Background The identification of pathogenic mutations in Alzheimer’s disease (AD) causal genes led to a better understanding of the pathobiology of AD. Familial Alzheimer’s disease (FAD) is known to be associated with mutations in the APP, PSEN1, and PSEN2 genes involved in Aβ production; however, these genetic defects occur in only about 10–20% of FAD cases, and more genes and new mechanism causing FAD remain largely obscure. Methods We performed exome sequencing on family members with a FAD pedigree and identified gene variant ZDHHC21 p.T209S. A ZDHHC21 T209S/T209S knock-in mouse model was then generated using CRISPR/Cas9. The Morris water navigation task was then used to examine spatial learning and memory. The involvement of aberrant palmitoylation of FYN tyrosine kinase and APP in AD pathology was evaluated using biochemical methods and immunostaining. Aβ and tau pathophysiology was evaluated using ELISA, biochemical methods, and immunostaining. Field recordings of synaptic long-term potentiation were obtained to examine synaptic plasticity. The density of synapses and dendritic branches was quantified using electron microscopy and Golgi staining. Results We identified a variant (c.999A > T, p.T209S) of ZDHHC21 gene in a Han Chinese family. The proband presented marked cognitive impairment at 55 years of age (Mini-Mental State Examination score = 5, Clinical Dementia Rating = 3). Considerable Aβ retention was observed in the bilateral frontal, parietal, and lateral temporal cortices. The novel heterozygous missense mutation (p.T209S) was detected in all family members with AD and was not present in those unaffected, indicating cosegregation. ZDHHC21 T209S/T209S mice exhibited cognitive impairment and synaptic dysfunction, suggesting the strong pathogenicity of the mutation. The ZDHHC21 p.T209S mutation significantly enhanced FYN palmitoylation, causing overactivation of NMDAR2B, inducing increased neuronal sensitivity to excitotoxicity leading to further synaptic dysfunction and neuronal loss. The palmitoylation of APP was also increased in ZDHHC21 T209S/T209S mice, possibly contributing to Aβ production. Palmitoyltransferase inhibitors reversed synaptic function impairment. Conclusions ZDHHC21 p.T209S is a novel, candidate causal gene mutation in a Chinese FAD pedigree. Our discoveries strongly suggest that aberrant protein palmitoylation mediated by ZDHHC21 mutations is a new pathogenic mechanism of AD, warranting further investigations for the development of therapeutic interventions.
Polylactic acid (PLA), as a bioplastic, is extensively utilized in bone tissue engineering for its biocompatibility, adaptability and affordability. However, the toxicological research of PLA is still limited. The hydrolysis products of PLA induced inflammatory response which caused inflammatory osteolysis mediated by oxidative damage through the recruitment of macrophages and the accumulation of foreign body multinucleated giant cells, ultimately leading to the failure of bone tissue regeneration. The lack of effective treatments highlights the importance of finding new therapies. This study systematically investigated the potential molecular mechanisms of PLA-induced inflammatory osteolysis by employing network toxicology and molecular docking techniques. We first conducted a network toxicology-based assessment according to the molecular structure of PLA. The result from integrating and screening targets from multiple databases identified 126 potential targets associated with PLA-induced inflammatory osteolysis, and then an interaction network diagram of the targets was constructed. Gene ontology (GO)/KEGG enrichment analysis clarified that PLA may cause inflammatory osteolysis via metabolic pathways and pathways in cancer, as well as lipid and atherosclerosis. Further analysis by STRING and Cytoscape software screened 25 core targets including HSP90AA1, AKT1, SRC, STAT1 and FYN. We found that the enriched highly correlated pathways covered 18 of the 25 core targets, supporting the scientific hypothesis that PLA induces inflammatory osteolysis. Moreover, the results of molecular docking confirmed that PLA displayed a strong binding ability with the core targets and formed stable binding. Taken together, this study not only revealed the potential biological mechanism of PLA-induced inflammatory osteolysis, but also provided new evidence for the future prevention and treatment of PLA-induced inflammation.
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