Robinson W P, Bernasconi F, Basaran S, Yüksel-Apak M, Neri G, Serville F, Balicek P, Haluza R, Farah L M, Lüleci G
Institute of Medical Genetics, University of Zurich, Switzerland.
Am J Hum Genet. 1994 Feb;54(2):290-302.
One t(14q14q), three t(15q15q), two t(21q21q), and two t(22q22q) nonmosaic, apparently balanced, de novo Robertsonian translocation cases were investigated with polymorphic markers to establish the origin of the translocated chromosomes. Four cases had results indicative of an isochromosome: one t(14q14q) case with mild mental retardation and maternal uniparental disomy (UPD) for chromosome 14, one t(15q15q) case with the Prader-Willi syndrome and UPD(15), a phenotypically normal carrier of t(22q22q) with maternal UPD(22), and a phenotypically normal t(21q21q) case of paternal UPD(21). All UPD cases showed complete homozygosity throughout the involved chromosome, which is supportive of a postmeiotic origin. In the remaining four cases, maternal and paternal inheritance of the involved chromosome was found, which unambiguously implies a somatic origin. One t(15q15q) female had a child with a ring chromosome 15, which was also of probable postmeiotic origin as recombination between grandparental haplotypes had occurred prior to ring formation. UPD might be expected to result from de novo Robertsonian translocations of meiotic origin; however, all de novo homologous translocation cases, so far reported, with UPD of chromosomes 14, 15, 21, or 22 have been isochromosomes. These data provide the first direct evidence that nonmosaic Robertsonian translocations, as well as isochromosomes, are commonly the result of a mitotic exchange.
对1例t(14q14q)、3例t(15q15q)、2例t(21q21q)和2例t(22q22q)非嵌合、明显平衡的新生罗伯逊易位病例进行了多态性标记研究，以确定易位染色体的起源。4例结果提示为等臂染色体：1例t(14q14q)病例伴有轻度智力障碍和14号染色体母源性单亲二体(UPD)，1例t(15q15q)病例患有普拉德-威利综合征和UPD(15)，1例表型正常的t(22q22q)携带者伴有母源性UPD(22)，以及1例表型正常的t(21q21q)病例伴有父源性UPD(21)。所有UPD病例在整个受累染色体上均表现为完全纯合性，这支持减数分裂后起源。在其余4例中，发现了受累染色体的母系和父系遗传，这明确提示为体细胞起源。1例t(15q15q)女性生育了1个患有15号环状染色体的孩子，该环状染色体也可能起源于减数分裂后，因为在环状染色体形成之前祖父母单倍型之间发生了重组。UPD可能是减数分裂起源的新生罗伯逊易位的结果；然而，迄今为止报道的所有伴有14、15、21或22号染色体UPD的新生同源易位病例均为等臂染色体。这些数据提供了首个直接证据，表明非嵌合罗伯逊易位以及等臂染色体通常是有丝分裂交换的结果。
