結締組織生長因子在小鼠大腦皮質中所扮演的角色

Abstract

結締組織生長因子(CTGF)是一種分泌性的胞外基質相關蛋白，在細胞功能調控上扮演許多角色。雖然如此，但是現今對於CTGF的功能研究主要還是在非神經組織上，而中樞神經系統中的CTGF所扮演的角色仍然不清楚。目前只知道，在中樞神經系統中，CTGF會表現於皮質底板上(cortical subplate)。因此，為了研究大腦中CTGF的功能，我們使帶有Ctgfflox/flox的基因轉殖小鼠與帶有Emx1-Cre的基因轉殖小鼠交配，所產出的後代小鼠的前腦(forebrain, Fb)，在出生前即表現重組脢蛋白(Cre)以達到Ctgf基因剔除(knockout, KO)的目的，利用此Ctgf前腦專一性剔除(FbCtgf KO)小鼠來做為本次實驗的研究對象。 我們利用免疫組織化學染色法來觀察幼鼠(4-5 weeks)與成鼠(10-12 weeks 以及16-18 weeks)體感皮質區(somatosensory cortex)中的神經細胞分布，藉此分析CTGF在維持皮質層以及皮質層發育上的功能為何。實驗結果顯示，在細胞分佈方面，包括神經細胞(neurons)與神經膠細胞(neural glia)，FbCtgf KO小鼠與野生型小鼠並沒有差異。近來不論是in vitro或是in vivo的研究皆顯示，CTGF的存在會抑制寡突細胞(oligodendrocytes)的分化。我們發現，比起野生型小鼠，在FbCtgf KO成鼠的大腦白質外囊(external capsule)中，有較多的成熟寡突細胞，此結果顯示了CTGF會抑制寡突細胞的成熟過程。

Connective tissue growth factor (CTGF) is a secreted extracellular matrix-associated protein that plays various roles in the regulation of cellular functions. While the roles of CTGF have been well-characterized in non-neural tissues, little is known regarding its function in the CNS. It has been reported that CTGF is expressed in the cortical subplate, but its role is still unknown. Thus, to explore the function of CTGF in the brain, a forebrain-specific Ctgf knockout (FbCtgf KO) mouse model was generated by crossing Ctgfflox/flox mice with Emx1-Cre transgenic mice in which the expression of Cre is prenatally initiated and the full length Ctgf is removed in the forebrain structures. We performed immunohistochemistry analyses to characterize neural patterning of the somatosensory cortex of juvenile (4-5 weeks) and adult (10-12 weeks and 16-18 weeks) mice to determine the effect of CTGF on the development and/or maintenance of cortical layers. Our results showed that the distribution of neurons and glia in FbCtgf KO mice did not exhibit differences compared to wild-type mice. Recent in vitro and in vivo studies have shown that CTGF hinders the differentiation of oligodendrocytes. In our mouse model, greater number of mature oligodendrocytes in the external capsule was noticed in adult FbCtgf KO mice, compared to wild-type mice, suggesting an inhibitory role of CTGF in the maturation of oligodendrocytes.