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Matrix metalloproteinase 9, MMP-9 is an extracellularly operating enzyme that has been demonstrated as an important regulatory molecule in control of synaptic plasticity, learning and memory. Either genetic or pharmacological inhibition of MMP-9 impairs late phase of long-term potentiation at various pathways, as well as appetitive and spatial memory formation, although aversive learning remains apparently intact in MMP-9 KO mice. MMP-9 is locally translated and released from the excitatory synapses in response to neuronal activity. Extrasynaptic MMP-9 is required for growth and maturation of the dendritic spines to accumulate and immobilize AMPA receptors, making the excitatory synapses more efficacious. Animal studies have implicated MMP-9 in such neuropsychiatric conditions, as e.g., epileptogenesis, autism spectrum disorders, development of addiction, and depression. In humans, MMP-9 appears to contribute to epilepsy, alcohol addiction, Fragile X Syndrome, schizophrenia and bipolar disorder. In aggregate, all those conditions may be considered as relying on alterations of dendritic spines/excitatory synapses and thus understanding the role played by MMP-9 in the synaptic plasticity may allow to elucidate the underpinnings of major neuropsychiatric disorders.

This review focuses on general optogenetics issues (in particular the choice of the necessary light exposure settings), as well as certain promising areas of research with optogenetics.

Maintenance of genome stability in the face of DNA damage is essential for cellular homeostasis and prevention of cancer and brain degeneration. The DNA damage response (DDR) is a complex response that is rapidly activated when a DNA lesion occurs in chromosomal DNA. Mutations affecting the proteins involved in the DDR can lead to genomic instability syndromes that involve tissue degeneration, cancer predisposition, premature aging, and brain mal-development and degeneration. Mutation of the kinase ATM leads to a prototype genomic instability syndrome, ataxia-telangiectasia (A-T). A-T is characterized by progressive cerebellar degeneration, immunodeficiency, genome instability, premature aging, gonadal dysgenesis, extreme radiosensitivity, and high incidence of lymphoreticular malignancies. One of the most devastating symptoms of A-T — cerebellar ataxia — develops progressively into general motor dysfunction. Based on our previous studies we hypothesized that the neurological deficits in genomic instability disorders stem (at least in part) from significant reduction in functionality of glial cells. We further hypothesized that impaired vascularization affects the environment in which the neurons and glial cells function, thereby reducing neuronal cell functionality. We found that ATM deficiency led to aberrant astrocytic morphology and alterations of vasculature both in cerebellum and the visual system. Moreover, we found reduced myelin basic protein immunoreactivity and signs of inflammation in ATM-deficient cerebella and optic nerve.  Interestingly, similar findings have been reported in patients with other genomic instability disorders. These observations bolster the notion that astrocyte-specific pathologies and hampered vascularization and astrocyte-neuron interactions in the CNS play crucial roles in the etiology of genome instability brain disorders and underlie brain degeneration at specific sites.