Differential expression of the methyl-cytosine binding protein 2 gene in embryonic and adult brain of zebrafish.

Epigenetic gene repression occurs as the result of the interactions between DNA and a number of proteins, including methyl-cytosine binding protein 2 (MeCP2). We have isolated a 1680 bps MeCP2 cDNA from zebrafish that shows deduced amino acid identity with Xenopus and mammalian MeCP2alpha protein sequences. The zebrafish MeCP2 gene was mapped to linkage group 8 using the LN54 radiation hybrid cell panel. The genomic organizations of the zebrafish MeCP2 and mammalian MeCP2alpha are highly similar. Relatively high levels of expression of MeCP2 mRNA were found in embryos at 1 to 4 h postfertilization (hpf), after 24 hpf, and in adult brain and eyes. Whole mount in situ hybridization was performed on embryos and revealed ubiquitous MeCP2 expression during early zebrafish development. At 24 and 48 hpf, the highest levels of expression are found in the epiphysis, midbrain, ventricular zone, and the otic vesicles. In adult zebrafish, MeCP2-expressing cells were found throughout the brain. Regions that are enriched in MeCP2 mRNA include the pallium layer of the telencephalon, the preoptic area, the periventricular grey zone, lobus caudalis, and the vagus lobes. In the cerebellum, high expression is found in the Purkinje and Golgi type 2 cells.