X-linked microtubule-associated protein, Mid1, regulates axon development

• Published in: Proceedings of the National Academy of Sciences - PNAS 2013-11, Vol.110 (47), p.19131-19136
• Main Authors: Lu, Tingjia, Chen, Renchao, Cox, Timothy C., Moldrich, Randal X., Kurniawan, Nyoman, Tan, Guohe, Perry, Jo K., Ashworth, Alan, Bartlett, Perry F., Li Xu, Zhang, Jing, Lu, Bin, Wu, Mingyue, Qi Shen, Liu, Yuanyuan, Richards, Linda J., Xiong, Zhiqi
• Format: Article
• Language: English
• Subjects: Animals; Axons; Axons - physiology; Biological and medical sciences; Biological Sciences; Brain; Cell growth; Cells; Cerebral Cortex - cytology; Cerebral Cortex - growth & development; Cleft Palate - physiopathology; Developmental biology; Esophagus - abnormalities; Esophagus - physiopathology; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Gene Knockdown Techniques; Genetic Diseases, X-Linked - physiopathology; Genotype & phenotype; Growth Cones - physiology; Hypertelorism - physiopathology; Hypospadias - physiopathology; Immunoblotting; In Situ Hybridization; Mice; Mice, Knockout; Microtubules; Neurological disorders; Neurons; Phenotypes; Phosphatases; Protein Phosphatase 2 - metabolism; Proteins; Proteins - genetics; Proteins - metabolism; Proteolysis; Real-Time Polymerase Chain Reaction; RNA Interference; Synapses; Time-Lapse Imaging; Ubiquitin-Protein Ligases; Vertebrates: nervous system and sense organs
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1303687110

Opitz syndrome (OS) is a genetic neurological disorder. The gene responsible for the X-linked form of OS, Midline-1 (MID1), encodes an E3 ubiquitin ligase that regulates the degradation of the catalytic subunit of protein phosphatase 2A (PP2Ac). However, how Mid1 functions during neural development is largely unknown. In this study, we provide data from in vitro and in vivo experiments suggesting that silencing Mid1 in developing neurons promotes axon growth and branch formation, resulting in a disruption of callosal axon projections in the contralateral cortex. In addition, a similar phenotype of axonal development was observed in the Mid1 knockout mouse. This defect was largely due to the accumulation of PP2Ac in Mid1-depleted cells as further down-regulation of PP2Ac rescued the axonal phenotype. Together, these data demonstrate that Mid1-dependent PP2Ac turnover is important for normal axonal development and that dysregulation of this process may contribute to the underlying cause of OS.