以前的研究表明,，在人類中，至少有四個肌管素（myotubularin）家族基因的突變會造成神經(jīng)性肌肉紊亂,，但是它們的信號通路和調(diào)節(jié)機制一直不清楚,。最近，中科院水生生物研究所淡水生態(tài)與生物技術(shù)國家重點實驗室由桂建芳研究員主持的魚類發(fā)育遺傳學(xué)學(xué)科組的一項研究發(fā)現(xiàn),，一個肌管素相關(guān)的（myotubularin-related）磷酸酶Mtmr8與磷脂酰肌醇-3激酶（phosphatidylinositol-3-kinase）PI3K合作調(diào)節(jié)斑馬魚的肌動蛋白纖維造型和肌肉發(fā)育,。
他們首先從斑馬魚中克隆鑒定出Mtmr8，發(fā)現(xiàn)Mtmr8在體節(jié)發(fā)生早期主要在眼部和體節(jié)部位表達,；然后,，他們用morpholino敲降策略來研究該基因的功能及其作用機制。他們發(fā)現(xiàn),，在Mtmr8敲降的胚胎中，肌節(jié)發(fā)生出現(xiàn)明顯畸形,，且Akt的磷酸化水平明顯上升,；進一步研究發(fā)現(xiàn)，雖然Mtmr8的PH/G結(jié)構(gòu)域缺失對胚胎發(fā)育沒有造成明顯影響,，但加入PI3K抑制劑LY294002后會造成明顯的胚胎發(fā)育缺陷,，表明PH/G結(jié)構(gòu)域?qū)τ贛tmr8的功能是必需的。接著,，他們進一步研究了Mtmr8和PI3K在肌動蛋白纖維造型和肌肉發(fā)育中的作用,，發(fā)現(xiàn)Mtmr8 morpholino敲降會導(dǎo)致胚胎肌動蛋白細胞骨架的解體混亂，而且證實這些作用是通過影響Hedgehog通路引起的,；細胞移植實驗研究表明,，Mtmr8以非細胞自主方式調(diào)節(jié)肌動蛋白造型。上述研究揭示出Mtmr8與PI3K協(xié)同作用調(diào)節(jié)斑馬魚肌動蛋白造型和肌肉發(fā)育,，而且證實Hedgehog信號通路參與其中,。由于截至目前為止,，還沒有有效的治療先天性肌管性肌病，他們的結(jié)果首次提供了一個在體內(nèi)研究MTM家族相關(guān)疾病分子機制的技術(shù)途徑,，這些結(jié)果對進一步研究有重要的指導(dǎo)意義,。
該研究得到國家基礎(chǔ)研究973計劃等項目的資助，主要是由博士研究生梅潔等完成,，研究論文3月26日在PLoS ONE 的Developmental Biology在線發(fā)表,。（生物谷Bioon.com）
生物谷推薦原始出處：
PLoS ONE 4(3): e4979. doi:10.1371/journal.pone.0004979
Cooperation of Mtmr8 with PI3K Regulates Actin Filament Modeling and Muscle Development in Zebrafish
Jie Mei, Zhi Li, Jian-Fang Gui*
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Wuhan, China
Background
It has been shown that mutations in at least four myotubularin family genes (MTM1, MTMR1, 2 and 13) are causative for human neuromuscular disorders. However, the pathway and regulative mechanism remain unknown.
Methodology/Principal Findings
Here, we reported a new role for Mtmr8 in neuromuscular development of zebrafish. Firstly, we cloned and characterized zebrafish Mtmr8, and revealed the expression pattern predominantly in the eye field and somites during early somitogenesis. Using morpholino knockdown, then, we observed that loss-of-function of Mtmr8 led to defects in somitogenesis. Subsequently, the possible underlying mechanism and signal pathway were examined. We first checked the Akt phosphorylation, and observed an increase of Akt phosphorylation in the morphant embryos. Furthermore, we studied the PH/G domain function within Mtmr8. Although the PH/G domain deletion by itself did not result in embryonic defect, addition of PI3K inhibitor LY294002 did give a defective phenotype in the PH/G deletion morphants, indicating that the PH/G domain was essential for Mtmr8's function. Moreover, we investigated the cooperation of Mtmr8 with PI3K in actin filament modeling and muscle development, and found that both Mtmr8-MO1 and Mtmr8-MO2+LY294002 led to the disorganization of the actin cytoskeleton. In addition, we revealed a possible participation of Mtmr8 in the Hedgehog pathway, and cell transplantation experiments showed that Mtmr8 worked in a non-cell autonomous manner in actin modeling.
Conclusion/Significance
The above data indicate that a conserved functional cooperation of Mtmr8 with PI3K regulates actin filament modeling and muscle development in zebrafish, and reveal a possible participation of Mtmr8 in the Hedgehog pathway. Therefore, this work provides a new clue to study the physiological function of MTM family members.
