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Identification of Munc13-3 as a candidate gene for critical-period neuroplasticity in visual cortex
Cui Bo Yang1, Yu Ting Zheng, Guang Yu Li
1Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
Insights
Munc13-3 gene expression in the visual cortex changes with age and dark rearing, mirroring critical period plasticity in cats. This finding identifies Munc13-3 as a key gene for visual cortex development.
Area of Science:
- Neuroscience
- Molecular Biology
- Developmental Biology
Background:
- Early life visual experience is crucial for visual cortex development and neuronal plasticity.
- The critical period for visual cortex plasticity has a defined timeline that can be altered by environmental factors like dark rearing.
Purpose of the Study:
- To identify genes involved in the critical period of visual cortex neuronal plasticity.
- To find genes whose expression patterns correlate with age- and rearing-dependent plasticity changes.
Main Methods:
- Differential display PCR was used to identify candidate genes.
- Gene expression analysis was performed on visual and frontal cortex samples from cats under normal and dark-rearing conditions at different ages.
Main Results:
- Munc13-3, a homolog of C. elegans unc-13, was identified as a candidate gene.
- Munc13-3 expression in the visual cortex showed opposite directional changes in young versus older animals reared in darkness, matching plasticity patterns.
- Munc13-1 and Munc13-2 did not meet this criterion.
Conclusions:
- Munc13-3 is specifically regulated in the visual cortex during the critical period in response to visual experience and age.
- Munc13-3 is a strong candidate gene for mediating neuronal plasticity during the visual cortical critical period.
Abstract:
The first several months of life are a critical period for neuronal plasticity in the visual cortex during which anatomic and physiological development depends on visual experience. In cats, electrophysiologically assessed neuronal plasticity is minimal until approximately 3 weeks, peaks at 5 weeks, gradually declines to low levels at 20 weeks, and disappears at approximately 1 year of age (Daw, 1994). Rearing in darkness slows the entire time course of this critical period, such that at 5 weeks of age, normal cats are more plastic than dark-reared cats, whereas at 20 weeks, dark-reared cats are more plastic (Mower, 1991; Beaver et al., 2001). Thus, a stringent criterion is that genes that are important for plasticity in visual cortex will show differences in expression between normal rearing and dark rearing that are of opposite direction in young versus older animals. The present study reports the identification by differential display PCR of Munc13-3, a mammalian homolog of the Caenorhabditis elegans "uncoordinated" gene (unc-13), as a candidate gene for critical-period neuronal plasticity, the expression of which is regulated according to this criterion specifically in visual cortex and not in frontal cortex. Other members of the Munc13 family (Munc13-1 and Munc13-2) do not meet this criterion in visual cortex, indicating that Munc13-3 is the only family member that is regulated by age and dark rearing in the same manner as physiological plasticity during the visual cortical critical period.