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INTRODUCTION: Triggering receptor expressed on myeloid cells 2 (TREM2) agonists are being clinically evaluated as disease-modifying therapeutics for Alzheimer's disease. Clinically translatable pharmacodynamic (PD) biomarkers are needed to confirm drug activity and select the appropriate therapeutic dose in clinical trials. METHODS: We conducted multi-omic analyses on paired non-human primate brain and cerebrospinal fluid (CSF), and stimulation of human induced pluripotent stem cell-derived microglia cultures after TREM2 agonist treatment, followed by validation of candidate fluid PD biomarkers using immunoassays. We immunostained microglia to characterize proliferation and clustering. RESULTS: We report CSF soluble TREM2 (sTREM2) and CSF chitinase-3-like protein 1 (CHI3L1/YKL-40) as PD biomarkers for the TREM2 agonist hPara.09. The respective reduction of sTREM2 and elevation of CHI3L1 in brain and CSF after TREM2 agonist treatment correlated with transient microglia proliferation and clustering. DISCUSSION: CSF CHI3L1 and sTREM2 reflect microglial TREM2 agonism and can be used as clinical PD biomarkers to monitor TREM2 activity in the brain. HIGHLIGHTS: CSF soluble triggering receptor expressed on myeloid cells 2 (sTREM2) reflects brain target engagement for a novel TREM2 agonist, hPara.09. CSF chitinase-3-like protein 1 reflects microglial TREM2 agonism. Both can be used as clinical fluid biomarkers to monitor TREM2 activity in brain.
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Human genetics and preclinical studies have identified key contributions of TREM2 to several neurodegenerative conditions, inspiring efforts to modulate TREM2 therapeutically. Here, we characterize the activities of three TREM2 agonist antibodies in multiple mixed-sex mouse models of Alzheimer's disease (AD) pathology and remyelination. Receptor activation and downstream signaling are explored in vitro, and active dose ranges are determined in vivo based on pharmacodynamic responses from microglia. For mice bearing amyloid-ß (Aß) pathology (PS2APP) or combined Aß and tau pathology (TauPS2APP), chronic TREM2 agonist antibody treatment had limited impact on microglia engagement with pathology, overall pathology burden, or downstream neuronal damage. For mice with demyelinating injuries triggered acutely with lysolecithin, TREM2 agonist antibodies unexpectedly disrupted injury resolution. Likewise, TREM2 agonist antibodies limited myelin recovery for mice experiencing chronic demyelination from cuprizone. We highlight the contributions of dose timing and frequency across models. These results introduce important considerations for future TREM2-targeting approaches.
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Doença de Alzheimer , Glicoproteínas de Membrana , Microglia , Esclerose Múltipla , Receptores Imunológicos , Animais , Receptores Imunológicos/agonistas , Receptores Imunológicos/metabolismo , Receptores Imunológicos/genética , Glicoproteínas de Membrana/agonistas , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Camundongos , Esclerose Múltipla/tratamento farmacológico , Esclerose Múltipla/imunologia , Feminino , Masculino , Microglia/efeitos dos fármacos , Microglia/metabolismo , Modelos Animais de Doenças , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Anticorpos/farmacologia , Humanos , Peptídeos beta-Amiloides/metabolismo , Proteínas tau/metabolismoRESUMO
Most lysosomal storage diseases (LSDs) involve progressive central nervous system (CNS) impairment, resulting from deficiency of a lysosomal enzyme. Treatment of neuronopathic LSDs remains a considerable challenge, as approved intravenously administered enzyme therapies are ineffective in modifying CNS disease because they do not effectively cross the blood-brain barrier (BBB). We describe a therapeutic platform for increasing the brain exposure of enzyme replacement therapies. The enzyme transport vehicle (ETV) is a lysosomal enzyme fused to an Fc domain that has been engineered to bind to the transferrin receptor, which facilitates receptor-mediated transcytosis across the BBB. We demonstrate that ETV fusions containing iduronate 2-sulfatase (ETV:IDS), the lysosomal enzyme deficient in mucopolysaccharidosis type II, exhibited high intrinsic activity and degraded accumulated substrates in both IDS-deficient cell and in vivo models. ETV substantially improved brain delivery of IDS in a preclinical model of disease, enabling enhanced cellular distribution to neurons, astrocytes, and microglia throughout the brain. Improved brain exposure for ETV:IDS translated to a reduction in accumulated substrates in these CNS cell types and peripheral tissues and resulted in a complete correction of downstream disease-relevant pathologies in the brain, including secondary accumulation of lysosomal lipids, perturbed gene expression, neuroinflammation, and neuroaxonal damage. These data highlight the therapeutic potential of the ETV platform for LSDs and provide preclinical proof of concept for TV-enabled therapeutics to treat CNS diseases more broadly.
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Barreira Hematoencefálica , Iduronato Sulfatase , Animais , Encéfalo , Modelos Animais de Doenças , Terapia de Reposição de Enzimas , Lisossomos , CamundongosRESUMO
Loss-of-function (LOF) variants of TREM2, an immune receptor expressed in microglia, increase Alzheimer's disease risk. TREM2 senses lipids and mediates myelin phagocytosis, but its role in microglial lipid metabolism is unknown. Combining chronic demyelination paradigms and cell sorting with RNA sequencing and lipidomics, we find that wild-type microglia acquire a disease-associated transcriptional state, while TREM2-deficient microglia remain largely homeostatic, leading to neuronal damage. TREM2-deficient microglia phagocytose myelin debris but fail to clear myelin cholesterol, resulting in cholesteryl ester (CE) accumulation. CE increase is also observed in APOE-deficient glial cells, reflecting impaired brain cholesterol transport. This finding replicates in myelin-treated TREM2-deficient murine macrophages and human iPSC-derived microglia, where it is rescued by an ACAT1 inhibitor and LXR agonist. Our studies identify TREM2 as a key transcriptional regulator of cholesterol transport and metabolism under conditions of chronic myelin phagocytic activity, as TREM2 LOF causes pathogenic lipid accumulation in microglia.
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Encéfalo/metabolismo , Colesterol/metabolismo , Macrófagos/metabolismo , Glicoproteínas de Membrana/genética , Microglia/metabolismo , Bainha de Mielina/metabolismo , Fagocitose/genética , Receptores Imunológicos/genética , Acetil-CoA C-Acetiltransferase/antagonistas & inibidores , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Animais , Ésteres do Colesterol/metabolismo , Modelos Animais de Doenças , Citometria de Fluxo , Humanos , Células-Tronco Pluripotentes Induzidas , Metabolismo dos Lipídeos/genética , Lipidômica , Receptores X do Fígado/agonistas , Camundongos , Camundongos Knockout , Camundongos Knockout para ApoE , RNA-SeqRESUMO
Duane retraction syndrome (DRS) is the most common form of congenital paralytic strabismus in humans and can result from α2-chimaerin (CHN1) missense mutations. We report a knockin α2-chimaerin mouse (Chn1KI/KI) that models DRS. Whole embryo imaging of Chn1KI/KI mice revealed stalled abducens nerve growth and selective trochlear and first cervical spinal nerve guidance abnormalities. Stalled abducens nerve bundles did not reach the orbit, resulting in secondary aberrant misinnervation of the lateral rectus muscle by the oculomotor nerve. By contrast, Chn1KO/KO mice did not have DRS, and embryos displayed abducens nerve wandering distinct from the Chn1KI/KI phenotype. Murine embryos lacking EPH receptor A4 (Epha4KO/KO), which is upstream of α2-chimaerin in corticospinal neurons, exhibited similar abducens wandering that paralleled previously reported gait alterations in Chn1KO/KO and Epha4KO/KO adult mice. Findings from Chn1KI/KI Epha4KO/KO mice demonstrated that mutant α2-chimaerin and EphA4 have different genetic interactions in distinct motor neuron pools: abducens neurons use bidirectional ephrin signaling via mutant α2-chimaerin to direct growth, while cervical spinal neurons use only ephrin forward signaling, and trochlear neurons do not use ephrin signaling. These findings reveal a role for ephrin bidirectional signaling upstream of mutant α2-chimaerin in DRS, which may contribute to the selective vulnerability of abducens motor neurons in this disorder.
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Quimerina 1/metabolismo , Síndrome da Retração Ocular/metabolismo , Embrião de Mamíferos/metabolismo , Neurônios Motores/metabolismo , Receptor EphA4/metabolismo , Transdução de Sinais , Animais , Córtex Cerebral/metabolismo , Córtex Cerebral/patologia , Quimerina 1/genética , Síndrome da Retração Ocular/genética , Humanos , Camundongos , Camundongos Knockout , Neurônios Motores/patologia , Receptor EphA4/genética , Medula Espinal/metabolismo , Medula Espinal/patologiaRESUMO
Duane retraction syndrome (DRS) is a congenital eye-movement disorder defined by limited outward gaze and retraction of the eye on attempted inward gaze. Here, we report on three heterozygous loss-of-function MAFB mutations causing DRS and a dominant-negative MAFB mutation causing DRS and deafness. Using genotype-phenotype correlations in humans and Mafb-knockout mice, we propose a threshold model for variable loss of MAFB function. Postmortem studies of DRS have reported abducens nerve hypoplasia and aberrant innervation of the lateral rectus muscle by the oculomotor nerve. Our studies in mice now confirm this human DRS pathology. Moreover, we demonstrate that selectively disrupting abducens nerve development is sufficient to cause secondary innervation of the lateral rectus muscle by aberrant oculomotor nerve branches, which form at developmental decision regions close to target extraocular muscles. Thus, we present evidence that the primary cause of DRS is failure of the abducens nerve to fully innervate the lateral rectus muscle in early development.
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Síndrome da Retração Ocular/etiologia , Perda Auditiva/etiologia , Doenças do Labirinto/etiologia , Fator de Transcrição MafB/genética , Fator de Transcrição MafB/fisiologia , Músculos Oculomotores/patologia , Animais , Síndrome da Retração Ocular/patologia , Embrião de Mamíferos/metabolismo , Embrião de Mamíferos/patologia , Feminino , Perda Auditiva/patologia , Humanos , Doenças do Labirinto/patologia , Masculino , Camundongos , Camundongos Knockout , Músculos Oculomotores/inervação , LinhagemRESUMO
The ocular motility disorder "Congenital fibrosis of the extraocular muscles type 1" (CFEOM1) results from heterozygous mutations altering the motor and third coiled-coil stalk of the anterograde kinesin, KIF21A. We demonstrate that Kif21a knockin mice harboring the most common human mutation develop CFEOM. The developing axons of the oculomotor nerve's superior division stall in the proximal nerve; the growth cones enlarge, extend excessive filopodia, and assume random trajectories. Inferior division axons reach the orbit but branch ectopically. We establish a gain-of-function mechanism and find that human motor or stalk mutations attenuate Kif21a autoinhibition, providing in vivo evidence for mammalian kinesin autoregulation. We identify Map1b as a Kif21a-interacting protein and report that Map1bâ»/â» mice develop CFEOM. The interaction between Kif21a and Map1b is likely to play a critical role in the pathogenesis of CFEOM1 and highlights a selective vulnerability of the developing oculomotor nerve to perturbations of the axon cytoskeleton.
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Axônios/patologia , Oftalmopatias Hereditárias/genética , Fibrose/genética , Cinesinas/genética , Cinesinas/metabolismo , Mutação/genética , Transtornos da Motilidade Ocular/genética , Nervo Oculomotor/patologia , Fatores Etários , Animais , Animais Recém-Nascidos , Axônios/ultraestrutura , Contagem de Células , Modelos Animais de Doenças , Embrião de Mamíferos , Oftalmopatias Hereditárias/patologia , Oftalmopatias Hereditárias/fisiopatologia , Movimentos Oculares/genética , Movimentos Oculares/fisiologia , Fibrose/patologia , Fibrose/fisiopatologia , Regulação da Expressão Gênica/genética , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HEK293 , Humanos , Camundongos , Camundongos Transgênicos , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/fisiologia , Vias Neurais/metabolismo , Vias Neurais/patologia , Vias Neurais/ultraestrutura , Transtornos da Motilidade Ocular/patologia , Transtornos da Motilidade Ocular/fisiopatologia , Nervo Oculomotor/ultraestruturaRESUMO
Axon pathfinding is essential for the establishment of proper neuronal connections during development. Advances in neuroimaging and genomic technologies, coupled with animal modeling, are leading to the identification of an increasing number of human disorders that result from aberrant axonal wiring. In this review, we summarize the recent clinical, genetic and molecular advances with regard to three human disorders of axon guidance: Horizontal gaze palsy with progressive scoliosis, Congenital mirror movements, and Congenital fibrosis of the extraocular muscles, Type III.