bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution and function of the lethal of scute gene product during early neurogenesis in Drosophila
Authors: Martín-Bermudo María D. , Martínez Carmen , Rodríguez Antonio , Jiménez Fernando 
Published: April 2021

ABSTRACT
Genes of the achaete –cute complex (ASC) participate in the formation of the central nervous system in the Drosophila embryo. Previous genetic analyses have indicated that lethal of scute (l’sc) is the most important gene of the complex in that process. We have obtained antibodies against the 1’sc protein to study the expression of the gene during early neurogenesis. The protein is found in groups of embryonic neuroectodermal cells, analogous to the proneural clusters that precede the appearance of precursors of peripheral sensory organs in imaginai epithelia. The groups appear in different regions of the neuroectoderm, accompanying the three successive waves of neuroblast segregation. Most neuroblasts delaminate from these clusters and express position-specific levels of 1’sc protein. No significant differences have been found between the distribution of l’sc RNA and protein. Phenotypic analysis of a l’sc deficiency has shown that the gene is required for neuroblast commitment, although this requirement is less widespread than the domain of l’sc expression, suggesting a high degree of redundancy in the function of genes that participate in the process of neuroblast segregation. The ASC genes have been postulated to play a role in the control of NB identity, revealed by the generation of a defined lineage of identifiable neurons. However, our study in l’sc mutants of the expression of fushi tarazu, engrailed, and even-skipped, used as markers of neuronal identity, has not provided evidence to support this hypothesis.
The sisterless-b function of the Drosophila gene scute is restricted to the stage when the X:A ratio determines the activity of Sex-lethal
Authors: Torres Miguel , Sánchez Lucas 
Published: April 2021

ABSTRACT
The gene scute (sc) has a dual function: the scute function which is involved in neurogenesis and the sisterless-b function which is involved in generating the X:A signal that determines the state of activity of Sxl, a gene that controls sex determination and dosage compensation. We show here that the lethal phase of sc- females is embryonic and caused by the lack of Sxl function. We also analyze the time in development when sc and Sxl interact by means of (a) determining the thermosensitive phase (TSP) of the interaction between Sxl and sc and (b) a chimeric gene in which sc is under the control of a heat-shock promoter (HSSC-3). Pulses of sc expression from the HSSC-3 activate Sxl only at a very specific and early stage in development, which coincides with the TSP of the interaction between sc and Sxl. It corresponds to the syncytial blastoderm stage and coincides with the time when the X:A signal regulates Sxl. At this stage sc undergoes a homogeneous transient expression in wild-type flies. We conclude that the sc expression at the syncytial blastoderm is responsible for its sisterless-b function. Since sc expression from the HSSC-3 fully suppresses the sisterless-b phenotype, we further conclude that the sisterless-b function is exclusively provided by the sc protein. Finally, we have analyzed, by in situ hybridization, the effect of sc and sis-a mutations on the embryonic transcription of Sxl. Our results support the view that the control of Sxl by the X:A signal occurs at the transcriptional level.
Cell polarity and microtubule organisation during mouse early embryogenesis
Authors: Maro Bernard , Gueth-Hallonet Catherine , Aghion Joël , Antony Claude 
Published: April 2021

Abstract
We have studied the distribution and the role of microtubules in the major developmental events occuring during early development of the mouse. These events are the setting up of asymmetries within blastomeres, the process of asymmetrical cell division and the changes in cellular organisation taking place during epithelial differentiation.
A PDGF receptor mutation in the mouse (Patch) perturbs the development of a non-neuronal subset of neural crest-derived cells
Authors: Morrison-Graham Kathleen , Schatteman Gina C. , Bork Tracie , Bowen-Pope Daniel F. , Weston James A. 
Published: April 2021

Abstract
The Patch (Ph) mutation in mice is a deletion of the gene encoding the platelet-derived growth factor receptor alpha subunit (PDGFR α). Patch is a recessive lethal recognized in heterozygotes by its effect on the pattern of neural crest-derived pigment cells, and in homozygous mutant embryos by visible defects in craniofacial structures. Since both pigment cells and craniofacial structures are derived from the neural crest, we have examined the differentiation of other crest cell-derived structures in Ph/Ph mutants to assess which crest cell populations are adversely affected by this mutation. Defects were found in many structures populated by non-neuronal derivatives of cranial crest cells including the thymus, the outflow tract of the heart, cornea, and teeth. In contrast, crest-derived neurons in both the head and trunk appeared normal.
The expression pattern of PDGFR α mRNA was determined in normal embryos and was compared with the defects present in Ph/Ph embryos. PDGFR α mRNA was expressed at high levels in the non-neuronal derivatives of the cranial neural crest but was not detected in the crest cell neuronal derivatives. These results suggest that functional PDGF α is required for the normal development of many non-neuronal crest-derived structures but not for the development of crest-derived neuronal structures.
Abnormal development of the non-neuronal crest cells in Ph/Ph embryos was also correlated with an increase in the diameter of the proteoglycan-containing granules within the crest cell migratory spaces. This change in matrix structure was observed both before and after crest cells had entered these spaces. Taken together, these observations suggest that functional PDGFR α can affect crest development both directly, by acting as a cell growth and/or survival stimulus for populations of non-neurogenic crest cells, and indirectly, by affecting the structure of the matrix environment through which such cells move.
The Drosophila orb gene is predicted to encode sex-specific germline RNA-binding proteins and has localized transcripts in ovaries and early embryos
Authors: Lantz Valerie , Ambrosio Linda , Schedl Paul 
Published: April 2021

Abstract
We report the identification of a new gene, orb, which appears to be expressed only in the gennline and encodes ovarian-and testis-specific transcripts. The predicted proteins contain two regions with similarity to the RRM family of RNA-binding proteins but differ at their amino termini. In testes, orb RNA accumulates in the primary spermatocytes and at the caudal ends of the spermatid bundles. In ovaries, orb transcripts display an unusual spatial pattern of accumulation in the oocyte. Preferen-tial accumulation in the oocyte of orb RNA is first detected in region 2 of the germanium and is dependent on Bicaudal-D and egalitarian. While in stage 7 egg chambers orb RNA is localized posteriorly in the oocyte, during stages 8-10 it is localized at the anterior of the oocyte, asymmetrically along the dorsal-ventral axis. In embryos the transcripts accumulate at the posterior end and are included in the pole cells. This pattern of localization and the similarity to RNA-binding proteins suggest that the orb gene product may mediate the localization of maternal RNAs during oogenesis and early embryogenesis.
Asymmetrical retinoic acid synthesis in the dorsoventral axis of the retina
Authors: Mccaffery Peter , Lee Mi-Ock , Wagner Michael A. , Sladek Norman E. , Dräger Ursula C. 
Published: April 2021

Abstract
An aldehyde dehydrogenase present at high levels in the dorsal retina of the embryonic and adult mouse was identified as the isoform AHD-2 known to oxidize retinaldehyde to retinoic acid. Comparative estimates of retinoic acid levels with a reporter cell line placed the retinas among the richest tissues in the entire body of the early embryo; levels in ventral retina, however, exceeded dorsal levels. Retinoic acid synthesis from retinaldehyde in the dorsal pathway was less effective than the ventral pathway at low substrate levels and more effective at high levels. The dorsal pathway was preferentially inhibited by disulfiram, while ventral synthesis was preferentially inhibited by p-hydroxymer-curibenzoate. When protein fractions separated by isoelectric focusing were analyzed for retinoic acid synthesizing capacity by a zymography-bioassay, most of the synthesis in dorsal retina was found to be mediated by AHD-2, and ventral synthesis was mediated by dehydrogenase activities distinct in charge from AHD-2. Postnatally, levels of highest retinoic acid synthesis shifted from ventral to dorsal retina. In the adult retina, the dorsal pathway persisted, but the preferential ventral pathway was no longer detectable. Our observations raise the possibility that retinoic acid plays a role in the determination and maintenance of the dorsoventral axis of the retina, and that the morphogenetically significant asymmetry here lies in the spatial arrangement of synthetic pathways.
PDGF receptors in the rat CNS: during late neurogenesis, PDGF alpha-receptor expression appears to be restricted to glial cells of the oligodendrocyte lineage
Authors: Pringle Nigel P. , Mudhar Hardeep S. , Collarini Ellen J. , Richardson William D. 
Published: April 2021

Abstract
Using in situ hybridization, we have visualized cells in the rat central nervous system (CNS) that contain mRNA encoding the platelet-derived growth factor alpha receptor (PDGF-αR). After embryonic day 16 (E16), PDGF-αR mRNA appears to be expressed by a subset of glial cells, but not by neurons. The temporal and spatial distribution of PDGF-αR+ cells, together with 125I-PDGF binding studies on subsets of glial cells in vitro, suggests that PDGF-αR may be expressed predominantly, or exclusively, by cells of the oligodendrocyte-type-2 astrocyte (O-2A) lineage. This conclusion is supported by the fact that the numbers of PDGF-αR+ cells in developing and adult optic nerves correlate well with independent estimates of the number of O-2A progenitor cells in the nerve at equivalent ages. Small numbers of PDGF-αR+ cells are present in the brain at E16, at which time they are found outside the subventricular germinal zones, suggesting that these cells do not express PDGF-αR until after, or shortly before they start to migrate away from the subventricular layer towards their final destinations. Reduced numbers of PDGF-αR+ cells persist in the adult CNS. PDGF-αR is also expressed strongly in the meningeal membranes and choroid plexus, and in the inner limiting membrane of the retina.
Hox-4 gene expression in mouse/chicken heterospecific grafts of signalling regions to limb buds reveals similarities in patterning mechanisms
Authors: Izpisúa-Belmonte J.-C. , Brown J. M. , Crawley A. , Duboule D. , Tickle C. 
Published: April 2021

Abstract
The products of Hox-4 genes appear to encode position in developing vertebrate limbs. In chick embryos, a number of different signalling regions when grafted to wing buds lead to duplicated digit patterns. We grafted tissue from the equivalent regions in mouse embryos to chick wing buds and assayed expression of Hox-4 genes in both the mouse cells in the grafts and in the chick cells in the responding limb bud using species specific probes. Tissue from the mouse limb polarizing region and anterior primitive streak respecify anterior chick limb bud cells to give posterior structures and lead to activation of all the genes in the complex. Mouse neural tube and genital tubercle grafts, which give much less extensive changes in pattern, do not activate 5’-located Hox-4 genes. Analysis of expression of Hox-4 genes in mouse cells in the grafted signalling regions reveals no relationship between expression of these genes and strength of their signalling activity. Endogenous signals in the chick limb bud activate Hox-4 genes in grafts of mouse anterior limb cells when placed posteriorly and in grafts of mouse anterior primitive streak tissue. The activation of the same gene network by different signalling regions points to a similarity in patterning mechanisms along the axes of the vertebrate body.
Bone morphogenetic protein 4: a ventralizing factor in early Xenopus development
Authors: Dale L. , Howes G. , Price B. M. J. , Smith J. C. 
Published: April 2021

Abstract
The mesoderm of amphibian embryos such as Xenopus laevis arises through an inductive interaction in which cells of the vegetal hemisphere of the embryo act on overlying equatorial and animal pole cells. Three classes of ‘mesoderm-inducing factor’ (MIF) that might be responsible for this interaction in vivo have been discovered. These are members of the transforming growth factor type β (TGF-β), flbroblast growth factor (FGF) and Wnt families. Among the most potent MIFs are the activins, members of the TGF-βfamily, but RNA for activin A and B is not detectable in the Xenopus embryo until neurula and late blastula stages, respectively, and this is probably too late for the molecules to act as natural inducers. In this paper, we use the polymerase chain reaction to clone additional members of the TGF-β family that might possess mesoderminducing activity. We show that transcripts encoding Xenopus bone morphogenetic protein 4 (XBMP-4) are detectable in the unfertilized egg, and that injection of XBMP-4 RNA into the animal hemisphere of Xenopus eggs causes animal caps isolated from the resulting blastulae to express mesoderm-specific markers. Surprisingly, however, XBMP-4 preferentially induces ventral mesoderm, whereas the closely related activin induces axial tissues. Furthermore, the action of XBMP-4 is ‘dominant’ over that of activin. In this respect, XBMP-4 differs from basic FGF, another ventral inducer, where simultaneous treatment with FGF and activin results in activin-like responses. The dominance of XBMP-4 over activin may account for the ability of injected XBMP-4 RNA to ‘ventralize’ whole Xenopus embryos. It is interesting, however, that blastopore formation in such embryos can occur perfectly normally. This contrasts with embryos ventralized by UV-irradiation and suggests that XBMP-4-induced ventral-ization occurs after the onset of gastrulation.
IGF binding protein-2 gene expression and the location of IGF-I and IGF-II in fetal rat lung
Authors: Klempt Martin , Hutchins Anne-Marie , Gluckman Peter D. , Skinner Stephen J. M. 
Published: April 2021

ABSTRACT
Binding proteins for the insulin-like growth factors (IGF-BPs) are important modulators of the biological actions of IGF-I and IGF-II. The generation of IGFBPs within developing organs, and their spatial arrangement, may similarly determine IGF action at specific microanatomical sites. In situ hybridization studies with late gestation (days 16, 18 and 20) fetal rat lung using a cDNA probe for IGFBP-2 showed strong gene expression in the fetal lung epithelial structures (alveoli and airways). The sites of IGFBP-2 gene expression were associated with immunoreactive IGF-II at the apical surface of the epithelium. By day 20, there was also some IGFBP-2 gene expression and immunoreactive IGF-II at discrete sites in the mesenchyme. In contrast, immunoreactive IGF-I was found predominantly distributed in a punctate pattern, consistent with its presence in the lumen or walls of small vessels or capillaries, and in a granular, intracellular form in both epithelial and mesenchymal cells. These studies suggest that endogenously generated IGFBP-2 may determine the distribution of IGF-II, principally at the apical surface of lung epithelia. IGF-I does not colocalise with IGF-II peptide or the sites of IGFBP-2 gene expression. We conclude that the spatial distributions of these two related growth factors are separately controlled, to some extent by endogenously generated binding proteins.
Ectopic sensory neurons in mutant cockroaches compete with normal cells for central targets
Authors: Bacon Jonathan P. , Blagburn Jonathan M. 
Published: April 2021

ABSTRACT
The cercus of the first instar cockroach, Periplaneta americana, bears two filiform hairs, lateral (L) and medial (M), each of which is innervated by a single sensory neuron. These project into the terminal ganglion of the CNS where they make synaptic connections with a number of ascending interneurons. We have discovered mutant animals that have more hairs on the cercus; the most typical phenotype, called “Space Invader” (SI), has an extra filiform hair in a proximo-lateral position on one of the cerci. The afferent neuron of this supernumerary hair (SIN) “invades the space” occupied by L in the CNS and makes similar synaptic connections to giant interneurons (GIs). SIN and L compete for these synaptic targets: the size of the L EPSP in a target interneuron GI3 is significantly reduced in the presence of SIN. Morphometric analysis of the L afferent in the presence or absence of SIN shows no anatomical concomitant of competition. Ablation of L afferent allows SIN to increase the size of its synaptic input to GI3. Less frequently in the mutant population, we find animals with a supernumerary medial (SuM) sensillum. Its afferent projects to the same neuropilar region as the M afferent, makes the same set of synaptic connections to GIs, and competes with M for these synaptic targets. The study of these competitive interactions between identified afferents and identified target interneurons reveals some of the dynamic processes that go on in normal development to shape the nervous system.
The development of eyespot patterns on butterfly wings: morphogen sources or sinks?
Authors: French Vernon , Brakefield Paul M. 
Published: April 2021

ABSTRACT
We have studied the development of the eyespot colour pattern on the adult dorsal forewing of the nymphalid butterflies, Bicyclus safitza and B. anynana, by cauterising the presumptive eyespot centres (the foci) on the pupal wing. The effects on pattern depended on age at cautery. Early focal cautery (at 1-12 hours after pupation) usually reduced or eliminated the eyespot, while cautery at a non-focal site usually had no effect. These results resemble those of a previous study on another species but, in addition, we find that a later cautery (at 12-24 hours) had the converse effect of generating pattern, so that focal cautery enlarged the anterior eyespot (but usually not the large posterior eyespot) and nonfocal cautery induced a new ectopic eyespot.
The effects of cautery on patterning are more extensive by an order of magnitude than the cell death which is caused, so implicating a long-range mechanism, such as a morphogen gradient, in eyespot development. The focus clearly acts to establish the normal eyespot pattern, but a simple source/diffusion model is not supported by the response to late cautery. We suggest two alternative forms of gradient model in which late damage can mimic and augment the action of a focus. In the Source/Threshold model, the focus is a morphogen source, and cautery can remove the focus but also transiently lowers the response threshold in surrounding cells. In the Sink model, the focus generates the gradient by removing morphogen, and cautery can eliminate the focus but it also causes a transient destruction or leakage of morphogen. These models can explain most features of the results of cautery.
Exogenous retinoic acid rapidly induces anterior ectopic expression of murine Hox-2 genes in vivo
Authors: Conlon Ronald A. , Rossant Janet 
Published: April 2021

ABSTRACT
Exogenous retinoic acid (RA) has teratogenic effects on vertebrate embryos and alters Hox-C gene expression in vivo and in vitro. We wish to examine whether RA has a role in the normal regulation of Hox-C genes, and whether altered Hox-C gene expression in response to RA leads to abnormal morphology. The expression of 3′ Hox-2 genes (Hox-2.9, Hox-2.8, Hox-2.6 and Hox-2.1) and a 5′ gene (Hox-2.5) were examined by whole-mount in situ hybridization on embryos 4 hours after mater-nal administration of teratogenic doses of RA on embry-onic day 7 to 9. The expression of the 3′ Hox-2 genes was found to be ectopically induced in anterior regions in a stage-specific manner. The Hox-2.9 and Hox-2.8 genes were induced anteriorly in the neurectoderm in response to RA on day 7 but not at later stages. Expression of Hox-2.6 and Hox-2.1 was ectopically induced anteriorly in neurectoderm in response to RA on day 8. Hox-2.1 remained responsive on day 9, whereas Hox-2.6 was no longer responsive at this stage. The expression of the 5′ gene Hox-2.5 was not detectably altered at any of these stages by RA treatments. We also examined the response of other genes whose expression is spatially regulated in early embryos. The expression of En-2 and Wnt-7b was not detectably altered by RA, whereas RAβ expression was induced anteriorly by RA on day 7 and 8. Krox-20 expression was reduced in a stage- and region-specific manner by RA. The ectopic anterior expression of Hox-2.8 and Hox-2.9 induced by RA on day 7 was persistent to day 8, as was the altered expression of Krox-20. The altered pattern of expression of these genes in response to RA treatment on day 7 may be indicative of a transformation of anterior hind-brain to posterior hindbrain, specifically, a transforma-tion of rhombomeres 1 to 3 towards rhombomere 4 iden-tity with an anterior expansion of rhombomere 5. The ectopic expression of the 3′ Hox-2 genes in response to RA is consistent with a role for these genes in mediat-ing the teratogenic effects of RA; the rapid response of the Hox-C genes to RA is consistent with a role for endogenous RA in refining 3′ Hox-C gene expression boundaries early in development.
The Drosophila cdc25 homolog twine is required for meiosis
Authors: Courtot Catherine , Fankhauser Christian , Simanis Viesturs , Lehner Christian F. 
Published: April 2021

ABSTRACT
We have identified a second cdc25 homolog in Drosophila. In contrast to string (the first homolog identified in Drosophila) this second homolog, twine, does not function in the mitotic cell cycle, but is specialized for meiosis. Expression of twine was observed exclusively in male and female gonads. twine transcripts are present in germ cells during meiosis, and appear only late during gametogenesis, well after the end of the mitotic germ cell divisions. The sterile Drosophila mutant, mat(2)synHB5, which had previously been isolated and mapped to the same genomic region as twine (35F), was found to carry a missense mutation in the twine gene. This missense mutation in twine abolished its ability to complement a mutation in Schizosaccharomyces pombe cdc25. Phenotypic analysis of mat(2)synHB5 mutant flies revealed a complete block of meiosis in males and severe meiotic defects in females.