International Mammalian Genome Society

17th International Mouse Genome Conference

9-12 November 2003, Braunschweig, Germany


POSTER 64 - NESPAS: THE UNRAVELLING STORY OF ITS FUNCTION IN THE GNAS IMPRINTING CLUSTER

Turner MD
MRC Harwell, Mammalian Genetics Unit

Co-Authors: Williamson C, Nottingham W, Ball S, Maconochie M, Peters J
Institutions: MRC Harwell, Mammalian Genetics Unit

Non-coding antisense RNA transcripts are implicated in the regulation of gene expression. However, their role is not fully understood. Nespas is a paternally expressed transcript that lies antisense to the maternally expressed Nesp transcript in the Gnas imprinting cluster. On the paternal chromosome Nespas is expressed, while Nesp is not expressed and the promoter of Nesp is methylated. The objective of the project is to determine whether Nespas is a cis-acting control element. A 1.6 kb targeted deletion encompassing the promoter of Nespas, exon one of Nespas and some intronic sequence on the paternal chromosome were made, and chimaeric mice generated. Chimaeric males were mated with wild-type females. The offspring carrying the deletion were collected and used to analyse the effect of the targeted deletion on gene expression from the paternally derived chromosome. The results of RT-PCR analysis on newborn brain from the deletion carrier mice showed that Nespas is no longer expressed from the paternal allele. Northern analysis of mRNA from 15.5 dpc embryos showed increased levels of Nesp in the deletion carrier mice. RT-PCR on newborn brain using a variant showed that expression of Nesp is present from both the wild-type maternal chromosome and the deleted paternally derived chromosome. Hence, Nesp expression is biallelically expressed. Furthermore, analysis of the Nesp promoter reveals that the promoter is unmethylated on the deleted paternally derived chromosome. Thus, the deletion has converted the paternal imprint mark to a maternal one.


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