bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mouse NCAM gene displays a biphasic expression pattern during neural tube development
Authors: Bally-Cuif Laure , Goridis Christo , Santoni Marie-Josée 
Published: April 2021

ABSTRACT
The neural cell adhesion molecule (NCAM) is one of the most abundant cell adhesion molecules expressed in vertebrates and it is thought to play important roles as a regulator of morphogenetic processes, but little is known of its expression pattern in mammalian embryos. In this study, we have examined the developmental profile of NCAM gene expression in mouse embryos from gestational day 7.5 to 12.5, focusing on the developing neural tube. NCAM transcripts were first detected around day 8.5 in the somites and the forming neural tube. At this stage, NCAM transcripts were expressed in the neuroepithelium throughout the width of the neural groove and tube up to a rostral boundary within the hindbrain, whereas NCAM mRNA levels were very low or undetectable in the neuroepithelium of the head region. The positional restriction of NCAM expression was con-firmed by immunohistochemistry at the protein, and by polymerase chain reaction analysis at the RNA level. Expression in the neuroepithelium was transient as the level of NCAM transcripts declined in the germinal layer beyond day 8.5. By day 9.5, strong NCAM expression had appeared on the earliest postmitotic neurones along the entire neuraxis, and this pattern of expression in all regions with differentiating neurones was maintained until day 12.5. We conclude that NCAM expression in the neural tube occurs in two spatiotemporal distinct waves : a first wave in the proliferating neuroepithelium showing positional dependence along the rostrocaudal axis, and a second wave on essentially all neurones that have become postmitotic.
Multiple restricted lineages in the embryonic rat cerebral cortex
Authors: Grove Elizabeth A. , Williams Brenda P. , Li Da-Qing , Hajihosseini Mohammad , Friedrich André , Price Jack 
Published: April 2021

ABSTRACT
We have labelled precursor cells in the embryonic rat cerebral cortex using BAG, a retroviral vector that expresses β -galactosidase. We had previously reported that labelled precursor cells gxenerate clusters of labelled cells that could be classified into four types by their morphological appearance and anatomical distribution (Price and Thurlow, 1988). In this study, we have used immunohistochemistry and intracellular dye labelling to identify the cell types that make up these clusters. We discovered that clusters are almost always composed of a single cell type. In addition to clusters composed entirely of neurones, we found four different types of glial cell clusters. In the grey matter, glial clusters are composed either of protoplasmic astrocytes, or of cells that have an astrocyte morphology, but no glial filaments. In the white matter, clusters are composed of either fibrous astrocytes or oligodendocytes. Our results indicate that each of these different cortical cell types is generated from a separate population of precursor cells.
The Polycomb group gene Posterior Sex Combs encodes a chromosomal protein
Authors: Martin Elisabeth C. , Adler Paul N. 
Published: April 2021

ABSTRACT
The Posterior Sex Combs (Psc) gene of Drosophila has been studied at the molecular level both because it is a Polycomb group (Pc-G) gene and hence required for the maintenance of segmental determination, and because it is the Drosophila homolog of the murine bmi-1 onco-gene. Although genetic interactions indicated that Psc functioned as a Pc-G gene, the zygotic mutant pheno-type of Psc showed little evidence of segmental transformations. We have examined mutant embryos derived from a mutant maternal germ line and found a stronger mutant phenotype, indicating that the weak zygotic phenotype of Psc is due to maternal rescue. We have found that Psc RNA accumulates in developing oocytes and this maternal RNA is presumably responsible for the maternal rescue. We have studied the expression of the Psc gene at both the RNA and protein levels. On northern blots, we find evidence for two Psc mRNAs and, on western blots, we find evidence for two Psc proteins that are altered either in abundance or size in Psc mutants. The Psc protein accumulates in all regions of the embryo and also in many tissues in a variety of developmental stages. In all cases, it is nuclear, as is its mammalian homolog, the bmi-1 protein. On polytene chromosomes, we find Psc at 45 chromosomal loci where two other Pc-G proteins are present.
Expression of the mouse goosecoid gene during mid-embryogenesis may mark mesenchymal cell lineages in the developing head, limbs and body wall
Authors: Gaunt Stephen J. , Blum Martin , De Robertis Eddy M. 
Published: April 2021

ABSTRACT
After an earlier, transient phase of expression in the developing primitive streak of 6.4-to 6.8-day mouse embryos, the homeobox gene goosecoid is now shown to be expressed in a later phase of mouse development, from 10.5 days onwards. The later, spatially restricted domains of goosecoid expression are detected in the head, limbs and ventrolateral body wall. At all sites, the domains of expression are first detected in undifferen-tiated tissue, and then expression persists as these tissues undergo subsequent morphogenesis. For example, goosecoid expression is noted in the first branchial arch at 10.5 days, and then expression persists as this tissue undergoes morphogenesis to form the lower jaw and the body of the tongue. Expression in tissues around the first branchial cleft persists as these undergo morphogenesis to form the base of the auditory meatus and eustachian tube. Expression in tissues around the newly formed nasal pits persists as these elongate to form the nasal chambers. Expression in the ventral epithelial lining of the otic vesicle persists as this eventually gives rise to the non-sensory epithelium of the cochlea. Expression in the proximal limb buds and ventrolateral body wall persists as these tissues undergo morphogenesis to form proximal limb structures and ventral ribs respectively. Our findings lead us to suggest that the goosecoid gene product plays a role in spatial programming within dis-crete embryonic fields, and possibly lineage compart-ments, during organogenesis stages of mouse develop-ment.
Site-specific cleavage of basement membrane collagen IV during Drosophila metamorphosis
Authors: Fessler Liselotte I. , Condic Maureen L. , Nelson Robert E. , Fessler John H. , Fristrom James W. 
Published: April 2021

ABSTRACT
Breakdown of basement membranes is an important step in the controlled rearrangement of cells during metamorphosis, cell migration, and metastatic spread of tumor cells. One of our two laboratories found a unique collagenous peptide that only appears during metamor-phosis of Drosophila melanogaster. The other laboratory previously reported that during 20-hydroxyecdysone-induced eversion of Drosophila imaginal discs a glyco-protein named gp125 arises (Birr et al., 1990). We show that these two peptides are identical and that they are formed from basement membrane collagen IV. Cleav-age occurs at an imperfection of this homotrimeric col-lagen helix between residues 755/756 in the sequence CALDE/IKMPAK. The peptide is the carboxyl frag-ment, 100,647 Mr, as derived from the amino acid sequence of the collagen 1(IV) chain. The correspond-ing amino fragment was also recovered from a disul-fide-linked aggregate. This specific cleavage supports the concept of highly targeted, controlled breakdown of basement membranes during metamorphosis. Further-more, these cuts occur at strategic sites of the predicted supramolecular network of collagen IV molecules of Drosophila basement membranes.
Cell interactions control the direction of outgrowth, branching and fasciculation of the HSN axons of Caenorhabditis elegans
Authors: Garriga Gian , Desai Chand , Horvitz H. Robert 
Published: April 2021

ABSTRACT
The two serotonergic HSN motor neurons of the nema-tode Caenorhabditis elegans innervate the vulval mus-cles and stimulate egg laying by hermaphrodites. By analyzing mutant and laser-operated animals, we find that both epithelial cells of the developing vulva and axons of the ventral nerve cord are required for HSN axonal guidance. Vulval precursor cells help guide the growth cone of the emerging HSN axon to the ventral nerve cord. Vulval cells also cause the two HSN axons to join the ventral nerve cord in two separate fascicles and to defasciculate from the ventral nerve cord and branch at the vulva. The axons of either the PVP or PVQ neurons are also necessary for the HSN axons to run in two separate fascicles within the ventral nerve cord. Our observations indicate that the outgrowth of the HSN axon is controlled in multiple ways by both neuronal and nonneuronal cells.
Expression and function of c-Kit in fetal hemopoietic progenitor cells: transition from the early c-Kit-independent to the late c-Kit-dependent wave of hemopoiesis in the murine embryo
Authors: Ogawa Minetaro , Nishikawa Satomi , Yoshinaga Kazuya , Hayashi Shin-Ichi , Kunisada Takahiro , Nakao Junji , Kina Tatsuo , Sudo Tetsuo , Kodama Hiroaki , Nishikawa Shin-Ichi 
Published: April 2021

ABSTRACT
The protooncogene c-kit encodes a receptor type tyro-sine kinase and is allelic with the W locus of mice. SLF, the c-Kit ligand which is encoded by the Sl locus, has growth promoting activity for hemopoietic stem cells. Previous studies demonstrated that c-Kit is functionally required for the proliferation of hemopoietic progenitor cells at various differentiation stages in adult bone marrow. However, the absence of functional SLF and c-Kit in fetuses with mutant alleles of Sl and W loci pro-duces only minor effects on the myeloid and early ery-throid progenitor cells in the fetal liver, although the level of the late erythroid progenitor cells is significantly affected. We used an anti-c-Kit monoclonal antibody to investigate the expression and function of c-Kit in murine fetal hemopoietic progenitor cells. Flow-cyto-metric analysis showed that hemopoiesis in the yolk sac and fetal liver started from cells that express c-Kit. The c-Kit expression decreased upon maturation into ery-throcytes in each organ. By fluorescence activated cell sorting, the c-Kit+ cell population was enriched with the hemopoietic progenitor cells clonable in vitro (CFU-E, BFU-E and GM-CFC). To elucidate whether c-Kit func-tions in these progenitor cells in vivo, we took advan-tage of the antagonistic anti-c-Kit monoclonal antibody, ACK2, which can block the function of c-Kit. Adminis-tration of ACK2 after 12.5 days of gestation rapidly eliminated BFU-E and GM-CFC as well as CFU-E from the fetal liver. However, the number of these progeni-tor cells in the yolk sac and fetal liver was less affected when the fetuses were given ACK2 before 12.5 days of gestation. Our results provide evidence that there are two waves of hemopoiesis in murine embryos relative to c-Kit dependency. The c-Kit has an essential role on the growth of hemopoietic progenitor cells in the fetal liver after 12.5 days of gestation, whereas the progenitor cells in the liver and yolk sac of the earlier embryo do not depend on c-Kit and its ligand SLF.
Distal-less is a downstream gene of Deformed required for ventral maxillary identity
Authors: O’Hara Edward , Cohen Barbara , Cohen Stephen M. , McGinnis William 
Published: April 2021

ABSTRACT
The homeotic selector (HOM) proteins are required for the diversification of the anterior-posterior axis of the Drosophila body plan, assigning unique identities to regional domains of cells comprising one or a few parasegments or segments. The HOM proteins apparently accomplish this task by the transcriptional regulation of numerous downstream genes. At present few downstream genes are known, so models of how downstream genes mediate HOM functions are based more on intuition than information. Our results indicate that Distal-less is a downstream gene of the HOM gene Deformed, and Distal-less function is required for the elaboration of a subset of the maxillary epidermal identities specified by Deformed. The regulatory effect of Deformed on Distal-less is mediated by a ventral maxillary-specific enhancer located 3 of the Distal-less transcription unit. We propose that Deformed and Distalless, both of which encode homeodomain transcription factors that are persistently expressed in ventral maxillary cells, combinatorially specify a subsegmental code required for a group of cells to differentiate maxillary cirri.
Two types of pole cells are present in the Drosophila embryo, one with and one without splicing activity for the third P-element intron
Authors: Kobayashi Satoru , Kitamura Tomiichiro , Sasaki Hitoshi , Okada Masukichi 
Published: April 2021

ABSTRACT
In Drosophila, it has been postulated that the third intron of the P-element is spliced only in germ-line cells. To test whether this postulate is applicable to pole cells, the progenitor cells of germ line, we carried out a histochemical assay to detect the splicing activity in embryos. The splicing activity was detected in pole cells and primordial germ cells. The activity increased to reach a maximum at 5-6 hours AEL (after egg laying), then decreased to an undetectable level by 8-9 hours AEL. The splicing activity showed a small second peak at 12-15 hours AEL. It was rather unexpected that not all pole cells were capable of splicing the third intron.
Almost all pole cells that had the splicing activity at 5-6 hours AEL penetrated the embryonic gonads and differentiated into primordial germ cells. Our findings suggest that pole cells are selected to penetrate the gonads while they are migrating from the proctodeal cavity to the gonads. Furthermore, these results suggest that the machinery to splice the P-element is active in some pole cells, and that this activity is used for processing transcripts of genes that play important roles in the differentiation of pole cells into primordial germ cells.
Altered rhombomere-specific gene expression and hyoid bone differentiation in the mouse segmentation mutant, kreisler (kr)
Authors: Frohman Michael A. , Martin Gail R. , Cordes Sabine P. , Halamek Louis P. , Barsh Gregory S. 
Published: April 2021

ABSTRACT
Rhombomeres appear transiently in the vertebrate hindbrain shortly after neurulation and are thought to represent embryologic compartments in which the expression of different combinations of genes leads to segment-specific differentiation of the developing hind-brain, the cranial ganglia, and the branchial arches. To determine the extent to which gene expression is related to the formation of visible rhombomere boundaries, we have examined, by in situ hybridization, the expression of five rhombomere-specific genes in mouse embryos homozygous for the kreisler (kr) mutation, in which rhombomeres 4-7 are replaced by a smooth morpho-logically unsegmented neural tube.
Using molecular probes specific for Hoxb-1 (Hox-2.9), Hoxb-3 (Hox-2.7), Hoxb-4 (Hox-2.6), Krox-20, or Fgf-3 (Int-2), we found that the kr mutation affects the expression of all the genes we examined, but, surprisingly, the altered patterns of expression are not restricted to that portion of the mutant hindbrain which is morphologically abnormal. Rostral expression boundaries of Hoxb-3 and Hoxb-4 are displaced from their normal positions at r4/5 and r6/7 to the approximate positions of r3/4 and r4/5, respectively. The expression domains of Krox-20 and Fgf-3 are also displaced in a rostral direction and the intensity of Fgf-3 hybridization is greatly reduced. The expression domain of Hoxb-1 is affected differently from the other genes in kr/kr embryos; its rostral boundary at r3/4 is intact but the caudal boundary is displaced from its normal location at r4/5 to the approximate position of r5/6. Because boundaries of gene expression for Hoxb-1 and Hoxb-4 are found in a region of the kr/kr hindbrain that lacks visible rhombomeres, establishment of regional identity, as reflected by differential gene expression, does not require overt segmentation.
To investigate whether the altered patterns of gene expression we observed in the kr/kr embryonic hind-brain are associated with morphologic changes in the adult, we examined neural crest-derived tissues of the second and third branchial arches, which normally arise from rhombomeres 4 and 6, respectively. We found that the hyoid bone in kr/kr animals exhibited an accessory process on the greater horn (a third arch structure) most easily explained by ectopic development of a second arch structure (the hyoid lesser horn) in an area normally derived from the third arch.
Development of Drosophila wing sensory neurons in mutants with missing or modified cell surface molecules
Authors: Whitlock Kathleen E. 
Published: April 2021

Abstract
The neurons of the sensory receptors on the wing of Drosophila melanogaster have highly characteristic axon projections in the central nervous system (CNS). The morphology of these projections was studied in flies bearing mutations that affect cell surface molecules thought to be important in axon guidance. The animals used were mutant for the fasciclinI (fasI), fasciclinII (fasII), fasciclinIII (fasIII) and neurally altered carbohy - drate (nac) genes. Axon populations were visualized by staining with DiI and light-reacting the dye with diaminobenzidine to yield permanent preparations.
The fasI, fasII and fasIII mutants as well as the nac mutant display altered axonal trajectories in the CNS. One phenotype seen in fasII mutants and in animals mutant for both fasI and fasIII was extra branching within the axon projection pattern. A second phenotype observed was a reduction or complete loss of one of the tracts, apparently due to the axons shifting to a neigh-boring tract. This was seen in the most extreme form in nac mutants and to a lesser degree in fasIII mutants.
To determine if the mutations discussed here affected axon guidance, wing discs were analyzed using the anti- body 22C10 to label sensory neurons in the wing during metamorphosis. Both misrouting of axons and the appearance of ectopic neurons in the wing were observed. In the fasI;fasIII, the fasII and the nac mutants, there was misrouting of sensory axons in the developing wing. In addition, the fasII and nac mutants displayed ectopic sensory neurons in the wing. This implies that the cell surface molecules missing (fasci - clins) or modified (by the nac gene product), in these mutants may play a role in both neurogenesis and axon guidance.
Mesodermal cell interactions in the sea urchin embryo: properties of skeletogenic secondary mesenchyme cells
Authors: Ettensohn Charles A. , Ruffins Seth W. 
Published: April 2021

Abstract
An interaction between the two principal populations of mesodermal cells in the sea urchin embryo, primary and secondary mesenchyme cells (PMCs and SMCs, respectively), regulates SMC fates and the process of skeleto-genesis. In the undisturbed embryo, skeletal elements are produced exclusively by PMCs. Certain SMCs also have the ability to express a skeletogenic phenotype; however, signals transmitted by the PMCs direct these cells into alternative developmental pathways. In this study, a combination of fluorescent cell-labeling meth-ods, embryo microsurgery and cell-specific molecular markers have been used to study the lineage, numbers, normal fate(s) and developmental potential of the skeletogenic SMCs. Previous fate-mapping studies have shown that SMCs are derived from the veg2 layer of blastomeres of the 64-cell-stage embryo and from the small micromeres. By specifically labeling the small micromeres with 5-bromodeoxyuridine, we demonstrate that descendants of these cells do not participate in skeletogenesis in PMC-depleted larvae, even though they are the closest lineal relatives of PMCs. Skeleto-genic SMCs are therefore derived exclusively from the veg2 blastomeres. Because the SMCs are a heteroge-neous population of cells, we have sought to gain information concerning the normal fate(s) of skeletogenic SMCs by determining whether specific cell types are reduced or absent in PMC( ) larvae. Of the four known SMC derivatives: pigment cells, blastocoelar (basal) cells, muscle cells and coelomic pouch cells, only pig-ment cells show a major reduction (&gt;50%) in number following SMC skeletogenesis. We therefore propose that the PMC-derived signal regulates a developmental switch, directing SMCs to adopt a pigment cell pheno-type instead of a default (skeletogenic) fate. Ablation of SMCs at the late gastrula stage does not result in the recruitment of any additional skeletogenic cells, demon-strating that, by this stage, the number of SMCs with skeletogenic potential is restricted to 60-70 cells. Previ-ous studies showed that during their switch to a skele-togenic fate, SMCs alter their migratory behavior and cell surface properties. In this study, we demonstrate that during conversion, SMCs become insensitive to the PMC-derived signal, while at the same time they acquire PMC-specific signaling properties.
Developmental regulation of transcription of a novel prespore-specific gene (Dp87) in Dictyostelium discoideum
Authors: Ozaki Toshinori , Nakao Hajime , Orii Hidefumi , Morio Takahiro , Takeuchi Ikuo , Tasaka Masao 
Published: April 2021

Abstract
The Dp87 is a novel prespore specific gene of Dictyostelium discoideum which has a long open reading frame of 555 amino acids. The entire amino acid sequence had low but significant homology to the spore coat proteins, SP96 and SP70, of this organism. When a chimeric gene, containing a 1380 bp of the 5 upstream region of this gene fused with CAT gene, as reporter, was introduced into cells of this organism, it was expressed only in prespore cells of the slug. Transformation experiments, using chimeric genes, containing a series of 5 deletions of the upstream region, showed that 447 bp to 357 bp is an important cis-acting regulatory region for transcription. A nuclear factor(s) that specifically bind to this cis-acting region were detected from slug cell nuclei. Transformation experiments using a chimeric gene consisting of the 5 region between 666 bp and +149 bp of this gene, a β-galactosidase reporter and an actin 8 terminator, showed that the reporter gene was expressed as early as in aggregation streams, indicating that Dp87 become transcribed a few hours earlier than the other prespore-specific genes so far reported. This was confirmed by northern hybridization detected using an image plate analyzer. The fact that cells expressing Dp87 appeared at random in aggregation streams gives solid support to the idea that position-independent differentiation of prespore and pre-stalk cells, followed by their sorting, brings about pattern formation in this organism.