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Apical constriction and epithelial invagination are regulated by BMP activity
Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
2015 (English)In: Biology open, ISSN 2046-6390, Vol. 4, no 12, 1782-1791 p.Article in journal (Refereed) Published
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Text
Abstract [en]

Epithelial invagination is a morphological process in which flat cell sheets transform into three-dimensional structures through bending of the tissue. It is accompanied by apical constriction, in which the apical cell surface is reduced in relation to the basal cell surface. Although much is known about the intra-cellular molecular machinery driving apical constriction and epithelial invagination, information of how extra-cellular signals affect these processes remains insufficient. In this study we have established several in vivo assays of placodal invagination to explore whether the external signal BMP regulates processes connected to epithelial invagination. By inhibiting BMP activity in prospective cranial placodes, we provide evidence that BMP signals are required for RhoA and F-actin rearrangements, apical constriction, cell elongation and epithelial invagination. The failure of placode invagination after BMP inhibition appears to be a direct consequence of disrupted apical accumulation of RhoA and F-actin, rather than changes in cell death or proliferation. In addition, our results show that epithelial invagination and acquisition of placode-specific identities are two distinct and separable developmental processes. In summary, our results provide evidence that BMP signals promote epithelial invagination by acting upstream of the intracellular molecular machinery that drives apical constriction and cell elongation.

Place, publisher, year, edition, pages
2015. Vol. 4, no 12, 1782-1791 p.
Keyword [en]
BMP, F-actin, Invagination, RhoA, Apical constriction, Placodes
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
URN: urn:nbn:se:umu:diva-114017DOI: 10.1242/bio.015263ISI: 000366672900021PubMedID: 26621830OAI: oai:DiVA.org:umu-114017DiVA: diva2:894736
Available from: 2016-01-15 Created: 2016-01-11 Last updated: 2016-04-28Bibliographically approved
In thesis
1. BMP - a key signaling molecule in specification and morphogenesis of sensory structures
Open this publication in new window or tab >>BMP - a key signaling molecule in specification and morphogenesis of sensory structures
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cranial placodes are transient thickenings of the vertebrate embryonic head ectoderm that will give rise to sensory (olfactory, lens, and otic) and non-sensory (hypophyseal) components of the peripheral nervous system (PNS). In most vertebrate embryos, these four sensory placodes undergo invagination. Epithelial invagination is a morphological process in which flat cell sheets transform into three-dimensional structures, like an epithelial pit/cup. The process of invagination is crucial during development as it plays an important role for the formation of the lens, inner ear, nasal cavity, and adenohypophysis. Using the chick as the model system the following questions were addressed. What signals are involved in placode invagination? Is there any common regulatory molecular mechanism for all sensory placode invagination, or is it controlled by unique molecular codes for each individual placode? Are placode invagination and acquisition of placode-specific identities two independent developmental processes or coupled together? To address this we used in vivo assays like electroporation and whole embryo culture. Our in vivo results provide evidence that RhoA and F-actin rearrangements, apical constriction, cell elongation and epithelial invagination are regulated by a common BMP (Bone morphogenetic protein) dependent molecular mechanism. In addition, our results show that epithelial invagination and acquisition of placode-specific identities are two independent developmental processes.

BMP signals have been shown to be essential for lens development and patterning of the retina. However, the spatial and temporal requirement of BMP activity during early events of lens development has remained elusive. Moreover, when and how retinal cells are specified, and whether the lens plays any role for the early development of the retina is not completely known. To address these questions, we have used gain- and loss-of-function analyses in chick explant and intact embryo assays. Here, we show that during lens development BMP activity is both required and sufficient to induce the lens specific marker, L-Maf. After the L-Maf upregulation the cells are no longer dependent on BMP signaling for the next step of fiber cell differentiation, which is characterized by up-regulation of δ-crystallin expression. Regarding the specification of retinal cells our results provide evidence that at blastula stages, BMP signals inhibit the acquisition of eye-field character. Furthermore, from optic vesicle stages, BMP signals emanating from the lens are essential for maintaining eye-field identity, inhibiting telencephalic character and inducing neural retina cells.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 64 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1812
Keyword
BMP signaling, Placode morphogenesis, lens, retina, olfactory, otic
National Category
Developmental Biology
Research subject
Developmental Biology
Identifiers
urn:nbn:se:umu:diva-119696 (URN)978-91-7601-468-4 (ISBN)
Public defence
2016-05-20, Hörsal B Unod T 9, Norrlands universitetssjukhus, Umeå, 09:00 (English)
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Supervisors
Available from: 2016-04-29 Created: 2016-04-25 Last updated: 2016-04-28Bibliographically approved

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Jidigam, Vijay K.Patthey, CedricGunhaga, Lena
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