RESUMEN
BACKGROUND: Genes with multiple co-active promoters appear common in brain, yet little is known about functional requirements for these potentially redundant genomic regulatory elements. SCN1A, which encodes the NaV1.1 sodium channel alpha subunit, is one such gene with two co-active promoters. Mutations in SCN1A are associated with epilepsy, including Dravet syndrome (DS). The majority of DS patients harbor coding mutations causing SCN1A haploinsufficiency; however, putative causal non-coding promoter mutations have been identified. METHODS: To determine the functional role of one of these potentially redundant Scn1a promoters, we focused on the non-coding Scn1a 1b regulatory region, previously described as a non-canonical alternative transcriptional start site. We generated a transgenic mouse line with deletion of the extended evolutionarily conserved 1b non-coding interval and characterized changes in gene and protein expression, and assessed seizure activity and alterations in behavior. RESULTS: Mice harboring a deletion of the 1b non-coding interval exhibited surprisingly severe reductions of Scn1a and NaV1.1 expression throughout the brain. This was accompanied by electroencephalographic and thermal-evoked seizures, and behavioral deficits. CONCLUSIONS: This work contributes to functional dissection of the regulatory wiring of a major epilepsy risk gene, SCN1A. We identified the 1b region as a critical disease-relevant regulatory element and provide evidence that non-canonical and seemingly redundant promoters can have essential function.
Asunto(s)
Epilepsia/genética , Regulación de la Expresión Génica , Canal de Sodio Activado por Voltaje NAV1.1/genética , Eliminación de Secuencia/genética , Animales , Atención , Secuencia de Bases , Encéfalo/metabolismo , Encéfalo/patología , Cromatina/metabolismo , Secuencia Conservada/genética , Modelos Animales de Enfermedad , Electroencefalografía , Epilepsia/diagnóstico por imagen , Evolución Molecular , Femenino , Células HEK293 , Heterocigoto , Homocigoto , Humanos , Masculino , Aprendizaje por Laberinto , Trastornos de la Memoria/genética , Ratones Endogámicos C57BL , Neuronas/metabolismo , Prueba de Campo Abierto , Fenotipo , Unión Proteica , Secuencias Reguladoras de Ácidos Nucleicos/genética , Análisis de Supervivencia , Temperatura , Transactivadores/metabolismoRESUMEN
In utero exposure to maternal immune activation (MIA) is an environmental risk factor for neurodevelopmental and neuropsychiatric disorders. Animal models provide an opportunity to identify mechanisms driving neuropathology associated with MIA. We performed time-course transcriptional profiling of mouse cortical development following induced MIA via poly(I:C) injection at E12.5. MIA-driven transcriptional changes were validated via protein analysis, and parallel perturbations to cortical neuroanatomy were identified via imaging. MIA-induced acute upregulation of genes associated with hypoxia, immune signaling, and angiogenesis, by 6 hr following exposure. This acute response was followed by changes in proliferation, neuronal and glial specification, and cortical lamination that emerged at E14.5 and peaked at E17.5. Decreased numbers of proliferative cells in germinal zones and alterations in neuronal and glial populations were identified in the MIA-exposed cortex. Overall, paired transcriptomic and neuroanatomical characterization revealed a sequence of perturbations to corticogenesis driven by mid-gestational MIA.
