Perturbational phenotyping of human blood cells reveals genetically determined latent traits associated with subsets of common diseases

Although genome-wide association studies (GWAS) have successfully linked genetic risk loci to various disorders, identifying underlying cellular biological mechanisms remains challenging due to the complex nature of common diseases. We established a framework using human peripheral blood cells, physical, chemical and pharmacological perturbations, and flow cytometry-based functional readouts to reveal latent cellular processes and performed GWAS based on these evoked traits in up to 2,600 individuals. We identified 119 genomic loci implicating 96 genes associated with these cellular responses and discovered associations between evoked blood phenotypes and subsets of common diseases. We found a population of pro-inflammatory anti-apoptotic neutrophils prevalent in individuals with specific subsets of cardiometabolic disease. Multigenic models based on this trait predicted the risk of developing chronic kidney disease in type 2 diabetes patients. By expanding the phenotypic space for human genetic studies, we could identify variants associated with large effect response differences, stratify patients and efficiently characterize the underlying biology.

Discovery of suppressors of CRMP2 phosphorylation reveals compounds that mimic the behavioral effects of lithium on amphetamine-induced hyperlocomotion

The effective treatment of bipolar disorder (BD) represents a significant unmet medical need. Although lithium remains a mainstay of treatment for BD, limited knowledge regarding how it modulates affective behavior has proven an obstacle to discovering more effective mood stabilizers with fewer adverse side effects. One potential mechanism of action of lithium is through inhibition of the serine/threonine protein kinase GSK3β, however, relevant substrates whose change in phosphorylation may mediate downstream changes in neuroplasticity remain poorly understood. Here, we used human induced pluripotent stem cell (hiPSC)-derived neuronal cells and stable isotope labeling by amino acids in cell culture (SILAC) along with quantitative mass spectrometry to identify global changes in the phosphoproteome upon inhibition of GSK3α/β with the highly selective, ATP-competitive inhibitor CHIR-99021. Comparison of phosphorylation changes to those induced by therapeutically relevant doses of lithium treatment led to the identification of collapsin response mediator protein 2 (CRMP2) as being highly sensitive to both treatments as well as an extended panel of structurally distinct GSK3α/β inhibitors. On this basis, a high-content image-based assay in hiPSC-derived neurons was developed to screen diverse compounds, including FDA-approved drugs, for their ability to mimic lithium's suppression of CRMP2 phosphorylation without directly inhibiting GSK3β kinase activity. Systemic administration of a subset of these CRMP2-phosphorylation suppressors were found to mimic lithium's attenuation of amphetamine-induced hyperlocomotion in mice. Taken together, these studies not only provide insights into the neural substrates regulated by lithium, but also provide novel human neuronal assays for supporting the development of mechanism-based therapeutics for BD and related neuropsychiatric disorders.

Structural Basis for Achieving GSK-3β Inhibition with High Potency, Selectivity, and Brain Exposure for Positron Emission Tomography Imaging and Drug Discovery

Using structure-guided design, several cell based assays, and microdosed positron emission tomography (PET) imaging, we identified a series of highly potent, selective, and brain-penetrant oxazole-4-carboxamide-based inhibitors of glycogen synthase kinase-3 (GSK-3). An isotopologue of our first-generation lead, [3H]PF-367, demonstrates selective and specific target engagement in vitro, irrespective of the activation state. We discovered substantial ubiquitous GSK-3-specific radioligand binding in Tg2576 Alzheimer's disease (AD), suggesting application for these compounds in AD diagnosis and identified [11C]OCM-44 as our lead GSK-3 radiotracer, with optimized brain uptake by PET imaging in nonhuman primates. GSK-3β-isozyme selectivity was assessed to reveal OCM-51, the most potent (IC50 = 0.030 nM) and selective (>10-fold GSK-3β/GSK-3α) GSK-3β inhibitor known to date. Inhibition of CRMP2T514 and tau phosphorylation, as well as favorable therapeutic window against WNT/β-catenin signaling activation, was observed in cells.