Drosophila neural progenitor polarity and asymmetric division.
ABSTRACT In the Drosophila embryonic central nervous system, the neural precursor cells called neuroblasts undergo a number of asymmetric divisions along the apical-basal axis to give rise to different daughter cells of distinct fates. This review summarizes recent progress in understanding the mechanisms of these asymmetric cell divisions. We discuss proteins that are localized at distinct domains of cortex in the neuroblasts and their role in generating asymmetry. We also review uniformly cortical localized factors and actin cytoskeleton-associated motor proteins with regard to their potential role to serve as a link between distinct cortical domains in the neuroblasts. In this review, asymmetric divisions of sensory organ precursor and larval neuroblasts are also briefly discussed.
Chapter: Asymmetric Behavior in Stem Cells[show abstract] [hide abstract]
ABSTRACT: Asymmetry in the stem cell niche refers to the notion that daughter cells are different from each other. There is significant evidence that many stem cell divisions result in one daughter cell that is similar to the parent cell and, hence, necessarily allows for self-renewal of the stem cell phenotype, whereas the other daughter cell is a differentiated or committed cell type. In this chapter we will discuss the role of asymmetry in stem cell divisions and the evidence that supports different asymmetric scenarios in different model systems. We first present the early asymmetric divisions that have been described in first divisions of the zygote and in gametogenesis. Next, we will discuss evidence of asymmetry in postnatal stem cells. Here we will describe two systems in particular – the hematopoietic system and muscle stem cells. Lastly, we will present a theory of the immortal strand hypothesis in which the role of DNA strand segregation is discussed as it relates to asymmetry in cell divisions and the protection of the self-renewing stem cell. KeywordsPolarized–Polarity–Niche–Microenvironment–Immortal strand–Cancer–Cell expansion–Cell therapy–Lineage–Division history12/2008: pages 13-26;
Article: Differential requirements for Wnt and Notch signaling in hematopoietic versus thymic niches.[show abstract] [hide abstract]
ABSTRACT: All blood cells are derived from multipotent stem cells, the so-called hematopoietic stem cells (HSCs), that in adults reside in the bone marrow. Most types of blood cells also develop there, with the notable exception of T lymphocytes that develop in the thymus. For both HSCs and developing T cells, interactions with the surrounding microenvironment are critical in regulating maintenance, differentiation, apoptosis, and proliferation. Such specialized regulatory microenvironments are referred to as niches and provide both soluble factors as well as cell-cell interactions between niche component cells and blood cells. Two pathways that are critical for early T cell development in the thymic niche are Wnt and Notch signaling. These signals also play important but controversial roles in the HSC niche. Here, we review the differences and similarities between the thymic and hematopoietic niches, with particular focus on Wnt and Notch signals, as well as the latest insights into regulation of these developmentally important pathways.Annals of the New York Academy of Sciences 08/2012; 1266:78-93. · 3.15 Impact Factor
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ABSTRACT: Asymmetric cell division is an important and conserved strategy in the generation of cellular diversity during animal development. Many of our insights into the underlying mechanisms of asymmetric cell division have been gained from Drosophila, including the establishment of polarity, orientation of mitotic spindles and segregation of cell fate determinants. Recent studies are also beginning to reveal the connection between the misregulation of asymmetric cell division and cancer. What we are learning from Drosophila as a model system has implication both for stem cell biology and also cancer research.Seminars in Cell and Developmental Biology 07/2008; 19(3):283-93. · 6.65 Impact Factor