Kawatani, Keiji

Abstract Background Progressive supranuclear palsy (PSP) is a devastating neurodegenerative disorder with rapid progression to death. Multiple efforts to develop a disease‐modifying therapy for PSP have yet to succeed. We previously reported the discovery of three potential therapeutic targets for PSP. These three genes, DDR2, KANK2, and STOM, are consistently upregulated in the brains of PSP patients and mouse models of tauopathy. Reducing their expression in a drosophila model significantly rescued the tau‐induced eye degeneration and tau seeding activity. To translate these targets into the clinic, we are developing antisense oligonucleotides (ASO) as potential therapies. Method We screened candidate ASOs in neuroglioma cell line H4. ASO hits were validated for their potency and safety. We also used iPSC‐derived neurons from PSP patients to test the potency and potential toxicity of our ASOs. To investigate target engagement, therapeutic efficacy and preliminary pharmacodynamic properties, we treated iPSC‐derived midbrain organoids with the ASO leads. Lastly, we will assess the off‐target effects of the ASOs by investigating the levels of mRNA transcripts that share similar sequences as our targets using RNAseq. Result Our in vitro screening identified ASO leads that significantly reduce the target gene expressions at mRNA and protein levels in a dose‐dependent manner. The ASO hits also exhibit low cellular toxicity in the H4 cell line. Upon treating iPSC neurons with ASO hits, we were able to validate the dose‐dependent reduction of target mRNAs. Cell viability analysis indicated low toxicity, suggesting that these ASOs are potent and safe. In midbrain organoid model, DDR2‐targeting ASO showed time‐dependent target engagement and were prioritized for further development. Conclusion We developed candidate therapeutics for PSP using ASOs that silence novel therapeutic targets discovered in our systems based cross‐species screening. We showed that our ASOs have low toxicity and confirmed target engagement at both mRNA and protein levels in vitro. The results suggest a favorable preclinical profile of our ASO leads that warrants additional investigations. Importantly, PSP shares congruent pathophysiological changes with other tauopathies, such as Alzheimer’s disease. These common perturbed pathways indicate that our ASOs can be potentially repurposed for multiple neurodegenerative tauopathies.

Abstract Smith-Lemli-Opitz syndrome (SLOS) is a rare, autosomal recessive disorder characterized by congenital malformations, intellectual disability, and behavioral abnormalities. SLOS results from mutations in the DHCR7 gene, leading to impaired cholesterol biosynthesis due to dysregulation of 7-dehydrocholesterol reductase. Cholesterol plays crucial roles in neurophysiology, including synaptic formation and neurotransmitter receptor regulation, which likely contribute to neurological manifestations in SLOS patients. While astrocytes are the main cholesterol producing cells in the brain, their specific role in SLOS pathogenesis remains unclear. In this study, we utilized induced pluripotent stem cell (iPSC)-derived astrocytes from a SLOS patient with DHCR7 c.C278T mutation and the isogenic control. We found decreased lipid droplet formation in SLOS iPSC astrocytes compared to controls, accompanied with diminished efflux of cholesterol and apolipoprotein E. Lipidomics revealed reduced cholesterol and cholesterol esters, as well as altered profiles of other lipids in SLOS iPSC astrocytes. While RNA-sequencing identified various genes and pathways affected by the disease status, those related to mitochondria functions were top-ranked. Mitochondrial electron transport chain oxidative phosphorylation gene expression decreased in SLOS iPSC astrocytes, alongside impaired mitochondrial respiration. Furthermore, SLOS iPSC astrocytes less effectively mediated neuroprotection on iPSC neurons than control astrocytes in serum-starvation conditions. SLOS iPSC astrocytes also poorly contributed to synaptic networks when co-cultured with iPSC neurons. Overall, our findings provide mechanistic insights into how DHCR7 disruption impacts astrocyte function, contributing to SLOS neuropathology by dysregulating lipid metabolism, mitochondrial respiration, and impaired neuroprotection.

Abstract INTRODUCTION Loss‐of‐function variants of the ABCA7 gene are associated with an increased risk of Alzheimer's disease (AD). How neuronal ABCA7 contributes to AD pathogenesis is unknown. METHODS Using neuron‐specific Abca7 KO mice (n Abca7 −/− ) with or without 5×FAD amyloid model background and post mortem AD brains, we investigated AD‐related phenotypes through comprehensive approaches including transcriptomics and lipidomics. RESULTS Lipidomics analysis detected altered lipid profiles in the brains and synaptosomes of 5×FAD; n Abca7 −/− mice compared to controls. Transcriptomics profiling revealed that neuronal ABCA7 deficiency altered the expression of genes and pathways related to mitochondrial homeostasis and apoptosis, particularly in excitatory neurons. Consistently, synaptosomes isolated from 5×FAD; n Abca7 −/− mice showed diminished mitochondria respiration and reduced synaptic protein levels, which is further supported by results from human AD brains. DISCUSSION Our findings reveal that neuronal ABCA7 plays a critical role in mitochondrial homeostasis important for neuronal function and survival in the presence of AD pathology. Highlights Neuronal ABCA7 deficiency exacerbates Aβ pathology and neuronal damage in 5×FAD mice. Neuronal ABCA7 deficiency alters brain transcriptomes and lipidomes of 5×FAD mice. Neuronal ABCA7 deficiency disturbs mitochondria functions in synaptosomes from 5×FAD mice. Neuronal ABCA7 expression associates with genes and pathways related to mitochondrial homeostasis in AD brains.

AbstractBackgroundAlzheimer’s disease (AD) is the most common cause of age‐related dementia, and the presence of amyloid‐β (Aβ) plaques and tau‐containing neurofibrillary tangles is associated with the neurodegeneration and cognitive impairment in this incurable disease. Growing evidence shows that epigenetic dysregulation through histone deacetylases (HDACs) plays a critical role in synaptic dysfunction and memory loss in AD, and HDACs have been highlighted as a novel class of anti‐Alzheimer targets. Moreover, restoring Wnt/β‐catenin signaling, which is greatly suppressed in AD brains, is a promising therapeutic strategy for AD. CI‐994 is an orally active class I HDAC inhibitor that has undergone several phase II/III clinical trials on cancer treatment. Importantly, CI‐994 can cross the blood‐brain barrier and is a cognitive enhancer.MethodWe evaluated the therapeutic potential of CI‐994 in human patient‐specific iPSC‐derived neurons and cerebral organoids with APOE ε4/ε4 genotype or carrying MAPT p.P301L mutation.ResultWe found that CI‐994 is not only a potent class I HDAC inhibitor but also a novel modulator of Wnt/β‐catenin signaling, and that activation of Wnt/β‐catenin signaling by CI‐994 is associated with elevated Wnt co‐receptor LRP6 protein level. Moreover, CI‐994 increased synaptic protein levels, enhanced spontaneous synaptic firing and network formation, and decreased tau phosphorylation in iPSC‐derived neurons. Finally, CI‐994 significantly increased histone acetylation, activated Wnt/β‐catenin signaling, and decreased Aβ production and tau phosphorylation in AD patient‐specific iPSC‐derived cerebral organoids.ConclusionOur findings indicate that CI‐994 is a novel potential therapeutic candidate for AD.

AbstractBackgroundProgressive supranuclear palsy (PSP) is a devastating primary tauopathy with rapid progression to death. Although several therapies currently in the development pipeline show promising safety profiles and robust target engagement, few demonstrated significant efficacy in patients, underscoring the need to interrogate additional targets with novel therapeutic modalities to expand the potential therapeutic arsenal. To diversify the therapeutic avenues for PSP and related tauopathies (e.g. Alzheimer’s disease), we systematically integrated multi‐omics data from human brains of PSP and control donors with cross‐species validation to nominate high‐confidence therapeutic targets. We plan to translate our findings into safe and effective treatments for PSP using antisense oligonucleotides (ASO).MethodWe analyzed brain gene expression profiles in PSP and control individuals at bulk tissue (N = 408) and single‐cell levels (snRNAseq, N = 36). Cell‐type‐specific expression perturbations were systematically prioritized using a cross‐species validation paradigm, including rTG4510 tau mice and tau‐overexpressing Drosophila models. We conducted in vitro screening of ASO candidates against our prioritized target genes. ASO efficacy and toxicity were measured. RNAseq experiments will be performed to interrogate off‐target effects. The safety and efficacy of the lead ASOs will be assessed in PSP‐patient‐derived iPSC models.ResultWe previously reported discovery of novel genes with significant differential expression in PSP brains, characterized their brain cell‐specificity and validated them using snRNAseq data. We prioritized 21 genes using gene expression data from a mouse tauopathy model. Validation of these 21 high‐priority genes using a Drosophila tau model nominated astrocytic STOM, KANK2, and DDR2 as potential therapeutic targets for PSP. Knocking down their expression in Drosophila significantly rescues tau‐mediated neurodegenerative pathology. In vitro screening identified ASO leads that reduced the target expressions at mRNA and protein levels with low cellular toxicity.ConclusionWe developed a systems biology pipeline and nominated STOM, KANK2, and DDR2 as candidate gene targets for PSP. We identified ASOs that modulate these targets’ expression without cellular toxicity, suggesting they may be suitable as potential therapeutic candidates. Importantly, the shared pathophysiology and molecular aberrations between PSP and other tauopathies, such as Alzheimer’s disease, suggests that such therapeutic candidates may be repurposed for multiple neurodegenerative diseases, further accelerating, and streamlining the therapeutic pipeline.

Cerebrovasculature is critical in maintaining brain homeostasis; its dysregulation often leads to vascular cognitive impairment and dementia (VCID) during aging. VCID is the second most prevalent cause of dementia in the elderly, after Alzheimer’s disease (AD), with frequent cooccurrence of VCID and AD. While multiple factors are involved in the pathogenesis of AD and VCID, APOE4 increases the risk for both diseases. A major apolipoprotein E (apoE) receptor, the low-density lipoprotein receptor-related protein 1 (LRP1), is abundantly expressed in vascular mural cells (pericytes and smooth muscle cells). Here, we investigated how deficiency of vascular mural cell LRP1 affects the cerebrovascular system and cognitive performance using vascular mural cell–specific Lrp1 -KO mice ( smLrp1 –/– ) in a human APOE3 or APOE4 background. We found that spatial memory was impaired in the 13- to 16-month-old APOE4 smLrp1 –/– mice but not in the APOE3 smLrp1 –/– mice, compared with their respective littermate control mice. These disruptions in the APOE4 smLrp1 –/– mice were accompanied with excess paravascular glial activation and reduced cerebrovascular collagen IV. In addition, blood-brain barrier (BBB) integrity was disrupted in the APOE4 smLrp1 –/– mice. Together, our results suggest that vascular mural cell LRP1 modulates cerebrovasculature integrity and function in an APOE genotype–dependent manner.