Cloning, characterisation and expression of the alpha-tubulin genes of theleech, Hirudo medicinalis

We have isolated two alpha-tubulin cDNAs from the leech, Hirudo medicinalis . Both encode putative proteins of 451 amino-acids which differ from each o ther at only two positions. Southern blotting suggests that there are only two alpha-tubulin genes in the leech. The genes contain two introns and, be cause of the extremely high homology of the nucleotide sequence from the se cond intron to the end of the genes, we have inferred that a gene conversio n event about 9.5 million years ago has homogenised the Hirudo alpha-tubuli n sequences. Using in situ hybridisation to tissue sections, we have shown that the two genes are probably expressed in all neurons of the leech gangl ia and that their spatial distribution remains unchanged during neuronal re generation. The deduced amino-acid sequences of the leech alpha-tubulins sh ow that they have greatest Similarity to those from a platyhelminth, echiur an and mollusc with rather less to arthropod alpha-tubulins. The protein se quences of the leech alpha-tubulins have been compared with representatives of those from across all phyla to determine if any specific feature labels certain isotypes of tubulin for neuronal expression. (C) 1999 Elsevier Sci ence B.V. All rights reserved.