UBIQUITOUS EXPRESSION AND IMPRINTING OF SNRPN IN THE MOUSE

Snrpn is known to be abundantly expressed in rodent brain and heart, and in two separate studies with neonatal mouse brain it has been shown to be maternally imprinted, that is, the maternal allele is normally repressed. We now provide evidence on the expression profile and imprinting status of Snrpn throughout development. Using RT-PCR, we have established that Snrpn is further expressed at low levels in lung, liver, spleen, kidney, skeletal muscle, and gonads. Moreover, using mice with only maternal copies of Snrpn (maternal duplication for the chromosome region involved and parthenagenotes), we have shown that the gene is imprinted in all of these tissues and, generally, from the time the gene is first expressed at 7.5 days gestation. In contrast to the findings made with the imprinted genes, Igf2, Ins1, and Ins2, there is no evidence of tissue-specific imprinting in the embryo with Snrpn. Nor, as found with Igf2 and Igf2r, is there evidence of a window of biallelic expression between the germ line imprint and the time of gene repression. The absence of Snrpn expression in early embryos contrasts with the findings in ES cells.