Synuclein Analysis in Adult Xenopus laevis

The alpha-, beta- and gamma-synucleins are small soluble proteins expressed in the nervous system of mammals and evolutionary conserved in vertebrates. After being discovered in the cartilaginous fish Torpedo californica, synucleins have been sequenced in all vertebrates, showing differences in the number of genes and splicing isoforms in different taxa. Although alpha-, beta- and gamma-synucleins share high homology in the N-terminal sequence, suggesting their evolution from a common ancestor, the three isoforms also differ in molecular characteristics, expression levels and tissue distribution. Moreover, their functions have yet to be fully understood. Great scientific interest on synucleins mainly derives from the involvement of alpha-synuclein in human neurodegenerative diseases, collectively named synucleinopathies, which involve the accumulation of amyloidogenic alpha-synuclein inclusions in neurons and glia cells. Studies on synucleinopathies can take advantage of the development of new vertebrate models other than mammals. Moreover, synuclein expression in non-mammalian vertebrates contribute to clarify the physiological role of these proteins in the evolutionary perspective. In this paper, gene expression levels of alpha-, beta- and gamma-synucleins have been analysed in the main organs of adult Xenopus laevis by qRT-PCR. Moreover, recombinant alpha-, beta- and gamma-synucleins were produced to test the specificity of commercial antibodies against alpha-synuclein used in Western blot and immunohistochemistry. Finally, the secondary structure of Xenopus synucleins was evaluated by circular dichroism analysis. Results indicate Xenopus as a good model for studying synucleinopathies, and provide a useful background for future studies on synuclein functions and their evolution in vertebrates.