Numb与神经发育

不对称性细胞分裂是一个母细胞通过一次分裂,产生两个不同命运的子细胞的分裂方式,是单细胞生物向多细胞生物进化的关键一步。根据现有的证据推论,不称性细胞分裂是在器官发育过程中产生细胞多样化的一种基本方式。Numb是第一个被发现决定多细胞生物不对称细胞分裂的信号蛋白。在果蝇中,Numb通过促进Notch泛素化拮抗Notch信号通路,从而决定子细胞的命运,后来的研究表明Numb是细胞内吞调节蛋白,并用通过内吞参与调节神经细胞的粘附,轴突的生长及细胞迁移等过程;并且发现Numb与肿瘤抑制基因p53、泛素化蛋白HDM2形成三聚体抑制p53的泛素化,从而调节肿瘤的恶性程度。本文系统地分析了Numb发现的历史及后来在脊椎动物中的作用和机制,重点介绍了Numb在神经发育过程中的功能。     

Numb与神经发育

不对称性细胞分裂是一个母细胞通过一次分裂,产生两个不同命运的子细胞的分裂方式,是单细胞生物向多细胞生物进化的关键一步。根据现有的证据推论,不称性细胞分裂是在器官发育过程中产生细胞多样化的一种基本方式。Numb是第一个被发现决定多细胞生物不对称细胞分裂的信号蛋白。在果蝇中,Numb通过促进Notch泛素化拮抗Notch信号通路,从而决定子细胞的命运,后来的研究表明Numb是细胞内吞调节蛋白,并用通过内吞参与调节神经细胞的粘附,轴突的生长及细胞迁移等过程;并且发现Numb与肿瘤抑制基因p53、泛素化蛋白HDM2形成三聚体抑制p53的泛素化,从而调节肿瘤的恶性程度。本文系统地分析了Numb发现的历史及后来在脊椎动物中的作用和机制,重点介绍了Numb在神经发育过程中的功能。     

Notch 信号通路与淋巴细胞发育

Notch 信号通路为一广泛应用且高度保守的信号转导途径,决定多能祖细胞的分化方向,其中在共同淋巴祖细胞向 T 淋巴细胞或 B 淋巴细胞分化选择中具有决定性作用 . Notch 信号通路参与淋巴细胞的发育过程,促进 Tαβ细胞的形成、诱导处女型 T 细胞变为调节型 T 细胞、阻止 CD4+T 细胞向 Th1 类型分化,以及增加外周免疫器官边缘区 B 细胞的数量 . 在分析 Notch 蛋白结构的基础上,综合最新进展,系统阐明了 Notch 信号通路的组成、作用机制、参与的淋巴细胞发育过程以及所起的作用 .     

Numb在肿瘤发生中的研究进展

Numb是重要的细胞命运决定因子,通过选择性剪接和不对称分裂方式来控制细胞的命运。Numb参与肿瘤信号通路,上游有Musashi2、HMGA1途径调控,下游调控Notch、p53、Hedgehog途径,涉及Wnt、TLR等途径,在致癌信号中影响较大。Numb也是Notch信号的负调控因子,通过参与肿瘤抑制,调控血管生成,以及增加癌症的放射敏感性等生理过程来抑制肿瘤的形成。总之,Numb作为重要的调节因子,为肿瘤的治疗提供了新的治疗靶点,具有很大的潜在治疗前景。本文对Numb在肿瘤发病中作用的近期研究予以简要概述。     

Numb基因在乳腺癌细胞分化中的作用

Numb基因是细胞的命运决定因子,生物学作用广泛.Notch1及BIRC5是其下游的两个主要通路,Notch在乳腺癌的不同发育阶段均呈激活状态,其量决定了细胞的分裂方向;而BIRC5则经由影响细胞的凋亡而影响乳腺癌的临床病理特征.二者与Numb相互作用,共同在乳腺癌的发生、分化、发展的各阶段发挥重要作用,从而影响乳腺癌干细胞分化为不同的乳腺癌临床亚型.明确Numb在乳腺癌干细胞分化中的作用,对探索更为有效的针对不同乳腺癌亚型的治疗方法至关重要.     

神经发育中的细胞周期时程

哺乳动物的神经发育经历一系列神经前体细胞的形态结构和机能改变,其细胞周期时程也呈现动态变化,从神经发生早期至后期,神经前体细胞的细胞周期时程逐渐延长,并与细胞发育命运转归有关,其调节因素包括周期蛋白复合体、Notch信号通路、原神经基因靶向蛋白、微管与分子马达蛋白等。细胞周期长度假说认为,细胞周期的长度影响到命运决定子的积累,因而决定细胞的命运。文章综述了相关的研究进展。     

Wnt信号转导通路与神经发育研究进展

Wnt蛋白是一类分泌型糖蛋白家族,Wnt信号蛋白与细胞表面的多种受体相互作用,参与诸多生命过程。对神经系统发育的研究表明,Wnt信号通路在神经发生,神经祖细胞增值、分化,神经干细胞的自我更新,轴突导向等过程中起重要调控作用。多项研究已经证实,Wnt通路失调与诸多神经系统疾病有密切关系。Wnt信号通路的突变或异常,将会引起神经系统发育缺陷。然而,对Wnt非经典信号通路的研究,尤其是新受体Ryk的调控作用的认识迄今仍不全面。根据国内外相关研究,阐述了经典Wnt信号通路Wnt/β-catenin途径的同时也对Wnt/Ryk非经典信号途径这一研究新领域做了讨论。在非经典信号通路中,Ryk-ICD的剪接对于前体细胞的神经分化起重要作用。本文分析了Wnt/β-catenin和Wnt/Ryk信号通路在神经发育中的作用,有助于深入理解神经发育过程中Wnt信号通路的作用机制。然而,Ryk-ICD引导因子、分子机制等问题仍待进一步研究,而这将有利于理解神经干细胞分化机理。     

Notch 信号通路与Neuralized蛋白

Notch信号通路在脊椎动物和无脊椎动物许多组织的发育过程和细胞间通讯中都发挥了关键的作用,包括调控细胞命运,调节细胞迁移,分化和增殖.Notch信号通路由Notch受体及其跨膜配体如Delta（Dl）和Serrate组成.Neuralized 蛋白（Neur）编码1个E3泛素连接酶,是Notch配体D1内吞所必需的.Neur蛋白包括3个从线虫到人高度保守的结构域：2个Neur同源重复结构域（NHR1和NHR2）和1个C端RING结构域.本文就Notch信号通路主要元件和Neru的结构与功能及其关系进行综述.     

ELF5在正常乳腺发育和乳腺肿瘤发生中的作用

ELF5(E74-like factor 5)也被称为ESE2,属于ETS(E-twenty-six)转录因子家族成员之一,它在调控胚胎发育以及乳腺组织发育中起到重要作用。在桑椹胚时期,ELF5在调控胚胎内细胞团向胚胎形成过程中或是在胎盘发育的细胞命运决定中起到关键作用。在哺乳动物正常乳腺发育中,ELF5可通过诱导细胞定向分化而获得孕期乳腺分泌细胞类型,从而调控乳腺干/祖细胞的命运。在人类乳腺癌中,ELF5是诱导乳腺肿瘤细胞由表达雌激素受体阳性(ER+)的luminal亚型向表达雌激素受体阴性(ER-)的basal亚型转化的一个关键调控因子,并抑制细胞获得雌激素敏感表型。现主要综述了ELF5的结构特点、功能以及其在哺乳动物乳腺发育中的调控作用。     

Notch信号通路与生殖干细胞研究进展

Notch信号通路是一个在进化中高度保守的信号通道,具有调控细胞增殖、分化及凋亡的作用。近年来,随着研究的不断深入,发现Notch信号通路与生殖干细胞的增殖分化及干细胞微环境的作用机理密切关联,Notch信号通路在生殖系统发育及疾病治疗中的作用机制逐渐引起人们的广泛关注。该文综合论述了Notch信号通路的生理特性及功能,重点阐述Notch信号通路在精原干细胞、卵巢生殖干细胞及生殖干细胞微环境系统中的调控机制。     

Multifunctional protein 4.1R regulates the asymmetric segregation of Numb during terminal erythroid maturation

The asymmetric cell division of stem or progenitor cells generates daughter cells with distinct fates that balance proliferation and differentiation. Asymmetric segregation of Notch signaling regulatory protein Numb plays a crucial role in cell diversification. However, the molecular mechanism remains unclear. Here, we examined the unequal distribution of Numb in the daughter cells of murine erythroleukemia cells (MELCs) that undergo DMSO-induced erythroid differentiation. In contrast to the cytoplasmic localization of Numb during uninduced cell division, Numb is concentrated at the cell boundary in interphase, near the one-spindle pole in metaphase, and is unequally distributed to one daughter cell in anaphase in induced cells. The inheritance of Numb guides this daughter cell toward erythroid differentiation while the other cell remains a progenitor cell. Mitotic spindle orientation, critical for distribution of cell fate determinants, requires complex communication between the spindle microtubules and the cell cortex mediated by the NuMA-LGN-dynein/dynactin complex. Depletion of each individual member of the complex randomizes the position of Numb relative to the mitotic spindle. Gene replacement confirms that multifunctional erythrocyte protein 4.1R (4.1R) functions as a member of the NuMA-LGN-dynein/dynactin complex and is necessary for regulating spindle orientation, in which interaction between 4.1R and NuMA plays an important role. These results suggest that mispositioning of Numb is the result of spindle misorientation. Finally, disruption of the 4.1R-NuMA-LGN complex increases Notch signaling and decreases the erythroblast population. Together, our results identify a critical role for 4.1R in regulating the asymmetric segregation of Numb to mediate erythropoiesis.     

Asymmetric Numb distribution is critical for asymmetric cell division of mouse cerebral cortical stem cells and neuroblasts

Stem cells and neuroblasts derived from mouse embryos undergo repeated asymmetric cell divisions, generating neural lineage trees similar to those of invertebrates. In Drosophila, unequal distribution of Numb protein during mitosis produces asymmetric cell divisions and consequently diverse neural cell fates. We investigated whether a mouse homologue m-numb had a similar role during mouse cortical development. Progenitor cells isolated from the embryonic mouse cortex were followed as they underwent their next cell division in vitro. Numb distribution was predominantly asymmetric during asymmetric cell divisions yielding a beta-tubulin III(-) progenitor and a beta-tubulin III(+) neuronal cell (P/N divisions) and predominantly symmetric during divisions producing two neurons (N/N divisions). Cells from the numb knockout mouse underwent significantly fewer asymmetric P/N divisions compared to wild type, indicating a causal role for Numb. When progenitor cells derived from early (E10) cortex undergo P/N divisions, both daughters express the progenitor marker Nestin, indicating their immature state, and Numb segregates into the P or N daughter with similar frequency. In contrast, when progenitor cells derived from later E13 cortex (during active neurogenesis in vivo) undergo P/N divisions they produce a Nestin(+) progenitor and a Nestin(-) neuronal daughter, and Numb segregates preferentially into the neuronal daughter. Thus during mouse cortical neurogenesis, as in Drosophila neurogenesis, asymmetric segregation of Numb could inhibit Notch activity in one daughter to induce neuronal differentiation. At terminal divisions generating two neurons, Numb was symmetrically distributed in approximately 80% of pairs and asymmetrically in 20%. We found a significant association between Numb distribution and morphology: most sisters of neuron pairs with symmetric Numb were similar and most with asymmetric Numb were different. Developing cortical neurons with Numb had longer processes than those without. Numb is expressed by neuroblasts and stem cells and can be asymmetrically segregated by both. These data indicate Numb has an important role in generating asymmetric cell divisions and diverse cell fates during mouse cortical development.     

Numb modulates intestinal epithelial cells toward goblet cell phenotype by inhibiting the Notch signaling pathway

Numb was originally identified as an important cell fate determinant that is asymmetrically inherited during mitosis and controls the fate of sibling cells by inhibiting the Notch signaling pathway in neural tissue. The small intestinal epithelium originates from the division of stem cells that reside in the crypt, which further differentiate into goblet cells, absorptive cells, paneth cells, and enteroendocrine cells. However, Numb's involvement in the differentiation process of intestinal epithelium is largely unknown. In the present study, we confirm that both the Numb mRNA and protein isoforms are expressed in adult mouse intestinal mucosa. Numb protein is ubiquitously expressed throughout the crypt–villus axis of the small intestinal epithelium and is mainly localized to the cytoplasmic membrane. Down-regulation of endogenous Numb using RNA interference in cultured intestinal LS174T cells increased Notch signaling, leading to the up-regulation of Hes1 and the down-regulation of Hath1. Knockdown of Numb alleviated MUC2 protein expression and led to loss of the goblet cell phenotype in LS174Tl cells. Our results provide the first evidence that Numb, an important cell fate determinant, modulates intestinal epithelial cells towards the goblet cell phenotype by inhibiting the Notch signaling pathway.     

Asymmetric cell division

Asymmetric cell division is a conserved mechanism for partitioning information during mitosis. Over the past several years, significant progress has been made in our understanding of how cells establish polarity during asymmetric cell division and how determinants, in the form of localized proteins and mRNAs, are segregated. In particular, genetic studies in Drosophila and Caenorhabditis elegans have linked cell polarity, G protein signaling and regulation of the cytoskeleton to coordination of mitotic spindle orientation and localization of determinants. Also, several new studies have furthered our understanding of how asymmetrically localized cell fate determinants, such as the Numb, a negative regulator Notch signaling, functions in biasing cell fates in the developing nervous system in Drosophila. In vertebrates, analysis of dividing neural progenitor cells by in vivo imaging has raised questions about the role of asymmetric cell divisions during neurogenesis.     

The regulation of Notch signaling controls satellite cell activation and cell fate determination in postnatal myogenesis

We have studied the role of Notch-1 and its antagonist Numb in the activation of satellite cells during postnatal myogenesis. Activation of Notch-1 promoted the proliferation of myogenic precursor cells expressing the premyoblast marker Pax3. Attenuation of Notch signaling by increases in Numb expression led to the commitment of progenitor cells to the myoblast cell fate and the expression of myogenic regulatory factors, desmin, and Pax7. In many intermediate progenitor cells, Numb was localized asymmetrically in actively dividing cells, suggesting an asymmetric cell division and divergent cell fates of daughter cells. The results indicate that satellite cell activation results in a heterogeneous population of precursor cells with respect to Notch-1 activity and that the balance between Notch-1 and Numb controls cellular homeostasis and cell fate determination.     

Numb Independently Antagonizes Sanpodo Membrane Targeting and Notch Signaling in Drosophila Sensory Organ Precursor Cells

In Drosophila, mitotic neural progenitor cells asymmetrically segregate the cell fate determinant Numb in order to block Notch signaling in only one of the two daughter cells. Sanpodo, a membrane protein required for Notch signaling in asymmetrically dividing cells, is sequestered from the plasma membrane to intracellular vesicles in a Numb-dependent way after neural progenitor cell mitosis. However, the significance of Numb-dependent Sanpodo regulation is unclear. In this study, we conducted a structure–function analysis to identify the determinants of Sanpodo targeting in vivo. We identified an NPAF motif in the amino-terminal cytoplasmic tail of Sanpodo, which is conserved among insect Sanpodo homologues. The Sanpodo NPAF motif is predicted to bind directly to the Numb phosphotyrosine-binding domain and is critical for Numb binding in vitro. Deletion or mutation of the NPAF motif results in accumulation of Sanpodo at the plasma membrane in Numb-positive cells in vivo. Genetic analysis of Sanpodo NPAF mutants shows that Numb-dependent Sanpodo endocytic targeting can be uncoupled from Notch signaling regulation. Our findings demonstrate that Sanpodo contains an evolutionarily conserved motif that has been linked to Numb-dependent regulation in vertebrates and further support the model that Numb regulates Notch signaling independently of Sanpodo membrane trafficking in neural progenitor cells.     

Murine numb regulates granule cell maturation in the cerebellum

Notch is a key regulator of vertebrate neurogenesis and the cytoplasmic adaptor protein Numb is a modulator of the Notch signaling pathway. To address the role of murine Numb in development of the central nervous system, we used a conditional gene ablation approach. We show that Numb is involved in the maturation of cerebellar granule cells. Although the specification of neural cell fates in the cerebellum is not affected in the absence of Numb, the transition from a mitotic progenitor to a mature granule cell is aberrant and migration of postmitotic granule cells to the internal granule cell layer is delayed. In some animals, this results in a complete agenesis of granule cells and a strong ataxia. We confirmed these findings in vitro and found that Numb-deficient cerebellar progenitor cells show a marked delay in granule cell maturation. Our results suggest that Numb plays a role in the transition of a mitotic progenitor to a fully differentiated granule cell in the cerebellum. In addition, the maturation of Purkinje cells is also delayed in Numb-deficient mice.     

Eya1 controls cell polarity, spindle orientation, cell fate and Notch signaling in distal embryonic lung epithelium

Cell polarity, mitotic spindle orientation and asymmetric division play a crucial role in the self-renewal/differentiation of epithelial cells, yet little is known about these processes and the molecular programs that control them in embryonic lung distal epithelium. Herein, we provide the first evidence that embryonic lung distal epithelium is polarized with characteristic perpendicular cell divisions. Consistent with these findings, spindle orientation-regulatory proteins Insc, LGN (Gpsm2) and NuMA, and the cell fate determinant Numb are asymmetrically localized in embryonic lung distal epithelium. Interfering with the function of these proteins in vitro randomizes spindle orientation and changes cell fate. We further show that Eya1 protein regulates cell polarity, spindle orientation and the localization of Numb, which inhibits Notch signaling. Hence, Eya1 promotes both perpendicular division as well as Numb asymmetric segregation to one daughter in mitotic distal lung epithelium, probably by controlling aPKCζ phosphorylation. Thus, epithelial cell polarity and mitotic spindle orientation are defective after interfering with Eya1 function in vivo or in vitro. In addition, in Eya1(-/-) lungs, perpendicular division is not maintained and Numb is segregated to both daughter cells in mitotic epithelial cells, leading to inactivation of Notch signaling. As Notch signaling promotes progenitor cell identity at the expense of differentiated cell phenotypes, we test whether genetic activation of Notch could rescue the Eya1(-/-) lung phenotype, which is characterized by loss of epithelial progenitors, increased epithelial differentiation but reduced branching. Indeed, genetic activation of Notch partially rescues Eya1(-/-) lung epithelial defects. These findings uncover novel functions for Eya1 as a crucial regulator of the complex behavior of distal embryonic lung epithelium.