ANALYSIS OF INSERTIONAL MUTATIONS IN TRANSGENIC MICE

具有插入突变的转基因小鼠构成了潜在的丰富的 分子标记重要基因的来源。 我们选择了两个 插入突变进行更仔细的检查。 插入的小鼠 11号染色体（图谱位置58）显示轻度发育异常 以椎骨融合和椎骨分裂为特征的椎骨 特别是在胸部和腰部区域。 该表型 这让人想起脊椎动物pax 1基因突变所产生的 转录因子，其基因位于2号染色体上。是 可以想象，11号染色体上的中断基因是其中之一， Pax 1的靶基因。我们发现了一段 侧翼插入的转基因。 相应的序列表示为 在成人组织如肌肉和心脏中发现的2.8 kb mRNA上。 目前，我们正在鉴定第二段侧翼DNA， 允许我们映射可能伴随着的任何删除的程度 插入。 然后我们将着手确定该地区的成绩单 11号染色体上的一个基因。 第二次插入发生在基因定义的mi位点上， 小鼠6号染色体。mi突变的特点是三联体，丢失 被毛色素、小红眼和听力缺陷。 共同 这些缺陷的分母可能是发展不足，或损失， 全身的黑色素细胞。 事实上，分析 这些转基因小鼠的内耳显示， 血管层不含黑色素细胞，这种现象与 外毛细胞的退化。 我们发现了两件 插入的转基因侧翼的基因组DNA。 这些序列 存在于6.6 kb的单个基因组片段上，并在 另一种在mi基因突变的小鼠。 其中一个探测器探测到 在北方印迹上，在成人皮肤中发现约7.0 kb mRNA， 黑素细胞系，而不是在许多其他器官。 因此，这种mRNA 很可能是mi基因的转录本 转基因插入突变分析的重要性 不仅在于对发育重要基因的分析， 在分子水平上表征人类遗传疾病的潜力， 类似的现象学。 脊椎异常定义为 11号染色体的插入让人联想到某些人类脊椎 畸形，mi突变是一种特殊形式的模型， 以听力缺陷为特征的人类Waardenburg综合征， 色素异常

Transgenic mice with insertional mutations constitute a potentially rich source of molecularly tagged important genes. We have selected two insertional mutations for closer scrutiny. Mice with an insertion on chromosome 11 (map position 58) display a mild developmental abnormality of the vertebrae characterized by vertebral fusions and split vertebrae particularly in the thoracic and lumbar regions. This phenotype is reminiscent of that created by mutations in pax 1, a vertebrate transcription factor, whose gene, however, is on chromosome 2. It is conceivable that the interrupted gene on chromosome 11 is one of the elusive target genes of Pax 1. We have identified a piece of genomic DNA flanking the inserted transgene. The corresponding sequence is expressed on a 2.8 kb mRNA found in adult tissues such as muscle and heart. Currently, we are identifying a second piece of flanking DNA that might allow us to map the extent of any deletion that may have accompanied the insertion. We will then proceed to identify the transcript of the region of chromosome 11 that is responsible for the phenotype. A second insertion occurred into the genetically defined mi locus on mouse chromosome 6. Mutations in mi are characterized by the triad, loss of coat pigment, small red eyes, and hearing deficiency. The common denominator of these defects may be the underdevelopment, or loss, of functional melanocytes throughout the body. In fact, analysis of the inner ear of these transgenic mice has revealed that the so-called stria vascularis is free of melanocytes, a phenomenon that is associated with degeneration of the outer hair cells. We have identified two pieces of genomic DNA flanking the inserted transgenes. These sequences are present on a single genomic fragment of 6.6 kb and define an RFLP in another line of mice with a mutation at mi. One of these probes detects on Northern blots approximately 7.0 kb mRNA found in adult skin and melanocyte cell lines, and not in many other organs. Thus, this mRNA likely represents a transcript of the mi gene. The importance of the analysis of transgenic insertional mutations not only lies in the analysis of developmentally important genes but also in the potential to molecularly characterize human genetic diseases with similar phenomenology. The vertebral abnormality defined by the chromosome 11 insertion is reminiscent of certain human vertebral malformations, and the mi mutation is a model for particular forms of human Waardenburg syndrome characterized by hearing deficiency and pigment abnormalities.