Unmasking Proteolytic Activity for Adult Visual Cortex Plasticity by the Removal of Lynx1.



Experience-dependent cortical plasticity declines with age. At the molecular level, experience-dependent proteolytic activity of tissue plasminogen activator (tPA) becomes restricted in the adult brain if mice are raised in standard cages. Understanding the mechanism for the loss of permissive proteolytic activity is therefore a key link for improving function in adult brains. Using the mouse primary visual cortex (V1) as a model, we demonstrate that tPA activity in V1 can be unmasked following 4 d of monocular deprivation when the mice older than 2 months are raised in standard cages by the genetic removal of Lynx1, a negative regulator of adult plasticity. This was also associated with the reduction of stubby and thin spine density and enhancement of ocular dominance shift in adult V1 of Lynx1 knock-out (KO) mice. These structural and functional changes were tPA-dependent because genetic removal of tPA in Lynx1 KO mice can block the monocular deprivation-dependent reduction of dendritic spine density, whereas both genetic and adult specific inhibition of tPA activity can ablate the ocular dominance shift in Lynx1 KO mice. Our work demonstrates that the adult brain has an intrinsic potential for experience-dependent elevation of proteolytic activity to express juvenile-like structural and functional changes but is effectively limited by Lynx1 if mice are raised in standard cages. Insights into the Lynx1-tPA plasticity mechanism may provide novel therapeutic targets for adult brain disorders.

Significance statement

Experience-dependent proteolytic activity of tissue plasminogen activator (tPA) becomes restricted in the adult brain in correlation with the decline in cortical plasticity when mice are raised in standard cages. We demonstrated that removal of Lynx1, one of negative regulators of plasticity, unmasks experience-dependent tPA elevation in visual cortex of adult mice reared in standard cages. This proteolytic elevation facilitated dendritic spine reduction and ocular dominance plasticity in adult visual cortex. This is the first demonstration of adult brain to retain the intrinsic capacity to elevate tPA in an experience-dependent manner but is effectively limited by Lynx1. tPA-Lynx1 may potentially be a new candidate mechanism for interventions that were shown to activate plasticity in adult brain.





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Publication Info

Bukhari, Noreen, Poromendro N Burman, Ayan Hussein, Michael P Demars, Masato Sadahiro, Daniel M Brady, Stella E Tsirka, Scott J Russo, et al. (2015). Unmasking Proteolytic Activity for Adult Visual Cortex Plasticity by the Removal of Lynx1. The Journal of neuroscience : the official journal of the Society for Neuroscience, 35(37). pp. 12693–12702. 10.1523/jneurosci.4315-14.2015 Retrieved from https://hdl.handle.net/10161/22507.

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Noreen Bukhari-Parlakturk

Assistant Professor of Neurology

I have a long standing interest in developing disease-modifying therapies for movement disorders, a major unmet clinical need. I work at the interface of neuroscience and neurology to apply mechanistic understanding of neurological disease to develop targeted neuromodulatory therapies and in the process further disease mechanisms and medical therapy.

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