G蛋白偶联受体56对小鼠脑胼胝体轴突髓鞘化的影响

Effect of G-protein coupled receptor 56 on axonal myelination in the corpus callosum of mouse brain

目的探讨G蛋白偶联受体56(GPR56)对小鼠脑胼胝体轴突髓鞘化的影响。方法筛选出GPR56基因杂合型(GPR56+/-)小鼠(GPR56+/-组)和敲除型(GPR56-/-)小鼠(GPR56-/-组)各38只。每组选在小鼠出生后7 d、14 d、21 d、28 d(P7d、P14d、P21d、P28d)进行研究。应用免疫组化染色和Western Blot方法监测髓鞘碱性蛋白(MBP)和2、3-环核苷酸3-磷酸二酯酶(CNPase)在P7d、P14d、P21d、P28d两组小鼠脑胼胝体白质中的表达;用电镜观察P28d小鼠胼胝体白质内轴突髓鞘化,比较轴突髓鞘的厚度。用荧光免疫组化染色观察P7d两组小鼠胼胝体内PDGF-aR阳性(PDGF-aR+)细胞的数量。用原位杂交检测P28d两组小鼠胼胝体内髓鞘蛋白脂质蛋白(PLP)阳性(PLP+)细胞数。结果与GPR56+/-小鼠比较,MBP在P14d、P21d、P28d GPR56-/-小鼠脑胼胝体白质中的表达明显下降,CNPase在P7d、P14d、P21d、P28d GPR56-/-小鼠脑胼胝体白质中的表达明显下降(均P<0.01)。电镜见P28d GPR56-/-小鼠脑胼胝体白质内髓鞘化轴突的数量明显减少,轴突髓鞘的g-ratio值升高(P<0.05),髓鞘的厚度变薄。荧光免疫组化和原位杂交结果显示P7d GPR56+/-和GPR56-/-小鼠胼胝体内PDGF-aR+细胞数量无差异,但P28d GPR56+/-小鼠胼胝体内PLP+细胞数明显多于P28d GPR56-/-小鼠(P<0.01)。结论 GPR56蛋白分子可能通过影响少突胶质前体细胞分化成熟参与了脑白质轴突髓鞘化。

Objective To explore the effect of G-protein coupled receptor 56 （GPR56） on axonal myelination in the corpus callosum （ CC ） of mouse brain. Methods Thirty-eight GPR56 ＋/- mice （ GPR56 ＋/- group ） and 38 GPR56-/- mice（ GPR56 -/- group） were selected. According to day after birth, each group was divided into P7d, P14d, P21d and P28d subgroups. Expression of MBP and CNPase was measured in the CC of P7d,P14d,P21d,P28d GPR56 ＋/- and GPR56-/- mice by immunostaining and Western blot. Axonal myelination in the CC of P28d mice brain was observed by electron microscopy and the thickness of axonal myelin sheath was compared. The number of PDGF-aR positive（ PDGF-aR ＋ ）cells in the CC of P7d mice brain were detected by immunofiuorescence, and number of PLP positive（ PLP＋ ） cells in the CC of P28d mice brain were detected in situ hybridization. Results Compared with GPR56＋/- mice, expression of MBP in the CC of P14d, P21d, P28d GPR56 -/- mice decreased significantly, CNPase in the CC of P7d,P14d,P21d,P28d GPR56-/- mice decreased significantly（all P 〈0.01 ）. The number of myelinated axons was obviously reduced in the CC of P28d GPR56-/- mice. The value of g-ratio is smaller and thickness of myelin sheath became thinner in the GPR56 -/- mice（ P 〈 0.05 ）. There was no significant difference in the number of PDGF-aR ＋ cells in the CC of P7d GPR56＋/ and GPR56 -/- mice brain. The number of PLP ＋ cells was significantly decreased in the CC of P28d GPR56 -/- mice when compared with GPR56 ＋/- mice（ P 〈 0.01 ）. Condusion GPR56 may be involved in axonal myelination by affecting oligodendroglial precursor cells differentiation and maturation in the CC of mouse brain.