MAPPING OF REPETITIVE AND NONREPETITIVE DNA PROBES TO CHROMOSOMES OF THE MICROSPORIDIAN ENCEPHALITOZOON-CUNICULI

The molecular karyotype of a murine isolate of Encephalitozoon cunicul i, a microsporidian with a wide range of mammalian hosts, comprises el even chromosomes ranging in size between 217 and 315 kb. To determine specific chromosomal markers, a partial genomic library was constructe d and cloned DNA fragments were hybridized to chromosomal bands separa ted by pulsed-field gel electrophoresis. Most probes were assigned to single chromosomes, indicating prevalence of low-copy number nucleotid e sequences within the very small genome of E. cuniculi (2.9 Mb). A fe w probes were shown to hybridize to all chromosomes. These repetitive DNA fragments corresponded to either rRNA genes or some non-coding reg ions whose sequences were characterized by short micro- and minisatell ites. The chromosomal locations of beta-tubulin genes and six newly id entified protein-encoding genes were determined. Genes encoding dihydr ofolate reductase, thymidylate synthase, serine hydroxymethyl transfer ase, a cdc2 kinaselike protein and helicase ERCC6-like protein were ea ch located on a single chromosome whereas genes for both beta-tubulin and aminopeptidase were on two different chromosomes. The mapping will serve as a reference for further analysis of intraspecific karyotype polymorphism in different isolates from different host species. (C) 19 97 Elsevier Science B.V.