Modeling the phenotype of spinal muscular atrophy by the direct conversion of human fibroblasts to motor neurons

Abstract

// Qi-Jie Zhang 1,* , Jin-Jing Li 1,* , Xiang Lin 1 , Ying-Qian Lu 1 , Xin-Xin Guo 1 , En-Lin Dong 1 , Miao Zhao 1 , Jin He 1 , Ning Wang 1,2 and Wan-Jin Chen 1,2 1 Department of Neurology and Institute of Neurology, First Affiliated Hospital, Fujian Medical University, Fuzhou, China 2 Fujian Key Laboratory of Molecular Neurology, Fuzhou, China * These authors have contributed equally to this work Correspondence to: Wan-Jin Chen, email: // Keywords : direct reprogramming; fibroblast; induced motor neuron; spinal muscular atrophy Received : June 08, 2016 Accepted : November 22, 2016 Published : January 13, 2017 Abstract Spinal muscular atrophy (SMA) is a lethal autosomal recessive neurological disease characterized by selective degeneration of motor neurons in the spinal cord. In recent years, the development of cellular reprogramming technology has provided an alternative and effective method for obtaining patient-specific neurons in vitro . In the present study, we applied this technology to the field of SMA to acquire patient-specific induced motor neurons that were directly converted from fibroblasts via the forced expression of 8 defined transcription factors. The infected fibroblasts began to grow in a dipolar manner, and the nuclei gradually enlarged. Typical Tuj1-positive neurons were generated at day 23. After day 35, induced neurons with multiple neurites were observed, and these neurons also expressed the hallmarks of Tuj1, HB9, ISL1 and CHAT. The conversion efficiencies were approximately 5.8% and 5.5% in the SMA and control groups, respectively. Additionally, the SMA-induced neurons exhibited a significantly reduced neurite outgrowth rate compared with the control neurons. After day 60, the SMA-induced neurons also exhibited a liability of neuronal degeneration and remarkable fracturing of the neurites was observed. By directly reprogramming fibroblasts, we established a feeder-free conversion system to acquire SMA patient-specific induced motor neurons that partially modeled the phenotype of SMA in vitro .