Cooperation of Mtmr8 with PI3K Regulates Actin Filament Modeling and Muscle Development in Zebrafish

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.

中学生强迫症状及其心理、环境危险因素和整合模型研究

Obsessive-Compulsive Symptoms, which are one of common factors effected on mental health of secondary school students, have been rarely studied at home and abroad. In accordance with the problems existed in these literature up till now, the thesis had mainly studied the measured tool, contents and structure, developmental features, psychosocial risk factors and integrated model of obsessive-compulsive symptoms from them by means of investigation with quetionnaires. The entire research was divided into three phases. 3185 students(age 14.68±1.75 years) were firstly measured with the 20-item Leyton Obsessional Inventory-Child Version(LOI-CV) at four secondary schools including six grades in Beijing city, which was applied to revise LOI-CV, and to study the structure and contents, developmental features and screen of obsessive-compulsive symptoms. Then, 216 subjects with obsessive-compulsive symptoms, paired with controls in the light of school, grade and gender, were investigated with 10 self-rating scales on obsessive-compulsive symptoms, anxiety, depression, personality, coping and attributional style, negative life events, parent's rearing style, family environment and life adaptation in school, and with an inventory on social demography. The results were used to explore psychosocial risk factors and integrated model of obsessive-compulsive symptoms. The third survey was only carried out, about two months after the second, among 264 subjects with obsessive-compulsive symptoms through MMOCI and Negative Life Event Scale for Adolescents, in order to probe into the integrated model. The research had mainly found: (1) LOI-CV can be used as a screen tool for obsessive-compulsive symptoms in urban adolescents in China; (2) Total screening-out ratio of obsessive-compulsive symptoms was 13.6% (male:15.0%, female:12.2%). The most common manifestations of obsessive-compulsive symptoms were hating dirt and contamination, doing things in exact manner, angry if someone messes desk, bad conscience but no one else, worry about cleanliness, repeated thoughts or words; the least were favorite or special number, spending extra time on homework, special number or words to avoid, talking or moving to avoid bad luck, fussy about hands. The checking and repetition, cleanliness and tidiness, general obsessions were more common forms than numbers-luck; (3) No differences were existed in serious degree of obsessive-compulsive symptoms, but the screening-out ratio in male was higher than it in female; (4) No differences were detected in the serious degree of obsessive-compulsive symptoms except the scores of cleanliness and tidiness among grades, but the screening-out ratio of the grades justly entering secondary school or going to graduate were higher than other ones; (5) The main psychosocial risk factors for obsessive-compulsive symptoms included anxiety, mother's over-protecting and over-interfering, fantasy, flexibility, self-actualization, peers relationship, sense of responsibility, negative life events, mother's occupation, help-seeking, and (6) The integrated model on psychosocial risk factors suggested that the possible developed and sustained mechanism of obsessive-compulsive symptoms was that personality, coping and attributional styles constructed the developmental diathesis foundation of obsessive-compulsive symptoms; negative life events were promoting factors of them. There was a dynamic interaction between personality and environmental factors. Negative emotion played a core role in the developmental process of them. The continued existence of obsessive-compulsive symptoms was related to pre-existed obsessive-compulsive symptoms and negative life events experienced by an individual. Therefore, this research not only let us get a deeper understanding of obsessive-compulsive symptoms and more entirely find out psychosocial risk factors, firstly applied diathesis-stress theory to comprehend the psychological mechanism of obsessive-compulsive symptoms and, moreover, elaborate and expand it, but also has more important practice significance of treatment, prevent and education for obsessive-compulsive symptoms in secondary school students.