International Mammalian Genome Society

The 15th International Mouse Genome Conference (2001)


Rebecca Holmes
MRC Mammalian Genetics Unit
Didcot OX11 0RD

Co-Authors: Williamson CM, Skinner JA, Beechey CV, Peters J.
Institutions: MRC Mammalian Genetics Unit

The Gnas cluster on Chromosome (Chr) 2 of the mouse produces a number of imprinted and alternatively spliced transcripts.  On the sense strand these include Nesp, which is maternally expressed, Gnasxl and Gnas exon1a, which are paternally expressed.  All three splice into exon 2 of Gnas itself and act as alternative first exons for Gnas.  Gnas itself is biallelically expressed in most tissues and encodes a G protein alpha sub-unit; Gnasxl encodes an extra large form of the G protein and Nesp a neuroendocrine secretory protein whereas the Gnas exon 1a transcript appears to be non-coding.  Genomically Gnas lies at one end of the cluster with Gnas exon 1a, Gnasxl and Nesp 2kb, 30 kb and 45kb upstream, respectively.  Analysis of the 15kb genomic sequence between Nesp and Gnasxl has revealed a number of ESTs.  These are organised into four groups that lie 2, 4, 6.5 and 10kb downstream from Nesp.  Their imprinting status has been analysed in mice carrying either two maternal copies and no paternal copies (MatDp) or two paternal copies and no maternal copies (PatDp) of distal Chr 2.  A transcript was found in the MatDp(dist2) mice which was not present in the PatDp(dist2) mice.  Preliminary analysis suggests this new maternal transcript links the groups of ESTs lying between Nesp and Gnasxl.  One of the ESTS links to exon 2 of Gnas and thus would appear to represent a new alternative first exon of Gnas.

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