bluuebunny/crossref_metadata_2025_split huggingface dataset:
The neurogenic locus brainiac cooperates with the Drosophila EGF receptor to establish the ovarian follicle and to determine its dorsal-ventral polarity
Authors: Goode Scott , Wright David , Mahowald Anthony P. 
Published: April 2021

ABSTRACT
We have characterized the function of a new neurogenic locus, brainiac (brn), during oogenesis. Homozygous brn females lay eggs with fused dorsal appendages, a phenotype associated with torpedo (top) alleles of the Drosophila EGF receptor (DER) locus. By constructing double mutant females for both brn and top, we have found that brn is required for determining the dorsalventral polarity of the ovarian follicle. However, embryos from mature brn eggs develop a neurogenic phenotype which can be zygotically rescued if a wildtype sperm fertilizes the egg. This is the first instance of a Drosophila gene required for determination of dorsal-ventral follicle cell fates that is not required for determination of embryonic dorsal-ventral cell fates. The temperature-sensitive period for brn dorsal-ventral patterning begins at the inception of vitellogenesis.
The interaction between brn and DER is also required for at least two earlier follicle cell activities which are necessary to establish the ovarian follicle. Prefollicular cells fail to migrate between each oocyte/nurse cell complex, resulting in follicles with multiple sets of oocytes and nurse cells. brn and DER function is also required for establishing and/or maintaining a continuous follicular epithelium around each oocyte/nurse cell complex. These brn functions as well as the brn requirement for determination of dorsal-ventral polarity appear to be genetically separable functions of the brn locus. Genetic mosaic experiments show that brn is required in the germline during these processes whereas the DER is required in the follicle cells. We propose that brn may be part of a germline signaling pathway differentially regulating successive DER-dependent follicle cell activities of migration, division and/or adhesion and determination during oogenesis. These experiments indicate that brn is required in both tyrosine kinase and neurogenic intercellular signaling pathways. Moreover, the functions of brn in oogenesis are distinct from those of Notch and Delta, two other neurogenic loci that are known to be required for follicular development.
NeuN, a neuronal specific nuclear protein in vertebratesxs
Authors: Mullen Richard J. , Buck Charles R. , Smith Alan M. 
Published: April 2021

ABSTRACT
A battery of monoclonal antibodies (mAbs) against brain cell nuclei has been generated by repeated immunizations. One of these, mAb A60, recognizes a vertebrate nervous systemand neuron-specific nuclear protein that we have named NeuN (Neuronal Nuclei). The expression of NeuN is observed in most neuronal cell types throughout the nervous sytem of adult mice. However, some major cell types appear devoid of immunoreactivity including cerebellar Purkinje cells, olfactory bulb mitral cells, and retinal photoreceptor cells. NeuN can also be detected in neurons in primary cerebellar cultures and in retinoic acid-stimulated P19 embryonal carcinoma cells. Immunohistochemically detectable NeuN protein first appears at developmental timepoints which correspond with the withdrawal of the neuron from the cell cycle and/or with the initiation of terminal differentiation of the neuron. NeuN is a soluble nuclear protein, appears as 3 bands (46-48 103Mr) on immunoblots, and binds to DNA in vitro. The mAb crossreacts immunohistochemically with nervous tissue from rats, chicks, humans, and salamanders. This mAb and the protein recognized by it serve as an excellent marker for neurons in the central and peripheral nervous systems in both the embryo and adult, and the protein may be important in the determination of neuronal phenotype.
Differential expression and regulation of two distinct fibroblast growth factor receptors during early development of the urodele amphibian Pleurodeles waltl
Authors: Shi De-Li , Feige Jean-Jacques , Riou Jean-François , Desimone Douglas W. , Boucaut Jean-Claude 
Published: April 2021

ABSTRACT
Fibroblast growth factor (FGF) has been shown to be involved in mesoderm induction during amphibian development. Its presence in the embryo suggests that FGF is an endogenous inducer. By polymerase chain reaction (PCR) methods and by screening a Pleurodeles waltl tail-bud cDNA library with a cDNA probe for human FGF receptor, we have isolated two full-length cDNA clones, which we designate PFR1 and PFR4 based on their homology to the human FGF receptors FGFR1 and FGFR-4. Both cDNA clones encode Pleurodeles FGF receptors that share characteristics common to members of the FGF receptor superfamily. The deduced amino acid sequence of PFR1 is 85% identical overall with the human fms-like-gene (FLG). PFR4 is most closely related to the human FGFR-4 (66% overall identity). The tyrosine kinase catalytic domains of both receptors are remarkably conserved. The two receptors show distinct patterns of regulation during early development. PFR1 first appears as a maternally derived mRNA and mRNA levels remain constant during early developmental stages. However, PFR4 mRNA is first expressed at the late blastula stage, which suggests that its expression is a result of zygotic transcription. Furthermore, northern blot analysis indicates that PFR1 mRNA is distributed evenly in the early gastrula while PFR4 mRNA is predominantly localized to the presumptive ectoderm. At tail-bud stage, PFR1 transcripts are localized primarily to the neural and mesodermal tissues, PFR4 transcripts are most abundantly expressed in neural tissue, and more transcripts are detected in lateral plate mesoderm than in the somites. When animal cap explants of blastulae are cultured in the presence of mesoderm-inducing factors, PFR1 mRNA levels are maintained by bFGF and activin A. In contrast, PFR4 mRNA levels are significantly down-regulated. These observations suggest a differential expression and regulation of FGF receptors in early amphibian development.
Parthenogenetic stem cells in postnatal mouse chimeras
Authors: Jägerbauer Eva-Maria , Fraser Audrey , Herbst Eberhard W. , Kothary Rashmi , Fundele Reinald 
Published: April 2021

ABSTRACT
The ability of parthenogenetic (pg) cells to contribute to proliferating stem cell populations of postnatal aggregation chimeras was investigated. Using DNA in situ analysis, pg participation was observed in highly regenerative epithelia of various regions of the gastrointestinal tract, e.g., stomach, duodenum and colon, in the epithelia of tongue and uterus and in the epidermis. Pg cells also contributed to the epithelium of the urinary bladder, which is characterized by a relatively slow cellular turnover.
Using a sensitive proliferation marker to determine division rate of pg and normal (wt) cells in tissues of a 24-day-old chimera, no significant differences between pg and fertilized cells were observed. However, in colon and uterus of a pg↔wt chimera aged 101 days, a significant loss of proliferative capacity of pg cells was found. In the colon, this loss of proliferative potential was accompanied by an altered morphology of pg crypts. In general, they were situated at the periphery of the epithelium and lacked access to the lumen, with consequent cystic enlargement and flattened epithelium. No obvious morphological changes were observed in the pg-derived areas of the uterine epithelium of this chimera.
Our results provide evidence that pg cells can persist as proliferating stem cells in various tissues of early postnatal chimeras. They suggest that pg-derived stem cells may cease to proliferate in restricted areas of the gastrointestinal tract and in the uterine epithelium of pg ↔wt chimeras of advanced age. However, no indications of such a loss of proliferative potential of pg cells could be observed in other areas of the digestive tract, e.g., in the stomach and duodenum, or in oral epithelium and in the epidermis.
These findings argue for a high degree of specificity of selection against pg cells in postnatal life. They also suggest that an impaired proliferative capacity is not a general feature of pg cells. Hence, it is possible that, to explain the impaired growth of of pg↔wt chimeras and the overall stringent selection against pg cells in such chimeras during fetal development, additional and/or alternative causes apart from a decreased proliferative potential of pg cells have to be considered.
Apart from their contribution to the endodermderived epithelia of stomach, gut and uterus, to the mesoderm-derived epithelium of uterus and to ectoderm-derived oral epithelium and epidermis, pg-derived cells differentiated into the mesoderm-derived mesenchymal cells of the stromal layers that lie between the epithelial cells and smooth muscle of stomach, gut, uterus and urinary bladder. Contribution to smooth muscle was also observed.
Thus our results show that pg cells are able to differentiate into various cell types of different embryonic origin in tissues of composite structure.
Mouse Wnt genes exhibit discrete domains of expression in the early embryonic CNS and limb buds
Authors: Parr Brian A. , Shea Martin J. , Vassileva Galya , McMahon Andrew P. 
Published: April 2021

ABSTRACT
Mutation and expression studies have implicated the Wnt gene family in early developmental decision making in vertebrates and flies. In a detailed comparative analysis, we have used in situ hybridization of 8.0- to 9.5-day mouse embryos to characterize expression of all ten published Wnt genes in the central nervous system (CNS) and limb buds. Seven of the family members show restricted expression patterns in the brain. At least three genes (Wnt-3, Wnt-3a, and Wnt-7b) exhibit sharp bound-aries of expression in the forebrain that may predict sub-divisions of the region later in development. In the spinal cord, Wnt-1, Wnt-3, and Wnt-3a are expressed dorsally, Wnt-5a, Wnt-7a, and Wnt-7b more ventrally, and Wnt-4 both dorsally and in the floor plate. In the forelimb primordia, Wnt-3, Wnt-4, Wnt-6 and Wnt-7b are expressed fairly uniformly throughout the limb ectoderm. Wnt-5a RNA is distributed in a proximal to distal gradient through the limb mesenchyme and ectoderm. Along the limb’s dorsal-ventral axis, Wnt-5a is expressed in the ventral ectoderm and Wnt-7a in the dorsal ectoderm. We discuss the significance of these patterns of restricted and partially overlapping domains of expression with respect to the putative function of Wnt signalling in early CNS and limb development.
Root development in Arabidopsis: four mutants with dramatically altered root morphogenesis
Authors: Benfey Philip N. , Linstead Paul J. , Roberts Keith , Schiefelbein John W. , Hauser Marie-Theres , Aeschbacher Roger A. 
Published: April 2021

ABSTRACT
A genetic analysis of root development in Arabidopsis thaliana has identified mutants that have abnormal morphogenesis. Four of these root morphogenesis mutants show dramatic alterations in post-embryonic root development. The short-root mutation results in a change from indeterminate to determinate root growth and the loss of internal root cell layers. The cobra and lion’s tail mutations cause abnormal root cell expansion which is conditional upon the rate of root growth. Expansion is greatest in the epidermal cells in cobra and in the stele cells in lion’s tail . The sabre mutation causes abnormal cell expansion that is greatest in the root cortex cell layer and is independent of the root growth rate. The tissuespecific effects of these mutations were characterized with monoclona antibodies and a transgenic marker line. Genetic combinations of the four mutants have provided insight into the regulation of growth and cell shape during Arabidopsis root development.
Cellular organisation of the Arabidopsis thaliana root
Authors: Dolan Liam , Janmaat Kees , Willemsen Viola , Linstead Paul , Poethig Scott , Roberts Keith , Scheres Ben 
Published: April 2021

ABSTRACT
The anatomy of the developing root of Arabidopsis is described using conventional histological techniques, scanning and transmission electron microscopy. The root meristem is derived from cells of the hypophysis and adjacent cells of the embryo proper. The postembryonic organization of the root is apparent in the mature embryo and is maintained in the growing primary root after germination. Cell number and location is relatively invariant in the primary root, with 8 cortical and endo-dermal cell files but more variable numbers of pericycle and epidermal cells. The organisation of cells in lateral roots is similar to that of the primary root but with more variability in the numbers of cell files in each layer. [3H]thymidine labeling of actively growing roots indicates that a quiescent centre of four central cells (derived from the hypophysis) is located between the root cap columella and the stele. This plate of four cells is surrounded by three groups of cells in, proximal, distal and lateral positions. The labeling patterns of these cells suggest that they are the initials for the files of cells that comprise the root. They give rise to four sets of cell files: the stele, the cortex and endodermis, the epidermis and lateral root-cap and the columella. A model of meristem activity is proposed based on these data. This description of Arabidopsis root structure underpins future work on the developmental genetics of root morphogenesis.
Activity and expression pattern of cyclin-dependent kinase 5 in the embryonic mouse nervous system
Authors: Tsai Li-Huei , Takahashi Takao , Caviness Verne S. , Harlow Ed 
Published: April 2021

ABSTRACT
Cyclin-dependent kinase 5 (cdk5) was originally isolated on the basis of its close primary sequence homology to the human cdc2 serine/threonine kinase, the prototype of the cyclin-dependent kinases. While kinase activities of both cdc2 and cdk2 are detected in proliferating cells and are essential for cells to progress through the key transition points of the cell cycle, cdk5 kinase activity has been observed only in lysates of adult brain. In this study, we compared the activity and expression of cdk5 with that of cdc2 and cdk2 in the embryonic mouse forebrain. The expression and activity of cdk5 increased progressively as increasing numbers of cells exited the proliferative cycle. In contrast, the expression and activity of cdc2 and cdk2 were maximum at gestational day 11 (E11) when the majority of cells were proliferating and fell to barely detectable levels at E17 at the end of the cytogenetic period. Immunohistochemical studies showed that cdk5 is expressed in postmitotic neurons but not in glial cells or mitotically active cells. Expression of cdk5 was concentrated in fasciculated axons of postmitotic neurons. In contrast to other cell division cycle kinases to which it is closely related, cdk5 appears not to be expressed in dividing cells in the developing brain. These observations suggest that cdk5 may have a role in neuronal differentiation but not in the cell division cycle in the embryonic nervous system.
Xwnt-11: a maternally expressed Xenopus wnt gene
Authors: Ku Min , Melton Douglas A. 
Published: April 2021

ABSTRACT
We have isolated and characterized a novel Xenopus wnt gene, Xwnt-11, whose expression pattern and overexpression phenotype suggest that it may be important for dorsal-ventral axis formation. Xwnt-11 mRNA is present during oogenesis and embryonic development through swimming tadpole stages. Xwnt-11 mRNA is ubiquitous in early oocytes and is localized during mid-oogenesis. By late oocyte stages, Xwnt-11 mRNA is localized to the vegetal cortex, with some mRNA in the vegetal cytoplasm. After egg maturation, Xwnt-11 mRNA is released from the vegetal cortex and is found in the vegetal cytoplasm. This early pattern of Xwnt-11 mRNA localization is similar to another vegetally localized maternal mRNA, Vg1 (D. A. Melton (1987)Nature 328, 80–82). In the late blastula, Xwnt-11 mRNA is found at high levels in the dorsal marginal zone. As gastrulation proceeds, Xwnt-11 mRNA appears in the lateral and ventral marginal zone and, during tadpole stages, it is found in the somites and first branchial arch. Injection of Xwnt-11 mRNA into UV-ventralized embryos can substantially rescue the UV defect by inducing the formation of dorsal tissues. The rescued embryos develop somitic muscle and neural tube; however, they lack notochord and anterior head structures.
In vitro manipulation of early mouse embryos induces HIV1-LTRlacZ transgene expression
Authors: Vernet Muriel , Cavard Catherine , Zider Alain , Fergelot Patricia , Grimber Gisèle , Briand Pascale 
Published: April 2021

ABSTRACT
We report here that the transcriptional activity of early mouse embryos is affected by their manipulation and culture in vitro, using transgenic embryos that express the reporter gene lacZ. We examined the pattern of expression of the lacZ gene fused to the human immunodeficiency virus type 1 long terminal repeat during the preimplantation stages. Transgene expression is induced as early as the two-cell stage in embryos developed in vitro, while there is no constitutive expression at the same stage in embryos developed in vivo. We have established a relation between this inducible expression occurring in vitro and an oxidative stress phenomenon. Indeed, when the culture medium is supplemented with antioxidants such N-acetyl-cysteine or CuZn-superoxide dismutase the transgene expression is markedly reduced. We also present evidence that the transgene expression in vitro coincides with the onset of the embryonic genome activation as attested by the synthesis of the 70 ×103Mr protein complex. Therefore, this transgene expression could prove to be a useful tool in our understanding of the molecular mechanisms involved in this crucial developmental event.
From growth cone to synapse: the life history of the RP3 motor neuron
Authors: Broadie Kendal , Sink Helen , Vactor David Van , Fambrough Douglas , Whitington Paul M. , Bate Michael , Goodman Corey S. 
Published: April 2021

ABSTRACT
In Drosophila, the ability to analyze the development of individually identified neurons with a variety of imaging and biophysical techniques can be complemented by sophisticated genetics and molecular biology. This powerful combination is allowing the development and function of single neurons and their synaptic connections to be unraveled at an unparalleled level of resolution. In this article, we focus on a single, identified motoneuron – RP3 – arguably the best understood neuron in the fruitfly. Many events in the life history of RP3 are well characterized, including cell migration, axon outgrowth and pathfinding within the central nervous system, pathfinding in the periphery to its appropriate muscle target domain, the specific recognition of its muscle targets, the events of synapse formation and maturation, and its mature function in the locomotion of the fly larva. Genetic analysis has revealed mutations in a number of different genes which affect specific aspects of RP3 development from axon outgrowth to synapse formation.
Genetic analysis of the sevenless signal transduction pathway of Drosophila
Authors: Hafen E. , Dickson B. , Raabe T. , Brunner D. , Oellers N. , van der Straten A. 
Published: April 2021

ABSTRACT
The specification of tlie R7 photoreceptor cell fate in the devloping eye of Drosophila depends on the local activation of the sevenless (sev) receptor tyrosine kinase (RTK) by boss, a protein expressed on the membrane of the neighboring RS cell. Constitutive activation of the sevreceptor results in a dosage dependent increase in the number tuber of R7 cells per ommatidium. Genetic screens have been used to identify mutations that alter the efficiency of signal transduction. Subsequent molecular characterization of the corresponding genes has led to the identification of a number of proteins involved in transducing the signal from the receptor to the nucleus. In contrast to the receptor and its ligand, these components are shared between different signal transduction pathways not only in Drosophila but homologous components are also involved in signal transduction in other organisms.
The torso pathway in Drosophila: a model system to study receptor tyrosine kinase signal transduction
Authors: Lu Xiangyi , Perkins Lizabeth A. , Perrimon Norbert 
Published: April 2021

ABSTRACT
In the Drosophila embryo, specification of terminal cell fates that result in the formation of both the head (acron) and tail (telson) regions is under the control of the torso (tor) receptor tyrosine kinase. The current knowledge suggests that activation of tor at the egg pole initiates a signal transduction pathway that is mediated sequentially by the guanine nucleotide releasing factor son of sevenless (Sos), the p21Rasl GTPase, the serine/threonine kinase D-raf and the tyrosine/threonine kinase MAPKK (Dsorl). Subsequently, it is postulated that activation, possibly by phosphorylation, of a transcription factor at the egg poles activates the transcription of the terminal gap genes tatlless and huckehein. These gap genes, which encode putative transcription factors, then control the expression of more downstream factors that ultimately result in head and tail differentiation. Also involved in tor signaling is the non-receptor protein tyrosine phosphatase corkscrew (csw). Here, we review the current model and discuss future research directions in this field.
Wingless, the Drosophila homolog of the proto-oncogene Wnt-1, can transform mouse mammary epithelial cells
Authors: Ramakrishna Naren R. , Brown Anthony M. C. 
Published: April 2021

ABSTRACT
The segment polarity gene wingless is the Drosophila ortholog of mouse Wni-1, a proto-oncogene capable of causing transformation of mammary epithelial cells. These two genes presently represent the best studied members of the Wnt gene family. To evaluate the functional significance of the sequence conservation between wingless and Wnt-1, we have examined the effects of expressing the Drosophila gene in mouse mammary epithelial cell lines, wingless induced morphological transformation, focus formation, and mitogenesis in confluent cultures of these cells, with resulting phenotypes comparable to those obtained with mouse Bnt-1. In addition, RAC311c mammary cells expressing wingless were tumorigenic, indicating that the Drosophila gene is capable of inducing full neoplastic transformation. In cell co-culture experiments, wingless caused transformation via a paracrine mechanism, consistent with the extracellular location of its product and its proposed mechanism of action in Drosophila embryos. Our results indicate that wingless is functionally analogous to Wnt-1 in these mammary cell transformation assays and imply a striking conservation in the properties of the two gene products and their mechanisms of action.
The mechanism of cleavage in amphibian and sturgeon eggs
Authors: Zotin A. I. 
Published: April 2021

ABSTRACT
The Cleavage plane in animal cells and eggs is known to be determined by the position of the mitotic apparatus (cf. Wilson, 1925). A displacement of the mitotic apparatus by centrifugation (Harvey, 1935), mechanical deformation of eggs (Rappaport, 1960, 1961) or by microsurgical operation (Carlson, 1952; Waddington, 1952; Kawamura, 1960; Chambers & Chambers, 1961; Dan & Kuno Kojima, 1963) results in a corresponding change in the location of the cleavage furrow. This shows that the position of the cleavage furrow is determined by the mitotic apparatus of the cell.