Résumé
Experimental and computer-assisted approaches have led to the identification of hundreds of imprinted small RNA genes, mainly clustered in two chromosomal domains (human 15q11-->q13 and 14q32 loci). The genes are only detected in placental mammals and belong to the C/D RNA and microRNA gene families. These are small non-coding RNAs involved in RNA-guided post-transcriptional RNA modifications and RNA-mediated gene silencing, respectively. Here, we discuss their potential functions and report the identification of novel small RNA genes lying within (or nearby) known imprinted chromosomal domains.