Epithelial-Mesenchymal Transitions in Development and Disease (original) (raw)

Pattern formation during gastrulation in the sea urchin embryo

Development (Cambridge, England). Supplement, 1992

The sea urchin embryo follows a relatively simple cell behavioral sequence in its gastrulation movements. To form the mesoderm, primary mesenchyme cells ingress from the vegetal plate and then migrate along the basal lamina lining the blastocoel. The presumptive secondary mesenchyme and endoderm then invaginate from the vegetal pole of the embryo. The archenteron elongates and extends across the blastocoel until the tip of the archenteron touches and attaches to the opposite side of the blastocoel. Secondary mesenchyme cells, originally at the tip of the archenteron, differentiate to form a variety of structures including coelomic pouches, esophageal muscles, pigment cells and other cell types. After migration of the secondary mesenchyme cells from their original position at the tip of the archenteron, the endoderm fuses with an invagination of the ventral ectoderm (the stomodaem), to form the mouth and complete the process of gastrulation. A larval skeleton is made by primary mesen...

The prickle-Related Gene in Vertebrates Is Essential for Gastrulation Cell Movements

Current Biology, 2003

The Graduate University for Advanced Studies Using our own Xenopus EST database (XDB; http:// 38 Nishigonaka Xenopus.nibb.ac.jp/), we identified Xpk, a homolog of Myodaiji, Okazaki 444-8585 acidian [14] and Drosophila prickle that was reported Japan to be a critical gene for establishing PCP [11-13]. Xpk 3 Division of Early Embryogenesis encodes an 835-amino acid protein with a single PET National Institute of Genetics domain and three repetitive LIM domains in its N-ter-1111 Yata minal half. Mishima 411-8540 As previously reported [15], Xpk transcripts become Japan restricted to the marginal zone with a steep gradient 4 Laboratory of Developmental Genetics from the dorsal to the ventral side at the start of gastrula-Department of Biological Science tion (Figures 1A a and 1A b ). As gastrulation proceeded, Graduate School of Sciences the expression domain became localized to the involut-University of Tokyo ing edge of the blastopore (Figures 1A c and 1A d ), then 7-3-1 Hongo accumulated toward the posterior end of the midline Bunkyo-ku, Tokyo 113-0033 and finally extended along the anterior-posterior axis Japan (Figures 1A e and 1A f ). Northern blot analysis demonstrated that two prickle transcripts of approximately 5 kb were maternally encoded and expressed throughout Summary development, at least to the tadpole stage, with slight changes in their level, which peaked around the onset of Involving dynamic and coordinated cell movements gastrulation ( . These spatially and temporally that cause drastic changes in embryo shape, gastrularegulated profiles of Xpk suggest that XPK plays a role tion is one of the most important processes of early in gastrulation.

The Mouse Snail Gene Encodes a Key Regulator of the Epithelial-Mesenchymal Transition

Molecular and Cellular Biology, 2001

Snail family genes encode DNA binding zinc finger proteins that act as transcriptional repressors. Mouse embryos deficient for the Snail (Sna) gene exhibit defects in the formation of the mesoderm germ layer. In Sna ؊/؊ mutant embryos, a mesoderm layer forms and mesodermal marker genes are induced but the mutant mesoderm is morphologically abnormal. Lacunae form within the mesoderm layer of the mutant embryos, and cells lining these lacunae retain epithelial characteristics. These cells resemble a columnar epithelium and have apical-basal polarity, with microvilli along the apical surface and intercellular electron-dense adhesive junctions that resemble adherens junctions. E-cadherin expression is retained in the mesoderm of the Sna ؊/؊ embryos. These defects are strikingly similar to the gastrulation defects observed in snail-deficient Drosophila embryos, suggesting that the mechanism of repression of E-cadherin transcription by Snail family proteins may have been present in the metazoan ancestor of the arthropod and mammalian lineages.

The βL Integrin Subunit Is Necessary for Gastrulation in Sea Urchin Embryos

Developmental Biology, 1998

Integrins are a family of cell adhesion molecules reported to mediate cellular interactions essential for normal embryonic morphogenesis. Here we describe a ␤ integrin subunit that is expressed during early embryogenesis in the sea urchin embryo and appears to be necessary for normal development. The deduced amino acid sequence of ␤L is similar to vertebrate ␤ integrin subunits, but is most closely related to the sea urchin ␤G subunit. Northern blots show that ␤L is expressed at all stages with maximum expression beginning during gastrulation. Immunolocalization and in situ RNA hybridization show that in blastulae ␤L is expressed in the blastoderm and by the ring of bottle cells in the vegetal plate during the initial phase of gastrulation. Presumptive secondary mesenchyme cells express high levels of ␤L throughout elongation of the archenteron and in the pluteus ␤L is expressed by blastocoelar cells, skeletal mesenchyme, and pigment cells. Antibodies and Fab fragments against ␤L block spreading of dissociated embryonic cells on RGD (arginine-glycine-aspartate)containing substrates. Treating embryos with anti-␤L antibodies blocks the initial phase of gastrulation and interferes with the organization of actin filaments. Prior to gastrulation, the antibodies cause thickening of the blastoderm and later in development defects in skeletal patterning result. Probing for antibody in treated embryos indicates that it penetrates the ectoderm to cells within the blastocoel and is actively endocytosed. We propose that ␤L forms receptors that bind to RGD-containing ligands and anchors actin filaments. These receptors appear to be essential in several aspects of morphogenesis.