ALLELE-SPECIFIC METHYLATION AND EXPRESSION OF AN IMPRINTED U2AF1-RS1 (SP2) GENE

The mouse U2af1-rs1(SP2) gene, which was cloned by a two-dimensional g enome scanning method, is expressed exclusively from the paternally in herited chromosome. This gene has significant similarity to U2AF and l ocated in chromosome 11, of which maternal duplication/paternal defici ency results in a small body. In this report, we cloned genomic U2af1- rs1(SP2)and found its promoter was methylated in a maternal-allele-spe cific manner. This allelic methylation was not established in parental gametes, but established between 1.5 d.p.c. and 12.5 d.p.c. on the co ntrary, the allele-specific expression occurred in the two-cell stage when transcription initiates. Absence of the methylation of the upstre am region in this stage indicates that methylation is not necessary fo r inactivation of the expression.