Sumario:
The International Journal of Developmental Biology
Euskal Herriko Unibertsitateko Argitalpen Zerbitzua/Servicio Editorial de la Universidad del País Vasco.
Vol. 51/2, 2007
Más información en http://www.ijdb.ehu.es/web/contents.php?vol=51&issue=2
Meeting Report
5th Congress of the Spanish Society of Developmental Biology
Jaume Baguñà
Department of Genetics, Faculty of Biology, University of Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
Int. J. Dev. Biol. (2007) 51: 91-96
ABSTRACT: The Spanish Society of Developmental Biology (Sociedad Española de Biologia del Desarrollo - SEBD) has been organizing periodic meetings for over 10 years now, since its first Congress in 1996 (Leioa, Vizcaya). The objective of these Congresses is to gather Developmental Biology researchers from Spain and different parts of the world, for interaction and exchange of ideas. After the successful meetings in Leioa (1996), Barcelona (1999, the only all-English one so far), Málaga (2001) and Santander (2004), it was time to hold the 5th venue.
Key words: SEBD, development, Spain, Antonio García-Bellido, Eric Davidson
Original Articles
Fate of cranial neural crest cells during craniofacial development in endothelin-A receptor-deficient mice.
Makoto Abe, Louis-Bruno Ruest and David E. Clouthier
Department of Craniofacial Biology, University of Colorado at Denver and Health Sciences Center, Aurora CO, USA
Int. J. Dev. Biol. (2007) 51: 97-105
ABSTRACT: Most of the bone, cartilage and connective tissue of the lower jaw is derived from cranial neural crest cells (NCCs) arising from the posterior midbrain and hindbrain. Multiple factors direct the patterning of these NCCs, including endothelin-1-mediated endothelin A receptor (Edn1/Ednra) signaling. Loss of Ednra signaling results in multiple defects in lower jaw and neck structures, including homeotic transformation of lower jaw structures into upper jaw-like structures. However, since the Ednra gene is expressed by both migrating and post-migrating NCCs, the actual function of Ednra in cranial NCC development is not clear. Ednra signaling could be required for normal migration or guidance of NCCs to the pharyngeal arches or in subsequent events in post-migratory NCCs, including proliferation and survival. To address this question, we performed a fate analysis of cranial NCCs in Ednra-/- embryos using the R26R;Wnt1-Cre reporter system, in which Cre expression within NCCs results in permanent beta-galactosidase activity in NCCs and their derivatives. We find that loss of Ednra does not detectably alter either migration of most cranial NCCs into the mandibular first arch and second arch or their subsequent proliferation. However, mesenchymal cell apoptosis is increased two fold in both E9.5 and E10.5 Ednra-/- embryos, with apoptotic cells being present in and just proximal to the pharyngeal arches. Based on these studies, Ednra signaling appears to be required by most cranial NCCs after they reach the pharyngeal arches. However, a subset of NCCs appear to require Ednra signaling earlier, with loss of Ednra signaling likely leading to premature cessation of migration into or within the arches and subsequent cell death.
Key words: neural crest, facial morphogenesis, loxP/Cre, fate mapping
Genetic control of dorsoventral patterning and neuroblast specification in the Drosophila Central Nervous System.
Guoyan Zhao, Scott R. Wheeler and James B. Skeath
1Program in Molecular Cell Biology, 2Program in Neuroscience and 3Department of Genetics, Washington University School of Medicine, St Louis, MO, USA
Int. J. Dev. Biol. (2007) 51: 107-115
ABSTRACT: The Drosophila embryonic Central Nervous System (CNS) develops from the ventrolateral region of the embryo, the neuroectoderm. Neuroblasts arise from the neuroectoderm and acquire unique fates based on the positions in which they are formed. Previous work has identified six genes that pattern the dorsoventral axis of the neuroectoderm: Drosophila epidermal growth factor receptor (Egfr), ventral nerve cord defective (vnd), intermediate neuroblast defective (ind), muscle segment homeobox (msh), Dichaete and Sox-Neuro (SoxN). The activities of these genes partition the early neuroectoderm into three parallel longitudinal columns (medial, intermediate, lateral) from which three distinct columns of neural stem cells arise. Most of our knowledge of the regulatory relationships among these genes derives from classical loss of function analyses. To gain a more in depth understanding of Egfr-mediated regulation of vnd, ind and msh and investigate potential cross-regulatory interactions among these genes, we combined loss of function with ectopic activation of Egfr activity. We observe that ubiquitous activation of Egfr expands the expression of vnd and ind into the lateral column and reduces that of msh in the lateral column. Through this work, we identified the genetic criteria required for the development of the medial and intermediate column cell fates. We also show that ind appears to repress vnd, adding an additional layer of complexity to the genetic regulatory hierarchy that patterns the dorsoventral axis of the CNS. Finally, we demonstrate that Egfr and the genes of the achaete-scute complex act in parallel to regulate the individual fate of neural stem cells.
Key words: Egfr, vnd, ind, CNS, dorsoventral patterning
NMDA-receptor blockade enhances cell apoptosis in the developing retina of the postnatal rat.
María Hernández1, Inmaculada Guerrikagoitia2, Luis Martínez-Millan2 and Elena Vecino1
1Department of Cell Biology and 2Departament of Neuroscience, Faculty of Medicine, University of the Basque Country, Leioa, Vizcaya, Spain
Int. J. Dev. Biol. (2007) 51: 117-122
ABSTRACT: During visual system development, programmed cell death occurs in order to facilitate the establishment of correct connections and synapses. During this period, glutamate plays a very important role as an excitatory neurotransmitter. With a view to evaluating if NMDA glutamate receptors participate in the regulation of apoptosis which occurs during the development of the rat retina, we subcutaneously injected the NMDA receptor antagonist MK-801 into rats at different stages of early postnatal development (P2 to P9). Ensuing cell death in the retina and superior colliculus was analyzed by using the Feulgen method. MK-801 administration had no effect on the survival of photoreceptor cells. In contrast, the presence of this antagonist induced a significant increase in the number of apoptotic cells in the neuroblastic layer (P7 and P8) and ganglion cell layer (P6-P8), as well as in the superior colliculus which receives afferent contacts from retinal ganglion cells during P7-P9. We conclude that during development, specific types of cells in the mammalian retina are critically dependent for their survival on glutamate stimulation through NMDA receptors. These findings thus throw fresh light on the mechanisms of development of the rat visual system by identifying NMDA glutamate receptors as participants in the regulation of apoptotic processes which occur during the initial stages of development.
Key words: apoptosis, retina, glutamate receptor, retinal ganglion cell, MK-801, NMDA
Cadherin-6 is required for zebrafish nephrogenesis during early development.
Fumitaka Kubota1, Tohru Murakami1, Kenji Mogi2 and Hiroshi Yorifuji1
1Neuromuscular and Developmental Anatomy and 2Stomatology and Maxillofacial Surgery, Gunma University Graduate School of Medicine, Gunma, Japan
Int. J. Dev. Biol. (2007) 51: 123-129
ABSTRACT: We performed functional analyses of cadherin-6 (cdh6) in zebrafish nephrogenesis using antisense morpholino oligonucleotide (MO) inhibition combined with in situ hybridization. We have cloned a zebrafish homolog (accession number AB193290) of human K-cadherin (CDH6), which showed 6063% identity and 7678% similarity to the human, mouse, chicken and Xenopus homologs. Whole-mount in situ hybridization showed that cdh6 is expressed in the pronephric ducts and nephron primordia in addition to the central and peripheral nervous systems. Expression of cdh6 in the pronephric ducts was first detected at 14 hours post-fertilization (hpf) and increased to 24 hpf. Embryos injected with MOs directed against cdh6 (cdh6MOs) showed developmental defects, including a small head, body axis curvature, short yolk extension and a short bent tail by 30 hpf and edema appeared in the thorax by 42 hpf. Such defects and edema became more marked by 52 hpf and most of the affected embryos died by 5 days post-fertilization. Embryos injected with cdh6MOs were subjected to in situ hybridization with probes for the pronephric markers, wt1 and pax2.1, to examine disturbed development of the anterior region of the pronephric ducts and the nephron primordia. Histological studies showed malformation of the pronephros as abnormally fused glomerulus primordia, fused or abnormally bent pronephric tubule anlagen and coarctated pronephric ducts. These results suggest that cdh6 plays pivotal roles in the development of the pronephros in zebrafish embryos.
Key words: cadherin-6, K-cadherin, zebrafish, morpholino, pronephros
The importance of the posterior midline region for axis initiation at early stages of the avian embryo.
Oded Khaner
Department of Health Sciences, Hadassah Academic College, Jerusalem, Israel
Int. J. Dev. Biol. (2007) 51: 131-137
ABSTRACT: The avian blastoderm acts during its early stages of development as an integrative system programmed to form a single embryonic axis. Here, I report the results of a variety of transplantation experiments of the midline region at stages X-XII, which were carried out to study their relevance for axis initiation. The results of the experimental series discussed herein emphasizes the importance of the posterior midline region (including the marginal zone and Koller's sickle) for axis initiation. This ability resides mainly at stage X in the posterior side of a narrow midline region, while at stages XI-XII it is exhibited at the region which is located more anterior and lateral to the posterior midline region. This posterior midline region has developmental abilities which allow it to initiate a single embryonic axis and at the same time to prevent other regions that also have such abilities to do so. Therefore, in normal development only one embryonic axis develops in the avian blastoderm. It is proposed that the cells which are important to initiate the avian embryonic axis are concentrated mainly at the region of the posterior midline region. These cells may have organizer properties which determine the initiation site of the axis in the avian embryo.
Key words: avian embryo, axis initiation, posterior midline region, transplantation of midline region
Equivalent genetic regulatory networks in different contexts recover contrasting spatial cell patterns that resemble those in Arabidopsis root and leaf epidermis: a dynamic model.
Mariana Benítez1, Carlos Espinosa-Soto1, Pablo Padilla-Longoria2, José Díaz3 and Elena R. Alvarez-Buylla1.
1Instituto de Ecología and 2Instituto de Investigación en Matemáticas Aplicadas y Sistemas, Universidad Nacional Autónoma de México, Mexico, D.F. and 3Facultad de Ciencias, UAEM, Cuernavaca, Morelos, Mexico.
Int. J. Dev. Biol. (2007) 51: 139-155
ABSTRACT: In Arabidopsis thaliana, leaf and root epidermis hairs exhibit contrasting spatial arrangements even though the genetic networks regulating their respective cell-fate determination have very similar structures and components. We integrated available experimental data for leaf and root hair patterning in dynamic network models which may be reduced to activator-inhibitor models. This integration yielded expected results for these kinds of dynamic models, including striped and dotted cell patterns which are characteristic of root and leaf epidermis, respectively. However, these formal tools have led us to novel insights on current data and to put forward precise hypotheses which can be addressed experimentally. In particular, despite subtle differences in the root and leaf networks, these have equivalent dynamical behaviors. Our simulations also suggest that only when a biasing signal positively affects an activator in the network, the system recovers striped cellular patterns similar to those of root epidermis. We also postulate that cell shape may affect pattern stability in the root. Our results thus support the idea that in this and other cases, contrasting spatial cell patterns and other evolutionary morphogenetic novelties originate from conserved genetic network modules subject to divergent contextual traits.
Key words: gene network, activator-inhibitor, hair patterning
Technical Article
Isolation of apoptotic mouse fetal oocytes by AnnexinV assay.
Anna-Maria Lobascio, Francesca-Gioia Klinger and Massimo De Felici
Department of Public Health and Cell Biology, Section of Histology and Embryology, University of Rome "Tor Vergata", Rome, Italy.
Int. J. Dev. Biol. (2007) 51: 157-160
ABSTRACT: Expression of phosphotidylserine by fetal oocytes in culture renders significant numbers of such cells able to bind AnnexinV-coated microbeads and allows their separation from Annexin V-negative oocytes on a Magnetic Cell Separation (MACS) column in a magnetic field. The majority of oocytes >=75%) which bound Annexin V-coated microbeads were viable, as indicated by their propidium iodine (PI) negativity. However, they showed apoptotic morphologies and were found to be TUNEL-positive. On the other hand, AnnexinV-negative oocytes, besides being PI negative, appeared morphologically healthy and TUNEL negative. Moreover, AnnexinV-positive oocytes showed a marked lower ratio of Bcl-xL/Bax transcripts in comparison to AnnexinV-negative oocytes. We conclude that the present method is able to separate fetal oocytes in two distinct populations: AnnexinV-positive oocytes showing features typical of apoptotic cells and AnnexinV-negative oocytes comprising for the most part viable non-apoptotic cells. This procedure should greatly facilitate studies aimed to identify the currently poorly understood molecular pathways governing apoptosis in mammalian fetal oocytes.
Key words: apoptosis, oocytes, annexinV, meiosis
Developmental Expression Patterns
Expression of Bmp ligands and receptors in the developing Xenopus retina.
Jennifer C. Hocking and Sarah McFarlane
University of Calgary, Hotchkiss Brain Institute, Calgary, Canada.
Int. J. Dev. Biol. (2007) 51: 161-165
ABSTRACT: Bone morphogenetic proteins (BMPs) act repeatedly in the development of nervous system tissues. While BMP signaling is critical for the early growth and patterning of the eye, we are interested in possible later functions of BMPs in the morphological development of retinal neurons and formation of synaptic connections. Therefore, we conducted an in situ hybridization analysis of the mRNA expression for the ligands Bmp2, -4 and 7 and the type Ia, Ib and II receptors (BmprIa, BmprIb and BmprII) during development of the retina of Xenopus laevis. Bmp4 mRNA is expressed in the dorsal retina and Bmp7 in the distal peripheral retina during the period of cell differentiation, while Bmp2 is not present in the eye. The type I receptors are expressed predominantly ventrally, from the optic vesicle stage until at least stage 35/36, after most cells have differentiated and many synaptic connections have formed. BmprII mRNA, however, is distributed evenly across the dorsoventral axis, with highest expression in retinal ganglion cell and inner nuclear layers.
Key words: ALK3, ALK6, BMP, Xenopus, retinal development
Gene expression analysis reveals that formation of the mouse anterior secondary palate involves recruitment of cells from the posterior side.
Qun Li and Jixiang Ding
Department of Molecular, Cellular & Craniofacial Biology and Birth Defects Center, University of Louisville, Kentucky, USA
Int. J. Dev. Biol. (2007) 51: 167-172
ABSTRACT: Cleft palate is a common birth defect caused by disruptions in secondary palate development. Anterior-posterior (A-P) regional specification plays a critical role in palate development and fusion. Previous studies have shown that at the molecular level, the anterior palate can be defined by the expression of Shox-2 and the posterior palate by Meox-2 expression in certain mouse strains. Here, we have extended previous studies by performing a more detailed analysis of these genes during mouse palate development. We found that the expression patterns of Shox-2 and Meox-2 are dynamic during palate development. At embryonic day 12.5 (E12.5), Shox-2 expression is localized to the anterior end and its expression domain covers less than 25% of the length of the palate shelf. The Shox-2 expression domain then gradually expands towards the posterior end and ultimately occupies more than 60% of the palate shelf by E14.5. The expansion of the Shox-2 domain may involve induction of Shox2 expression in additional cells. Reciprocally, the Meox-2 expression domain at E12.5 covers a large portion of the palate shelf, a region more than 70% of the entire palate, but then regresses to the posterior 25% by E14.5. This regression is likely caused by the repression of Meox-2 expression in certain Meox2 expressing cells, rather than the cessation of cell proliferation. Therefore, certain Meox-2 positive "primitive posterior cells" are differentiated/converted into Shox-2 positive "definitive anterior cells" during A-P regional specification.
Key words: Shox-2, Meox-2, secondary palate, regional specification, craniofacial development
The expression of Fat-1 cadherin during chick limb development.
Terence G. Smith1, Nick Van Hateren2, Cheryll Tickle1 and Stuart A. Wilson2
1Division of Cell and Developmental Biology, University of Dundee, U.K. and 2Department of Molecular Biology and Biotechnology, University of Sheffield, U.K.
Int. J. Dev. Biol. (2007) 51: 173-176
ABSTRACT: Cellular adhesion is fundamental to the behaviour of cell populations during embryonic development and serves to establish correct tissue pattern and architecture. The cadherin superfamily of cell adhesion proteins regulates cellular organization and additionally influences intracellular signalling cascades. Here we present for the first time a detailed account of chick Fat-1 gene expression during embryogenesis visualised by whole-mount in situ hybridisation. In part, we focus on the expression pattern in limb buds that has not been accurately documented. While Fat-1 is generally expressed in epithelial tissues and its Drosophila counterpart Fat-like regulates formation of ectodermally-derived organs, in limb buds we have found that chick Fat-1 is uniquely restricted to mesenchyme. This Fat-1 expression pattern is remarkably dynamic throughout tissue differentiation, limb maturation and pattern formation. Diffuse expression of Fat-1 begins at stage HH17 as the limb bud is forming. It then becomes more proximal as the limb bud grows and is expressed within both tendon and muscle progenitors in the dorsal and ventral subectodermal mesenchyme. Later, Fat-1 transcripts were more abundant in anterior and posterior domains of the limb bud. During hand plate formation, Fat-1 transcripts were expressed in the mesenchyme adjacent to the wrist joint zone and in the interdigit mesenchyme.
Key words: Fat-1, cadherin, limb bud, cell adhesion, tendon
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