Transcription and site-specific hypomethylation of the delta-crystallin genes in the embryonic chicken lens.

Abstract

Chicken delta-crystallin has at least two similar genes containing multiple intervening sequences. Hybridization experiments utilizing DNA probes derived from intervening sequences contained within cloned delta-crystallin gene fragments indicated that both of these two delta-crystallin genes are transcribed in the embryonic lens. No evidence for transcription of these genes was found in nuclei prepared from decapitated chicken embryos. Comparison of restriction enzyme digests of genomic DNA prepared from lens and non-lens tissues showed that the delta-crystallin gene sequences are not grossly rearranged in the lens during development. Msp I and Hpa II digests revealed that there are at lest three -CCGG- sites in the delta-crystallin genes that are hypomethylated in the embryonic lens DNA but are hypermethylated in sperm, red blood cell, or headless embryo DNAs. The delta-crystallin genes were not transcribed and these three sites were methylated in embryonic lens epithelial cells that were transformed with a temperature-sensitive Rous sarcoma virus. These results associate delta-crystallin gene transcription and site-specific hypomethylation of the delta-crystallin DNA.