Lloyd V K, Sinclair D A, Grigliatti T A
Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
Genetics. 1999 Apr;151(4):1503-16. doi: 10.1093/genetics/151.4.1503.
Genomic imprinting is a phenomenon in which the expression of a gene or chromosomal region depends on the sex of the individual transmitting it. The term imprinting was first coined to describe parent-specific chromosome behavior in the dipteran insect Sciara and has since been described in many organisms, including other insects, plants, fish, and mammals. In this article we describe a mini-X chromosome in Drosophila melanogaster that shows genomic imprinting of at least three closely linked genes. The imprinting of these genes is observed as mosaic silencing when the genes are transmitted by the male parent, in contrast to essentially wild-type expression when the same genes are maternally transmitted. We show that the imprint is due to the sex of the parent rather than to a conventional maternal effect, differential mitotic instability of the mini-X chromosome, or an allele-specific effect. Finally, we have examined the effects of classical modifiers of position-effect variegation on the maintenance and the establishment of the imprint. Factors that modify position-effect variegation alter the somatic expression but not the establishment of the imprint. This suggests that chromatin structure is important in maintenance of the imprint, but a separate mechanism may be responsible for its initiation.
基因组印记是一种基因或染色体区域的表达取决于传递它的个体性别的现象。“印记”一词最初是用来描述双翅目昆虫Sciara中亲本特异性的染色体行为，此后在许多生物体中都有描述，包括其他昆虫、植物、鱼类和哺乳动物。在本文中，我们描述了黑腹果蝇中的一个微型X染色体，它显示出至少三个紧密连锁基因的基因组印记。当这些基因由雄性亲本传递时，会观察到基因印记表现为镶嵌沉默，而当这些相同基因由母本传递时，则表现为基本的野生型表达。我们表明，印记是由于亲本的性别，而不是传统的母体效应、微型X染色体有差异的有丝分裂不稳定性或等位基因特异性效应。最后，我们研究了位置效应斑驳的经典修饰因子对印记维持和建立的影响。修饰位置效应斑驳的因子会改变体细胞表达，但不会影响印记的建立。这表明染色质结构在印记维持中很重要，但可能有一个独立的机制负责印记的起始。
