Ohashi H, Wakui K, Ogawa K, Okano T, Niikawa N, Fukushima Y
Division of Medical Genetics, Saitama Children's Medical Center, Iwatsuki, Japan.
Am J Hum Genet. 1994 Dec;55(6):1202-8.
A centromere is considered to be an essential chromosomal component where microtubule-kinetochore interaction occurs to segregate sister chromatids faithfully and acentric chromosomes are unstable and lost through cell divisions. We report a novel marker chromosome that was acentric but stable through cell divisions. The patient was a 2-year-old girl with mental retardation, patent ductus arteriosus, and mild dysmorphic features. G-banded chromosome analysis revealed that an additional small marker chromosome was observed in all 100 cells examined. By the reverse-chromosome-painting method, the marker was found to originate from the distal region of 8p, and a subsequent two-color FISH analysis with cosmid probes around the region revealed that the marker was an inverted duplication interpreted as 8pter-->p23.1::p23.1-->8pter. No centromeric region was involved in the marker. By FISH, no alpha-satellite sequence was detected on the marker, while a telomere sequence was detected at each end. Anti-kinetochore immunostaining, using a serum from a patient with CREST (calcinosis, Raynaud syndrome, esophageal dismotility, sclerodactyly, and telangiectasia) syndrome, showed a pair of signals on the marker, which indicated that a functional kinetochore was present on the marker. The analysis of this patient might suggest the possibility that an ancient centromere sequence exists at distal 8p (8p23.1-pter) and was activated through the chromosome rearrangement in the patient.
着丝粒被认为是染色体的一个重要组成部分，微管与动粒在此相互作用，以确保姐妹染色单体准确分离，而无着丝粒染色体不稳定，会在细胞分裂过程中丢失。我们报告了一种新型标记染色体，它无着丝粒，但在细胞分裂过程中稳定存在。该患者为一名2岁女童，患有智力发育迟缓、动脉导管未闭和轻度畸形特征。G带染色体分析显示，在所有100个检测细胞中均观察到一条额外的小标记染色体。通过反向染色体涂染法，发现该标记染色体起源于8p的远端区域，随后用该区域周围的黏粒探针进行双色荧光原位杂交分析表明，该标记染色体是一个倒位重复，解释为8pter→p23.1::p23.1→8pter。该标记染色体不涉及着丝粒区域。通过荧光原位杂交，在该标记染色体上未检测到α卫星序列，而在其两端均检测到端粒序列。使用进行性系统性硬皮病（钙质沉着、雷诺综合征、食管运动障碍、指端硬化和毛细血管扩张）患者的血清进行抗动粒免疫染色，在该标记染色体上显示出一对信号，这表明该标记染色体上存在功能性动粒。对该患者的分析可能提示，在8p远端（8p23.1 - pter）存在一个古老的着丝粒序列，并通过患者的染色体重排而被激活。
