UNDERSTANDING OUTFLOW TRACT DEFECTS IN DIGEORGE SYNDROME--CHROMOSOME ENGINEERING

人类22q11染色体区域的半合子缺失是 几种不同临床发育缺陷的遗传学基础 严肃性。临床表现可能符合以下诊断标准 DiGeorge综合征(DGS)、血管心面综合征(VCFS)或非常轻微 或者很复杂。约80%的患者22q11缺失(De122q11) 表现为先天性心脏缺陷，大多起源于圆锥干和 影响心脏流出道的。心脏缺陷是最常见的 戏剧性的临床表现，并对几乎所有早期 这些患者的死亡人数。因为22q11的缺失是最多的 与异常表型相关的频繁的染色体缺失 在人类中已知，这种遗传损伤是导致 心脏缺陷。此外，我们已经表明，对于某些特定的 缺陷，如B型主动脉弓中断，该缺失见于 50%的病例，因此这是一个主要的遗传原因 异常点。“关键区域”，删除该区域就足以 产生de122q11的表型已经确定。至少到今天为止， 在这个300-400kb的区间内，已鉴定出9个基因。然而，它是 目前还不清楚这些基因中是否有任何在病因学上是重要的 对于表型或这是单基因缺陷还是多基因缺陷。 我们提出了一种新颖而强大的方法来对此进行建模 重要的缺失综合征。我们将使用染色体工程来 生成模拟人工删除的鼠标删除。删除将 在胚胎干细胞(ES)中使用Cre-loxP策略产生。 将获得携带缺陷的小鼠来测试表型 这些缺陷的影响。转基因救援实验将是 以补充体内的缺陷并识别基因组 足以挽救表型的片段。通过这些方法，我们将 能够从基因上剖析导致 典型的de122q11表型的发育性心脏缺陷。

The hemizygous deletion of a chromosomal region of human 22q11 is the genetic basis for several developmental defects with variable clinical severity. The clinical presentations may fit the diagnostic criteria for DiGeorge syndrome (DGS), Velocardiofacial syndrome (VCFS) or be very mild or complex. Approximately 80% of patients with a 22q11 deletion (de122q11) presents with a congenital heart defects, mostly of conotruncal origin and affecting the outflow tract of the heart. Heart defects represent the most dramatic clinical findings and are responsible for virtually all the early deaths in these patients. As the 22q11 deletion is one of the most frequent chromosomal deletions associated with an anomalous phenotype known in humans, this genetic lesions represents an important cause of heart defects. Furthermore, we have shown that for certain specific defects, such as interrupted aortic arch type B, the deletion is found in 50% of the cases, hence representing a major genetic cause for this anomaly. A 'critical region' the deletion of which is sufficient to produce the de122q11 phenotype has been delineated. As of today, at least 9 genes have been identified in this 300-400 kb interval. However, it is still unknown whether or not any of these genes is etiologically important for the phenotype or whether this is a single or multiple gene defect. We propose a novel and powerful approach for the modeling of this important deletion syndrome. We will use chromosome engineering to generate mouse deletions which simulate the human deletion. Deletions will be generated using the Cre-loxP strategy in embryonic stem (ES) cells. Mice carrying the deficiencies will be obtained to test the phenotypic effects of the deficiencies. Transgenic rescue experiments will be performed to complement in vivo the deficiencies and identify a genomic segment sufficient to rescue the phenotype. With these approaches we will be able to dissect genetically the mechanisms which lead to the developmental heart defects typical of the de122q11 phenotype.