Analysis of molecular abnormalities in DiGeorge syndrome

digegeorge综合征（DGS）和圆锥锥体异常面部综合征的微缺失定位于22q11。为了分离这些综合征的相关基因，我们从包含完整的人类22号染色体的体细胞杂种中构建了cosmid文库。另一种携带不同人类染色体易位的体细胞杂交体使我们能够将其中一些cosmids分配到22q11上，然后通过剂量分析选择位于微缺失的cosmids。为进一步分离缺失克隆，对22q11进行显微解剖构建微克隆文库，并通过用量分析筛选缺失克隆。cosmid文库的筛选和随后的cosmid行走使我们获得了两个cosmid contigs，其顺序通过荧光原位杂交鉴定。采用直接选择策略，从胎儿脑cDNA文库中获得4.3kb的cDNA。cDNA序列分析显示，该开放阅读框编码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。这个被命名为LZTR-1的基因在几个重要的胎儿器官中被转录，在大多数患者中被证明是半合子缺失的，但在GM00980中没有，它的缺失划定了重叠的最短区域。然而，它的一些结构特征表明它是一个转录因子，这表明它在胚胎发生中起着至关重要的作用，该基因的单倍性不足可能部分与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.