Distribution of erythroid spectrin (α, β) immunoreactivity in the human retina

Abstract

Spectrin ( and ) is a tetrameric, key membrane skeletal protein initially reported to be present in erythrocytes. It is also present in other cells, neurones and the retina. This study reports immunoreactivity (IR) to erythroid spectrin in human retina at different ages (56-91 years), as examined by immunohistochemistry and immuno-electron microscopy (IEM). Spectrin IR was localised moderately in ganglion cell layer, inner- and outer plexiform layers and predominantly in photoreceptor inner segments and macular fibres of Henle. As the latter are interleaved by outer processes of Müller cells, IEM was used to see which cellular processes contained spectrin. IEM revealed that gold particles were associated with microtubules of cone inner segments and in fibres of Henle, but were absent in Müller cell processes, supporting immunohistochemical data on the absence of IR in Müller cells (stained with vimentin antibody). In fibres of Henle, a steady expression of spectrin was seen until eighth decade, and then a decreased expression beyond ninth decade, which paralleled with degenerative microtubule changes (seen by transmission electron microscopy) in them. These changes could be responsible for agerelated down-regulation of spectrin expression in fibres of Henle. It is likely that one specific role of spectrin in the human retina could be maintenance of the macular fibres of Henle. Its reduction with age may cause alterations in cone membrane, which may be responsible for their vulnerability in ageing.