Parental 5-methylcytosine methylation patterns are stable upon inter-species hybridization of Xiphophorus (Teleostei: Poeciliidae) fish.

Cytosine methylation appears to be established as an important DNA base modification involved in regulation of gene expression but is poorly understood from an evolutionary viewpoint. Xiphophorus progeny from inter-species crosses and backcrosses that are utilized in contemporary tumor induction studies were analyzed for cytosine methylation pattern inheritance using Southern blot analyses. Methylation patterns at CCGG sequences of 411 independent chromosomes in three distinct inter-species crosses were analyzed. In every case the non-recurrent parental methylation pattern remained unaltered for each of the genes studied, once introduced into the recurrent parental genetic background. Through F(1) inter-species hybridization and succeeding meiosises leading to first generation (BC(1)) and second generation (BC(2)) backcross hybrid progeny, we demonstrate that parental species methylation patterns are stable.