RESUMEN
Transcription Factor 4 (TCF4) has been associated with autism, schizophrenia, and other neuropsychiatric disorders. However, how pathological TCF4 mutations affect the human neural tissue is poorly understood. Here, we derive neural progenitor cells, neurons, and brain organoids from skin fibroblasts obtained from children with Pitt-Hopkins Syndrome carrying clinically relevant mutations in TCF4. We show that neural progenitors bearing these mutations have reduced proliferation and impaired capacity to differentiate into neurons. We identify a mechanism through which TCF4 loss-of-function leads to decreased Wnt signaling and then to diminished expression of SOX genes, culminating in reduced progenitor proliferation in vitro. Moreover, we show reduced cortical neuron content and impaired electrical activity in the patient-derived organoids, phenotypes that were rescued after correction of TCF4 expression or by pharmacological modulation of Wnt signaling. This work delineates pathological mechanisms in neural cells harboring TCF4 mutations and provides a potential target for therapeutic strategies for genetic disorders associated with this gene.
Asunto(s)
Discapacidad Intelectual , Neuronas , Proliferación Celular/genética , Niño , Humanos , Hiperventilación/metabolismo , Discapacidad Intelectual/genética , Neuronas/metabolismo , Factor de Transcripción 4/genética , Factor de Transcripción 4/metabolismoRESUMEN
The Reelin-DAB1 signaling pathway plays a crucial role in regulating neuronal migration and synapse function. Although many rare heterozygous variants in the Reelin gene (RELN) have been identified in patients with autism spectrum disorder (ASD), most variants are still of unknown clinical significance. Also, genetic data suggest that heterozygous variants in RELN alone appear to be insufficient to cause ASD. Here, we describe the identification and functional characterization of rare compound heterozygous missense variants in RELN in a patient with ASD in whom we have previously reported hyperfunctional mTORC1 signaling of yet unknown etiology. Using iPSC-derived neural progenitor cells (NPCs) from this patient, we provide experimental evidence that the identified variants are deleterious and lead to diminished Reelin secretion and impaired Reelin-DAB1 signal transduction. Also, our results suggest that mTORC1 pathway overactivation may function as a second hit event contributing to downregulation of the Reelin-DAB1 cascade in patient-derived NPCs, and that inhibition of mTORC1 by rapamycin attenuates Reelin-DAB1 signaling impairment. Taken together, our findings point to an abnormal interplay between Reelin-DAB1 and mTORC1 networks in nonsyndromic ASD.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Trastorno del Espectro Autista/genética , Trastorno del Espectro Autista/metabolismo , Moléculas de Adhesión Celular Neuronal/genética , Moléculas de Adhesión Celular Neuronal/metabolismo , Proteínas de la Matriz Extracelular/genética , Proteínas de la Matriz Extracelular/metabolismo , Variación Genética , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Serina Endopeptidasas/genética , Serina Endopeptidasas/metabolismo , Transducción de Señal , Proteínas Adaptadoras Transductoras de Señales/química , Alelos , Trastorno del Espectro Autista/diagnóstico , Biomarcadores , Estudios de Casos y Controles , Moléculas de Adhesión Celular Neuronal/química , Niño , Preescolar , Proteínas de la Matriz Extracelular/química , Femenino , Expresión Génica , Heterocigoto , Humanos , Células Madre Pluripotentes Inducidas/citología , Células Madre Pluripotentes Inducidas/metabolismo , Masculino , Modelos Moleculares , Proteínas del Tejido Nervioso/química , Células-Madre Neurales/citología , Células-Madre Neurales/metabolismo , Conformación Proteica , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteína Reelina , Serina Endopeptidasas/química , Relación Estructura-Actividad , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
Whereas autism spectrum disorder (ASD) exhibits striking heterogeneity in genetics and clinical presentation, dysfunction of mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway has been identified as a molecular feature common to several well-characterized syndromes with high prevalence of ASD. Additionally, recent findings have also implicated mTORC1 signaling abnormalities in a subset of nonsyndromic ASD, suggesting that defective mTORC1 pathway may be a potential converging mechanism in ASD pathology across different etiologies. However, the mechanistic evidence for a causal link between aberrant mTORC1 pathway activity and ASD neurobehavioral features varies depending on the ASD form involved. In this review, we first discuss six monogenic ASD-related syndromes, including both classical and potentially novel mTORopathies, highlighting their contribution to our understanding of the neurobiological mechanisms underlying ASD, and then we discuss existing evidence suggesting that aberrant mTORC1 signaling may also play a role in nonsyndromic ASD.