Kurahashi H, Akagi K, Inazawa J, Ohta T, Niikawa N, Kayatani F, Sano T, Okada S, Nishisho I
Department of Medical Genetics, Osaka University Medical School, Japan.
Hum Mol Genet. 1995 Apr;4(4):541-9. doi: 10.1093/hmg/4.4.541.
The region commonly deleted in DiGeorge syndrome (DGS) has been localized at 22q11.1-q11.2 with the aid of a high resolution banding technique. A 22q11 specific plasmid library was constructed with a microdissection and microcloning method. Dosage analysis proved three of 144 randomly selected microclones to detect hemizygosity in two patients with DGS. Two of the clones were found to contain independent low-copy-number repetitive sequences, all of which were included in the region deleted in the DGS patients. Screening of the cosmid library and subsequent cosmid walking allowed us to obtain two cosmid contigs corresponding to the microclones within the deletion (contig 1 and contig 2), whose order fluorescence in situ hybridization identified as centromere-contig 1-contig 2-telomere on 22q. By direct selection strategy using one of the cosmids of contig 1, a 4.3 kb 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. The gene, designated LZTR-1, which was transcribed in several essential fetal organs, proved to be hemizygously deleted in seven of eight DGS patients or its variants, but not in one DGS patient and GM00980. Although LZTR-1 does not locate in the shortest region of overlap, several of its structural characteristics identifying it as transcriptional regulator suggest that it plays a crucial role in embryogenesis and that haploinsufficiency of this gene may be partly related to the development of DGS.
借助高分辨率显带技术，已将常见于DiGeorge综合征（DGS）中缺失的区域定位在22q11.1 - q11.2。采用显微切割和微克隆方法构建了一个22q11特异性质粒文库。剂量分析证明，在144个随机选择的微克隆中，有3个可检测到两名DGS患者的半合子状态。发现其中两个克隆包含独立的低拷贝数重复序列，所有这些序列都包含在DGS患者缺失的区域内。对黏粒文库的筛选及随后的黏粒步移使我们获得了与缺失区域内的微克隆相对应的两个黏粒重叠群（重叠群1和重叠群2），通过荧光原位杂交确定其在22q上的顺序为着丝粒 - 重叠群1 - 重叠群2 - 端粒。利用重叠群1中的一个黏粒通过直接选择策略，从胎儿脑cDNA文库中获得了一个4.3 kb的cDNA。对该cDNA的序列分析揭示了一个编码552个氨基酸的开放阅读框，该氨基酸具有DNA结合蛋白的几个特征。该基因命名为LZTR - 1，在几个重要的胎儿器官中表达，结果证明在8名DGS患者或其变体中的7名中存在半合子缺失，但在1名DGS患者和GM00980中未发现。尽管LZTR - 1并不位于最短的重叠区域，但它的几个结构特征表明它是一种转录调节因子，这表明它在胚胎发生中起关键作用，并且该基因的单倍剂量不足可能部分与DGS的发生有关。
