Fiber FISH reveals different patterns of high-resolution physical mapping for repetitive DNA in fish

Fiber fluorescence in situ hybridization (fiber-FISH) has improved physical gene mapping very much since it allows ascertaining the relative position of two or more genes or repetitive DNA sequences. But this technique has never been employed in fish. Here we show that the standard fiber-FISH protocol can be employed on normally fixed cells stocked in many laboratories. We analyze here possible outcomes of this technique in three species of fish from two different orders. In every case, we performed double fiber-FISH for two different repetitive DNAs and observed three different patterns depending on whether the two probes were at independent (separately in interphase nuclei and on two different pairs of chromosomes), adjacent or interspersed locations. This high-resolution method can thus be employed on the same cell suspensions routinely used for chromosome analysis, and this can be an excellent complementary resource for compositional, structural and functional analysis of DNA sequences in the genomes of fish and other aquatic organisms.

► Our standard fiber-FISH protocol can be employed on fixed cells stocked in many laboratories.
► We performed double fiber-FISH in species of fish from different orders.
► Fiber-FISH is a resource for compositional, structural and functional analysis of fish DNA.