Drift of Cell Function Through Serial Divisions

The classical experiments of Meselson and Stahl showing that the synthesis of DNA is semiconservative led to the belief that at each division each daughter cell receives the same kind of genetic information and hence that both sister cells are identical. However, when one follows a cell population during serial proliferation in vitro different parameters show that the cell functions evolve in many respects. Human fibroblasts proliferating in vitro were extensively analyzed in this respect since...

Polarity and Orientation of Cell Division in Plants

Cell polarity is the development of asymmetry within a cell which can be monitored by physical changes in cell shape or localized distribution of molecular components. Cell polarity provides information for axis formation, patterning, growth and asymmetric cell division. Asymmetric distribution of the plant hormone auxin is instrumental in regulating many polar growth and division responses at the tissue level (summarized in Dhonukshe et al. 2005) but is also implicated in specific cases of...

References

Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002) Molecular biology of the cell. Garland Science, New York Arnholdt H, Meisel F, Fandrey K, Lohrs U (1991) Proliferation of villous tro-phoblast of the human placenta in normal and abnormal pregnancies. Virchows Arch B Cell Pathol Incl Mol Pathol 60 365-372 Aspinall R (2000) Longevity and the immune response. Biogerontology 1 273-278 Bousfield GR, Butnev VY, Gotschall RR, Baker VL, Moore WT (1996) Structural features of mammalian...

Induction of Tumor Growth by Impaired Progenitor Cell Differentiation in Drosophila

Clonal analysis and genetic interaction studies show that the tumor suppressor Brat and the adaptor molecule Mira are required for asymmetric segregation of the cell fate determinant Pros and hence the restriction of GMC proliferation to one terminal division. Moreover, impaired Brat, Mira, or Pros activity results in impaired GMC cell fate determination eventually leading to neoplastic tissue formation and the concomitant loss of differentiated ganglion cells in the larval brain of Drosophila...

Unequal Cell Division at First Cleavage

In Helobdella as in other unequally cleaving spiralians, the chain of events initiated by the unequal first cleavage is critical to the normal development of the body plan. Centrifugation experiments showed that factors permitting the expression of the D quadrant fates are associated with the telo-plasm. For instance, when zygotes are compressed to re-orient the mitotic apparatus and both daughters inherit teloplasm at first cleavage, they both make teloblasts (Nelson and Weisblat 1992). And...

Gametogenesis

Plant Gametogenesis

It is noteworthy that, in flowering plants, male gamete formation involves a 1M-2DD type of ACD see Fig. 3A whereas female gamete formation involves a C-C pathway see Fig. 4A . At least 200 genes are estimated to be required for gametophyte development see Bonhomme et al. 1998 Yang and Sundaresan 2000 Wilson and Yang 2004 . Microsporogenesis and Male Gametophyte Development The microspore undergoes an ACD, giving rise to two daughter cells of different fates - the larger vegetative cell VC and...

Asymmetric Germline Stem Cell Division During Drosophila Gametogenesis

Egfr Pathway Germline Stem Cell

Stem cells are characterized by both their ability to make more stem cells, a process called self-renewal, and their capacity to generate specialised cells forming organs Fuchs and Segre 2000 . While symmetric division is required for the expansion of a stem cell population after an injury for example , asymmetric division allows the simultaneous production of two cell types, a new stem cell and a cell fated to differentiate Morrison and Kimble 2006 . Germline stem cells have been described in...

Asymmetric Divisions in Embryogenesis

As different as the shapes and sizes of higher and lower plants appear, the early steps in embryogenesis show profound similarities. Embryos of higher plants develop deep inside maternal tissues and thus are difficult to use for experimental manipulation. Therefore research on embryogenesis has focused on genetics as an important tool. Lower plants such as the brown alga Fucus have free-living zygotes and have provided a valuable system to study asymmetric division Fowler and Quatrano 1997...