Multilevel Screening Platform Utilizing Cellular and Zebrafish Models to Identify Short Peptides with High Improvement of Motor Neuron Growth.

Zebrafish is emerging as a model animal for phenotype-based drug screening. Drugs screened from the zebrafish platform have advanced into clinical trials, underscoring their translational potential. Amyotrophic lateral sclerosis is a progressive motor neurons (MN) degenerative disease with few approved drugs. Previously, supplementation with exogenous recombinant phosphoglycerate kinase 1 (Pgk1) was found to improve MN growth through its interaction with receptor Eno2. To bypass the high complexity and cost of full-length Pgk1 production, a short segment within Pgk1 (M08) was predicted as the key motif interacting with Eno2, and a zebrafish phenotypic screening platform was established to find the most neurotrophic compound(s) among M08 and its mutants. We first found that M08-injected zebrafish embryos significantly increased branched caudal primary MNs (CaPMNs). However, compared to M08 (59.20 ± 1.80%), M039, among 17 mutants further screened, showed even more improvement of branched CaPMNs, up to 74.54 ± 3.73%. Next, when we administered the M039 peptide to C9ORF72-knockdown ALS-like zebrafish embryos, it improved axonal growth and swimming ability. Then, we employed a cellular model as a secondary screen, and M039 exhibited improved neurite outgrowth of MN (NOMN) and reduced p-Cofilin in NSC34 neural cells grown in ALS-like condition. Therefore, by using a zebrafish MN phenotype as a primary screening platform, we identified a mutated short peptide M039 having the most pronounced positive effect on improving neurite growth among all 17 mutants in comparison to parental M08, demonstrating the feasibility of zebrafish screening as a cost-effective strategy for finding promising neuroprotective short peptides that serve as neurotherapeutic potentials.