MOUSE U2AF1-RS1 IS A NEOMORPHIC IMPRINTED GENE

The mouse U2af1-rs1 gene is an endogenous imprinted gene on the proxim al region of chromosome 11. This gene is transcribed exclusively from the unmethylated paternal allele, while the methylated maternal allele is silent. An analysis of genome structure of this gene revealed that the whole gene is located in an intron of the Murr1 gene. Although no ne of the three human U2af1-related genes have been mapped to chromoso me 2, the human homolog of Murr1 is assigned to chromosome 2. The mous e Murr1 gene is transcribed biallelically, and therefore it is not imp rinted in neonatal mice. Allele-specific methylation is limited to a r egion around U2af1-rs1 in an intron of Murr1. These results suggest th at in chromosomal homology and genomic imprinting, the Maf1-rs1 gene i s distinct from the genome region surrounding it. We have proposed the neomorphic origin of the U2af1-rs1 gene by retrotransposition and the particular mechanism of genomic imprinting of ectopic genes.