Graves J A
School of Genetics and Human Variation, La Trobe University, Melbourne, Vic, Australia.
Reprod Fertil Dev. 1998;10(1):23-9. doi: 10.1071/r98014.
Several genes in conserved clusters are expressed from only the maternal or the paternal allele. The other allele has been genetically silenced ('imprinted') by its passage through one sex. Many known imprinted genes have effects on embryonic or trophoblast growth or fetal development, and mutation or loss of the single active copy causes diseases such as Prader-Willi, Angelmann and Beckwith-Wiederman syndromes. Imprinted genes show an unusual mode of inheritance, since mutant genes have an effect on the phenotype only if they come from the parent from which they are expressed. This may explain some conditions which appear to be heritable but show an inconsistent pattern in affected families. Of particular interest is pre-eclampsia/eclampsia, the most serious complication of pregnancy, which has some features suggesting that it results from fetal expression of the mutant gene, but others which imply it results from maternal expression. This could be resolved by proposing that the condition is due to mutation in a paternally imprinted, maternally active gene which must be expressed by the fetus in order to establish a normal placenta in the first pregnancy.
保守基因簇中的几个基因仅从母本或父本等位基因表达。另一个等位基因在通过某一性别时被遗传沉默（“印记”）。许多已知的印记基因对胚胎或滋养层细胞生长或胎儿发育有影响，单一活性拷贝的突变或缺失会导致普拉德-威利综合征、安吉尔曼综合征和贝克威思-维德曼综合征等疾病。印记基因显示出一种不寻常的遗传模式，因为突变基因只有来自其表达的亲本时才会对表型产生影响。这可能解释了一些看似可遗传但在受影响家庭中表现出不一致模式的情况。特别值得关注的是先兆子痫/子痫，这是妊娠最严重的并发症，它有一些特征表明是由突变基因的胎儿表达引起的，但其他特征则暗示是由母体表达引起的。提出这种情况是由于父本印记、母本活性基因的突变可能解决这一问题，该基因必须由胎儿表达才能在首次妊娠时建立正常胎盘。
