Global methylation in eutherian hybrids

• Published in: Nature (London) Vol. 401; no. 6749; pp. 131 - 132
• Main Authors: ROEMER, I, GRÜTZNER, F, GRAVES, J. A. M, WINKING, H, HAAF, T, ORTH, A, SKIDMORE, L, ANTCZAK, D, FUNDELE, R, O'NEILL, R. J. W, O'NEILL, M. J
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 09.09.1999
• Subjects: Biological and medical sciences; Biological evolution; Camelidae; Equidae; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Macropus bicolor; Macropus eugenii; Muridae; Petrogales; Vertebrata; Mammalia; Biological evolution; Interspecific hybridization; Rodentia; Chromosome DNA; Artiodactyla; Genome; Methylation; Ungulata; Speciation
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/43607

O'Neill et al. propose that epigenetic processes help to drive karyotypic evolution in marsupials. Here we present evidence that global methylation patterns do not undergo dramatic changes in interspecific hybrids among three orders of placental mammals, indicating that the mechanisms underlying genome evolution may be different in placental mammals and marsupials. Interspecific hybridization in mammals, frequently results in male sterility, abnormal growth and placental dysplasia, which together may cause post-meiotic reproductive isolation. It has been proposed that incompatibility between rapidly evolving genes that interact normally in the intraspecific context and genomic rearrangements may explain interspecific hybrid defects. O'Neill et al. have given a striking example for the latter mechanism in an interspecific hybrid of the marsupials Macropus eugenii and M. bicolor. This first-generation (F sub(1)) hybrid exhibited genome-wide demethylation, retrotransposon amplification and centromere expansion on the autosomes derived from M. eugenii. Undermethylation of F sub(1) genomes compared with those of the parental species was also seen in two hybrids of other species within the genus Petrogale. These findings were taken to indicate that retrotransposon amplification and chromosome expansion secondary to genome-wide undermethylation could be a frequent phenomenon in mammalian hybrids, leading to rapid karyotipic evolution and finally to reproductive isolation. We have analyzed genome-wide methylation in interspecific hybrids ni the placental mammalian families of three orders, Equidae (Perissodactyla), Muridae (Rodentia) and Camelidae (Artiodactyla), by following the digestion of genomic DNA with the methylation-sensitive and methylation-insensitive enzymes HpaII and MspI, respectively, and Southern blotting the digest. This analysis included hybrids between horse and donkey, three species of mouse (Mus musculus, Mus spretus and Mus macedonicus), and llama (Lama glama) and dromedary (Camelus dromedarius).