Monoallelic expression of the odourant receptor gene and axonal projection of olfactory sensory neurones.
BACKGROUND
We have previously generated transgenic mice carrying the murine odourant receptor gene, MOR28, tagged with lacZ. In this animal, the endogenous MOR28 is differently tagged with GFP. It was found that the transgenic and endogenous MOR28 genes are expressed in a mutually exclusive manner and that the two sets of olfactory sensory neurones (OSNs), each expressing either the transgenic or the endogenous MOR28, project their axons to separate glomeruli.


RESULTS
Our fluorescent in situ hybridization (FISH) revealed that the two endogenous alleles of MOR28 are also mutually excluded for their transcriptional activation. Therefore, we studied whether there would be any segregation in the projection of the two subsets of OSNs: one set expressing the paternal and the other expressing the maternal allele. It was found that the OSNs for both alleles shared the same glomerulus for their projection, but the projection targets were segregated within the glomerular structure.


CONCLUSIONS
Two subsets of neurones expressing either the transgenic or the endogenous MOR28 target their axons to two separate glomeruli based on the differences in the genetic backgrounds, nature of tagging, and chromosomal locations. In contrast, neurones expressing a maternal or paternal allele share the same glomeruli, but tend to target to segregated areas within the glomerular structure. The segregation was more prominent with increased differences in the genetic background between the two alleles.
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Japan.
T
T
Ishii
S
S
Serizawa
A
A
Kohda
H
H
Nakatani
T
T
Shiroishi
K
K
Okumura
Y
Y
Iwakura
F
F
Nagawa
A
A
Tsuboi
H
H
Sakano
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons; D005260:Female; D018392:Genomic Imprinting; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009833:Olfactory Pathways / Q000166:cytology*; D018035:Receptors, Odorant / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
C427664:Olfr1507 protein, mouse; D018035:Receptors, Odorant