RESUMEN
SOX4, together with SOX11 and SOX12, forms group C of SRY-related (SOX) transcription factors. They play key roles, often in redundancy, in multiple developmental pathways, including neurogenesis and skeletogenesis. De novo SOX11 heterozygous mutations have been shown to cause intellectual disability, growth deficiency, and dysmorphic features compatible with mild Coffin-Siris syndrome. Using trio-based exome sequencing, we here identify de novo SOX4 heterozygous missense variants in four children who share developmental delay, intellectual disability, and mild facial and digital morphological abnormalities. SOX4 is highly expressed in areas of active neurogenesis in human fetuses, and sox4 knockdown in Xenopus embryos diminishes brain and whole-body size. The SOX4 variants cluster in the highly conserved, SOX family-specific HMG domain, but each alters a different residue. In silico tools predict that each variant affects a distinct structural feature of this DNA-binding domain, and functional assays demonstrate that these SOX4 proteins carrying these variants are unable to bind DNA in vitro and transactivate SOX reporter genes in cultured cells. These variants are not found in the gnomAD database of individuals with presumably normal development, but 12 other SOX4 HMG-domain missense variants are recorded and all demonstrate partial to full activity in the reporter assay. Taken together, these findings point to specific SOX4 HMG-domain missense variants as the cause of a characteristic human neurodevelopmental disorder associated with mild facial and digital dysmorphism.
Asunto(s)
Anomalías Múltiples/genética , Mutación Missense/genética , Trastornos del Neurodesarrollo/genética , Factores de Transcripción SOXC/genética , Secuencia de Aminoácidos , Animales , Niño , Preescolar , Síndrome de Coffin-Lowry/genética , Estudios de Cohortes , Secuencia Conservada , ADN/genética , ADN/metabolismo , Femenino , Dominios HMG-Box/genética , Heterocigoto , Humanos , Masculino , Factores de Transcripción SOX/química , Factores de Transcripción SOX/genética , Factores de Transcripción SOXC/química , Factores de Transcripción SOXC/metabolismo , Activación Transcripcional , Xenopus/anatomía & histología , Xenopus/embriología , Xenopus/genética , Proteínas de Xenopus/química , Proteínas de Xenopus/genéticaRESUMEN
BACKGROUND: The nitric oxide synthase interacting protein (Nosip) has been associated with diverse human diseases including psychological disorders. In line, early neurogenesis of mouse and Xenopus is impaired upon Nosip deficiency. Nosip knockout mice show craniofacial defects and the down-regulation of Nosip in the mouse and Xenopus leads to microcephaly. Until now, the exact underlying molecular mechanisms of these malformations were still unknown. RESULTS: Here, we show that nosip is expressed in the developing ocular system as well as the anterior neural crest cells of Xenopus laevis. Furthermore, Nosip inhibition causes severe defects in eye formation in the mouse and Xenopus. Retinal lamination as well as dorso-ventral patterning of the retina were affected in Nosip-depleted Xenopus embryos. Marker gene analysis using rax, pax6 and otx2 reveals an interference with the eye field induction and differentiation. A closer look on Nosip-deficient Xenopus embryos furthermore reveals disrupted cranial cartilage structures and an inhibition of anterior neural crest cell induction and migration shown by twist, snai2, and egr2. Moreover, foxc1 as downstream factor of retinoic acid signalling is affected upon Nosip deficiency. CONCLUSIONS: Nosip is a crucial factor for the development of anterior neural tissue such the eyes and neural crest cells. Developmental Dynamics 247:1070-1082, 2018. © 2018 Wiley Periodicals, Inc.
Asunto(s)
Ojo/crecimiento & desarrollo , Cresta Neural/crecimiento & desarrollo , Ubiquitina-Proteína Ligasas/genética , Proteínas de Xenopus/genética , Xenopus laevis/crecimiento & desarrollo , Animales , Cartílago/embriología , Cartílago/crecimiento & desarrollo , Embrión no Mamífero , Desarrollo Embrionario , Ojo/embriología , Técnicas de Silenciamiento del Gen , Ratones , Cresta Neural/embriología , Neurogénesis , Cráneo , Xenopus laevis/embriologíaRESUMEN
BACKGROUND: Genetic deletion of Nosip in mice causes holoprosencephaly, however, the function of Nosip in neurogenesis is currently unknown. RESULTS: We combined two vertebrate model organisms, the mouse and the South African clawed frog, Xenopus laevis, to study the function of Nosip in neurogenesis. We found, that size and cortical thickness of the developing brain of Nosip knockout mice were reduced. Accordingly, the formation of postmitotic neurons was greatly diminished, concomitant with a reduced number of apical and basal neural progenitor cells in vivo. Neurospheres derived from Nosip knockout embryos exhibited reduced growth and the differentiation capability into neurons in vitro was almost completely abolished. Mass spectrometry analysis of the neurospheres proteome revealed a reduced expression of Rbp1, a regulator of retinoic acid synthesis, when Nosip was absent. We identified the homologous nosip gene to be expressed in differentiated neurons in the developing brain of Xenopus embryos. Knockdown of Nosip in Xenopus resulted in a reduction of brain size that could be rescued by reintroducing human NOSIP mRNA. Furthermore, the expression of pro-neurogenic transcription factors was reduced and the differentiation of neuronal cells was impaired upon Nosip knockdown. In Xenopus as well as in mouse we identified reduced proliferation and increased apoptosis as underlying cause of microcephaly upon Nosip depletion. In Xenopus Nosip and Rbp1 are similarly expressed and knockdown of Nosip resulted in down regulation of Rbp1. Knockdown of Rbp1 caused a similar microcephaly phenotype as the depletion of Nosip and synergy experiments indicated that both proteins act in the same signalling pathway. CONCLUSIONS: Nosip is a novel factor critical for neural stem cell/progenitor self-renewal and neurogenesis during mouse and Xenopus development and functions upstream of Rbp1 during early neurogenesis.