bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Drosophila segment polarity gene patched is involved in a position-signalling mechanism in imaginal discs
Authors: Phillips Roger G. , Roberts Ian J. H. , Ingham Philip W. , Whittle J. Robert S. 
Published: April 2021

Abstract
We demonstrate the role of the segment polarity gene patched (ptc) in patterning in the cuticle of the adult fly. Genetic mosaics of a lethal allele of patched show that the contribution of patched varies in a position-specific manner, defining three regions in the wing where ptc clones, respectively, behave as wild-type cells, affect vein formation, or are rarely recovered. Analysis of twin clones demonstrates that the reduced clone frequency results from a proliferation failure or cell loss. In the region where clones upset venation, they autonomously fail to form veins and also non-autonomously induce ectopic veins in adjacent wild-type cells. In heteroallelic combinations with lethal alleles, two viable alleles produce distinct phenotypes: (1) loss of structures and mirror-image duplications in the region where patched clones fail to proliferate; (2) vein abnormalities in the anterior compartment. We propose that these differ-enees reflect independently mutable functions within the gene. We show the pattern of patched transcription in the developing imaginal wing disc in relation to the expression of certain other reporter genes using a novel double-labelling method combining non-radioactive detection of in situ hybridization with β-galactosidase detection. The patched transcript is present throughout the anterior compartment, with a stripe of maximal intensity along the A/P compartment border extending into the posterior compartment. We propose that the patched product is a component of a cell-to-cell positionsignalling mechanism, a proposal consistent with the predicted structure of the patched protein.
Orientation of commissural axons in vitro in response to a floor plate-derived chemoattractant
Authors: Placzek Marysia , Tessier-Lavigne Marc , Jessell Thomas , Dodd Jane 
Published: April 2021

Abstract
Developing axons are guided to their targets by molecular cues in their local environment. Some cues are shortrange, deriving from cells along axonal pathways. There is also increasing evidence for longer-range guidance cues, in the form of gradients of diffusible chemoattractant molecules, which originate from restricted populations of target cells. The guidance of developing commissural axons within the spinal cord depends on one of their intermediate cellular targets, the floor plate. We have shown previously that floor plate cells secrete a diffusible factor(s) that can alter the direction of commissural axon growth in vitro. Here we show that the factor is an effective chemoattractant for commissural axons. It can diffuse considerable distances through a collagen gel matrix and through dorsal and ventral neural epithelium in vitro to reorient the growth of virtually all commissural axons. The orientation of axons occurs in the absence of detectable effects on the survival of commissural neurons or on the rate of commissural axon extension. The regionally restricted expression of the factor suggests that it is present in the embryonic spinal cord in a gradient with its high point at the floor plate. These observations support the idea that the guidance of commissural axons to the ventral midline of the spinal cord results in part from the secretion of a chemoattractant by the floor plate.
A Dictyostelium morphogen that is essential for stalk cell formation is generated by a subpopulation of prestalk cells
Authors: Kwong Linda , Xie Yinjuan , Daniel Juliet , Robbins Stephen M. , Weeks Gerald 
Published: April 2021

Abstract
The stalk cell differentiation inducing factor (DIF) has the properties required of a morphogen responsible for pattern regulation during the pseudoplasmodial stage of Dictyostelium development. It induces prestalk cell formation and inhibits prespore cell formation, but there is as yet no strong evidence for a morphogenetic gradient of DIF. We have measured DIF accumulation by monolayers of isolated prestalk and prespore cells in an attempt to provide evidence for such a gradient. DIF is accumulated in the largest quantities by a subpopu lation of prestalk cells that specifically express the DIF-inducible genes pDd56 and pDd26. Since it has been shown recently that cells that express pDd56 are localized in the central core of the prestalk cell region of the pseudoplasmodia, our current results suggest a morphogenetic gradient generated by this region.
daughterless-abo-like, a Drosophila maternal-effect mutation that exhibits abnormal centrosome separation during the late blastoderm divisions
Authors: Sullivan William , Minden Jonathan S. , Alberts Bruce M. 
Published: April 2021

ABSTRACT
daughterless-abo-like (dal) is a maternal-effect semilethal mutation in Drosophila. The nuclear divisions of embryos derived from homozygous dal females are normal through nuclear cycle 10. However, during nuclear cycles 11, 12 and 13, a total of about half of the nuclei in each embryo either fail to divide or fuse with a neighboring nucleus during telophase. These abnormal nuclei eventually sink into the interior of the embryo, leaving their centrosomes behind on the surface. The loss of about one-half of the peripheral nuclei into the interior of the embryo results in these embryos cellularizing during nuclear cycle 14 with about one-half the normal number of cells. Surprisingly, many of these embryos develop a nearly normal larval cuticle and 8 % develop to adulthood.
Observations of live embryos doubly injected with tubulin and histones that have been fluorescently labeled allows nuclear and centrosomal behavior to be directly followed as the embryo develops. We find that the abnormal nuclei arise from nuclei whose centrosomes have failed to separate normally in the previous interphase. These incompletely separated centrosomes can cause a non-functional spindle to form, leading to a nuclear division failure. Alternatively, they can form an abnormal spindle with a centrosome from a neighboring nucleus, causing two nuclei to share a common spindle pole. Such nuclei with a shared centrosome will undergo telophase fusions, unequal divisions, or division failures later in mitosis. These findings have helped us to understand the function of the centrosome in the Drosophila embryo.
The cellular retinoic-acid-binding protein is expressed in tissues associated with retinoic-acid-induced malformations
Authors: Vaessen Marie-Josée , Meijers J. H. Carel , Bootsma Dirk , Van Kessel Ad Geurts 
Published: April 2021

ABSTRACT
Retinoic acid (RA) is thought to play a role in embryonic pattern formation in vertebrates. A naturally occurring gradient of endogenous RA has been demonstrated in the developing chick limb bud, while local application of RA leads to the formation of additional digits. In mammals, a well-defined spectrum of birth defects has been reported as a result of fetal exposure to excess RA. In analogy to the chick limb bud, it may be speculated that these malformations are the result of disturbance of morphogenetic RA concentration gradients.
A candidate gene involved in the regulation of endogenous RA concentrations is the gene encoding cellular RA binding protein (CRABP). We have isolated a partial cDNA clone corresponding to the chicken homolog of CRABP, and performed in situ hybridization experiments on sections of embryos at various stages of development. CRABP expression was detected in the CNS, the craniofacial mesenchyme, ganglia of the peripheral nervous system, the limb bud, and the visceral arch area. Our results indicate that the spatiotemporally specified expression pattern displayed by the CRABP gene exhibits a striking correspondence to the tissues that are affected by exposure of avian or mammalian embryos to RA. We hypothesize that CRABP plays an important role in normal embryogenesis and that embryonic tissues showing high CRABP expression are susceptible to the adverse effects of excess RA.
Pathfinding during spinal tract formation in the chick-quail chimera analysed by species-specific monoclonal antibodies
Authors: Tanaka Hideaki , Kinutani Masae , Agata Akemi , Takashima Youichiro , Obata Kunihiko 
Published: April 2021

ABSTRACT
In order to analyse the spinal tract formation at early stages of development in avian embryos, chick-quail spinal cord chimeras were prepared and species-specific monoclonal antibodies (MAb) were developed. MAbs CN, QN and CQN uniquely stained chick, quail, and both chick and quail nervous tissues, respectively. All three antibodies appeared to bind to the same membrane molecule, but to different epitopes. Cord reversal revealed the features of axonal growth of both cord interneurons and dorsal root ganglion cells. Quail cord interneurons grew along an originally ventral marginal layer in the quail cord transplanted in a reversed position, then turned toward the ventral side at the boundary between the graft and the host, and grew along the host chick ventral marginal layer. Central axons of dorsal root ganglia were restricted to the ventrolateral region of the cord which originally formed the dorsal funiculus. These results suggest that cord interneurons and dorsal root ganglion cells actively select to grow along specific regions of the cord and that spinal tract formation appears to be determined by cord cells, and not by sclerotome cells.
In situ hybridization analysis of TGFβ3 RNA expression during mouse development: comparative studies with TGFβ1 and β2
Authors: Pelton Ron W. , Dickinson Mary E. , Moses Harold L. , Hogan Brigid L. M. 
Published: April 2021

ABSTRACT
To date, three closely-related TGFβ genes have been found in the mouse; TGFβ1, TGFβ2 and TGFβ3. Previous experiments have indicated that TGFβ1 and TGFβ2 may play important roles during mouse embryo-genesis. The present study now reports the distribution of transcripts of TGFβ3 in comparison to the other two genes and reveals overlapping but distinct patterns of RNA expression. TGFβ3 RNA is expressed in a diverse array of tissues including perichondrium, bone, intervertebral discs, mesenteries, pleura, heart, lung, palate, and amnion, as well as in central nervous system (CNS) structures such as the meninges, choroid plexus and the olfactory bulbs. Furthermore, in several organ systems, TGFβ3 transcripts are expressed during periods of active morphogenesis suggesting that the protein may be an important factor for the growth and differentiation of many embryonic tissues.
Establishment of germ-line-competent embryonic stem (ES) cells using differentiation inhibiting activity
Authors: Nichols Jennifer , Evans Edward P. , Smith Austin G. 
Published: April 2021

Abstract
The regulatory factor Differentiation Inhibiting Activity/Leukaemia Inhibitory Factor (DIA/LIF) suppresses the differentiation of cultured embryonic stem (ES) cells. In the present study, it is shown that ES cell lines can be derived and maintained in the absence of feeder layers using medium supplemented with purified DIA/LIF. These cells can differentiate normally in vitro and in vivo and they retain the capacity for germ-line transmission. DIA/LIF therefore fulfils the essential function of feeders in the isolation of pluripotential stem cells.
α-actin proteins and gene transcripts are colocalized in embryonic mouse muscle
Authors: Lyons Gary E. , Buckingham Margaret E. , Mannherz Hans G. 
Published: April 2021

Abstract
The α-actins are among the earliest muscle-specific mRNAs to appear in developing cardiac and skeletal muscle. To determine if there is coexpression of the α-actin proteins at early stages of myogenesis, we have used an α-actins-specific polyclonal antibody and in situ hybridization with specific cRNA probes to cardiac and skeletal α-actins transcripts on serial slides of mouse embryo sections. As soon as we can detect α-actins mRNAs in embryonic striated muscle, we also detect the protein suggesting that α-actins transcripts are translated very rapidly after transcription during myogenesis. In skeletal muscle, this colocalization of α-actins mRNA and protein was observed both in the myotomes of somites and in developing muscles in the limbs. In cardiac muscle, α-actins transcripts and proteins are abundantly expressed as soon as a cardiac tube forms.
Early expression of the myogenic regulatory gene, myf-5, in precursor cells of skeletal muscle in the mouse embryo
Authors: Ott Marie-Odile , Bober Eva , Lyons Gary , Arnold Hans , Buckingham Margaret 
Published: April 2021

ABSTRACT
We have analysed by in situ hybridization the expression of myf-5, the murine homologue of the human myogenic regulatory sequence myf5, during embryogenesis in the mouse, myf-5 sequences were first detected in the earliest somites (from about 8 days p.c.) in the dermomyotome, before formation of the dermatome, myotome and sclerotome. The dermomyotome is classically considered to give rise to the precursor muscle cells of body and limb skeletal muscle. myf-5 -positive cells were also detected early in the visceral arches and limb buds. In this case, as in somites, myf-5 expression precedes that of the two related myogenic regulatory sequences, myogenin and MyoDl, and indeed any other skeletal muscle marker examined to date, myf-5 is not detected at any stage in developing cardiac muscle. From 11.5 days p.c., the level of myf-5 transcripts begins to decrease to become undetectable (by in situ hybridization) from 14 days p.c. Both the appearance and disappearance of myf-5 follow the anteroposterior gradient of somite formation and maturation in the embryo. The time and place of myf-5 expression are consistent with a role in the early events of myogenic differentiation, possibly during determination of the myogenic lineage.
Mis-regulating segmentation gene expression in Drosophila
Authors: Parkhurst Susan M. , Ish-Horowicz David 
Published: April 2021

ABSTRACT
We have used the hunchback (hb) gap-gene promoter to drive ectopic expression of the pair-rule genes fushi tarazu (fiz), even-skipped (eve) and hairy (h). Unexpectedly, flies transformed with such constructs are viable, despite spatial and temporal mis-regulation of pair-rule expression caused by the fusion genes. We show that fusion gene expression is transcriptionally regulated, such that ectopic expression is suppressed when pattern is established, and present evidence indicating that interstripe hb – fiz expression is repressed by eve. These results are considered in terms of redundant control of pair-rule gene striping. We also discuss the potential dangers of using mis-regulated gene expression to analyse normal function.
Differentiating and mature neurons express the acidic fibroblast growth factor gene during chick neural development
Authors: Schnürch Harald , Risau Werner 
Published: April 2021

ABSTRACT
We have previously isolated and characterized acidic fibroblast growth factor (aFGF) from the embryonic chick brain. To analyze the expression of the gene encoding this growth factor a cDNA clone was isolated. The predicted amino acid sequence was found to be highly conserved (90 %) between human and chick. Using single-stranded DNA probes, aFGF gene expression was detectable at day 3.5 in the embryonic chick brain. The mRNA level of the 1.7 kb transcript increased during embryonic development and reached the highest level in the adult brain. In situ hybridization results confirmed these developmental changes and revealed a localized expression in neurons. In the adult, Purkinje cells, deep cerebellar and brainstem neurons showed a high level of aFGF mRNA. In the embryonic brain, localized expression in neurons was detectable from day 6 onward. aFGF mRNA was also present in neurons of the peripheral nervous system. In dorsal root ganglia, aFGF was found to be expressed after embryonic day 6. Cells of blood vessels and the ependyma did not express detectable amounts of aFGF mRNA. These results suggest that aFGF may have a function as a differentiation or maintenance factor for postmitotic neurons or as a growth or differentiation factor for other cells in the nervous system mainly in later stages of development.
The transient expression of type II collagen at tissue interfaces during mammalian craniofacial development
Authors: Wood Andrew , Ashhurst Doreen E. , Corbett Andrew , Thorogood Peter 
Published: April 2021

ABSTRACT
Using immunocytochemical techniques, the spatiotemporal distribution of the major collagen isoform of cartilage, type II collagen, has been investigated during early craniofacial development in the mouse embryo. Early and transient expression was associated with the otic and optic vesicles, the ventrolateral surfaces of the developing brain, olfactory conchi, endocardial and mesocardial tissues, the lateral and basal surfaces of the pharyngeal endoderm and beneath the ectoderm of the branchial arches. A number of these locations are sites of epithelial-mesenchymal tissue interaction believed to generate the component parts of the chondrocranium; here, type II collagen appears transiently in advance of overt chondrogenesis in the mesenchyme. At such sites, immunofluorescence is typically localised along the basal surface of the epithelial partner, with the strongest reaction detected between the basal aspects of the otic and rhombencephalic epithelia. Immunoelectron microscopy, using pre-embedding immunostaining and a protein G-gold technique, reveals that the type II collagen is adjacent to, but not integral with, the basal laminae. Gold particles are clearly associated with 10-15 nm fibrils of the extracellular matrix in the reticulate lamina region.
The pattern of type II collagen expression in the mouse closely correlates with that demonstrated previously in the quail, indicating a high degree of phylogenetic conservation between these two vertebrate species. These findings are consistent with the hypothesis that the pattern of epithelial secretion of type II collagen, or a coexpressed matrix molecule, constitutes a morphogenetic signal, realised as a matrix-mediated tissue interaction, and specifying the form of the vertebrate chondrocranium. Three-dimensional reconstruction of early type II collagen distribution, and of the subsequent chondrocranial cartilages, reveals that chondrocranial form can be derived from a ‘pre-pattern’ of epithelially derived type n collagen expressed at epithelial-mesenchymal tissue interfaces.
Genetic interactions among floral homeotic genes of Arabidopsis
Authors: Bowman John L. , Smyth David R. , Meyerowitz Elliot M. 
Published: April 2021

ABSTRACT
We describe allelic series for three loci, mutations in which result in homeotic conversions in two adjacent whorls in the Arabidopsis thaliana flower. Both the structure of the mature flower and its development from the initial primordium are described by scanning electron microscopy. New mutations at the APETALA2 locus, ap2-2, ap2-8 and ap2-9, cause homeotic conversions in the outer two whorls: sepals to carpels (or leaves) and petals to stamens. Two new mutations of PISTILLATA, pi-2 and pi-3, cause second and third whorl organs to differentiate incorrectly. Homeotic conversions are petals to sepals and stamens to carpels, a pattern similar to that previously described for the apetala3-l mutation. The AGAMOUS mutations, ag-2 and ag-3, affect the third and fourth whorls and cause petals to develop instead of stamens and another flower to arise in place of the gynoecium. In addition to homeotic changes, mutations at the APETALA2, APETALAS and PISTILLATA loci may lead to reduced numbers of organs, or even their absence, in specific whorls. The bud and flower phenotypes of doubly and triply mutant strains, constructed with these and previously described alleles, are also described. Based on these results, a model is proposed that suggests that the products of these homeotic genes are each active in fields occupying two adjacent whorls, AP2 in the two outer whorls, PI and AP3 in whorls two and three, and AG in the two inner whorls. In combination, therefore, the gene products in these three concentric, overlapping fields specify the four types of organs in the wild-type flower. Further, the phenotypes of multiple mutant lines indicate that the wild-type products of the AGAMOUS and APETALA2 genes interact antagonistically. AP2 seems to keep the AG gene inactive in the two outer whorls while the converse is likely in the two inner whorls. This field model successfully predicts the phenotypes of all the singly, doubly and triply mutant flowers described.
A secreted 80 × 103M
r protein mediates sensing of cell density and the onset of development in Dictyostelium
Authors: Gomer Richard H. , Yuen Ita S. , Firtel Richard A. 
Published: April 2021

ABSTRACT
In submerged monolayer culture, Dictyostelium cells can differentiate into prespore and prestalk cells at high cell densities in response to cAMP but not at low cell densities. However, cells at low densities will differentiate in medium taken from developing cells starved at a high density. The putative factor in the medium was designated CMF for conditioned medium factor (Mehdy and Firtel, Molec. cell. Biology 5, 705 – 713,1985). In this report, we size-fractionate conditioned medium and show that the activity that allows low density cells to differentiate can be separated into high and low Mr (relative molecular mass) fractions. Interestingly, the two fractions both have the same activity and do not need to be combined to allow differentiation. The large conditioned medium factor is a protein, as determined by trypsin sensitivity, that can be purified to a single 80 × 103Mr band on a silver-stained SDS-polyacrylamide gel, and has CMF activity at a concentration of ∼ 4pM (0.3 ng ml-1). Our results suggest that CMF is a secreted factor that functions in vivo as an indicator of cell density in starved cells. At high cell densities, the concentration of CMF is sufficient to enable cells to enter the multicellular stage of the developmental cycle. When present below a threshold concentration, cells do not initiate the expression of genes required for early development. This factor plays an essential role in the regulatory pathway necessary for cells to obtain the developmental competence to induce prestalk and prespore gene expression in response to cAMP.
The maternal gene nanos has a central role in posterior pattern formation of the Drosophila embryo
Authors: Lehmann Ruth , Nüsslein-Volhard Christiane 
Published: April 2021

ABSTRACT
A group of maternal genes, the posterior group, is required for the development of the abdominal region in the Drosophila embryo. We have used genetic as well as cytoplasmic transfer experiments to order seven of the posterior group genes (nanos, pumilio, oskar, valois, vasa, staufen and tudor) into a functional pathway. An activity present in the posterior pole plasm of wild-type embryos can restore normal abdominal development in posterior group mutants. This activity is synthesized during oogenesis and the gene nanos most likely encodes this activity. The other posterior group genes have distinct accessory functions: pumilio acts downstream of nanos and is required for the distribution or stability of the nanos-dependent activity in the embryo. Staufen, oskar, vasa, valois and tudor act upstream of nanos. Embryos from females mutant for these genes lack the specialized posterior pole plasm and consequently fail to form germ-cell precursors. We suggest that the products of these genes provide the physical structure necessary for the localization of nanos-dependent activity and of germ line determinants.