RETROVIRUSES AS PROBES FOR DEVELOPMENT

影响小鼠胚胎早期发育的突变将在 在胚胎干细胞（ES）中使用基因陷阱产生。在这种方法中， 通过逆转录病毒将报道基因导入ES细胞， 报告基因的表达只能来源于基因的启动子 它所插入的。 由于这些中使用的报告基因 实验编码β-半乳糖苷酶活性，突变的 在杂合子小鼠中可以方便地跟踪基因。后果 可以通过将小鼠繁殖为纯合性来评估基因破坏的程度。 在以前的工作中，已经产生了42个小鼠突变株系， 显示β-半乳糖苷酶表达模式的多样性， 发展高比例的显性表型观察到， 这些菌株，因为前病毒插入导致胚胎死亡，在18 在另外两个菌株中，在一种致命的菌株中， 前病毒破坏了编码转录因子的基因 TEF 1，导致心脏和中枢神经系统缺陷， 妊娠中期我们将继续通过组织学分析这些菌株， 了解突变胚胎的缺陷，并通过克隆突变基因。 我们还将使用基因陷阱来鉴定发育过程中诱导的基因 针对被认为在以下两类因素中起关键作用的两类因素， 早期发育：视黄酸，一种被认为具有 和生长因子，其受体是蛋白质酪氨酸 与几种影响早期免疫缺陷的经典小鼠突变有关的激酶 小鼠发育预计这些研究将导致 鉴定在小鼠早期发育中起关键作用的基因，以及 利用遗传学帮助识别特定信号传导中的关键成分 途径。

Mutations affecting early development of the mouse embryo will be generated using gene traps in embryonic stem (ES) cells. In this approach, a reporter gene is introduced into ES cells by a retrovirus, but expression of the reporter can only originate from the promoter of a gene into which it has inserted. Since the reporter gene used in these experiments encodes beta-galactosidase activity, expression of the mutated gene can be conveniently followed in heterozygous mice. The consequences of gene disruption can be assessed by breeding the mice to homozygosity. In previous work, 42 lines of mouse mutants have been generated, which display a diversity of beta-galactosidase expression pattern during development. A high proportion of overt phenotypes was observed among these strains, since provirus insertion leads to embryonic lethality in 18 strains and to male sterility in two others. In one lethal strain, the provirus has disrupted the gene which encodes the transcription factor TEF1, leading to cardiac and central nervous system defects at midgestation. We will continue to analyze these strains by histology to understand the defects in mutant embryos, and by cloning the mutated gene. We will also use gene traps to identify genes induced during development in response to two types of factors thought to play critical roles in early development: retinoic acid, a factor believed to have the properties of a morphogen; and growth factors, whose receptors are protein tyrosine kinases implicated in several classical mouse mutations affecting early mouse development. It is anticipated that these studies will lead to the identification of genes playing key roles in early mouse development, and help identify, using genetics, critical components in specific signaling pathways.