de la Puente Aránzazu, Hall Julia, Wu Yue-Zhong, Leone Gustavo, Peters Jo, Yoon Bong-June, Soloway Paul, Plass Christoph
Division of Human Cancer Genetics, Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, 420 West 12th Avenue, Columbus, OH 43210, USA.
Gene. 2002 May 29;291(1-2):287-97. doi: 10.1016/s0378-1119(02)00601-7.
Imprinted genes in mammals are expressed either from the maternally or the paternally inherited allele. Previously, a genome wide scan identified novel imprinted genes based on their association with differentially methylated regions (DMRs). One of the identified genes, Rasgrf1, showed paternal expression in neonatal brain and was located on mouse chromosome 9. This gene is associated with a DMR, located about 30 kb upstream of Rasgrf1 exon 1. In order to better understand and identify novel elements involved in the regulation of this gene we have isolated and characterized genomic clones coding for mouse and human Rasgrf1 and RASGRF1, respectively. The mouse gene consists of 26 exons spanning approximately 140 kb of genomic DNA while the human gene has 28 exons. The human gene has an additional 39 bp exon inserted between exons 13 and 14 and exon 18 is split in two separate exons in human. The major transcription start site of Rasgrf1, as identified by primer extension, is 1324 bp upstream of the ATG translation start codon. Finally, a genomic region upstream of exon 1, spanning 489 bp, was determined to possess the essential promoter activity for Rasgrf1 gene. A second gene, A19, located 10 kb upstream of the DMR has been characterized. A19 is mainly expressed in testis and at lower levels in neonatal and adult brain tissue. The A19 transcript is non-coding and expressed in mouse testis and brain. A19 is imprinted with expression occurring from just the paternal allele in brain.
哺乳动物中的印记基因要么从母本遗传的等位基因表达，要么从父本遗传的等位基因表达。此前，一项全基因组扫描基于与差异甲基化区域（DMRs）的关联鉴定出了新的印记基因。其中一个被鉴定出的基因Rasgrf1在新生小鼠大脑中呈父本表达，位于小鼠9号染色体上。该基因与一个DMR相关，该DMR位于Rasgrf1外显子1上游约30 kb处。为了更好地理解和鉴定参与该基因调控的新元件，我们分别分离并鉴定了编码小鼠和人类Rasgrf1以及RASGRF1的基因组克隆。小鼠基因由26个外显子组成，跨越约140 kb的基因组DNA，而人类基因有28个外显子。人类基因在第13和14外显子之间额外插入了一个39 bp的外显子，并且在人类中第18外显子被分成了两个独立的外显子。通过引物延伸鉴定出，Rasgrf1的主要转录起始位点位于ATG翻译起始密码子上游1324 bp处。最后，确定外显子1上游一个跨度为489 bp的基因组区域具有Rasgrf1基因的基本启动子活性。已对位于DMR上游10 kb处的另一个基因A19进行了表征。A19主要在睾丸中表达，在新生和成年脑组织中的表达水平较低。A19转录本是非编码的，在小鼠睾丸和大脑中表达。A19是印记基因，在大脑中仅从父本等位基因表达。
