摘要:

AbstractGrowth factors and their receptors play an important role in controlling cellular proliferation, migration, and differentiation during vertebrate embryogenesis. We have used the reverse transcription‐polymerase chain reaction to survey the repertoire of receptor tyrosine kinases (TK) expressed during early embryogenesis ofXenopus laevis. Twelve distinctXenopusTK cDNA classes were identified among a total of 352 cDNAs screened. A single TK cDNA class has been described previously and encodes the fibroblast growth factor receptor FGFR‐A1. The remaining 11 TK cDNA classes appear to encode novel genes of the FGFR, platelet‐derived growth factor receptor (PDGFR), Eph, Csk, Tyk2, and Klg subfamilies. By RNase protection assays,XenopusTK mRNAs are rare transcripts (≤107mRNA mol‐ecules/embryo), and are usually found to be expressed also maternally in the embryo. MostXenopusTK genes examined by whole‐mount in situ hybridization were expressed widely in tissues derived from multiple germ layers. Two Eck‐related genes, however, were found to be restricted in their expression to neural crest of the second (hyoid) arch. Our findings are consistent with the proposed function of TKs in the regulation of specification and differentiation of embryonic tissues. ©1995 W

ISSN:1058-8388    

DOI:10.1002/aja.1002030202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring the differentiation of the intestine epithelium, three cytoskeletal proteins, villin, fimbrin, and myosin I, are sequentially expressed and localized to the apical membrane. Recently, we found that in the adult mouse and human, three fimbrin isoforms are expressed in a cell specific manner. I‐fimbrin is expressed by intestine and kidney epithelial cells, L‐fimbrin is expressed by leukocytes and many tumors, while T‐fimbrin is expressed by various cells and tissues. Because non‐intestinal isoforms of fimbrin could be expressed early in development, the expression of fimbrin isoforms during days 10.5 to 16.5 of intestine development was investigated. By immunofluorescence microscopy, T‐fimbrin was detected in the early stages of intestinal epithelial cell differentiation until day 14.5 and was localized predominantly at the apical surface. L‐fimbrin was also detected during this period but it was localized to the basal surface of the epithelium instead of the apical surface. By day 16.5 no L or T‐fimbrin was detected in the epithelium. I‐fimbrin was first detected at day 14.5 and a brush border‐like apical localization pattern was seen by day 16.5. Unlike the intestinal cells, the visceral endoderm expressed I, L, and T‐fimbrin throughout the period examined, with the level of I‐fimbrin increasing as time progresses. L‐fimbrin was more evident at the earlier stage than at the later stage of the development. Collectively, these results suggest that three fimbrin isoforms play different roles during epithelial cell differentiation. T‐ and I‐fimbrin expression could be critical for the formation and extension of the microvilli whereas L‐fimbrin may play a role in controlling cell ad

ISSN:1058-8388    

DOI:10.1002/aja.1002030203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mechanisms by which the early limb cell condensations and interzone mesenchyme give rise to skeletal elements and joints are poorly understood. Previous work from this laboratory has shown that the extracellular matrix protein tenascin‐C is associated with articular cartilage and joint tissue development; others have shown that tenascin‐C may exert its biological activities via interactions with cell surface receptors, such as syndecans. To further analyze the roles of tenascin‐C and its putative receptors in skeletal development, we carried out a detailed in situ hybridization analysis of tenascin‐C and syndecan‐3 gene expression during development of chick limb skeletal elements and joints. We found that as the early mesenchymal condensations chondrify around day 5 (E5) of development, they become surrounded by a thick syndecan‐3 rich perichondrium while tenascin‐C transcripts are much fewer and restricted to diaphyseal perichondrium and developing interzones. Similar patterns were observed as distal carpal and digit condensations formed in older embryos. As the cartilaginous long bone models elongated proximo‐distally and joint formation proceeded with age, we observed that syndecan‐3 transcripts decrease significantly along the diaphysis and remain very abundant along the metaphysis and in the epiphyseal articular cap and interzone. Conversely, tenascin‐C RNAs remain abundant along the diaphysis and begin to increase at the epiphysis and in interzone‐derived tissues, such as menisci and joint capsule. By E10, the skeletal elements have well‐defined morphologies, endochondral ossification has initiated in their diaphysis, and diaphyseal perichondrium has become periosteum. These developmental changes were accompanied by equally marked changes in gene expression; these included a marked increase in tenascin‐C gene expression in articular cap, fragmentation of tenascin‐C gene expression along the periosteum, reinitiation of syndecan‐3 gene expression in periosteum, and differential gene expression in osteoprogenitor cells. The sheer complexity of the gene expression patterns documented in this study attests to the complexity of processes that bring about normal skelatogenesis. Clearly, tenascin‐C and syndecan‐3 appear to be closely associated with several of these processes, particularly in establishing tissue boundaries (perichondrium and periosteum) between condensations and surrounding mesenchymal cells, in regulating perichondral cell differentiation and incorporation into the growing skeletal elements, and in the genesis of epiphyseal chondrocytes and associated joi

ISSN:1058-8388    

DOI:10.1002/aja.1002030204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe family of dominant‐negative helix‐loop‐helix (dnHLH) transcriptional modulators consists of four mammalian genes known to date: Id1, Id2, Id3 (Id3 was formerly designated HLH462 or HEIR1 or HLH1R21), and Id4. We have performed a detailed study of Id3 expression in mouse embryos in order to gain insight into the possible developmental control functions of this gene and to compare its expression to that of other mammalian dnHLH genes. Employing RNA in situ hybridization on sectioned mouse embryos of gestational stages E9.5–17.5 and neonatal head, we generally detected a high abundance of transcripts at early stages that gradually declined at most sites toward E15.5. Expression of Id3 in embryos was detected in brain, spinal cord, olfactory system, branchial arches, limbs, sclerotome, endocardiac cushions, the outer lining of the gut, lung, retina, the collecting system of the kidney, and in tooth anlagen. Although the abundance of mRNA decreased toward later stages in most tissues, it remained high in teeth and kidney. This expression pattern suggests that Id3 functions both in undifferentiated tissues and in organs which are in the process of differentiation. When compared to the expression of other dnHLH genes, it becomes obvious that the pattern of Id3 mainly coincides with that of Id1. This may reflect a partial redundancy in gene function. Furthermore, previous experiments suggested a mutually exclusive expression of the proto‐oncogene N‐myc an Id3. The results of the present study confirm these data. ©1995 Wil

ISSN:1058-8388    

DOI:10.1002/aja.1002030205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe density and distribution of whole mount BrdU‐anti‐BrdU labeled endothelial cells (days 6–15) in the chick chorioallantoic membrane (CAM) was analyzed with computer‐assisted microscopy. A significant loss of proliferative activity was noted after day 10: the density of labeled nuclei (in 10−2mm−2) decreased from a median 7.78 (days 6, 8, 10) to 2.42 (days 12, 14, 15). CAMs initially showed random patterns of labeled endothelial cells, but changed to clearly focal patterns after day 12. A regular arrangement of labeled nuclei was never seen. After application of vascular endothelial growth factor (VEGF) to the day 13 CAM, a significant increase in proliferative activity (11.50) and a random distribution of labeled endothelial cells was observed on day 15. Development of CAM precapillary vessels was assessed in terms of length density (in mm−1, mean ± standard deviation), which was augmented threefold from day 6 (1.22 ± 0.05) to day 14 (3.54 ± 0.23) and then remained nearly constant. VEGF application from day 13 to 15 raised arterial length per unit area to 4.53 ± 0.77. It is concluded that normally a local regulation of endothelial proliferation and differentiation develops in the CAM, which doubles capillary endothelial cell density but simultaneously adapts to the decreasing need for endothelial cells, and thus maintains the quasi two‐dimensional vessel pattern. However, proliferative foci persist in the capillary layer after day 10, and precapillary vessel density continues to increase until day 14. VEGF enhances DNA synthesis in all capillary endothelial cells. This leads to the disappearance of proliferative foci, to multiple capillary layers, and to an excessive formation of precapillary vessels. We propose that CAM endothelial cell proliferation is regulated by factors like endothelial cell density and extension. The proliferative pattern in capillaries, and the length density of precapillary vessels should be used for the evaluation of angiogenesis in the CAM assay. We recommend the CAM after day 12 for evaluating putative angiogenic mitogens. ©

ISSN:1058-8388    

DOI:10.1002/aja.1002030206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe chicken mutant talpid3(ta3) has polydactylous limbs with up to 7–8 morphologically similar digits. This lack of antero–posterior polarity in digit pattern is correlated with symmetrical expression of genes of the HoxD complex. We determined the distribution of polarizing activity in limb buds of the chick mutantta3by assessing the ability of mesenchyme from various positions along the antero‐posterior axis to induce digit duplications when grafted anteriorly into a normal limb. Cells with highest polarizing activity were found at the posterior margin of the wing as in the polarizing region of normal limb buds. However, in contrast to normal limb buds,ta3anterior mesenchyme also had low polarizing activity. Application of retinoic acid or a polarizing region graft to the anterior ofta3limb buds changed digit morphology but did not induce digit duplications or digits with any characteristic a–p pattern. To determine which genes are associated with polarizing activity and which are associated with patterning of the digits, we examined expression of the genes Sonic hedgehog (shh),Bmp‐2, andBmp‐7, whose expression is normally confined to the posterior margin of the early wing bud and is associated with the polarizing region. In addition, we determined the distribution ofFgf‐4transcripts which in normal limb buds are restricted to the posterior part of the apical ectodermal ridge. Inta3limb buds,shhexpression is restricted to the posterior limb mesenchyme, which has high polarizing activity, but is not expressed in regions which have low polarizing activity. In contrast,Bmp‐2 andBmp‐7are expressed uniformly along the a–p axis.Fgf‐4transcripts are present throughout the apical ectodermal ridge inta3limb buds. In theta3mutant, there is both an abnormal distribution of signalling activity and response to polarizing signals. In addition, the dissociation between the expression ofshhandBmpssuggests distinct roles for the encoded molecules in signalling and response in a–p patterning of limb buds

ISSN:1058-8388    

DOI:10.1002/aja.1002030207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractExpression of the α1(II) procollagen gene is not confined to chondrogenic tissues during vertebrate development. Transcripts of the human gene (COL2A1) are alternatively spliced to give mRNAs which either exclude (type IIB mRNA) or include (type IIA mRNA) an exon encoding a cysteine‐rich domain in the amino‐propeptide. The distribution of COL2A1 mRNAs in 27‐ to 44‐day human embryos and 8‐ to 24‐week fetuses was studied by in situ hybridization and RNase protection analyses. Type IIA mRNAs were expressed in prechondrogenic cells and were also preferentially expressed in chondrogenic tissues at regions of chondrocyte commitment and cartilage growth. During maturation of chondrocytes, there is a switch to expression of type IIB mRNAs. In non‐chondrogenic tissues of early embryos, type IIA mRNA expression was associated with active tissue remodeling, epithelial organization, and sites of tissue interaction. Type IIA mRNAs were also expressed in some non‐chondrogenic tissues where expression had previously been undetected, such as the tooth bud, liver, adrenal cortex, apical ectodermal ridge, and indifferent gonad. In older fetuses type IIA mRNAs were the sole or major transcript in most non‐chondrogenic tissues except the choroid plexus and tendon. In the meninges there was a unique switch from type IIB to type IIA expression. The expression pattern of COL2A1 transcripts suggests that, in addition to contributing to the structural integrity of the cartilage extracellular matrix, type II procollagen may serve a morphogenetic role in embryonic development. Our findings clearly show that the pattern of expression of type II procollagen mRNAs is largely conserved between man and mouse. However, some differences exist, and these should be taken into consideration when animal models are used to study human diseases associated with COL2A1. ©1

ISSN:1058-8388    

DOI:10.1002/aja.1002030208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA new gene, nel, was isolated from a 9‐day‐old chick embryonic cDNA library. The gene encoes a protein of 835 amino acids (93,407 Mr) consisting of two hydrophobic domains presumed to be the signal and transmembrane sequences, a histidine rich domain, two repeats of a cysteine rich structure similar to the C‐terminal domain of von Willebrand factor, five EGF‐like repeats, and again two repeats of the cysteine rich sequence similar to the C‐terminal domain of von Willebrand factor in the presumed cytoplasmic domain. The expression of the nel gene was studied by Northern blot and in situ hybridization analyses of chick embryos. The mRNA of the gene was found in all tissues of 10‐ and 17‐day‐old embryos by Northern blot hybridization. Among the tissues examined, the level in the brain was highest and increased with age. After hatching, gene expression was retained in the brain at about the same level found in old embryos, increased in the retina, and disappeared from the other tissues. In situ hybridization with a nel gene probe revealed that the gene was strongly expressed in neural tissues such as brain, spinal cord, and dorsal root ganglia of early embryos. Gene expression was observed in the mantle layer of the neurepithelium of the brain and of the spinal cord. Gene expression in early embryos was not restricted to the neural tissues, but was also detected in the cells around cartilage, myocardium, lung mesenchymal cells, and in the liver, etc. One band of about 4.5 Kb mRNA was detected in all tissues and stages by Northern blot hybridization analysis. The possible function of the gene is discussed. ©1995

ISSN:1058-8388    

DOI:10.1002/aja.1002030209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMesenchymal cells are required for the induction of epithelial development during mammalian organogenesis. Keratinocyte growth factor (KGF) is a mesenchymally derived mitogen with specific activity for epithelial cells, suggesting that it may play a role in mediating these interactions. To further evaluate this hypothesis, in situ hybridization was used to examine the spatial distribution of KGF and KGF receptor (KGFR) transcripts during organogenesis and limb formation in mouse embryos (days 14.5 through 16.5). To facilitate this aim, mouse KGF cDNA clones were isolated. There was extensive identity between the deduced mouse KGF protein sequence and that of its human and rat cognates, indicating that this gene has been highly conserved during mammalian evolution. In addition, mouse KGF protein was purified from fibroblasts and demonstrated to be structurally and functionally similar to human KGF protein. For organs within the integumental, respiratory, gastrointestinal, and urogenital systems, whose development is dependent upon mesenchymal‐epithelial interactions, KGF mRNA was detected in mesenchymal cells, while epithelial cells expressed transcripts for the KGFR. KGF and KGFR mRNA was also expressed in certain other tissues such as perichondrium, cartilage of developing bones, developing skeletal muscle, and visceral smooth muscle whose development is not regulated by mesenchymal‐epithelial interactions. KGF expression was also detected in tissues isolated from human embryos, suggesting similar functions for KGF in human development. Taken together, our results suggest that KGF plays an important role in mediating mesenchymal‐epithelial interactions during organogenesis, but may also have other developmental functions in tissues not governed by such interactions. ©1995 Wiley‐L

ISSN:1058-8388    

DOI:10.1002/aja.1002030210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe galectins are a family of low molecular weight, calcium‐independent mammalian carbohydrate binding proteins that exhibit specificity for beta‐galactoside derivatives. We have examined the expression pattern of galectin‐3 in the developing mouse embryo by in situ hybridisation and immunohistochemistry. In the embryo proper, galectin‐3 message and protein are first detected in notochord, starting from 8.5 days post coitum (dpc), and persist until this structure disappears. Galectin‐3 is later found in cartilage primordia and in developing skin from 13.5 dpc. This very restricted and dynamic pattern suggests that galectin‐3 may participate in the establishment and/or maintenance of notochord as well as the formation of cartilage and differentiation of skin. Finally, we find that galectin‐3, which is identical to the macrophage marker Mac‐2, is also expressed in embryonic macrophages. © 1995

ISSN:1058-8388    

DOI:10.1002/aja.1002030211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY