Mechanisms underlying loss of neural stem cell competence.

神经干细胞能力丧失的机制。

• 批准号: 8458510
• 负责人: Minoree Kohwi
• 金额: $ 11.04万
• 依托单位: UNIVERSITY OF OREGON
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-12 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8458510
• 关键词: Address; Affect; Antibodies; Architecture; Binding; Biological Assay; Biological Models; Birth Order; Brain; Brain Diseases; Cell Separation; Cell model; Cells; ChIP-seq; Chromatin; Chromatin Structure; Competence; DNA; Data; Development; Disease; Distal; Drosophila genus; Embryo; Ensure; Epigenetic Process; Fluorescent in Situ Hybridization; Gene Targeting; Genes; Genetic; Genetic Transcription; Genome; Hematopoietic stem cells; Histones; Individual; Invertebrates; Label; Mammals; Mus; Neurons; Nuclear; Population; Positioning Attribute; Regulation; Replacement Therapy; Retina; Series; Specific qualifier value; Staging; Stem cells; Stereotyping; Testing; Time; Tissues; To specify; Transcriptional Activation; Translating; Vertebrates; Work; Zinc Fingers; base; cell type; chromatin immunoprecipitation; genome-wide; histone modification; insight; nerve stem cell; neuroblast; novel; relating to nervous system; research study; retinal progenitor cell; tool; transcription factor; Address; Affect; Antibodies; Architecture; Binding; Biological Assay; Biological Models; Birth Order; Brain; Brain Diseases; Cell Separation; Cell model; Cells; ChIP-seq; Chromatin; Chromatin Structure; Competence; DNA; Data; Development; Disease; Distal; Drosophila genus; Embryo; Ensure; Epigenetic Process; Fluorescent in Situ Hybridization; Gene Targeting; Genes; Genetic; Genetic Transcription; Genome; Hematopoietic stem cells; Histones; Individual; Invertebrates; Label; Mammals; Mus; Neurons; Nuclear; Population; Positioning Attribute; Regulation; Replacement Therapy; Retina; Series; Specific qualifier value; Staging; Stem cells; Stereotyping; Testing; Time; Tissues; To specify; Transcriptional Activation; Translating; Vertebrates; Work; Zinc Fingers; base; cell type; chromatin immunoprecipitation; genome-wide; histone modification; insight; nerve stem cell; neuroblast; novel; relating to nervous system; research study; retinal progenitor cell; tool; transcription factor

DESCRIPTION (provided by applicant): In both vertebrates and invertebrates, a vast diversity of neurons is generated from a relatively small pool of neural stem cells that undergo stereotyped temporal transitions to ensure that each cell type is made at the right time and in the right quantities. These transitions are highly regulated to ensure the development of a functional brain. Over time, neural stem cells lose competence to specify earlier-born fates; thus specific neuronal cell types can be generated only during a specific developmental time window. The mechanisms of how this occurs are totally unknown, but have wide implications in understanding the basic rules of brain development and how developmental brain disorders may arise. We have chosen to address this question in Drosophila, in which each of the ~30 neuroblasts (neural stem cells) gives rise to distinct lineages, but always in a stereotyped birth order. This order is specified by the neuroblasts' sequential expression of a series of temporal identity factors as they divide. The zinc-finger transcription factor, Hunchback (Hb) specifies first-born progeny, and consequently these neurons transcribe hb. First-born fate, characterized by hb transcription, can be specified for only a limited time during what is called the "early competence window," best characterized in neuroblast 7-1. Afterwards, the neuroblast can no longer respond to ectopic Hb expression to produce progeny that transcribes hb, suggesting epigenetic mechanisms may underlie competence loss. I recently established DNA fluorescent in situ hybridization (DNA-FISH) on whole-mount Drosophila embryo neuroblasts to track the subnuclear position of the hb gene. I found a robust repositioning of the hb gene from the nuclear interior in young neuroblasts to the nuclear periphery in older neuroblasts. Strikingly, th timing of hb gene repositioning to the nuclear periphery, generally associated with silent genes, is coincident with the end of the neuroblast 7-1 early competence window. Furthermore, the nuclear factor Distal antenna (Dan), which we found can extend neuroblast 7-1 competence, inhibits this gene repositioning. Based on the above observations, I hypothesize that genome reorganization underlies loss of competence and Dan functions in neuroblasts to establish a "early competence" genome architecture. Recent evidence indicates that Ikaros, the Hb orthologue in mammals, establishes early competence in mouse retinal progenitor cells, which undergo transitions between competence states to generate distinct progeny in a stereotyped birth order. Work on Ikaros function in hematopoietic stem cells suggest that perhaps chromatin organization may underlie transitions between competence states in retinal progenitors. I further propose to translate my work in Drosophila to the mouse retina model system to investigate the mechanisms underlying loss of competence during mammalian development. Together, the above information will provide crucial insight into the origins of neural diversity and have wide implications in harnessing stem cells for tissue replacement therapies.

描述（由申请人提供）：在脊椎动物和无脊椎动物中，从相对较小的神经干细胞池产生了大量的神经元，这些神经干细胞经历了定型的时间过渡，以确保每种细胞类型在正确的时间和适当的数量中进行。这些过渡受到高度调节，以确保功能性大脑的发展。随着时间的流逝，神经干细胞失去了指定早期出生的命运的能力。因此，只能在特定的发育时间窗口中生成特定的神经元细胞类型。这种发生方式的机制是完全未知的，但对理解大脑发育的基本规则以及发育性脑部疾病的产生可能具有广泛的影响。我们选择在果蝇中解决这个问题，其中约30个神经细胞（神经干细胞）中的每一个都会产生独特的谱系，但始终处于刻板印象的出生顺序。该顺序由神经细胞分裂时的一系列时间身份因子的顺序表达来指定。锌指转录因子Hunchback（HB）指定了前后的后代，因此这些神经元转录HB。以HB转录为特征的头出生的命运只能在所谓的“早期能力窗口”中仅以有限的时间来指定，这是神经细胞7-1最佳特征。之后，神经细胞无法再对异位HB表达做出反应，以产生转录HB的后代，这表明表观遗传机制可能是能力损失的基础。我最近建立了在整个果蝇胚胎神经细胞上的原位原位杂交（DNA-fish），以跟踪HB基因的亚核位置。我发现HB基因从幼体神经细胞中的核内部重新定位到较旧的神经细胞中的核周围。令人惊讶的是，HB基因重新定位对核外围的时间，通常与静音基因有关，与神经细胞7-1的早期能力窗口的结束是一致的。此外，我们发现的核因子远端天线（DAN）可以扩展神经细胞7-1的能力，抑制了该基因重新定位。基于上述观察结果，我假设基因组的重组是神经细胞中能力的丧失和DAN在建立“早期能力”基因组结构中的作用。最近的证据表明，哺乳动物中的HB直系同源物Ikaros在小鼠视网膜祖细胞中建立了早期能力，该细胞在能力状态之间经历了在刻板的出生顺序中产生独特的后代的过渡。造血干细胞中Ikaros功能的工作表明，染色质组织可能是视网膜祖细胞中能力状态之间过渡的基础。我进一步建议将果蝇中的工作转化为小鼠视网膜模型系统，以研究哺乳动物发育过程中能力丧失的机制。同时，以上信息将提供对神经多样性起源的关键见解，并对利用干细胞的组织替代疗法具有广泛的影响。