Retinal fascin: functional nature, subcellular distribution, and chromosomal localization

To investigate the functional properties, subcellular localization, and chromosomal location of retinal fascin.

Recombinant retinal fascin protein was prepared by using a baculovirus-insect expression system. Actin-binding and -bundling assays were performed with chick actin purified from skeletal muscle. Western blot analysis and immunohistochemistry were performed with a polyclonal antibody raised against bovine retinal fascin. A human retinal cDNA library was screened with an expressed sequence tag cDNA fragment. Chromosomal location was determined with fluorescent in situ hybridization.

The actin-binding and actin-bundling activities of retinal fascin were demonstrated by high- and low-speed centrifugation assays. Formation of filamentous (F)-actin bundles by retinal fascin in vitro was also morphologically confirmed by fluorescence microscopy and electron microscopy. Immunohistochemical analysis revealed that retinal fascin protein was localized specifically in the outer and inner segments of the photoreceptor cells in the retina. Two splicing variants of human retinal fascin cDNA were also located. One clone encoded 492 amino acids, and the other encoded 516 amino acids. The gene encoding retinal fascin was localized to human chromosome 17, region q24 -25.

These results suggest that retinal fascin may play a role in formation of unique morphologic structures of the photoreceptor cells and is a candidate gene for retinal degenerative disorders.