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Parkinson's disease (PD) is associated with a reduction in 26/20S proteasome and mitochondrial function and depletion of dopamine. Activation of mitochondrial function with the NAD + precursor nicotinamide riboside (NR) is a potential therapeutic for PD. However, despite recently started clinical trials, analysis of NR in mammalian animal PD models is lacking and data in simpler PD models is limited. We analyzed the effect of NR in C. elegans and in mouse 26/20S proteasome inhibition models of PD. In C. elegans , NR rescued α-synuclein overexpression induced phenotypes likely by activating the mitochondrial unfolded protein response. However, in a proteasome inhibitor-induced mouse model of PD, NR first partially rescued behavioural dysfunction, but later resulted in decrease in dopamine and its related gene expression in the substantia nigra. Our results suggest that reduction in 26/20S function with long term NR treatment may increase risk for developing reduced nigrostriatal DA function., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Charles Brenner reports a relationship with ChromaDex Inc that includes: consulting or advisory and equity or stocks. Charles Brenner reports a relationship with Athena Therapeutics that includes: equity or stocks. Charles Brenner reports a relationship with Juvenis that includes: equity or stocks. Eija Pirinen reports a relationship with ChromaDex Inc that includes: speaking and lecture fees. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

The 3' untranslated regions (UTRs) modulate gene expression levels by regulating mRNA stability and translation. We previously showed that the replacement of the negative regulatory elements from the 3'UTR of glial cell line-derived neurotrophic factor (GDNF) resulted in increased endogenous GDNF expression while retaining its normal spatiotemporal expression pattern. Here, we have developed a methodology for the generation of in vivo hyper- and hypomorphic alleles via 3'UTR targeting using the CRISPR/Cas9 system. We demonstrate that CRISPR/Cas9-mediated excision of a long inhibitory sequence from Gdnf native 3'UTR in mouse zygotes increases the levels of endogenous GDNF with similar phenotypic alterations in embryonic kidney development as we described in GDNF constitutive and conditional hypermorphic mice. Furthermore, we show that CRISPR/Cas9-mediated targeting of 3'UTRs in vivo allows the modulation of the expression levels of two other morphogens, Gdf11 and Bdnf . Together, our work demonstrates the power of in vivo 3'UTR editing using the CRISPR/Cas9 system to create hyper- and hypomorphic alleles, suggesting wide applicability in studies on gene function and potentially, in gene therapy., Competing Interests: The authors declare that they do not have competing interests., (© 2023 Published by Elsevier Ltd.)