Objective: To determine whether knockdown of transmembrane 9 super family 2 (TM9SF2) decreases the formation of alpha-synuclein inclusions and toxicity to nigral neurons in the rat a-syn preformed fibril (PFF) model.

Background: Transmission of pathological a-syn may drive neuronal dysfunction and degeneration. Therefore, strategies to prevent the uptake of pathological a-syn may be neuroprotective. We examined the impact of viral vector mediated knockdown of TM9SF2 in nigral neurons on accumulation of a-syn inclusions and degeneration of nigral dopamine neurons in the rat a-syn PFF model.

Method: Rats received intranigral injections of either rAAV2/9 TM9SF2 shRNA or rAAV2/9 scrambled shRNA of varying titers. One month following injection, transduction and expression levels of TM9SF2 in the substantia nigra (SN) were assessed using immunohistochemistry and in situ hybridization. Following optimal titer identification, a separate cohort of rats received intranigral injections of rAAV2/9 TM9SF2 shRNA, rAAV2/9 scrambled shRNA or an equal volume of vehicle. One month following vector surgery, rats received intrastriatal injections of a-syn PFFs or a-syn monomer. At 2 or 6 months following PFF/monomer injection, the SN was assessed for transduction, TM9SF2 knockdown, number of nigral neurons with pSyn inclusions, and number of TH and HuC immunoreactive nigral neurons,

Results: Intrastriatal injection of a-syn PFFs resulted in abundant pSyn inclusions in the SN. TM9SF2 knockdown was associated with a significant decrease in pSyn inclusions two months following PFF injection. PFF injection was associated with significant degeneration (~50%) of SN neurons at the 6-month time point but TM9SF2 knockdown did not rescue PFF-induced degeneration.

Conclusion: Our studies demonstrate that TM9SF2 is involved in the uptake of PFFs, facilitating the formation of a-syn inclusions. Knockdown of TM9SF2 can significantly attenuate these processes. However, TM9SF2 knockdown-associated reduction in nigral pSyn inclusions did not translate into decreased toxicity to nigral neurons at 6 months in the a-syn PFF model. It is possible that TM9SF2 knockdown delays the peak but does not decrease the overall magnitude of pSyn inclusion formation, resulting in equivalent degeneration after long post-PFF intervals. Studies are ongoing to further evaluate mechanisms involved in TM9SF2-mediated effects on a-synuclein uptake and seeding.

« Back to 2024 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/tm9sf2-knockdown-decreases-pathological-alpha-synuclein-aggregation-in-vivo/