Fig. 5.

Differential effects of arimoclomol and RGFP963 on the decline in Hspa8 mRNA levels in motor neurons expressing ALS variants. (a) and (b) Controls: Hspa8 mRNA expression remained unchanged over a 3-day period in (a) soma and (b) dendrites of control motor neurons (nonmicroinjected neurons labeled with MAP2 antibody and microinjected motor neurons expressing eGFP). (c) and (d) In somata of motor neurons expressing TDP-43^G348C, Hspa8 levels gradually declined over 3 days; Combined treatment with RGFP963 and arimoclomol prevented the decline from day 2 to day 3. (e) and (f) In motor neurons expressing FUS^R521G, Hspa8 mRNA levels declined in both somata and dendrites. Combination treatment failed to prevent this decline in somata, although decline in dendrites was less. (g) and (h) Spike in HSPA8 mRNA somata of SOD1^G93A-expressing motor neurons on day 1, but substantial decline by day 3, which was prevented by the drug combination. Similarly, drug combination maintained Hspa8 mRNA in dendrites. Data are presented as mean ± SD, n = 9–60 neurons. Statistical significance was evaluated through one-way ANOVA followed by Bonferroni post hoc analysis. *P < 0.05, **P < 0.01, ***P < 0.001, ****P< 0.0001. Abbreviations used: ALS, amyotrophic lateral sclerosis; FUS, fused in sarcoma; SD, standard deviation; SOD1, superoxide dismutase I; TDP-43, TAR DNA binding protein 43 kDa. eGFP; enhanced green fluorescent protein.