bluuebunny/crossref_metadata_2025_split huggingface dataset:
Motor neuron pathfinding following rhombomere reversals in the chick embryo hindbrain
Authors: Guthrie Sarah , Lumsden Andrew 
Published: April 2021

ABSTRACT
Motor neurons are segmentally organised in the developing chick hindbrain, with groups of neurons occupying pairs of hindbrain segments or rhombomeres. The branchiomotor nucleus of the trigeminal nerve occupies rhombomeres 2 and 3 (r2 and r3), that of the facial nerve r4 and r5, and that of the glossopharyngeal nerve r6 and r7. Branchiomotor neuron cell bodies lie within the basal plate, forming columns on either side of the ventral midline floor plate. Axons originating in rhombomeres 2, 4 and 6 grow laterally (dorsally) towards the exit points located in the alar plates of these rhombomeres, while axons originating in odd-numbered rhombomeres 3 and 5 grow laterally and then rostrally, crossing a rhombomere boundary to reach their exit point. Examination of the trajectories of motor axons in odd-numbered segments at late stages of development (19-25) showed stereotyped pathways, in which axons grew laterally before making a sharp turn rostrally. During the initial phase of outgrowth (stage 14-15), however, axons had meandering courses and did not grow in a directed fashion towards their exit point. When r3 or r5 was transplanted with reversed rostrocaudal polarity prior to motor axon outgrowth, the majority of axons grew to their appropriate, rostral exit point, despite the inverted neuroepithelial polarity. In r3 reversals, however, there was a considerable increase in the normally small number of axons that grew out via the caudal, r4 exit point. These findings are discussed with relevance to the factors involved in motor neuron specification and axon outgrowth in the developing hindbrain.
Early mRNAs, spatially restricted along the animal-vegetal axis of sea urchin embryos, include one encoding a protein related to tolloid and BMP-1
Authors: Reynolds Susan D. , Angerer Lynne M. , Palis James , Nasir Adnan , Angerer Robert C. 
Published: April 2021

ABSTRACTThe cloning and characterization of cDNAs representing four genes or small gene families that are coordinately expressed in a spatially restricted pattern during the very early blastula (VEB) stage of sea urchin development are presented. The VEB genes encode multiple transcripts that are expressed transiently in embryos of Strongylocentrotus purpuratus between 16-cell stage and hatching, with peak abundance 12 to 15 hours postfertilization (∼150-250 cells). The VEB transcripts share the same spatial pattern in the early blastula embryo: they are asymmetrically distributed along the animalvegetal axis but their distribution around this axis is uniform. Thus, the VEB transcripts are the earliest messages to reveal asymmetry along the primary axis in the sea urchin embryo. The temporal and spatial patterns of VEB transcript accumulation are not consistent with involvement of these gene products in cell division or in tissue-specific functions. Furthermore, VEB messages cannot be detected in either ovary or adult tissues, suggesting that these genes function exclusively during embryogenesis. We suggest that the VEB genes function in constructing the early blastula. Two VEB genes encode metalloendoproteases: one (SpHE) is hatching enzyme and the other (SpAN) is similar to bone morphogenetic protein-1 (BMP-1; Wozney et al., Science 242: 1528-1534, 1988) and the Tolloid gene product (tld) (Shimell et al., Cell 67: 459482, 1991). Several lines of evidence suggest that the VEB genes are regulated directly by factors or regulatory activities localized along the maternally specificed animal-vegetal axis.
Effects of W (c-kit) gene mutation on gametogenesis in male mice: agametic tubular segments in Wf/Wf testes
Authors: Koshimizu Uichi , Watanabe Daisuke , Tajima Youichi , Nishimune Yoshitake 
Published: April 2021

Abstract
Mutations of the W (e-kit) gene, which encodes a transmembrane tyrosine kinase receptor, affect the development and differentiation of many types of stem cell. Most homozygous W mutant mice are sterile, due to a lack of germ cells arising during embryonic development, but one of the notable exceptions is mice, which are fully fertile in both sexes. In order to elucidate the effects of the Wf mutation on spermatogenesis, postnatal spermatogenesis in Wf/Wf mice was histologically examined. The number of gonocytes at birth was significantly reduced and small portions of agametic seminiferous tubule segments were observed in mutant mice. It is suggested that this is due to a deficiency of primordial germ cells (PGC). Other than the agametic tubules, there was no evidence of reduced spermatogenesis after birth. These results indicate that the function of the W (e-kit) gene is more necessary for the development of PGC than for postnatal germ cells.
The mouse has a Polycomb-Wke chromobox gene
Authors: Pearce Jonathan J. H. , Singh Prim B. , Gaunt Stephen J. 
Published: April 2021

Abstract
The Drosophila gene Polycomb (Pc) has been implicated in the clonal inheritance of determined states and is a trans-regulator of the Antennapedia-like homeobox genes. Pc shares a region of homology (the chromobox) with the Drosophila gene Heterochromatin Protein 1 (HP1), a component of heterochromatin. The Pc chromobox has been used to isolate a mouse chromobox gene, M33, which encodes a predicted 519 amino acid protein. The M33 chromodomain is more similar to that in the Pc protein, than that in the HP1 protein. In addition to the chromodomain, the M33 and Pc proteins also share a region of homology at their C termini. The temporal and spatial expression patterns of M33 have been studied by in situ hybridization and northern analysis. During the final 10 days of embryonic development, M33 expression mirrors that of the cellcycle-specific cyclin B gene. It is therefore suggested that the rate of cellular proliferation controls M33 expression. From comparisons of the characteristics of M33 with those of Pc it is proposed that M33 is a Pc-like chromobox gene. The roles of M33 and Pc in models of cellular memory are examined and implications of the memory models addressed.
Afferent influences on cell death and birth during development of a cortical nucleus necessary for learned vocal behavior in zebra finches
Authors: Johnson Frank , Bottjer Sarah W. 
Published: April 2021

ABSTRACT
Forebrain nuclei that control learned vocal behavior in zebra finches are anatomically distinct and interconnected by a simple pattern of axonal pathways. In the present study, we examined afferent regulation of neuronal survival during development of the robust nucleus of the archistriatum (RA). RA projection neurons form the descending motor pathway of cortical vocal-control regions and are believed to be directly involved in vocal production. RA receives afferent inputs from two other cortical regions, the lateral magnocellular nucleus of the anterior neostriatum (lMAN) and the higher vocal center (HVC). However, because the ingrowth of HVC afferent input is delayed, lMAN projection neurons provide the majority of afferent input to RA during early vocal learning. lMAN afferent input to RA is of particular interest because lMAN is necessary for vocal learning only during a restricted period of development. By making lesions of lMAN in male zebra finches at various stages of vocal development (20-60 days of age) and in adults (&gt;90-days old), we asked whether the survival of RA neurons depends on lMAN afferent input, and if so whether such dependence changes over the course of vocal learning. The results showed that removal of lMAN afferent input induced the loss of over 40% of RA neurons among birds in early stages of vocal development (20 days of age). However, lMAN lesions lost the ability to induce RA neuron death among birds in later stages of vocal development (40 days of age and older). These findings indicate that many RA neurons require lMAN afferent input for their survival during early vocal learning, whereas the inability of lMAN lesions to induce RA neuron death in older birds may indicate a reduced requirement for afferent input or perhaps the delayed ingrowth of HVC afferent input (at approx. 35 days of age) provides an alternate source of afferent support. Removal of lMAN afferent input also dramatically increased the incidence of mitotic figures in RA, but only among 20-day-old birds at 2 days post-lesion. The early, acute nature of the mitotic events raises the possibility that cell division in RA may be regulated by lMAN afferent input.
Ciliary neurotrophic factor and leukemia inhibitory factor promote the generation, maturation and survival of oligodendrocytes in vitro
Authors: Mayer Margot , Bhakoo Kishore , Noble Mark 
Published: April 2021

ABSTRACT
We have found that CNTF and LIF are pleiotropic modulators of development in the O-2A lineage. Both molecules enhanced the generation of oligodendrocytes in cultures of dividing O-2A progenitors. CNTF and LIF also promoted oligodendrocyte maturation, as determined by expression of myelin basic protein, and could promote oligodendrocyte survival to an extent comparable with insulin-like growth factor-1 or insulin. In addition, LIF and CNTF both promoted the differentiation of O-2A progenitors into type-2 astrocytes but only when applied in the presence of extra-cellular matrix (EnMx) derived from cultures of endo-thelial cells. The ability of CNTF and LIF to enhance differentiation of O-2A progenitors along either of the alternative pathways of oligodendrocyte and astrocyte differentiation suggests that these proteins are able to enhance the process of differentiation per se, while the actual path of differentiation promoted is determined by the presence or absence of additional molecules in the extracellular environment.
A novel member of the transmembrane serine/threonine kinase receptor family is specifically expressed in the gonads and in mesenchymal cells adjacent to the müllerian duct
Authors: Baarends Willy M. , Helmond Marjolein J. L. van , Post Miriam , Schoot Pieter J. C. M. van der , Hoogerbrugge Jos W. , Winter Johan P. de , Uilenbroek Jan Th. J. , Karels Bas , Wilming Laurens G. , Meijers J. H. Carel , Themmen Axel P. N. , Grootegoed J. Anton 
Published: April 2021

ABSTRACT
The activin and TGF-β type II receptors are members of a separate subfamily of transmembrane receptors with intrinsic protein kinase activity, which also includes the recently cloned TGF-β type I receptor. We have isolated and characterized a cDNA clone (C14) encoding a new member of this subfamily. The domain structure of the C14-encoded protein corresponds with the structure of the other known transmembrane serine/threonine kinase receptors. It also contains the two inserts in the kinase domain that are characteristic for this subfamily. Using in situ hybridization, C14 mRNA was detected in the mesenchymal cells located adjacent to the müllerian ducts of males and females at day 15 (E15) of embryonic development. Marked C14 mRNA expression was also detected in the female gonads. In female E16 embryos, the C14 mRNA expression pattern remained similar to that in E15 embryos. However, in male E16 embryos C14 mRNA was detected in a circular area that includes the degenerating müllerian duct. The expression of C14 mRNA was also studied using RNase protection assays. At E15 and E16, C14 mRNA is expressed in the female as well as in the male urogenital ridge. However, at E19, a high C14 mRNA level in the female urogenital ridge contrasts with a lack of C14 mRNA in the male urogenital ridge. This correlates with the almost complete degeneration of the müllerian ducts in male embryos at E19. C14 mRNA expression was also detected in embryonic testes at E15, E16 and E19 using RNase protection assays, but at much lower levels than those found in the developing ovaries. In eleven other tissues no C14 mRNA was observed.
The results point to anti-müllerian hormone (AMH) being the most likely candidate ligand for C14. The embryonic C14 mRNA expression pattern in the urogenital ridge correlates with the expected site of AMH action, and C14 mRNA expression in the fetal ovary is in agreement with known effects of AMH on gonadal differentiation.
Postnatal C14 mRNA expression in rats was found to be confined mainly to the gonads. In the testis, C14 mRNA expression occurs in Sertoli cells. This testicular expression markedly increases during the first 3 weeks after birth, concurrent with the onset of spermatogenesis.
Neurogenic expression of snail is controlled by separable CNS and PNS promoter elements
Authors: Tony Ip Y. , Levine Michael , Bier Ethan 
Published: April 2021

ABSTRACT
The Drosophila snail (sna) gene is first expressed in cells giving rise to mesoderm and is required for mesoderm formation. sna is subsequently expressed in the developing nervous system. sna expression during neurogenesis evolves from segmentally repeated neuroectodermal domains to a pan-neural pattern. We have identified a 2.8kb regulatory region of the sna promoter that drives LacZ expression in a faithful neuronal pattern. Deletion analysis of this region indicates that the pan-neural element is composed of separable CNS and PNS components. This finding is unexpected since all known genes controlling early neurogenesis, including the proneural genes (i.e. da and AS-C), are expressed in both the CNS and PNS. We also show that expression of sna during neurogenesis is largely independent of the proneural genes da and AS-C. The separate control of CNS and PNS sna expression and independence of proneural gene regulation add to a growing body of evidence that current genetic models of neurogenesis are substantially incomplete.
Bone morphogenetic proteins and a signalling pathway that controls patterning in the developing chick limb
Authors: Francis Philippa H. , Richardson Michael K. , Brickell Paul M. , Tickle Cheryll 
Published: April 2021

ABSTRACT
We show here that bone morphogenetic protein 2 (BMP-2) is involved in patterning the developing chick limb. During early stages of limb development, mesenchymal expression of the Bmp-2 gene is restricted to the posterior part of the bud, in a domain that colocalizes with the polarizing region. The polarizing region is a group of cells at the posterior margin of the limb bud that can respecify the anteroposterior axis of the limb when grafted anteriorly and can activate expression of genes of the HoxD complex. We dissect possible roles of BMP-2 in the polarizing region signalling pathway by manipulating the developing wing bud. Retinoic acid application, which mimics the effects of polarizing region grafts, activates Bmp-2 gene expression in anterior cells. This shows that changes in anteroposterior pattern are correlated with changes in Bmp-2 expression. When polarizing region grafts are placed at the anterior margin of the wing bud, the grafts continue to express the Bmp-2 gene and also activate Bmp-2 expression in the adjacent anterior host mesenchyme. These data suggest that BMP-2 is part of the response pathway to the polarizing signal, rather than being the signal itself. In support of this, BMP-2 protein does not appear to have any detectable polarizing activity when applied to the wing bud. The pattern of Bmp-4 gene expression in the developing wing bud raises the possibility that BMP-2 and BMP-4 could act in concert. There is a close relationship, both temporal and spatial, between the activation of the Bmp-2 and Hoxd-13 genes in response to retinoic acid and polarizing region grafts, suggesting that expression of the two genes might be linked.
Expression of the zebrafish gene hlx-1 in the prechordal plate and during CNS development
Authors: Fjose Anders , Izpisúa-Belmonte Juan-Carlos , Fromental-Ramain Catherine , Duboule Denis 
Published: April 2021

ABSTRACT
The zebrafish hlx-1 gene belongs to the H2.0 subfamily of homeobox genes and is closely related to the mouse Dbx gene with respect to both homeodomain homology (96.7%) and neural expression during embryogenesis. Analysis of hlx-1 expression by in situ hybridization reveals several particularly interesting features. In late gastrula embryos, hlx-1 transcripts are detected within a circular area in the region of the presumptive rostral brain. Subsequently, the expression domain becomes restricted to the hypoblast and undergoes dynamic changes involving conversion into a longitudinal stripe which elongates and retracts following a temporal sequence. The site of transient hlx-1 expression along the ventral midline of the rostral neurectoderm, which in part corresponds to the prechordal plate, suggests a role in the determination of head mesoderm as well as in patterning of the rostral brain. As the midline stripe gradually disappears, the hlx-1 gene becomes regionally expressed within the diencephalon and at a specific dorsoventral level along the hindbrain and spinal cord. In the hindbrain, expression is initiated in dorsoventrally restricted transversal stripes which correlate with the segmental pattern of rhombomeres. The stripes fuse into bilateral columns that are later converted to two series of paired transversal stripes at the rhombomere borders. This pattern is consistent with the proposed subdivision of hindbrain segments into rhombomere centers separated by border regions.
Cell cycles and clonal strings during formation of the zebrafish central nervous system
Authors: Kimmel Charles B. , Warga Rachel M. , Kane Donald A. 
Published: April 2021

ABSTRACT
Cell lineage analysis of central nervous system progenitors during gastrulation and early segmentation in the zebrafish reveals consistent coupling of specific morphogenetic behaviors with particular cell cycles. Cells in single clones divide very synchronously. Cell divisions become progressively oriented, and act synergistically with oriented intercalations during the interphases of zygotic cell cycles 15 and 16 to extend a single lineage into a long, discontinuous string of cells aligned with the nascent embryonic axis. Dorsalwards convergence brings the string to the midline and, once there, cells enter division 16. This division, or sometimes the next one, and the following cell movement reorient to separate siblings across the midline. This change converts the single string into a bilateral pair of strings, one forming a part of each side of the neural tube. The stereotyped cellular behaviors appear to account for the previously reported clonal restriction in cell fate and to underlie morphogenesis of a midline organ of proper length and bilateral shape. Regulation of cellular morphogenesis could be cell-cycle dependent.
A maternal homeobox gene, Bombyx caudal, forms both mRNA and protein concentration gradients spanning anteroposterior axis during gastrulation
Authors: Xu Xin , Xu Pin-Xian , Suzuki Yoshiaki 
Published: April 2021

ABSTRACT
We have isolated a caudal (cad) homologue from a cDNA library of Bombyx mori embryos. The Bombyx cad cDNA encodes a protein of 244 amino acids. The homology between Drosophila and Bombyx homeodomains is 80%. Similar to Drosophila cad, there is no YPWM peptide sequence along the upstream of homeodomain. Northern blot hybridization with a Bombyx cad probe revealed the presence of single maternal transcript of 2.3 kb. A stronger signal of the transcripts was detected in unfertilized eggs and in eggs up to 36 hours after deposition. The transcripts decreased rapidly by 2 days and a weak signal was maintained until hatching. To analyse its spatial expression pattern, we have established a novel frozen sectioning method for in situ hybridization and immunohistochemistry experiments. The results showed that Bombyx cad transcripts accumulated first in the nurse cells and transferred into the oocyte at a defined time during oogenesis. The maternal transcripts of Bombyx cad formed a concentration gradient spanning the anteroposterior axis during the gastrulation stage and were restricted to the anal pad, the most posterior domain, after 2 days of embryogenesis; the Drosophila cad mRNA revealed the corresponding expression profile during the syncytial blastoderm stage. The Bombyx cad protein was not detected in the ovary and the first 9 hours of eggs, but was first detected evenly during cellular blastoderm stage. During gastrulation, Bombyx cad protein concentration gradients shifted along the anteroposterior axis coinciding with the shifting of the mRNA concentration gradients. This is the first example of a concentration gradient along anteroposterior axis that may be involved in segmentation in insect embryos other than the long germ-band type. A comparison of the timing and conservation of mRNA as well as protein gradient formation in Drosophila and Bombyx might help to explain differences in the body plans and give some clues to elucidate the mechanism and function related to mRNA and protein concentration gradients.
bcl-2 protein expression is widespread in the developing nervous system and retained in the adult PNS
Authors: Merry Diane E. , Veis Deborah J. , Hickey William F. , Korsmeyer Stanley J. 
Published: April 2021

ABSTRACT
Cell death is a common feature of neural development in all vertebrates. The bcl-2 proto-oncogene has been shown to protect a variety of cell types from programmed cell death. We have examined the distribution of bcl-2 protein in the developing and adult nervous systems. bcl-2 protein is widespread during embryonic development. Proliferating neuroepithelial cells of ventricular zones as well as the postmitotic cells of the cortical plate, cerebellum, hippocampus and spinal cord express bcl-2. Postnatally, bcl-2 is principally retained in the granule cells of the cerebellum and dentate gyrus of the hippocampus. bcl-2 expression in the CNS declines with aging. In the peripheral nervous system, neurons and supporting cells of sympathetic and sensory ganglia retain substantial bcl-2 protein throughout life. The widespread expression of bcl-2 in CNS and PNS neurons during embryonic development and its selective retention in the adult PNS is consistent with a role for bcl-2 in regulating neuronal survival. In addition, the expression of bcl-2 in some neuronal populations beyond the recognized period of cell death is suggestive of a role for bcl-2 beyond simply protecting neurons from developmental cell death.
Cell contact regulates neuroblast formation in the Caenorhabditis elegans lateral epidermis
Authors: Austin Judith , Kenyon Cynthia 
Published: April 2021

ABSTRACT
A single line of epidermal seam cells lies along each side of the nematode C. elegans. During normal development, one of these cells, V5, produces a neuroblast that will give rise to a sensory structure, the postdeirid. If seam cells located either anterior or posterior to V5 are ablated however, this neuroblast formation is blocked. Because of this requirement for the presence of adjacent seam cells, we have asked whether V5’s ability to produce a neuroblast depends on direct contact with its seam cell neighbors. We find that direct contact between seam cells is required for commitment to neuroblast production. Seam cells lose and reform their contacts with each other as they go through rounds of cell division during larval development. Signaling required for neuroblast formation occurs when the seam cells make contact after their first round of division. If this contact is prevented, no neuroblast is made; when it is delayed, the time of signaling is also delayed. The characteristics of these signals suggest that a seam cell must be part of a continuous epithelium in order to develop normally and that signaling may occur via a cell recognition/cell adhesion pathway. The effect of seam cell ablations on neuroblast formation is altered in mab-5(–) animals, suggesting that this HOM-C gene is part of the pathway by which seam cell signaling controls the decision to make a postdeirid neuroblast.