Khatib Hasan
Department of Dairy Science, 1675 Observatory Drive, University of Wisconsin, Madison, WI 53706, USA.
Bioessays. 2007 Oct;29(10):1022-8. doi: 10.1002/bies.20637.
Imprinted genes are monoallelically expressed in a parent-of-origin-specific manner, but for many genes reported to be imprinted, the occurrence of preferential expression--where both alleles are expressed but one is expressed more strongly than the other in a parent-of-origin-specific way--has been reported. This preferential expression found in genes described as imprinted has not been thoroughly addressed in genomic imprinting studies. To study this phenomenon, 50 genes, reported to be imprinted in the mouse, were chosen for investigation. Preferential expression was observed for 21 of 27 maternally expressed genes. However, only 5 of 23 paternally expressed genes showed preferential expression. Recently, it has been reported that a remarkable proportion of non-imprinted genes show differential allelic expression. If there is overlap between non-imprinted genes that are differentially expressed and imprinted genes that are preferentially expressed, we need to set new definitions of imprinted genes that, in turn, would probably lead to reassessments of the total number of imprinted genes in mammalian species.
印记基因以亲本来源特异性的方式单等位基因表达，但对于许多据报道为印记基因的基因，已经有报道称存在优先表达的情况——即两个等位基因都表达，但其中一个以亲本来源特异性的方式表达得比另一个更强。在基因组印记研究中，对于在被描述为印记基因的基因中发现的这种优先表达尚未进行深入探讨。为了研究这一现象，选择了50个据报道在小鼠中为印记基因的基因进行研究。在27个母源表达基因中有21个观察到优先表达。然而，在23个父源表达基因中只有5个显示出优先表达。最近，有报道称相当一部分非印记基因显示出差异等位基因表达。如果差异表达的非印记基因与优先表达的印记基因之间存在重叠，我们就需要对印记基因设定新的定义，这反过来可能会导致对哺乳动物物种中印记基因总数的重新评估。
