Tuason Maria Clarita, Rastikerdar Ali, Kuhlmann Tanja, Goujet-Zalc Cécile, Zalc Bernard, Dib Samar, Friedman Hana, Peterson Alan
Molecular Oncology Group, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
J Neurosci. 2008 Jul 2;28(27):6895-903. doi: 10.1523/JNEUROSCI.4579-07.2008.
The gene encoding DM20 emerged in cartilaginous fish, descending from a bilaterian ancestor of the M6 proteolipid gene family. Its proteolipid protein (PLP) isoform appeared in amphibians, contains an additional 35 amino acids, and, in the mammalian CNS, is the dominant myelin protein in which it confers an essential neuroprotective function. During development, the DM20 isoform is prominent in a number of tissues, and plp/DM20 transcripts are detected in multiple progenitor populations, including those that continue to express plp/DM20 as they differentiate into myelinating oligodendrocytes. The locus also encodes isoforms with extended leader sequences that accumulate in the cell bodies of several types of neurons. Here, to locate and characterize regulatory sequences controlling the complex plp/DM20 transcription program, putative regulatory sequences, suggested by interspecies conservation, were ligated individually to a minimally promoted eGFPlacZ reporter gene. These constructs were inserted in single copy at a common site adjacent to the hypoxanthine-guanine phosphoribosyltransferase locus in embryonic stem cells and their in vivo expression programs were compared in transgenic mice. Most expressed developmental and cell-specific subprograms accommodated within the known expression phenotype of the endogenous plp/DM20 locus, thus defining multiple components of the combinatorial mechanism controlling its normal temporal and cell-specific program. Along with previously characterized nervous system enhancers, those described here should help expose the content and configuration of elements that are operational in multiple glial and neuronal lineages. The transgenic lines derived here also provide effective markers for multiple stages of glial and neuronal lineage progression.
编码DM20的基因出现在软骨鱼类中，它起源于M6蛋白脂质基因家族的两侧对称动物祖先。其蛋白脂质蛋白（PLP）异构体出现在两栖动物中，含有额外的35个氨基酸，并且在哺乳动物中枢神经系统中是主要的髓鞘蛋白，具有重要的神经保护功能。在发育过程中，DM20异构体在许多组织中很突出，并且在多个祖细胞群体中检测到plp/DM20转录本，包括那些在分化为有髓鞘少突胶质细胞时继续表达plp/DM20的群体。该基因座还编码具有延长前导序列的异构体，这些异构体在几种类型神经元的细胞体中积累。在这里，为了定位和表征控制复杂的plp/DM20转录程序的调控序列，将种间保守性提示的推定调控序列分别连接到最小启动的eGFPlacZ报告基因上。这些构建体以单拷贝形式插入胚胎干细胞中次黄嘌呤 - 鸟嘌呤磷酸核糖基转移酶基因座附近的一个共同位点，并在转基因小鼠中比较它们的体内表达程序。大多数表达的发育和细胞特异性子程序都符合内源性plp/DM20基因座已知的表达表型特征，从而确定了控制其正常时间和细胞特异性程序的组合机制的多个组成部分。连同先前表征的神经系统增强子，这里描述的那些增强子应该有助于揭示在多个神经胶质细胞和神经元谱系中起作用的元件的内容和配置。这里衍生的转基因品系也为神经胶质细胞和神经元谱系进展的多个阶段提供了有效的标记。
