Molecular cytogenetic analysis of the highly repetitive DNA in the genome of Apodemus argenteus, with comments on the phylogenetic relationships in the genus Apodemus

The DNA of Apodemus argenteus was digested with DraI, and the resultant Dra I fragment of highly repetitive DNA was isolated and analyzed by DNA filter hybridization, cloning, sequencing, and fluorescence in situ hybridization (FISH). Southern blot hybridization and nucleotide sequencing revealed tha t most of the DraI fragment consisted of a 230-bp repeating unit and contai ned no sex-chromosome-specific nucleotide sequences. The DraI fragment incl uded the CENP-B box-like sequence, with a strong homology to the human CENP -B box sequence. FISH revealed that the DraI fragment was specific to all p ericentromeric C-band-positive regions, as well as to the C-block of the X chromosome. No hybridization signals were obtained from A. speciosus, A. pe ninsulae peninsulae, A.p. giliacus, A. agrarius, A. sylvaticus, A. semotus. or Mus musculus when the DraI fragment was used as probe. Peptide nucleic acid (PNA)-FISH using the CENP-B box-like sequence in the DraI fragments as probe suggested that this nucleotide sequence was also specific to all per icentromeric C-heterochromatic regions of A. argenteus chromosomes. Zoo-blo t hybridization using DraI-digested genomic DNA from three species of Apode mus (namely, A. argenteus, A. speciosus, and A. peninsulae) and from Mus mu sculus strongly suggested that the consensus DraI fragment contained nucleo tide sequences that were species-specific for A. argenteus. These results a lso suggest that A. argenteus is phylogenetically distant from other Apodem us species examined, as well as the possibility that the DraI fragment migh t be related directly to the delayed quinacrine mustard fluorescence of man y pericentromeric C-heterochromatic regions of the chromosomes in A. argent eus. Copyright (C) 2001 S. Karger AG, Basel.