Fugu rubripes and human survival motor neuron genes: structural and functional similarities in comparative genome studies.

The compactness of the Fugu rubripes (Fugu) genome has supported its use in comparative genome analysis. Nevertheless, as Fugu is distinct evolution-wise from humans, it is essential to determine the similarity between a Fugu gene and its human counterpart to confirm its potential for comparative genome analysis. We cloned and analyzed the Fugu survival motor neuron gene (fsmn) for similarities with human SMN gene (huSMN). The Fugu genome has a single fsmn that is 13.4 times smaller than huSMN. fsmn and huSMN are highly similar in their genome organization and tissue expression patterns. The functional domains of the Fugu smn and human SMN molecules are also highly conserved. In human MCF-7 cells, expression of fsmn protein resulted in the formation of "gems" in the cytoplasm and nucleus, similar to observations reported for huSMN protein. In these cells, fsmn RNA was also processed correctly and produced alternatively spliced transcripts like huSMN2. These findings indicate close structural and functional similarities between fsmn and huSMN, suggesting that regulation of the two genes may also be similar and supporting the use of fsmn in comparative genome studies for the identification of functional regulatory elements of huSMN.