The midline (notochord and notoplate) patterns the cell motility underlying convergence and extension of the Xenopus neural plate

Ezin, Akouavi M.; Skoglund, Paul; Keller, Ray

doi:10.1016/s0012-1606(02)00130-6

Cited by 37 publications

(30 citation statements)

References 23 publications

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“…7, diagrams). Signals emanating from the midline have been shown to direct the cellular behavior of deep neural cells engaged in convergent extension (Ezin et al, 2003), and it is possible that similar signals guide the orientation of cellular long axes in the superficial neural plate, which appear to impose the orientation of divisions. Regardless, the orientation of cell division is independent of normal neural morphogenesis, as disruption of neural tube closure by a variety of different molecular manipulations failed to alter cell-division orientation (Fig.…”

Section: Discussionmentioning

confidence: 99%

In vivo imaging reveals a role for Cdc42 in spindle positioning and planar orientation of cell divisions during vertebrate neural tube closure

Kieserman

Wallingford

2009

Journal of Cell Science

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Specialization of the cell-division process is a common feature of developing embryos, but most studies on vertebrate cell division have focused on cells dividing in culture. Here, we used in vivo four-dimensional confocal microscopy to explore the role of Cdc42 in governing cell division in the developing neural epithelium of Xenopus laevis. We find that Cdc42 is crucial for stable positioning of the metaphase spindle in these cells, but was not required for spindle positioning in epidermal epithelial cells. We also find that divisions in the Xenopus neural plate are planar oriented, and that rotations of mitotic spindles are essential for establishing this orientation. When Cdc42 is disrupted, spindles over-rotate and the final orientation of divisions is changed. Finally, the planar orientation of cell divisions in this tissue seems to be independent of planar cell polarity (PCP) signaling and does not require normal neural morphogenesis. Our data provide new insights into the coordination of cell division and morphogenesis in epithelial cell sheets and reveal novel, cell-type-specific roles for Cdc42 in spindle positioning and spindle orientation.

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Section: Discussionmentioning

confidence: 99%

In vivo imaging reveals a role for Cdc42 in spindle positioning and planar orientation of cell divisions during vertebrate neural tube closure

Kieserman

Wallingford

2009

Journal of Cell Science

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“…The 90°/270° axis was aligned with the A/P axis of the embryo. The average distribution of protrusions was determined by combining observations for all cells in each defined sector surrounding the PNC, and were analyzed as described previously Ezin et al, 2003;Ezin et al, 2006), using a χ 2 test to determine whether the distribution of protrusive activity was significantly different from random and the 2ai test (Baschelet, 1981;Zar, 1998) to determine whether they were monopolar or bipolar (Ezin et al, 2003). We computed 'preferred directions' of protrusion in a given section of the embryo by comparing the frequency of observed protrusion directions by a cell to that expected by chance, and permutation tests were used to assign a probability to the observed difference.…”

Section: Image Analysismentioning

confidence: 99%

“…Mediolateral intercalation of cells (MIB), driven by mediolateral bi-polarization of mesodermal cell motility (Keller and Tibbetts, 1989;Shih and Keller, 1992a;Shih and Keller, 1992b) and by medially directed cell motility in posterior neural tissues Elul and Keller, 2000;Ezin et al, 2003), produces a narrower, longer array of cells. In the fish, similar MIB (Kimmel et al, 1994;Myers et al, 2002) is driven by polarized motility in the notochord (Glickman et al, 2003) and dorsally directed migration in the lateral mesoderm (Trinkaus, 1998;Jessen et al, 2002;Lin et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

PTK7 is essential for polarized cell motility and convergent extension during mouse gastrulation

et al. 2009

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Despite being implicated as a mechanism driving gastrulation and body axis elongation in mouse embryos, the cellular mechanisms underlying mammalian convergent extension (CE) are unknown. Here we show, with high-resolution time-lapse imaging of living mouse embryos, that mesodermal CE occurs by mediolateral cell intercalation, driven by mediolaterally polarized cell behavior. The initial events in the onset of CE are mediolateral elongation, alignment and orientation of mesoderm cells as they exit the primitive streak. This cell shape change occurs prior to, and is required for, the subsequent onset of mediolaterally polarized protrusive activity. In embryos mutant for PTK7, a novel cell polarity protein, the normal cell elongation and alignment upon leaving the primitive streak, the subsequent polarized protrusive activity, and CE and axial elongation all failed. The mesoderm normally thickens and extends, but on failure of convergence movements in Ptk7 mutants, the mesoderm underwent radial intercalation and excessive thinning, which suggests that a cryptic radial cell intercalation behavior resists excessive convergence-driven mesodermal thickening in normal embryos. When unimpeded by convergence forces in Ptk7 mutants, this unopposed radial intercalation resulted in excessive thinning of the mesoderm. These results show for the first time the polarized cell behaviors underlying CE in the mouse, demonstrate unique aspects of these behaviors compared with those of other vertebrates, and clearly define specific roles for planar polarity and for the novel planar cell polarity gene, Ptk7, as essential regulators of mediolateral cell intercalation during mammalian CE.

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“…For example, the process of convergent extension appears to be a main contributor to the reshaping of an embryo from an ovoid into an elongated discoid shape, as was studied extensively in amphibian embryos (Keller et al 1992;Davidson and Keller 1999;Wallingford and Harland 2001;Ezin et al 2003). During convergent extension, a sheet of cells narrows in transverse direction by intercalation in the medial region and consequently elongates in cranio-caudal direction.…”

Section: Anterior Cell Movements Contribute To the Anterior Neural Platementioning

confidence: 99%

Morphogenetic movements during cranial neural tube closure in the chick embryo and the effect of homocysteine

et al. 2005

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In order to unravel morphogenetic mechanisms involved in neural tube closure, critical cell movements that are fundamental to remodelling of the cranial neural tube in the chick embryo were studied in vitro by quantitative time-lapse video microscopy. Two main directions of movements were observed. The earliest was directed medially; these cells invaginated into a median groove and were the main contributors to the initial neural tube closure. Once the median groove was completed, cells changed direction and moved anteriorly to contribute to the anterior neural plate and head fold. This plate developed into the anterior neuropore, which started to close from the 4-somite stage onwards by convergence of its neural folds. Posteriorly, from the initial closure site onwards, the posterior neuropore started to close almost instantaneously by convergence of its neural folds. Homocysteine is adversely involved in human neural tube closure defects. After application of a single dose of homocysteine to chick embryos, a closure delay at the initial closure site and at the neuropores, flattening of the head fold and neural tube, and a halt of cell movements was seen. A possible interference of Hcy with actin microfilaments is discussed.

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The midline (notochord and notoplate) patterns the cell motility underlying convergence and extension of the Xenopus neural plate

Cited by 37 publications

References 23 publications

In vivo imaging reveals a role for Cdc42 in spindle positioning and planar orientation of cell divisions during vertebrate neural tube closure

In vivo imaging reveals a role for Cdc42 in spindle positioning and planar orientation of cell divisions during vertebrate neural tube closure

PTK7 is essential for polarized cell motility and convergent extension during mouse gastrulation

Morphogenetic movements during cranial neural tube closure in the chick embryo and the effect of homocysteine

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