“The Tale of the Curly-Bearded Guest” 231Studies Bian, Xiaoxuan . “Lun ‘Qiu ran ke zhuan’ de zuozhe, zuonian ji zhengzhi beijing” , in Dongnan daxue xuebao. Vol. 3, 2005, pp. 93-98. Cai, Miaozhen . “Chongtu yu jueze — ‘Qiu ran ke zhuan’ de renweu xingge suzao ji qi yihan” in Xingda renwen xuebao . Vol. 34, 2004, pp. 153-180. Zhang, Hong . “Du Guangting ‘Qiu ran ke zhuan’ de liuchuan yu yingxiang” in Zhongguo daojiao, vol. 1, 1997, pp. 28-31. Liu, Zhiwei . “Gujin ‘Qiu ran ke zhuan’ de yanjiu fansi” in Xibei daxue xuebao. Vol. 1, 2000. Sun, Yiping . Du Guangting pingzhuan. Nanjing: Nanjing daxue chubanshe, 2005. ___. “‘Qiu xu ke’ yu ‘Qiu ran ke’” in Zhongguo daojiao. vol. 6, 2005, pp. 14-17. Luo, Zhengming . Du Guangting daojiao xiaoshuo yanjiu . Chengdu: Bashu shushe, 2005. Wang, Meng’ou . “Qiuran ke yu Tang zhi chuangye chuangshuo” in Tangren xiaoshuo yanjiu siji. Taipei: Yiwen chubanshe, 1978, p. 254. Xu, Jiankun . “‘Qiu ran ke zhuan’ jili jiegou xintan” in Donghai zhongwen xuebao . Vol. 11, 1994, pp. 61-72. Ye, Qingbing . “‘Qiu ran ke zhuan’ de xiezuo jiqiao” in Zhongguo gudian wenxue yanjiu congkan — Xiaoshuo zhi bu . Taipei: Juliu, 1977, pp. 167-79.
GCaMP6 was cloned into the pMXs-Dest-WRE retroviral vector and transduced into reprogramming cultures concurrently with the motor neuron factors. To assess GCaMP6 activity, 1.5 μm glutamate was added to iMN cultures and cells were imaged continuously for 2 minutes at 24 frames per second. GFP flashes were scored manually using the video recording. At least 3 different fields of view from three independent cultures, totalling 50–100 iMNs, were scored per condition.
Amongst four reproducible hit compounds, we identified a PIKFYVE kinase inhibitor (YM201636) that significantly increased C9ORF72 patient iMN survival (n=2 patients) (Fig. 6b, c and Supplementary Fig. 15a). PIKFYVE is a lipid kinase that converts phosphatidylinositol 3-phosphate (PI3P) into phosphtidylinositol (3,5)-bisphosphate (PI(3,5)P2)51(Fig. 6f). PI3P is primarily generated by PI3-kinases recruited to early endosomes by RAB5, and PI3P anchors EEA1 to early endosomes to drive endosomal maturation 52(Fig 6f). Following endosomal maturation into lysosomes, PI3P drives fusion of lysosomes with autophagosomes 53. PIKFYVE regulates PI3P levels by converting PI3P into PI(3,5)P2 52, which disfavors lysosomal fusion with endosomes and autophagosomes 53,54. Therefore, inhibition of PIKFYVEincreases autophagosome-lysosome fusion 53 and may compensate for reduced C9ORF72 activity and other disease processes by increasing PI3P levels to facilitate removal of glutamate receptors or DPRs (Fig. 6f). Interestingly, FIG4 is a phosphatase that opposes PIKFYVE kinase by converting PI(3,5)P2 to PI3P and loss-of-function mutations in FIG4 cause ALS 55. Thus, genetic evidence suggests that PIKFYVE inhibition may be capable of modulating ALS disease processes in humans.
Consistent with previous studies 3,4,6–8, patient iMNs (n=5 patients) had reduced C9ORF72 expression compared to controls (n=3; Fig. 2a and Supplementary Fig. 4a, 5b). While previous studies have linked low C9ORF72 levels to changes in vesicle trafficking or autophagy 18,20,30–33, it remains unknown if loss of C9ORF72 protein directly contributes to degeneration. Thus, we re-expressed C9ORF72 (isoform A or B) in iMNs using a retroviral cassette (Supplementary Fig. 4b) and found that both isoforms rescued C9ORF72 patient iMN survival in response to glutamate treatment (n=3 patients Fig. 2b and Supplementary Fig. 4c). This effect was specific for C9ORF72 iMNs, as forced expression of C9ORF72 did not rescue SOD1A4V iMN survival (Fig. 2c), nor did it improve the survival of control iMNs (n=2 controls Fig. 2d and Supplementary Fig. 4d).
All animal use and care were in accordance with local institution guidelines of the University Medical Center Utrecht (Utrecht, the Netherlands) and approved by the Dierexperimenten Ethische Commissie Utrecht with the protocol number DEC 2013.I.09.069. Wild-type C57BL6/J (strain: 000664), C9ORF72 KO (C57BL/6J-3110043021Rikem5Lutzy/J, strain: 027068), and C9-BAC (C57BL/6J-Tg(C9orf72_i3)112Lutzy/J, strain: 023099) were purchased from Jackson Laboratories (The Jackson Laboratory, Bar Harbor, USA). Mice were housed in standard conditions with food and water ad libitum in the conventional vivarium at the University of Southern California. All animal use and care were in accordance with local institution guidelines of the University of Southern California and the IACUC board of the University of Southern California (Los Angeles, USA) with the protocol numbers 20546 and 11938.