Isolation and chromosomal localization of ZFX homologue in genome of rice field eel (Monopterus albus Zuiew).

When used as a probe in rice field eel (Monopterus albus Zuiew) genomic Southern blotting hybridization, the giant panda Zfx gene hybridized strongly to a fragment of about 9.5 kb. A 512 bp long DNA fragment has been isolated by polymerase chain reaction from rice field eel genomic DNA using the primers for amplifying zinc finger repeats 7 to 13 of mammalian and reptilian ZFX-related genes. Cloned in pBS, four recombinant plasmids were selected randomly from male and female specimens and sequenced. The nucleotide sequences in these clones were identical and showed 88% and 87% identity to human ZFX and ZFY respectively. But its extent of homology was greater with American alligator Zfc (90%). And the amino acid sequences of the putative protein showed 95.9%, 95.9% and 93.5% identity to human ZFX and ZFY and American alligator Zfc respectively. Thus, the cloned sequence encodes a homologue of mammalian ZFX/ZFY and was named Zfa for rice field eel zinc finger domain gene. It appears that the mammalian and reptilian ZFX-related genes evolved from fish ancestors with a considerable degree of conservation. By fluorescence in situ hybridization, the Zfa has been mapped to rice field eel chromosome 1 and at the position of 60.1 +/- 0.38 from the centromere. Chromosomal mapping of fish genes related to mammalian X-linked genes might lead to further understanding of the evolution of vertebrate sex chromosomes.