SRF deletion results in earlier disease onset in a mouse model of amyotrophic lateral sclerosis
Jialei Song, Natalie Dikwella, Daniela Sinske, Francesco Roselli, Bernd Knöll
Jialei Song, Natalie Dikwella, Daniela Sinske, Francesco Roselli, Bernd Knöll
View: Text | PDF
Research Article Neuroscience

SRF deletion results in earlier disease onset in a mouse model of amyotrophic lateral sclerosis

Abstract

Changes in neuronal activity modulate the vulnerability of motoneurons (MNs) in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). So far, the molecular basis of neuronal activity’s impact in ALS is poorly understood. Herein, we investigated the impact of deleting the neuronal activity–stimulated transcription factor (TF) serum response factor (SRF) in MNs of SOD1G93A mice. SRF was present in vulnerable MMP9+ MNs. Ablation of SRF in MNs induced an earlier disease onset starting around 7–8 weeks after birth, as revealed by enhanced weight loss and decreased motor ability. This earlier disease onset in SRF-depleted MNs was accompanied by a mild elevation of neuroinflammation and neuromuscular synapse degeneration, whereas overall MN numbers and mortality were unaffected. In SRF-deficient mice, MNs showed impaired induction of autophagy-encoding genes, suggesting a potentially new SRF function in transcriptional regulation of autophagy. Complementary, constitutively active SRF-VP16 enhanced autophagy-encoding gene transcription and autophagy progression in cells. Furthermore, SRF-VP16 decreased ALS-associated aggregate induction. Chemogenetic modulation of neuronal activity uncovered SRF as having important TF-mediating activity–dependent effects, which might be beneficial to reduce ALS disease burden. Thus, our data identify SRF as a gene regulator connecting neuronal activity with the cellular autophagy program initiated in degenerating MNs.

Authors

Jialei Song, Natalie Dikwella, Daniela Sinske, Francesco Roselli, Bernd Knöll

×

Figure 9

Chemogenetics reveals a requirement of SRF for neuronal activity to modulate disease burden in ALS-affected MNs.

Options: View larger image (or click on image) Download as PowerPoint
Chemogenetics reveals a requirement of SRF for neuronal activity to modu...
(A) P26 mice were injected into the spinal cord (level T11–T13) with AAV9 particles driving inhibitory (inh. PSAM labeled with GFP in green) or activatory PSAM expression (act. PSAM labeled with BTX in red). At P33, mice were injected for 8 days with the PSEM ligand. After sacrifice, ventral horns were stained for misfolded SOD1 and LC3A (along with VAChT, BTX, and GFP). Diagram created with BioRender.com with agreement no. ON244OBBZ4. (B–G) MNs of mSOD1 (B–D) or mSOD1/Srf-KO (E–G) mice were stained for misfolded SOD1 abundance. In mSOD1 mice, activating PSAM (C) lowered, whereas inhibitory PSAM (D) enhanced misfolded SOD1 level compared with mock infection (ctr.; B). In mSOD1/Srf-KO mice, chemogenetic manipulation failed to alter misfolded SOD1 levels (E–G). Inserts in B–G show a merged picture of all channels. (H–M) LC3A levels were decreased by activating PSAM (I) and slightly enhanced by inhibitory PSAM (J) compared with control (H) in mSOD1 mice. In SRF-deleted mice, neuronal excitability did not change LC3A abundance (K–M). Inserts in H–M show a merged picture. (N and O) Quantification of mean gray values for misfolded SOD1 (N) or LC3A (O). In N and O, n values are indicated by dots each reflecting 1 animal. In N, n values for MNs in mSOD1 mice were 150 (PSAM neg.), 198 (activating PSAM), and 200 (inhibitory PSAM) and, for mSOD1/Srf-KO mice, 148 (PSAM neg.), 150 (activating PSAM), and 200 (inhibitory PSAM). In O, n values for MNs in mSOD1 mice were 153 (PSAM neg.), 200 (activating PSAM), and 200 (inhibitory PSAM) and, for mSOD1/Srf-KO mice, 191 (PSAM neg.), 150 (activating PSAM), and 200 (inhibitory PSAM). Statistical testing was performed by 1-way ANOVA with Tukey corrections. Scale bar: 30 μm.