Characterization of floor plate specific genes by using transgenic mice

底板是一组位于发育中的神经系统腹中线的非神经细胞，通过分泌形态因子和轴突引导分子，在神经模式形成中起重要作用。本研究旨在通过转基因小鼠阐明两个底板特异性基因sulfatase FP1 （SulfFP1）和Autotaxin的功能意义。SulfFP1是硫酸酯酶家族的新成员，在成人大脑的底板、脉络膜丛、骨形成区、肾脏和一些神经元中表达。为了表征SulfFP1在这些组织中的表达调控元件，在SulfFP1启动子的控制下，产生了含有绿色荧光蛋白（GFP）的转基因小鼠。SulfFP1转录起始位点上游的12kbp基因组序列驱动GFP在骨形成区、肾脏和成人脑中的表达，但在底板和脉络丛中不表达。上游2.3 kbp序列，而非1.8 kbp序列，在骨形成区驱动类似的表达。1.8 kbp和2.3 kbp之间的序列包括对骨发育至关重要的sox结合的共识序列。Autotaxin是外显/外显磷酸二酯酶家族的一员，最初被确定为细胞运动促进因子。最近有报道称，它具有在细胞外空间产生溶血磷脂酸所需的溶血磷脂酶D活性，尽管其生理作用尚不清楚。因此，我们试图在体内产生过表达Autotaxin的转基因小鼠，但只获得了弱表达的细胞系。在这些细胞系中观察到脑和脊髓中少突胶质细胞的轻微增加。这些结果表明Autotaxin参与了少突胶质细胞的分化，Autotaxin过表达可能导致发育早期的致死表型。

Floor plate, a group of non-neural cells located in the ventral midline of the developing nervous system, plays an important role in neural patterning by secreting morphogens and axon guidance molecules. This study aims to clarify the functional significance of two floor plate specific genes, sulfatase FP1 (SulfFP1) and Autotaxin by using transgenic mice.SulfFP1 is a novel member of the sulfatase family, and is expressed in the floor plate, choroid plexus, bone-forming regions, kidney, some neurons in the adult brain. To characterize the regulatory element of SulfFP1 expression in these tissues, transgenic mice harboring the green fluorescent protein (GFP) under the control of the SulfFP1 promoter were generated. The 12 kbp genomic sequence upstream of the SulfFP1 transcription initiation site drives GFP expression in bone-formmg regions, kidney, and adult brain, but not in the floor plate and choroid plexus. Upstream 2.3 kbp sequence, but not 1.8 kbp sequence, drives the similar expression in the bone-formmg regions. The sequence between 1.8 kbp and 2.3 kbp includes the consensus sequence for the Sox-binding that is essential for bone development.Autotaxin, a member of the ecto-/exo-phosphodiesterase family, is initially identified as a cell motility promoting factor. It is recently reported to possess the lysophospholipase D activity that is required lysophophatidic acid production in the extracellular space, although its physiological role remains unknown. We therefore tried to generate transgenic mice that are overexpressing Autotaxin in the body, but only weakly-expressing lines were obtained. Slight increase of oligodendrocytes in the brain and spinal cord were observed in these lines. These results indicate that Autotaxin is involved in the oligodendrocyte differentiation, and that Autotaxin overexpression may lead to lethal phenotype in the early development.