Biallelic transcription of Igf2 and H19 in individual cells suggests a post-transcriptional contribution to genomic imprinting.
The H19 and insulin-like growth factor 2 (Igf2) genes in the mouse are models for genomic imprinting during development. The genes are located only 90 kb apart in the same transcriptional orientation [1], but are reciprocally imprinted: Igf2 is paternally expressed while H19 is maternally expressed. It has been suggested that expression of H19 and repression of Igf2 (or the converse) on a given chromosome are mechanistically linked and that the parental imprint operates at the level of transcription [2]. Although expression of Igf2 and H19 is thought to be monoallelic, the data have so far been obtained exclusively by looking at steady-state RNA levels using techniques that reflect the average activity of the genes in a cell population [3] [4]. Here, we have adapted a fluorescent in situ hybridisation (FISH) method to detect nascent RNA molecules of Igf2 and H19 at the initial transcription sites in the nuclei of wild-type mouse embryonic liver cells. Nine different transcription patterns were observed, reflecting a high heterogeneity of transcription at the single-cell level. Our observations suggest that regulation of Igf2 and H19 by parental imprinting is much more complex than previously proposed and acts at both transcriptional and post-transcriptional levels.
Jouvenot
Y
Y
Institut Cochin de Génétique Moléculaire, INSERM U 257, 24 rue du Fbg St Jacques, 75014, Paris, France.
Poirier
F
F
Jami
J
J
Paldi
A
A
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D015342:DNA Probes / Q000235:genetics; D005314:Embryonic and Fetal Development / Q000235:genetics; D005260:Female; D018392:Genomic Imprinting; D017404:In Situ Hybridization, Fluorescence; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008297:Male; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics*; D011247:Pregnancy; D062085:RNA, Long Noncoding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
D015342:DNA Probes; C094335:H19 long non-coding RNA; D009124:Muscle Proteins; D062085:RNA, Long Noncoding; D012333:RNA, Messenger; D022661:RNA, Untranslated; D007335:Insulin-Like Growth Factor II