| Summary: | 碩士 === 國立臺灣大學 === 生物科技研究所 === 105 === Survival motor neuron (SMN) is an essential protein plays important roles in the assembly of small nuclear ribonucleoproteins (snRNPs), the components of the RNA spliceosome, and other functions include transcriptional regulation and cellular trafficking. From the aspect of evolution, SMN gene is highly conserved through diverse species and keeps fundamental functions. Deficiency of the ubiquitous SMN protein causes spinal muscular atrophy (SMA), a leading genetic cause of infant death and one of the most common autosomal recessive diseases. In addition to the roles in neuron cells, recent studies have linked the connection between SMN and stem cell potency. We and others showed that SMN regulates stem cell pluripotency, division, proliferation and differentiation in Drosophila and mouse model. On the other hand, SMN is abundantly expressed in mouse oocytes and embryonic stem cells, but low in mouse embryonic fibroblast cells (MEFs) and neurons. Therefore, we hypothesize that SMN may play important roles during the reprogramming process of induced pluripotent stem cell (iPSC) formation. The objective of this study is to examine the roles of SMN in cellular reprogramming and neuronal differentiation in normal and SMA cells. The results showed that SMN was up-regulated during the induced pluripotency reprogramming process by OSKM (Oct4, Sox2, Klf4, and cMyc) factors when ICR and C57BL/6s WT mouse MEFs were used, along with the typical pluripotency markers including Nanog, Oct4 and SSEA1. Over-expression of SMN in WT cells improved the iPSC formation efficiency as judged by real-time PCR and alkaline phosphatase (AP) activity; whereas knocking-down of SMN completely abolished the iPSC formation. Consistently, iPSC formation efficiency using SMA mouse tail-tip fibroblasts (TTFs) was extremely low, along with impaired pluripotent genes expression, including Oct4, Sox2, Klf4, Sall4 and Rex1. Reduced SMN also delayed neuronal differentiation when compared to those with normal SMN level. Finally, over-expression of SMN in SMA tail-tip fibroblasts improved the pluripotent genes expression in iPSC as well as the neurite in vitro differentiation. These findings indicate that SMN plays important roles during cellular reprogramming and neuronal differentiation.
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