IMPRINTING ANALYSIS OF 3 GENES IN THE PRADER-WILLI/ANGELMAN REGION - SNRPN, E6-ASSOCIATED PROTEIN, AND PAR-2 (D15S225E)

order to identify genes in the Prader - Willi/Angelman syndrome critical region, radiolabeled cDNA probes from poly(A)(+) RNA from mouse tissues were used to identify potential exon-containing genomic DNA fragments in cosmid or phage clones from appropriate yeast artificial chromosomes, and these fragments were subsequently used to screen human cDNA libraries. A mouse brain cDNA probe was effective in detecting control genes of various abundance including small nuclear ribonucleoprotein polypeptide N (SNRPN), hypoxanthine-guanine phosphoribosyl transferase, glyceraldehyde-3-phosphate dehydrogenase, and beta-actin. Two genes mapping within the Angelman syndrome critical region were isolated. One gene was found to encode the E6-associated protein (E6-AP; gene symbol HPVE6A), a protein which interacts with the E6 protein of human papilloma virus. The other gene is previously uncharacterized and is designated PAR-2 (D15S225E) for Prader-Willi and Angelman region-gene 2. Imprinting analysis using reverse transcription-polymerase chain reaction of RNA from fibroblasts and lymphoblasts of deletion Prader-Willi and Angelman patients demonstrated imprinting of SNRPN with exclusive expression from the paternal allele, but E6-AP and PAR-2 were not imprinted in these cultured human cells. The ability to analyze for imprinting and expression of SNRPN and other genes in this region in cultured human cells will be a valuable tool for analyzing the molecular basis of the Prader - Willi and Angelman syndromes, although imprinting may differ between cultured cells and tissues. Based on the biological information for EG-AP and on the imprinting analysis of E6-AP and PAR-2, neither of these genes are strong candidates to be the Angelman gene, but neither can be eliminated as possibilities with the available data.