Ferguson-Smith A C, Cattanach B M, Barton S C, Beechey C V, Surani M A
Department of Molecular Embryology, AFRC Institute of Animal Physiology & Genetics Research, Babraham, Cambridge, UK.
Nature. 1991 Jun 20;351(6328):667-70. doi: 10.1038/351667a0.
Mouse embryos with duplications of whole maternal (parthenogenetic and gynogenetic) or paternal (androgenetic) genomes show reciprocal phenotypes and do not develop to term. Genetic complementation has identified the distal region of chromosome 7 (Chr 7) as one of the regions for which both a maternal and paternal chromosome copy are essential for normal development, presumably because of the presence of imprinted genes whose expression is dependent on their parental origin. Embryos with the maternal duplication and paternal deficiency of distal Chr 7 are growth retarded and die around day 16 of gestation; the reciprocal paternal duplication embryos die at an unidentified earlier stage. We report here the incorporation of cells with the paternal duplication into chimaeras, resulting in a striking growth enhancement of the embryos. One gene located on mouse distal Chr 7 (ref. 5) is the insulin-like growth factor 2 (Igf2) gene, an embryonic mitogen. In embryos with the maternal duplication of distal Chr 7, the two maternal alleles of the Igf2 gene are repressed. The presence of two paternal alleles of this gene in many cells is probably responsible for the growth enhancement observed in chimaeras. We propose that there are other imprinted genes in this Chr 7 region. We also compare the imprinting of this subgenomic region with phenotypes resulting from the duplication of the whole parental genome in parthenogenones and androgenones.
具有整个母本（孤雌生殖和雌核发育）或父本（雄核发育）基因组重复的小鼠胚胎表现出相反的表型，且无法发育至足月。遗传互补分析已确定7号染色体（Chr 7）的远端区域是正常发育必需母本和父本染色体拷贝的区域之一，推测这是由于存在印记基因，其表达取决于亲本来源。具有母本Chr 7远端重复和父本缺失的胚胎生长迟缓，在妊娠第16天左右死亡；相反的父本重复胚胎在一个未明确的较早阶段死亡。我们在此报告将具有父本重复的细胞掺入嵌合体中，导致胚胎生长显著增强。位于小鼠Chr 7远端的一个基因（参考文献5）是胰岛素样生长因子2（Igf2）基因，一种胚胎有丝分裂原。在具有母本Chr 7远端重复的胚胎中，Igf2基因的两个母本等位基因被抑制。该基因的两个父本等位基因在许多细胞中的存在可能是嵌合体中观察到的生长增强的原因。我们推测在这个Chr 7区域存在其他印记基因。我们还比较了这个亚基因组区域的印记与孤雌生殖体和雄核发育体中整个亲本基因组重复所产生的表型。
