RESUMO
Traumatic Brain Injury (TBI) is a global driver of disability, and we currently lack effective therapies to promote neural repair and recovery. TBI is characterized by an initial insult, followed by a secondary injury cascade, including inflammation, excitotoxicity, and glial cellular response. This cascade incorporates molecular mechanisms that represent potential targets of therapeutic intervention. In this study, we investigate the response to focal impact injury to the optic tectum of Xenopus laevis tadpoles. This injury disrupts the blood-brain barrier, causing edema, and produces deficits in visually-driven behaviors which are resolved within one week. Within 3 h, injured brains show a dramatic transcriptional activation of inflammatory cytokines, upregulation of genes associated with inflammation, and recruitment of microglia to the injury site and surrounding tissue. Shortly afterward, astrocytes undergo morphological alterations and accumulate near the injury site, and these changes persist for at least 48 h following injury. Genes associated with astrocyte reactivity and neuroprotective functions also show elevated levels of expression following injury. Since our results demonstrate that the response to focal impact injury in Xenopus resembles the cellular alterations observed in rodents and other mammalian models, the Xenopus tadpole offers a new, scalable vertebrate model for TBI.
Assuntos
Astrócitos , Lesões Encefálicas Traumáticas , Animais , Astrócitos/metabolismo , Lesões Encefálicas Traumáticas/metabolismo , Modelos Animais de Doenças , Inflamação/metabolismo , Larva , Mamíferos , Camundongos , Camundongos Endogâmicos C57BL , Microglia/metabolismo , Doenças Neuroinflamatórias , Xenopus laevisRESUMO
To investigate microRNA (miR) functions in early eye development, we asked whether eye field transcription factors (EFTFs) are targets of miR-dependent regulation in Xenopus embryos. Argonaute (AGO) ribonucleoprotein complexes, including miRs and targeted mRNAs, were coimmunoprecipitated from transgenic embryos expressing myc-tagged AGO under the control of the rax1 promoter; mRNAs for all EFTFs coimmunoprecipitated with Ago in late neurulae. Computational predictions of miR binding sites within EFTF 3'UTRs identified miR-199a-3p ("miR-199") as a candidate regulator of EFTFs, and miR-199 was shown to regulate rax1 in vivo. Targeted overexpression of miR-199 led to small eyes, a reduction in EFTF expression, and reduced cell proliferation. Inhibition of interactions between mir-199 and the rax1 3'UTR reversed the small eye phenotype. Although targeted knockdown of miR-199 left the eye field intact, it reduced optic cup outgrowth and disrupted eye formation. Computational identification of candidate miR-199 targets within the Xenopus transcriptome led to the identification of ptk7 as a candidate regulator. Targeted overexpression of ptk7 resulted in abnormal optic cup formation and a reduction or loss of eye development, recapitulating the range of eye phenotypes seen following miR-199 knockdown. Our results indicate that miR-199 plays both positive and negative regulatory roles in eye development.
Assuntos
Olho/embriologia , Olho/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , MicroRNAs/genética , Interferência de RNA , Xenopus laevis/embriologia , Xenopus laevis/genética , Animais , Proteínas do Olho/genética , Proteínas do Olho/metabolismo , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Estudos de Associação Genética , Mutação com Perda de Função , Organogênese/genética , Fenótipo , Ligação Proteica , Receptores Proteína Tirosina Quinases/genética , Reprodutibilidade dos Testes , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismoRESUMO
The phenomenon of phase variation between yellow and tan forms of Myxococcus xanthus has been recognized for several decades, but it is not known what role this variation may play in the ecology of myxobacteria. We confirm an earlier report that tan variants are disproportionately more numerous in the resulting spore population of a M. xanthus fruiting body than the tan vegetative cells that contributed to fruiting body formation. However, we found that tan cells may not require yellow cells for fruiting body formation or starvation-induced sporulation of tan cells. Here we report three differences between the yellow and tan variants that may play important roles in the soil ecology of M. xanthus. Specifically, the yellow variant is more capable of forming biofilms, is more sensitive to lysozyme, and is more resistant to ingestion by bacteriophagous nematodes. We also show that the myxobacterial fruiting body is more resistant to predation by worms than are dispersed M. xanthus cells.
