Metabolic dysfunction-associated steatotic liver disease (MASLD) primarily results from dysregulated lipid metabolism in hepatocytes. However, the mechanisms governing hepatic lipid metabolism remain Show more
Metabolic dysfunction-associated steatotic liver disease (MASLD) primarily results from dysregulated lipid metabolism in hepatocytes. However, the mechanisms governing hepatic lipid metabolism remain incompletely understood. Our preliminary experiments demonstrated elevated expression of R-spondin 2 (RSPO2), a matricellular protein, in steatotic livers. Therefore, we investigated the role of RSPO2 in MASLD and potential underlying mechanisms. Comprehensive RSPO2 expression was significantly increased in steatotic livers of high-fat diet-fed wild-type ( These findings identify RSPO2 as a key suppressor of hepatic steatosis and fibrosis, and highlight its potential as a therapeutic target for MASLD. Given the hepatic/extrahepatic complications associated with MASLD (metabolic dysfunction-associated steatotic liver disease) and its high prevalence, it is crucial to decipher the precise molecular mechanisms regulating its pathogenesis to identify novel druggable targets. In this study, we demonstrate for the first time that hepatocyte RSPO2 plays a protective role against hepatic steatosis, fibrosis, and inflammation. Show less
Postmortem studies in schizophrenia consistently show reduced dendritic spines in the cerebral cortex but the mechanistic underpinnings of these deficits remain unknown. Recent genome-wide association Show more
Postmortem studies in schizophrenia consistently show reduced dendritic spines in the cerebral cortex but the mechanistic underpinnings of these deficits remain unknown. Recent genome-wide association studies and exome sequencing investigations implicate synaptic genes and processes in the disease biology of schizophrenia. We generated human cortical pyramidal neurons by differentiating iPSCs of seven schizophrenia patients and seven healthy subjects, quantified dendritic spines and synapses in different cortical neuron subtypes, and carried out transcriptomic studies to identify differentially regulated genes and aberrant cellular processes in schizophrenia. Cortical neurons expressing layer III marker CUX1, but not those expressing layer V marker CTIP2, showed significant reduction in dendritic spine density in schizophrenia, mirroring findings in postmortem studies. Transcriptomic experiments in iPSC-derived cortical neurons showed that differentially expressed genes in schizophrenia were enriched for genes implicated in schizophrenia in genome-wide association and exome sequencing studies. Moreover, most of the differentially expressed genes implicated in schizophrenia genetic studies had lower expression levels in schizophrenia cortical neurons. Network analysis of differentially expressed genes led to identification of NRXN3 as a hub gene, and follow-up experiments showed specific reduction of the NRXN3 204 isoform in schizophrenia neurons. Furthermore, overexpression of the NRXN3 204 isoform in schizophrenia neurons rescued the spine and synapse deficits in the cortical neurons while knockdown of NRXN3 204 in healthy neurons phenocopied spine and synapse deficits seen in schizophrenia cortical neurons. The antipsychotic clozapine increased expression of the NRXN3 204 isoform in schizophrenia cortical neurons and rescued the spine and synapse density deficits. Taken together, our findings in iPSC-derived cortical neurons recapitulate cell type-specific findings in postmortem studies in schizophrenia and have led to the identification of a specific isoform of NRXN3 that modulates synaptic deficits in schizophrenia neurons. Show less