Mechanisms Regulating Pattern Formation in the Amphibian Egg and Early Embryo

Gerhart, John C.

doi:10.1007/978-1-4684-9933-9_4

Cited by 170 publications

(103 citation statements)

References 476 publications

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“…We have identified this type of junction as epithelial zonula occludens (ZO). The finding of Kalt (1971b) that blastomeres of the 2-cell embryo form "close junctions" that are impermeable to the passage of electron dense tracers led to the idea that ZOs are already established at cleavage (Slack and Warner, 1973;Gerhart, 1980). In TEM studies we did not observe typical ZOs before the 32-cell stage (stage 6).…”

Section: Formation Of the Epithelial Junctional Complex During Early mentioning

confidence: 54%

“…The function of this primary epithelium has been discussed to be critical for the maintenance of the salt balance within the embryo and the formation of the blastocoel (Slack and Warner, 1973;Gerhart, 1980;Regen and Steinhardt, 1986). This function requires the presence of 406 MULLER AND HAUSEN junctions between the epithelial cells that restrict free diffusion of ions through the paracellular pathway.…”

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confidence: 99%

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Epithelial cell polarity in early Xenopus development

Müller

Hausen

1995

Developmental Dynamics

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The Xenopus blastula consists of two morphologically distinct cell types. Polarized epithelial cells build up the embryonic surface and fence off an inner non-polarized cell population. We examined the establishment of this early functional cell diversification in the embryo by single cell analysis, in vitro cell culture, and transplantation experiments. Single blastomeres from a 64-cell embryo (1/64 cells) exhibit several features of polarized cells. The plasma membrane of 1/64 cells consists of an apical domain, which is inherited from the original egg membrane, and a basolateral domain derived from newly formed membrane during cleavage. These are inherent, cell-autonomous properties of the blastomeres, as they form and are maintained in blastomeres raised in the absence of any cell interactions in calcium free medium. Upon in vitro culture a single 1/64 cell gives rise to an aggregate of two different cell types. Cells carrying a part of the former egg membrane domain differentiate into polarized epithelial cells, whereas cells lacking this membrane domain are not polarized. These results demonstrate that the inclusion of the egg membrane, rather than external signals related to the position of a cell in the intact embryo, is required for the apicalhasolateral differentiation of the surface epithelium. This view is supported by cell transplantation studies. A single 1/64 cell was implanted into the blastocoel of a stage 8 blastula embryo. The progeny of the implanted cell proliferate within the host embryo and split into two morphologically distinct populations with different cell behaviours. Cells incorporating a part of the egg membrane form coherent patches of polarized epithelial cell sheets in the interior of the host embryo. In contrast, cells lacking egg membrane do not exhibit any characteristics of polarized cells and eventually spread into different regions of the host embryo. Our results show that the egg membrane and/or components of the submembrane cortex play a determinative role in the formation of the blastula epithelium.

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Section: Formation Of the Epithelial Junctional Complex During Early mentioning

confidence: 54%

mentioning

confidence: 99%

Epithelial cell polarity in early Xenopus development

Müller

Hausen

1995

Developmental Dynamics

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“…This also appears to be true in the majority of model organisms in which transcript elimination has been studied (see text). Conversely, the term 'MBT' was first used to describe a developmental event in amphibian embryogenesis in which, after the first 11 or 12 synchronous cleavage divisions, the cell cycle lengthens, gap phases appear and mitoses become desynchronized (Gerhart, 1980). Since then, researchers have applied the term to analogous stages in other animals, such as fish (Kane and Kimmel, 1993) and flies (Blankenship and Wieschaus, 2001).…”

Section: Box 2 Mzt Versus Mbtmentioning

confidence: 99%

The maternal-to-zygotic transition: a play in two acts

2009

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All animal embryos pass through a stage during which developmental control is handed from maternally provided gene products to those synthesized from the zygotic genome. This maternal-to-zygotic transition (MZT) has been extensively studied in model organisms, including echinoderms, nematodes, insects, fish,amphibians and mammals. In all cases, the MZT can be subdivided into two interrelated processes: first, a subset of maternal mRNAs and proteins is eliminated; second, zygotic transcription is initiated. The timing and scale of these two events differ across species, as do the cellular and morphogenetic processes that sculpt their embryos. In this article, we discuss conserved and distinct features within the two component processes of the MZT.

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“…3A,B). It has been thought that the YPs of the gut are degraded extracellularly, by digestion of yolky cells within the intestinal lumen (Gerhart, 1980;Hausen and Riebesell, 1991). However, recent fate maps suggest that all deep endoderm cells are incorporated into the intestinal wall (Chalmers and Slack, 2000).…”

Section: Research Article Yolk Consumption In Xenopusmentioning

confidence: 99%

The mechanism and pattern of yolk consumption provide insight into embryonic nutrition inXenopus

Jorgensen

Steen

et al. 2009

Development

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Little is known about how metabolism changes during development. For most animal embryos, yolk protein is a principal source of nutrition, particularly of essential amino acids. Within eggs, yolk is stored inside large organelles called yolk platelets (YPs). We have gained insight into embryonic nutrition in the African clawed frog Xenopus laevis by studying YPs. Amphibians follow the ancestral pattern in which all embryonic cells inherit YPs from the egg cytoplasm. These YPs are consumed intracellularly at some point during embryogenesis, but it was not known when, where or how yolk consumption occurs. We have identified the novel yolk protein Seryp by biochemical and mass spectrometric analyses of purified YPs. Within individual YPs, Seryp is degraded to completion earlier than the major yolk proteins, thereby providing a molecular marker for YPs engaged in yolk proteolysis. We demonstrate that yolk proteolysis is a quantal process in which a subset of dormant YPs within embryonic cells are reincorporated into the endocytic system and become terminal degradative compartments. Yolk consumption is amongst the earliest aspects of differentiation. The rate of yolk consumption is also highly tissue specific, suggesting that nutrition in early amphibian embryos is tissue autonomous. But yolk consumption does not appear to be triggered by embryonic cells declining to a critically small size. Frog embryos offer a promising platform for the in vivo analysis of metabolism.

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Mechanisms Regulating Pattern Formation in the Amphibian Egg and Early Embryo

Cited by 170 publications

References 476 publications

Epithelial cell polarity in early Xenopus development

Epithelial cell polarity in early Xenopus development

The maternal-to-zygotic transition: a play in two acts

The mechanism and pattern of yolk consumption provide insight into embryonic nutrition inXenopus

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