Disrupted compartmental organization of axons and dendrites within olfactory glomeruli of mice deficient in the olfactory cell adhesion molecule, OCAM.
There is an overall topographic connectivity in the axonal projections of olfactory sensory neurons from the olfactory epithelium (OE) to the olfactory bulb (OB). The molecular determinants of this overall topographic OE-OB connectivity are not known. For 20 years, the intriguing expression pattern of the olfactory cell adhesion molecule (OCAM) has made it the leading candidate as determinant of overall topographic OE-OB connectivity. Here, we have generated a strain of OCAM knockout mice by gene targeting. There were no obvious alterations in the distribution of olfactory sensory neurons within the OE or in the coalescence of axons into specific glomeruli. However, the compartmental organization of dendrites and axons within the glomeruli was disrupted. Surprisingly, the mutant mice exhibited an increase in olfactory acuity; they appeared to have a better sense of smell. Thus, despite its striking expression pattern, OCAM is not essential for overall topographic OE-OB connectivity. Instead, OCAM is required for establishing or maintaining the compartmental organization and the segregation of axodendritic and dendrodendritic synapses within glomeruli.
The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Andreas
A
Walz
Peter
P
Mombaerts
Charles A
CA
Greer
Helen B
HB
Treloar
D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D002450:Cell Communication / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics*; D003712:Dendrites / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D019006:Neural Cell Adhesion Molecules / Q000172:deficiency / Q000235:genetics*; D009473:Neuronal Plasticity / Q000235:genetics; D019581:Neuropil / Q000378:metabolism / Q000648:ultrastructure; D009830:Olfactory Bulb / Q000002:abnormalities* / Q000166:cytology / Q000378:metabolism; D009832:Olfactory Nerve / Q000002:abnormalities / Q000166:cytology / Q000378:metabolism; D018034:Olfactory Receptor Neurons / Q000002:abnormalities* / Q000166:cytology / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D012903:Smell / Q000235:genetics
C108768:Ncam2 protein, mouse; D019006:Neural Cell Adhesion Molecules