Analysis of molecular abnormalities in DiGeorge syndrome

DiGeorge综合征(DGS)和圆锥干畸形面部综合征的微缺失已定位于22q11。为了寻找这些综合征的致病基因，我们从含有完整人类22号染色体的体细胞杂交体中构建了粘粒文库。另一种携带不同人类染色体易位的体细胞杂交种允许我们将其中一些粘粒分配给22q11，然后通过剂量分析选择位于微缺失的粘粒。在此基础上，利用22q11的显微切割技术构建微克隆文库，并通过剂量分析对缺失克隆进行筛选。粘粒文库的筛选和随后的粘粒行走使我们获得了两个粘粒重叠群，并通过荧光原位杂交鉴定了它们的顺序。采用直接选择策略，从胎脑cDNA文库中扩增出4.3kb的全长cDNA。序列分析显示，该基因编码552个氨基酸，具有碱性亮氨酸拉链结构域等DNA结合蛋白的特征。该基因被命名为LZTR-1，在几个必要的胎儿器官中转录，在大多数患者中被证明是半缺失的，但在GM00980中没有，GM00980有一个缺失，该缺失划分了最短的重叠区域。然而，它的一些结构特征表明它是转录因子，表明它在胚胎发育中起着至关重要的作用，该基因的单倍性不足可能与DGS的发育有关。

The microdeletion in DiGeorge syndrome(DGS) and conotruncal anomaly face syndrome has been localized at 22q11. In order to iosolate responsible gene for these syndromes, cosmid library was constructed from the somatic cell hybrid containing human intact chromosome 22 as its only human component. Another somatic cell hybrids carrying a different human chromosome translocation allowed us to assign some of these cosmids to 22q11, and then the cosmids which are located in the microdeletion were selected by dosage analysis. Further to isolate deleted clones, microclone library was constructed with the aid of microdissection of 22q11, and the deleted clones were also selected by dosage analysis. Screening of cosmid library and subsequent cosmid walking allowed us to obtain two cosmid contigs, whose order was identified by fluorescence in situ hybridization. By direct selection strategy, a 4.3kb cDNA was obtained from fetal brain cDNA library. Sequence analysis of the cDNA revealed an open reading frame encoding 552 amino acids which had several characteristics of DNA-binding proteins, such as basic-leucine-zipper domain. The gene, designated LZTR-1, which was transcribed in several essential fetal organs, proved to be hemizygously deleted in most patients, but not in GM00980, which has a deletion that demarcates the shortest region of overlap. However, several of its structural characteristics identifying it as transcriptional factor suggest that it plays a crucial role in embryogenesis and that haploinsufficiency of this gene may be partly related to development of DGS.