neuroEYEscience

In the last decades, the post-transcriptional control of gene expression has become an area of intense investigation, delineating a complex scenario where several factors (e.g. RNA-binding proteins, coding and non-coding RNAs) orchestrate the fate of a given transcript. An intriguing hypothesis suggests that loss of RNA homeostasis is a central feature of many pathological states, including eye diseases. Since the elav (embryonic lethal, abnormal visual system) gene discovery in the Drosophila melanogaster, the mammalian ELAV-like family has confirmed its leading role in controlling the RNA metabolism (from splicing to translation) of genes with a key function in many physio-pathological contexts. Some relevant findings suggest the involvement of the HuR/ELAV-like1 member and its potential as a therapeutic target in age-related ocular pathologies.

The seminar will present the origin of the hypothesis of electrical coupling between proximal axons, physiological and immunostaining evidence for the presence of the requisite gap junctions and will explain how electrical coupling could account for very fast network oscillations at >80 hz.

Axons in the optic nerve are arranged in bundles and conducting action potential with resistance related to their membrane. Optic nerve axons do not form absolutely independent conductive channels. They are directly coupled by gap junctions formed in majority by neuronal Cx45. Coupling of axons, except known transpassing functions, allows to reduce axonal membrane resistance of optic nerve and accelerates transduction of visual signal. This novel finding have substantial implications for understanding of the pathogenesis of various optic neuropathies and identifies a new potential target for a therapeutic approach.

Electrophysiology of eye and visual pathway is useful tool in ophthalmology and neurology. It covers a few examinations to find out if defect of vision is peripheral or central. Visual evoked potentials (VEP) are most frequently used in neurology and neuroophthalmology. VEP are evoked by flash or pattern stimulations. The combination of these both examinations gives more information about the visual pathway. It is very important to remember that VEP originate in the retina and reflect its function as well. In many cases not only VEP but also electroretinography (ERG) is essential for diagnosis. The seminar presents basic electrophysiological procedures used for diagnosis and follow-up of optic neuropathies and some of central nervous system diseases which affect vision (mostly multiple sclerosis, CNS tumors, stroke, traumas, intracranial hypertension).