Lactosamine differentially affects olfactory sensory neuron projections to the olfactory bulb
Gerald A Schwarting1, Timothy R Henion
1Shriver Center, Waltham, Massachusetts 02452, USA. gerald.schwarting@umassmed.edu
Developmental Neurobiology
|June 15, 2007
Summary
The glycosyltransferase beta3GnT1 is crucial for olfactory bulb (OB) development. Its absence disrupts lactosamine expression, leading to olfactory sensory neuron axon targeting errors and glomeruli malformation.
Area of Science:
- Neuroscience
- Developmental Biology
- Glycobiology
Background:
- Olfactory sensory neurons (OSNs) must accurately target their axons to specific glomeruli in the olfactory bulb (OB) for proper circuit formation.
- The glycosyltransferase beta3GnT1 enzyme regulates lactosamine glycan expression, which is known to be involved in OB glomerular organization.
- The precise role of lactosamine in OSN axon targeting and glomerulus formation remains incompletely understood.
Purpose of the Study:
- To investigate the function of beta3GnT1-dependent lactosamine expression in the targeting of specific olfactory sensory neuron populations to the olfactory bulb.
- To determine how the absence of lactosamine affects the development and survival of different OSN axon populations in the olfactory bulb.
Main Methods:
- Analysis of olfactory sensory neuron axon trajectories and their expression of 1B2-reactive lactosamine glycans in beta3GnT1 knockout (beta3GnT1-/-) mice.
- Comparison of axon pathfinding and glomerular targeting in wild-type and beta3GnT1-/- mice during early postnatal development and in adulthood.
- Examination of specific OSN populations (mI7, P2, M72) with distinct lactosamine expression patterns.
Main Results:
- Loss of beta3GnT1 and subsequent lactosamine expression resulted in differential effects on OSN axon targeting.
- OSN populations that normally express lactosamine (weakly 1B2+) failed to reach their correct positions in the OB and degenerated.
- OSN populations that are normally lactosamine-negative (M72 axons) survived but exhibited aberrant targeting to anterior regions of the OB, forming malformed glomeruli.
Conclusions:
- Lactosamine expression, regulated by beta3GnT1, plays a critical role in the precise targeting and stabilization of specific OSN axon populations within the olfactory bulb.
- The absence of lactosamine leads to the failure of connection formation for lactosamine-expressing OSNs and misrouting of lactosamine-negative OSNs.
- These findings highlight the differential requirement of lactosamine for the proper development of distinct OSN projection pathways in the OB.
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