Emanuel Beverly S
Division of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104-4318, USA.
Dev Disabil Res Rev. 2008;14(1):11-8. doi: 10.1002/ddrr.3.
Several recurrent, constitutional genomic disorders are present on chromosome 22q. These include the translocations and deletions associated with DiGeorge and velocardiofacial syndrome and the translocations that give rise to the recurrent t(11;22) supernumerary der(22) syndrome (Emanuel syndrome). The rearrangement breakpoints on 22q cluster around the chromosome-specific segmental duplications of proximal 22q11, which are involved in the etiology of these disorders. While the deletions are the result of nonallelic homologous recombination (NAHR) between low copy repeats or segmental duplications within 22q11, the t(11;22) is the result of rearrangement between palindromic AT-rich repeats on 11q and 22q. Here we describe the mechanisms responsible for these recurrent rearrangements, discuss the recurrent deletion endpoints that are the result of NAHR between chromosome 22q specific low copy repeats as well as present current diagnostic approaches to deletion detection.
22号染色体长臂（22q）上存在几种反复出现的、与体质相关的基因组疾病。这些疾病包括与迪格奥尔格综合征和腭心面综合征相关的易位和缺失，以及导致反复出现的t(11;22)额外der(22)综合征（伊曼纽尔综合征）的易位。22q上的重排断点聚集在近端22q11的染色体特异性节段重复区域周围，这些节段重复与这些疾病的病因有关。虽然缺失是22q11内低拷贝重复序列或节段重复之间非等位基因同源重组（NAHR）的结果，但t(11;22)是11q和22q上富含AT的回文重复序列之间重排的结果。在这里，我们描述了这些反复重排的机制，讨论了22号染色体特异性低拷贝重复序列之间NAHR导致的反复缺失端点，并介绍了目前检测缺失的诊断方法。
