bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Drosophila Ras2 and Rop gene pair: a dual homology with a yeast Ras-like gene and a suppressor of its loss-of-function phenotype
Authors: Salzberg Adi , Cohen Noa , Halachmi Naomi , Kimchie Ziva , Lev Zeev 
Published: April 2021

Abstract
The promoter of the Drosophila melanogaster Ras2 gene is bidirectional, regulating an additional gene oriented in the opposite polarity. The two divergently transcribed genes are only 93 bases apart and deletion analysis proved that common cis-acting elements within this promoter region are required for the transcriptional activity of both genes. We cloned the gene paired with Ras2 in the bidirectional promoter and isolated cDNAs corresponding to its mRNA. The Ras opposite (Rop) gene encodes for a 68 103Mr protein which shares sequence homology with the members of a novel Saccharomyces cerevisiae gene family, including the SLY1, SEC1 and VPS33 (SLP1) genes, all of which are involved in vesicle trafficking among yeast cellular compartments. A highly conserved motif in this family is also found in β-COP, a coat protein isolated from rat Golgi-bound non-clathrin vesicles. Thus, the Rop protein may be a component of one of the vesicle trafficking pathways in Drosophila cells. The Rop gene expression during embryogenesis is restricted to the central nervous system (CNS) and the garland cells, a small group of nephrocytes that takes up waste materials from the haemolymph by endocytosis. Ras2 is also expressed in the embryonic garland cells. In postembryonic stages, the two genes are co-expressed in the larval salivary glands and the central nervous system, and in the adult CNS and reproductive systems. Interestingly, the S. cerevisiae SLY1-20 allele is a suppressor of the loss of the YPT1 gene, a ras-like gene implicated in vesicle translocation, suggesting that the two genes may inter-act with one another. Since Sec1p and β-COP may also interact with small GTP-binding proteins of the ras superfamily, it is conceivable that the Rop and Ras2 gene products are not just co-expressed in common tissues, but may also functionally interact with one another in these tissues.
Control of imaginal cell development by the escargot gene of Drosophila
Authors: Hayashi Shigeo , Hirose Susumu , Metcalfe Tony , Shirras Alan D. 
Published: April 2021

ABSTRACT
Mutations in the escargot (esg) locus, which codes for a zinc-finger-containing protein with similarity to the product of the snail gene, cause a variety of defects in adult structures such as loss of abdominal cuticle and malformation of the wings and legs. esg RNA is expressed in wing, haltere, leg and genital imaginal discs and in abdominal histoblast nests in the embryo. Expression in imaginal tissues is also found in third instar larvae. In esg mutant larvae, normally diploid abdominal histoblasts replicate their DNA without cell division and become similar in appearance to the polytene larval epidermal cells. A similar phenotype was also found in imaginal discs of larvae mutant for both esg and the Drosophila raf gene. These results suggest that one of the normal functions of esg may be the maintenance of diploidy in imaginal cells.
Identification and characterization of a gene activated by the deformed homeoprotein
Authors: Mahaffey James W. , Jones Denise F. , Hickel Jo Ann , Griswold Charles M. 
Published: April 2021

ABSTRACT
In Drosophila, the homeotic genes encode transcription factors which control segment identity during embryogenesis by specifying the appropriate set of ‘target’ genes necessary to produce the individual segmental characteristics. Though we know much about the homeotic genes and the proteins they encode, we know little of their targets. Here we identify and characterize one such target gene, a gene activated by the product of the homeotic gene Deformed. DNA binding assays and expression of reporter gene constructs indicate that activation of this gene requires a direct interaction between the Deformed protein and an upstream enhancer element at this target gene. However, although Deformed is required to activate this gene in cells of the maxillary segment, ectopically expressed Deformed does not activate the gene in other regions of the embryo. We conclude from this and other observations that additional factors may be required to activate the target gene, and, therefore, Deformed may participate in either a combinatorial or hierarchical activation signal in the maxillary cells. This newly identified gene encodes a novel protein of unknown function, though proteins with similar amino acid composition have been found. The pattern of transcript accumulation during embryogenesis indicates that this gene may be regulated by other homeoproteins in addition to Deformed.
Analysis of the gooseberry locus in Drosophila embryos: gooseberry determines the cuticular pattern and activates gooseberry neuro
Authors: Gutjahr Thomas , Patel Nipam H. , Li Xuelin , Goodman Corey S. , Noll Markus 
Published: April 2021

ABSTRACT
The segment-polarity class of segmentation genes in Drosophila are primarily involved in the specification of sub-segmental units. In addition, some of the segmentpolarity genes have been shown to specify cell fates within the central nervous system. One of these loci, gooseberry, consists of two divergently transcribed genes, gooseberry and gooseberry neuro, which share a paired box as well as a paired-type homeobox. Here, the expression patterns of the two gooseberry gene products are described in detail. The gooseberry protein appears in a characteristic segment-polarity pattern of stripes at gastrulation and persists until head involution. It is initially restricted to the ectodermal and neuroectodermal germ layer, but is later detected in mesodermal and neuronal cells as well. The gooseberry neuro protein first appears during germ band extension in cells of the central nervous system and also, much later, in epidermal stripes and in a small number of muscle cells. P-elementmediated transformation with the gooseberry gene has been used to demonstrate that gooseberry transactivates gooseberry neuro and is sufficient to rescue the gooseberry cuticular phenotype in the absence of gooseberry neuro.
Isolation of the murine cyclin B2 cDNA and characterization of the lineage and temporal specificity of expression of the B1 and B2 cyclins during oogenesis, spermatogenesis and early embryogenesis
Authors: Chapman Deborah L. , Wolgemuth Debra J. 
Published: April 2021

ABSTRACT
A cDNA encoding the murine cyclin B2 (cycB2) was isolated from an adult mouse testis cDNA library as part of studies designed to identify cyclins involved in murine germ cell development. This cycB2 cDNA was then used to examine the pattern of cycB2 expression during male and female germ cell development and in early embryogenesis, and to compare this expression with the previously characterized expression of cycB1. A single 1.7 kb cycB2 transcript was detected by northern blot hybridization analysis of total RNA isolated from midgestation embryos and various adult tissues. Northern blot and in situ hybridization analyses revealed that cycB2 expression in the testis was most abundant in the germ cells, specifically in pachytene spermatocytes. This is in contrast to the highest levels of expression of cycB1 being present in early spermatids. In situ analysis of the ovary revealed cycB2 transcripts in both germ cells and somatic cells, specifically in the oocytes and granulosa cells of growing and mature follicles. The pattern of cycB1 and cycB2 expression in ovulated and fertilized eggs was also examined. While the steady state level of cycB1 and cycB2 signal remained constant in oocytes and ovulated eggs, signal of both appeared to decrease following fertilization. In addition, both cycB1 and cycB2 transcripts were detected in the cells of the inner cell mass and the trophectoderm of the blastocyst. These results demonstrate that there are lineageand developmental-specific differences in the pattern of the B cyclins in mammalian germ cells, in contrast to the coexpression of B cyclins in the early conceptus.
Isolated sequences from the linked Myf-5 and MRF4 genes drive distinct patterns of muscle-specific expression in transgenic mice
Authors: Patapoutian Ardem , Miner Jeffrey H. , Lyons Gary E. , Wold Barbara 
Published: April 2021

ABSTRACT
In developing mouse embryos, MyoD family regulatory genes are expressed specifically in muscle precursors and mature myofibers. This pattern, taken together with the well-established ability of MyoD family members to convert a variety of cell types to skeletal muscle, suggests a significant role for these genes in regulating skeletal myogenesis. The possibility that expression of these genes may be causally associated with segregation of the myogenic lineage from other mesodermal derivatives, or with the subsequent maintenance of muscle phenotypes at later times, raises the issue of how MyoD family genes are themselves regulated during development. In this work, we have initiated studies to identify DNA sequences that govern Myf-5 and MRF4 (herculin, myf-6) transcription. Myf-5 is the first of the MyoD family to be expressed in the developing mouse embryo, while MRF4 is the most abundantly expressed myogenic factor in postnatal animals. In spite of their strikingly divergent patterns of expression, Myf-5 and MRF4 are tightly linked in the mouse genome; their translational start codons are only 8.5 kilobases apart. Here, the 5′ flanking regions of the mouse Myf-5 and MRF4 genes were separately linked to a bacterial β-galactosidase (lacZ) gene, and these constructs were each used to produce several lines of transgenic mice. Transgene expression was monitored by X-gal staining of whole embryos and by in situ hybridization of embryo sections. For the Myf-5/lacZ lines, the most intense transgene expression was in the visceral arches and their craniofacial muscle derivatives, beginning at day 8.75 post coitum (p.c.). This correlates with endogenous Myf-5 expression in visceral arches. However, while Myf-5 is also expressed in somites starting at day 8 p.c., transgene expression in the trunk is not observed until day 12 p.c. Thus, the Myf-5/lacZ construct responds to early Myf-5 activators in the visceral arches but not in the somites, suggesting that myogenic determination in the nonsomitic head mesoderm may be under separate control from that of the somitic trunk mesoderm. MRF4/lacZ lines displayed an entirely different pattern from Myf-5. Transgene expression appeared in muscles starting at day 16.5 p.c. and became increasingly prominent at later times. However, an early wave of myotomal expression that is characteristic of the endogenous MRF4 was not recapitulated by the transgene.
Two distinct populations of prestalk cells within the tip of the migratory Dictyostelium slug with differing fates at culmination
Authors: Early Anne E. , Gaskell Michael J. , Traynor David , Williams Jeffrey G. 
Published: April 2021

ABSTRACT
The ecmA gene of Dictyostelium encodes an extracellular matrix protein and is selectively expressed in prestalk cells. We show that its promoter contains discrete elements that direct expression in different subpopulations of prestalk cells. Prestalk(pst)A cells occupy the front half of the prestalk region. Expression in pstA cells requires DNA sequences close to the cap site of the gene and a separate, upstream region that acts in combination with the gene proximal sequences. PstO cells are situated in the rear half of the prestalk region and at least two separate and redundant promoter regions direct expression within them. All constructs that are expressed in pstO cells are also expressed in anteriorlike cells (ALCs); cells that resemble prestalk cells but which are scattered throughout the prespore region.
This observation suggests that pstO cells and ALCs may be very similar in their properties. If development occurs under conditions in which a migratory slug is not formed, there is an ordered movement of cells into the stalk tube. PstA cells enter the stalk tube first, followed by a proportion of the pstO cells. The remainder of the pstO cells contribute to the upper cup, an ALC-derived subpopulation of prestalk cells which is located at the apex of the spore head. After prolonged slug migration, a discrete pstO zone appears not to be maintained and, at culmination, pstO cells are found scattered throughout the stalk.
Targeted gene expression as a means of altering cell fates and generating dominant phenotypes
Authors: Brand Andrea H. , Perrimon Norbert 
Published: April 2021

ABSTRACT
We have designed a system for targeted gene expression that allows the selective activation of any cloned gene in a wide variety of tissueand cell-specific patterns. The gene encoding the yeast transcriptional activator GAL4 is inserted randomly into the Drosophila genome to drive GAL4 expression from one of a diverse array of genomic enhancers. It is then possible to introduce a gene containing GAL4 binding sites within its promoter, to activate it in those cells where GAL4 is expressed, and to observe the effect of this directed misexpression on development. We have used GAL4-directed transcription to expand the domain of embryonic expression of the homeobox protein even-skipped. We show that even-skipped represses wingless and transforms cells that would normally secrete naked cuticle into denticle secreting cells. The GAL4 system can thus be used to study regulatory interactions during embryonic development. In adults, targeted expression can be used to generate dominant phenotypes for use in genetic screens. We have directed expression of an activated form of the Dras2 protein, resulting in dominant eye and wing defects that can be used in screens to identify other members of the Dras2 signal transduction pathway.
In vitro stalk cell differentiation in wild-type and ‘slugger’ mutants of Dictyostelium discoideum
Authors: Inouye Kei , Gross Julian 
Published: April 2021

ABSTRACT
In ‘slugger’ mutants of Dictyostelium discoideum, aggregates of cells remain for an abnormally long time in the migratory phase under conditions where wild-type aggregates form fruiting bodies. In the present work, we have examined the relationship between the defect in fruiting body formation in these mutants and their ability to form mature stalk cells. We dissociated anterior cells from slugs of the mutants and their parents and tested their ability to form stalk cells when incubated at low density in the presence of (1) the stalk cell morphogen Differentiation Inducing Factor-1 (DIF1) together with cyclic AMP, or (2) 8-Br-cAMP, which is believed to penetrate cell membrane and activate cAMPdependent protein kinase (PKA).
Most of the mutants were markedly defective in forming stalk cells in response to DIF-1 plus cAMP, confirming a close relationship between fruiting body formation and stalk cell maturation. On the other hand, many of these same mutants formed stalk cells efficiently in response to 8-Br-cAMP. This supports evidence for an essential role of PKA in stalk cell maturation and fruiting body formation. It also indicates that many of the mutants owe their slugger phenotype to defects in functions required for optimal adenylyl cyclase activity.
The role of the monopteros gene in organising the basal body region of the Arabidopsis embryo
Authors: Berleth Thomas , Jürgens Gerd 
Published: April 2021

ABSTRACT
The monopteros (mp) gene contributes to apical-basal pattern formation in the Arabidopsis embryo. mp mutant seedlings lack basal body structures such as hypocotyl, radicle and root meristem, and this pattern deletion has been traced back to alterations in the octant-stage embryo. Cells of the embryo proper and the uppermost cell of the suspensor fail to establish division patterns that would normally generate the basal body structures. The resulting absence of a morphological axis seems to be responsible for another phenotypic trait of mp seedlings, variable positioning of cotyledons. This relationship is suggested by weak mp seedling phenotypes in which the presence of a short hypocotyl is correlated with normal arrangement of cotyledons. Root formation has been induced in mp seedlings grown in tissue culture. This result supports the notion that the mp gene is required for organising the basal body region, rather than for making the root, in the developing embryo.
Histological studies on the development of retinotectal projections from nasoventral quarter-eyes in Xenopus laevis
Authors: Degen N. , Brändle K. , Peter L. 
Published: April 2021

ABSTRACT
In Xenopus larvae, the size and location of the retinotectal projection of nasoventral quarter-eyes was analyzed in early stages (43–47), midlarval stages (50 and 53) and metamorphic stages (56 and 60), by labelling the optic nerve with the cobalt-lysine complex or with horseradish-peroxidase (HRP). For direct comparison, both fragment and normal eye projections were determined simultaneously in the same specimen in brain whole mounts. During early stages (up to stage 47), the projection fields of normal eyes and quarter-eyes are confined to the rostral part of the tectum. The extension of the projection in rostrocaudal direction of eye fragments does not differ from that of normal eyes. During later development up to metamorphosis, normal eyes expand their projection over the newly formed tectal surface in a caudal direction, whereas the fiber terminations of nasoventral quarter-eyes still remain in the rostral part of the tectum. Quantitative studies revealed that there is no difference in the size of both halves of the tectum. At least for quarter-eyes, however, a strict correlation between eye size and extension of the contralateral projection field could be established. According to our results, it is unlikely that during development local tectal markers are involved in determining the location of the projection field and the retinotopic ordering of the optic fibers. Instead we suggest that the optic fibers separate in accordance with their retinal specificity.
Molecular characterization of the lethal of scute genetic function
Authors: Martín-Bermudo D. María , González Francisco , Domínguez María , Rodríjuez Isabel , Ruiz-Gômez Mar , Romani Susana , Modolell Juan , Jiménez Fernando 
Published: April 2021

ABSTRACT
The lethal of scute (l’sc) genetic function, which plays an essential role in the early development of the central nervous system of the Drosophila embryo, is localized within the achaete-scute complex (AS-C). Several lines of evidence have suggested that the AS-C T3 transcription unit corresponds to the l’sc function. We demonstrate that short fragments of DNA, containing the T3 transcribed region and a few kilobases of flanking sequences, rescue, albeit partially, the lethality and neural phenotype of l’sc deletions. Still, the complex wild-type pattern of expression of T3 is not reproduced by the transduced genes. This depends on cis-control elements scattered within the entire AS-C DNA and intermingled with regulatory elements specific for other AS-C transcription units. These elements are necessary for the initial activation of T3 in the neuroectoderm, probably mediated by axis-patterning genes. The presence of a cluster of E-boxes, upstream of the T3 transcribed region, suggests another level of control of T3 expression by basic-helix-loop-helix proteins, among them its own gene product.
Segmental migration of the hindbrain neural crest does not arise from its segmental generation
Authors: Sechrist J. , Serbedzija G. N. , Scherson T. , Fraser S. E. , Bronner-Fraser M. 
Published: April 2021

ABSTRACT
The proposed pathways of chick cranial neural crest migration and their relationship to the rhombomeres of the hindbrain have been somewhat controversial, with differing results emerging from grafting and DiI-labelling analyses. To resolve this discrepancy, we have examined cranial neural crest migratory pathways using the combination of neurofilament immunocytochemistry, which recognizes early hindbrain neural crest cells, and labelling with the vital dye, DiI. Neurofilament-positive cells with the appearance of premigratory and early-migrating neural crest cells were noted at all axial levels of the hindbrain. At slightly later stages, neural crest cell migration in this region appeared segmented, with no neural crest cells obvious in the mesenchyme lateral to rhombomere 3 (r3) and between the neural tube and the otic vesicle lateral to r5. Focal injections of DiI at the levels of r3 and r5 demonstrated that both of these rhombomeres generated neural crest cells. The segmental distribution of neural crest cells resulted from the DiI-labelled cells that originated in r3 and r5 deviating rostrally or caudally and failing to enter the adjacent preotic mesoderm or otic vesicle region. The observation that neural crest cells originating from r3 and r5 avoided specific neighboring domains raises the intriguing possibility that, as in the trunk, extrinsic factors play a major role in the axial patterning of the cranial neural crest and the neural crest-derived peripheral nervous system.
Analyses of PS integrin functions during Drosophila development
Authors: Zusman Susan , Grinblat Yevgenya , Yee Gene , Kafatos Fotis C. , Hynes Richard O. 
Published: April 2021

ABSTRACT
The Drosophila position-specific (PS) antigens are homologues of the vertebrate integrins, a family of trans-membrane proteins that function in cell-matrix and cell-cell adhesion. The common β subunit of PS integrins (PSβ) is encoded by the lethal(l)myospheroid gene (mys) and is required during wing, eye and muscle development. By expressing PSβ protein at defined developmental periods, we have shown that PS integrins are required throughout pupation, but not earlier, for normal development of wings. In contrast, the key requirement for PS integrins in eye development occurs only in the late pupa. Furthermore, PS integrins are apparently not required for the differentiation of the ommatidial cells; only for their organization. These results are consistent with roles for PS integrins in the interactions between the wing epithelia during the two phases of pupal wing expansion and in maintaining the attachment of a fully formed fenestrated membrane to the basement membrane of the retina.
We have also examined the functional significance of alternative splicing of the transcript of the mys gene using P element-mediated transformation to introduce transgenes producing only one of the two spliced forms of PSβ. We find that either form is sufficient to rescue postem-bryonic mys phenotypes in the wing, eye and muscle but that both of the two splice forms are necessary to rescue the mys embryonic defects. This result indicates a requirement for the alternative splicing of mys during embryogenesis. The location of the alternative exons suggests that the two forms of the PSβ integrin subunit may interact with alternative α subunits and/or ligands.
A common precursor for glia and neurons in the embryonic CNS of Drosophila gives rise to segment-specific lineage variants
Authors: Udolph Gerald , Prokop Andreas , Bossing Torsten , Technau Gerhard M. 
Published: April 2021

ABSTRACT
The nervous system consists of two classes of cells, neurons and glia, which differ in morphology and function. They derive from precursors located in the neurogenic region of the ectoderm. In this study, we present the complete embryonic lineage of a neuroectodermal precursor in Drosophila that gives rise to neurons as well as glia in the abdominal CNS. This lineage is conserved among different Drosophila species. We show that neuronal and glial cell types in this clone derive from one segregating precursor, previously described as NB1-1. Thus, in addition to neuroblasts and glioblasts, there exists a third class of CNS precursors in Drosophila, which we call neuroglioblasts. We further show that the NB 1-1 lineage exhibits characteristic segment-specific differences on the cellular level.