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Robert Gabriel Tripon, Tajwar Nasir, Lajos Csincsik, Judit Olah, Judit Ovadi, Imre Lengyel; Immunolocalisation of Tubulin Polymerisation Promoter Protein TPPP/p25 in the retina. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):193.
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© ARVO (1962-2015); The Authors (2016-present)
Tubulin Polymerization Promoting Protein (TPPP/p25), a brain-specific intrinsically unstructured protein, is a key player in the differentiation of oligodendrocytes; it induces aberrant microtubule assemblies in vitro, suppresses mitosis and accumulates in inclusion bodies of human pathological brain tissues. In this work we screen the expression of this protein in different regions of mice and human eyes by immunofluorescent confocal microscopy.<br />
Paraffin embedded sections from human and mice eyes of different ages were obtained from UCL Institute of Ophthalmology with Institutional Ethics Committee approval. Immunohistochemistry was performed using highly specific monoclonal or polyclonal TPPP/p25 antibodies on paraformaldehyde fixed samples. Co-labelling of the samples was carried out using acetylated-tubulin specific antibodies. The TPPP/p25 and acetylated-tubulin labelling were visualized by confocal microscopy using fluorescently labelled secondary antibodies.
TPPP/p25 immunoreactivity was strongly associated with the myelinated optic nerve distal to the lamina cribrosa in both human and mouse. No labelling was detected in the sclera, choroid or retinal pigment epithelium. In the neurosensory retina TPPP/p25 was detected only in the inner plexiform layer (IPL) as punctate labelling and in selected cell bodies in the inner nuclear layer (INL). The distribution in the IPL was striated, associated with the S1, S3 and S5 sub-laminas. Immunoreactivity in flat-mount retina showed that less than 10% of cell bodies of the innermost cells in the INL were labelled with TPPP/p25 antibodies. Occasionally immunoreactivity could be seen in the outer plexiform layer (OPL) in human but not in mice. Double-labelling with TPPP/p25 and acetylated-tubulin specific antibodies showed co-localisation.
This is the first demonstration that TPPP/p25 is present in the retina of both human and mice. The immunoreactivity is exclusively associated with a few cell bodies and structures that look like dendritic spines in the S1, S3 and S5 sub-lamina of the IPL, with occasional immunoreactivity in the OPL. Based on these results we propose that TPPP/p25 is associated with a subclass of amacrine cells probably with interplexyform projections, and could be involved in the organization and reorganization of synaptic connections and visual integration.
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