Fang Y Y, Eyre H J, Bohlander S K, Estop A, McPherson E, Träger T, Riess O, Callen D F
Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, North Adelaide, Australia.
Am J Hum Genet. 1995 Nov;57(5):1137-42.
Molecular cloning of a microdissected small accessary ring chromosome 4 from a moderately retarded and dysmorphic patient has been performed to identify the origin of the ring chromosome. FISH was performed with cosmids identified with the cloned, microdissected products and with other markers from chromosome 4. The present study clearly demonstrates that the small ring in this patient originates from three discontinuous regions of chromosome 4: 4p13 or 14, the centromere, and 4q31. It is suggested that the origin of the ring chromosome is a ring involving the entire chromosome 4, which has then been involved in breakage and fusion events, as a consequence of DNA replication generating interlocked rings. A second severely retarded and dysmorphic patient also had a small accessary ring derived from chromosome 4. FISH studies of this ring are consistent with an origin from a contiguous region including the centromere to band 4q12. It is apparent that there are at least two mechanisms for the formation of small ring chromosomes. This adds a further complication in any attempt to ascertain common phenotypes between patients known to have morphologically similar markers derived from the same chromosome.
为了确定一条小的副环形染色体4的起源，我们对一名中度智力发育迟缓且有畸形的患者的显微切割的小副环形染色体4进行了分子克隆。使用从克隆的显微切割产物鉴定出的黏粒以及来自4号染色体的其他标记进行了荧光原位杂交（FISH）。本研究清楚地表明，该患者的小环形染色体起源于4号染色体的三个不连续区域：4p13或14、着丝粒和4q31。有人提出，环形染色体的起源是一个涉及整个4号染色体的环，由于DNA复制产生互锁环，该环随后参与了断裂和融合事件。另一名严重智力发育迟缓且有畸形的患者也有一个源自4号染色体的小副环形染色体。对该环的FISH研究结果与起源于包括着丝粒至4q12带的连续区域一致。显然，小环形染色体的形成至少有两种机制。这在试图确定已知具有源自同一染色体的形态相似标记的患者之间的共同表型时又增加了一个复杂因素。
