DNA endoreplication in the clustered supramedullary neurons of the pufferfish Diodon holacanthus L. (Osteichthyes)

DNA contents, ranging from 4C to more than 500C, were determined by a quantitative microfluorimetric assay in supramedullary neuron nuclei of the pufferfish Diodon holacanthus. The distribution of C values after ethidium bromide staining indicates an inter- and intra-individual variation in DNA contents which do not correspond to duplications of the total genome, suggesting that DNA replication is specific for particular genes (endoreplication). Moreover, the DNA content appears to be correlated with nuclear size. A relationship between the DNA amounts and the presence of AT- and GC-rich sequences has been shown. This work demonstrates, for the first time, DNA endoreplication in a specific neuronal type in vertebrates.