentrated in the dendritic knob and endings of the cilia. Patch-clamp recordings show that these neurons respond to the MC4R selective agonist Ro27-3225. The axons from these neurons coalesce into smaller than normal glomeruli that are positioned in a more anterior position than the endogenous OLFR151 glomeruli normally are.

Development

The coding sequence of Or8a1 (formerly Olfr151) was replaced by the sequence encoding amino acids 1-333 of Mc4r and an IRES-tauGFP. The targeted mutation was generated in 129P2/OlaHsd-derived E14 ES cells. The ACNf neomycin cassette was self-excised by Cre recombination in the germline of the male chimeras, which were then bred with C57BL6/J females. After several generations of sibling breeding sperm was cryopreserved from homozygous males.

Allele

Symbol: Or8a1^{tm42(Mc4r)Mom}
Name: targeted mutation 42, Peter Mombaerts
MGI accession ID: MGI:5661034
Generation method: Targeted
Attributes: Reporter; Inserted expressed sequence
Marker symbol: Or8a1
Marker name: olfactory receptor family 8 subfamily A member 1
Chromosome: 9
Strain of origin: 129P2/OlaHsd
Expressed genes: Mc4r,melanocortin 4 receptor,mouse, laboratory; GFP,Green Fluorescent Protein,
Site of expression: Olfactory sensory neurons
Molecular note: The endogenous coding sequence was replaced by the sequence encoding amoino acids 1 through 333 of Mc4r followed by an IRES-tauGFP cassette for bicistronic expression. The ACNf neomycin selection cassette was self-excised by Cre recombination in the germline of the male chimera.