Analysis of the spermine synthase gene region in Fugu rubripes, Tetraodon fluviatilis, and Danio rerio

A prerequisite to understanding the evolution of the human X chromosome is the analysis of synteny of X-linked genes in different species. We have foc used on the spermine synthase gene in human Xp22.1. We show that whereas th e human gene spans a genomic region of 54 kb, the Fugu rubripes gene is enc ompassed in a 4.7-kb region. However, we could not find conserved synteny b etween this region of human Xp22 and the equivalent F. rubripes region. A c osmid clone containing the F. rubripes gene does not contain other X-linked genes. Instead we identified homologs of human genes that are autosomally localized: the ryanodine receptor type I (RYRI), which is implicated in mal ignant hyperthermia and central core disease, and the HE6 gene. Comparison of the F. rubripes, Tetraodon fluviatilis, mouse, human, and Danio rerio 5' UTRs of spermine synthase highlights conserved sequences potentially involv ed in regulation. Interestingly, pseudogenes of this gene that are present in the human and mouse genomes seem to be absent in the compact F. rubripes genome. Analysis of a D. rerio PAC clone containing spermine synthase show s an intermediate genomic size in this fish. Sequence analysis of this PAC clone did not reveal other known genes: neither the RYRI gene, nor the HE6 gene, nor other human Xp22 genes were identified. (C) 1999 Academic Press.