pinecone/core-2020-05-10-deduplication huggingface dataset:
Loss-of-Function Mutations Reveal That the Drosophila nautilus Gene Is Not Essential for Embryonic Myogenesis or Viability

Abstractnautilus (nau), the single Drosophila member of the bHLH-containing myogenic regulatory family of genes, is expressed in a subset of muscle precursors and differentiated fibers. It is capable of inducing muscle-specific transcription as well as myogenic transformation, and plays a role in the differentiation of a subset of muscle precursors into mature muscle fibers. In previous studies, the nau zygotic loss-of-function phenotype was determined using genetic deficiencies in which the gene is deleted. We note that this genetic loss-of-function phenotype differs from the loss-of-function phenotype determined using RNA interference (L. Misquitta and B. M. Paterson, 1999, Proc. Natl. Acad. Sci. USA 96, 1451–1456). The present study re-examines this loss-of-function phenotype using EMS-induced mutations that specifically alter the nau gene, and extends the genetic analysis to include the loss of both maternal and zygotic nau function. In brief, embryos lacking nau both maternally and zygotically are missing a distinct subset of muscle fibers, consistent with its apparent expression in a subset of muscle fibers. The muscle loss is tolerated, however, such that the loss of nau both maternally and zygotically does not result in lethality at any stage of development
Putative Stem Cells and the Lineage of Rod Photoreceptors in the Mature Retina of the Goldfish

AbstractThe retinas of teleost fish grow continuously, in part, by neuronal hyperplasia and when lesioned will regenerate. Within the differentiated retina, the growth-associated hyperplasia results in the generation of new rod photoreceptors only, whereas injury-induced neurogenesis results in the regeneration of all retinal cell types. It is believed, however, that both new rod photoreceptors and regenerated neurons originate from the same populations of intrinsic progenitors. Experiments are described here that attempt to identify in the normal retina of goldfish neuronal progenitors intrinsic to the retina, particularly those which have remained cryptic because they divide infrequently. Long-term, systemic exposure to bromodeoxyuridine (BrdU) was used to label these cells. Five populations of proliferative cells were labeled: microglia, which are briefly described but not studied further; retinal progenitors in the circumferential germinal zone (CGZ); and rod precursors in the outer nuclear layer (ONL), both of which have been well characterized previously; and two populations of slowly-dividing cells in the inner nuclear layer (INL). The majority of these cells have a fusiform morphology, whereas the remaining ones are spherical. Longitudinal BrdU labeling suggests that the fusiform cells migrate to the ONL to replenish the pool of rod precursors. A subset of the spherical cells express pax6, although none are stained with markers of differentiated amacrine or bipolar cells. It is hypothesized that these rare, pax6-expressing cells are retinal stem cells, which give rise to the pax6-negative fusiform cells. Based on these data, two models are proposed: the first describes the lineage of rod photoreceptors in goldfish; the second is a consensus model of neurogenesis in the retinas of all teleosts
A Role for BMP Signalling in Heart Looping Morphogenesis in Xenopus

AbstractThe heart develops from a linear tubular precursor, which loops to the right and undergoes terminal differentiation to form the multichambered heart. Heart looping is the earliest manifestation of left–right asymmetry and determines the eventual heart situs. The signalling processes that impart laterality to the unlooped heart tube and thus allow the developing organ to interpret the left–right axis of the embryo are poorly understood. Recent experiments in zebrafish led to the suggestion that bone morphogenetic protein 4 (BMP4) may impart laterality to the developing heart tube. Here we show that in Xenopus, as in zebrafish, BMP4 is expressed predominantly on the left of the linear heart tube. Furthermore we demonstrate that ectopic expression of Xenopus nodal-related protein 1 (Xnr1) RNA affects BMP4 expression in the heart, linking asymmetric BMP4 expression to the left–right axis. We show that transgenic embryos overexpressing BMP4 bilaterally in the heart tube tend towards a randomisation of heart situs in an otherwise intact left–right axis. Additionally, inhibition of BMP signalling by expressing noggin or a truncated, dominant negative BMP receptor prevents heart looping but allows the initial events of chamber specification and anteroposterior morphogenesis to occur. Thus in Xenopus asymmetric BMP4 expression links heart development to the left–right axis, by being both controlled by Xnr1 expression and necessary for heart looping morphogenesis
Regulation of Transcription Factors MHR4 and βFTZ-F1 by 20-Hydroxyecdysone during a Larval Molt in the Tobacco Hornworm, Manduca sexta

AbstractDuring the last larval molt in Manduca sexta, a number of transcription factors are sequentially expressed. Unlike E75A and MHR3, whose mRNAs are induced when the ecdysteroid titer increases, the expression of MHR4 mRNA occurs transiently at the onset of the decline of ecdysteroid titer followed by βFTZ-F1 mRNA expression when the ecdysteroid titer becomes low. When day 2 fourth epidermis was exposed to 20-hydroxyecdysone (20E) in vitro, MHR4 mRNA appeared between 12 and 21 h, peaked at 24 h, and then declined. Using the protein synthesis inhibitors cycloheximide and anisomycin both in vivo and in vitro, we found that the MHR4 transcript was directly induced by 20E and required the presence of 20E for its expression. The accumulation of MHR4 mRNA, however, did not occur until a 20E-induced inhibitory protein(s) disappeared. This control of MHR4 expression is unique among the ecdysone-induced transcription factors. When the epidermis was cultured with 20E, βFTZ-F1 mRNA was not induced until after the removal of 20E as previously found for Drosophila and the silkworm Bombyx mori. The presence of juvenile hormone had no effect on accumulation of either transcript
Analysis of Loss of Adhesive Function in Sperm Lacking Cyritestin or Fertilin β

AbstractWe produced mice lacking the sperm surface protein cyritestin (ADAM 3) and found mutant males are infertile. Similar to fertilin beta (ADAM 2) null sperm (C. Cho et al., 1998, Science 281, 1857–1859), cyritestin null sperm are drastically deficient in adhesion to the egg zona pellucida (0.3% of wild type) and to the egg plasma membrane (9% of wild type). Thus sperm from male mice with a gene deletion of either ADAM have a loss of adhesive function in at least two steps of fertilization. We found deletion of either ADAM gene resulted in the loss of multiple gene products. This loss of multiple gene products (sperm membrane proteins) appears to result from a novel, developmental mechanism during sperm differentiation. Because the altered sperm protein expression must be responsible for the fertilization defects, our data suggest new models for the molecular basis of the affected steps in fertilization
Analysis of Melanocyte Precursors in Nf1 Mutants Reveals That MGF/KIT Signaling Promotes Directed Cell Migration Independent of Its Function in Cell Survival

AbstractNeural crest-derived melanocyte precursors (MPs) in avian and murine embryos emerge from the dorsal neural tube into a migration staging area (MSA). MPs subsequently migrate from the MSA on a dorsolateral pathway between the dermamyotome and the overlying epithelium. In mouse embryos, MPs express the receptor tyrosine kinase, KIT, and require its cognate ligand, Mast cell growth factor (MGF), for survival and differentiation. Prior to the onset of MP migration, MGF is expressed on the dorsolateral pathway at some distance from cells in the MSA and appears to be required for normal MP development. To learn if MGF is required solely for MP survival on this pathway, or if it also provides directional cues for migration, we uncoupled survival from chemoattractive or motogenic functions of this ligand using mice that carry a targeted mutation at the Neurofibromin (Nf1) locus and consequently lack RAS-GAP function. We show that Nf1-mutant MPs survive in the absence of MGF in vitro and in vivo and that Nf1-mutant MPs disperse normally on the lateral migration pathway in the presence of MGF. In contrast, Nf1-mutant MPs persist in the location of the MSA but are not observed on the lateral migration pathway in double-mutant mice that also lack MGF. We conclude that MGF/KIT function provides a signal required for directed migration of the MPs on the lateral pathway in vivo, independent of its function in survival. We further suggest that the MGF mediates MP migration through a signaling pathway that does not involve RAS
Mice Deficient for Spermatid Perinuclear RNA-Binding Protein Show Neurologic, Spermatogenic, and Sperm Morphological Abnormalities

AbstractSpermatid perinuclear RNA-binding protein (SPNR) is a microtubule-associated RNA-binding protein that localizes to the manchette in developing spermatids. The Spnr mRNA is expressed at high levels in testis, ovary, and brain and is present in these tissues in multiple forms. We have generated a gene trap allele of the murine Spnr, named Spnr+/GT. SpnrGT/GT mutants show a high rate of mortality, reduced weight, and an abnormal clutching reflex. In addition to minor anatomical abnormalities in the brain, males exhibit defects in spermatogenesis that include a thin seminiferous epithelium and disorganization of spermatogenesis. Most of the sperm from mutant males display defects in the flagellum and consequently show decreased motility and transport within the oviducts. Furthermore, sperm from mutant males achieve in vitro fertilization less frequently. Our findings suggest that SPNR plays an important role in normal spermatogenesis and sperm function. Thus, the SpnrGT/GT mutant male mouse provides a unique model for some human male infertility cases
Bicaudal-D Is Essential for Egg Chamber Formation and Cytoskeletal Organization in Drosophila Oogenesis

AbstractBicaudal-D (Bic-D) is required for the transport of determinant mRNAs and proteins to the presumptive oocyte, an essential step in the differentiation of the oocyte. Bic-D protein contains four well-defined heptad repeat domains characteristic of intermediate filament proteins. We characterized the ovarian phenotypes of females expressing mutant Bic-D proteins (Bic-DH) deleted for each of the heptad repeat domains. The altered migration of follicle cells we observe in mutant ovaries suggests that Bic-D functions in the germline and directs the inward migration of somatic follicle cells. In the germarium Bic-D is required for the organization of the egg chamber and the structural integrity of the oocyte and nurse cells. Examination of the polarized microtubule network in Bic-DH ovaries shows thatBic-D function is required for both the establishment of the polarized microtubule network and its maintenance throughout oogenesis. To explain the multiple functions suggested by the pleiotropic Bic-D phenotype, we propose that Bic-D protein could form itself a filamentous structure and represent an integral, essential part of the cytoskeleton
Protein Tyrosine Phosphatase PTP1 Negatively Regulates Dictyostelium STATa and Is Required for Proper Cell-Type Proportioning

AbstractThe protein tyrosine phosphatase PTP1, which mediates reversible phosphorylation on tyrosine, has been shown to play an important regulatory role during Dictyostelium development. Mutants lacking PTP1 develop more rapidly than normal, while strains that overexpress PTP1 display aberrant morphology. However, the signalling pathways involved have not been characterised. In reexamining these strains, we have found that there is an inverse correlation between levels of PTP1 activity, the extent of tyrosine phosphorylation on Dictyostelium STATa after treatment with cAMP, and the proportion of the slug population exhibiting STATa nuclear enrichment in vivo. This suggests that PTP1 acts to attenuate the tyrosine phosphorylation of STATa and downstream STATa-mediated pathways. Consistent with this, we show that when PTP1 is overexpressed, there is increased expression of a prestalk cell marker at the slug posterior, a phenocopy of STATa null slugs. In ptp1 null strains, STATa tyrosine phosphorylation and nuclear enrichment in the slug anterior is increased. There is also a change in the prestalk to prespore cell ratio. Synergy experiments suggest that this is due to a cell-autonomous defect in forming the subset of prespore cells that are located in the anterior prespore region
Contribution of BDNF-Mediated Inhibition in Patterning Avian Skin Innervation

AbstractMultiple factors are involved in the development and regulation of sensory innervation in skin. The findings we report here suggest that brain-derived neurotrophic factor (BDNF)-mediated inhibition may play an important role in determining the pattern of sensory innervation in avian skin. In birds, cutaneous innervation is restricted to dermis, where axons form a ring of innervation around the base of each feather. Here we show that both BDNF message and protein are more abundant in avian epidermis than dermis when innervation is being established; the BDNF in dermis is localized to feather buds. In vitro, BDNF caused growth cones of NGF-dependent dorsal root ganglion neurons to collapse. Similarly, outgrowth of neurites toward BDNF-secreting fibroblasts was inhibited. The inhibitory effects of BDNF appear to be mediated by the low-affinity p75 neurotrophin receptor, rather than a trk receptor. Thus, the distribution of BDNF in embryonic avian skin and the inhibitory effects of BDNF on cutaneous neurites in vitro suggest that BDNF may be important in restricting axons from entering the epidermis and the core of feather buds during development in vivo
Cooperation of Endoderm-Derived BMP2 and Extraembryonic Ectoderm-Derived BMP4 in Primordial Germ Cell Generation in the Mouse

AbstractThe primordial germ cells (PGCs) of the mouse are derived from proximal epiblast cells that are adjacent to the extraembryonic ectoderm during gastrulation. Previous studies have demonstrated that extraembryonic ectoderm-derived BMP4 and BMP8B are both required for PGC generation. Here we show that Bmp2, a member of the Dpp class of the Bmp superfamily, also plays a role in PGC generation. PGC number is significantly reduced in Bmp2 heterozygous and homozygous embryos at the N2 generation onto C57BL/6 background. Bmp2 homozygous embryos also have a short allantois and about 50% of them do not undergo normal chorioallantoic fusion. Using whole-mount in situ hybridization, we show that Bmp2 is primarily expressed in the endoderm of mouse pregastrula and gastrula embryos. Using a genetic approach, we further show that Bmp2 and Bmp4, but not Bmp2 and Bmp8b, have an additive effect on PGC generation. These results suggest that PGC generation in the mouse embryo is regulated not only by extraembryonic ectoderm-derived BMP4 and BMP8B, but also by endoderm-derived BMP2
Drosophila Single-minded Represses Gene Transcription by Activating the Expression of Repressive Factors

AbstractThe Drosophila single-minded gene controls CNS midline cell development by both activating midline gene expression and repressing lateral CNS gene expression in the midline cells. The mechanism by which Single-minded represses transcription was examined using the ventral nervous system defective gene as a target gene. Transgenic-lacZ analysis of constructs containing fragments of the ventral nervous system defective regulatory region identified sequences required for lateral CNS transcription and midline repression. Elimination of Single-minded:Tango binding sites within the ventral nervous system defective gene did not affect midline repression. Mutants of Single-minded that removed the DNA binding and transcriptional activation regions abolished ventral nervous system defective repression, as well as transcriptional activation of other genes. The replacement of the Single-minded transcriptional activation region with a heterologous VP16 transcriptional activation region restored the ability of Single-minded to both activate and repress transcription. These results indicate that Single-minded indirectly represses transcription by activating the expression of repressive factors. Single-minded provides a model system for how regulatory proteins that act only as transcriptional activators can control lineage-specific transcription in both positive and negative modes
Development and Evolution of a Variable Left–Right Asymmetry in Nematodes: The Handedness of P11/P12 Migration

AbstractIn Caenorhabditis elegans, two lateral blast cells called P(11/12)L and P(11/12)R are symmetric left–right homologs at hatching, migrate subsequently in opposite anteroposterior directions during the first larval stage, and adopt two different fates, thus breaking the symmetry between them. Our results show that, unlike most other cell fate decisions in C. elegans, the orientation of P(11/12)L/R migration is highly biased, but not fixed. The handedness of their migration is linked to whole body handedness and is randomized in lin-12/Notch mutants and by ablation of the Y cell. Migration handedness is independent of P11 and P12 fate determination, previously shown to require the LIN-44/Wnt and the LIN-3/EGF pathways (L. I. Jiang and P. W. Sternberg, 1998, Development 125, 2337–2347). We further show that several changes in P(11/12)L/R asymmetry have occurred during nematode evolution: loss of asymmetry or reversals in orientation of migration. Strikingly, for most species studied, handedness of migration is highly biased but not fixed. Thus, whereas the final cell fate pattern of P11/12 is invariant, the developmental route leading to it is subject both to developmental indeterminacy and to evolutionary variations
Pulmonary Hypoplasia in Mice Lacking Tumor Necrosis Factor-α Converting Enzyme Indicates an Indispensable Role for Cell Surface Protein Shedding during Embryonic Lung Branching Morphogenesis

AbstractMany membrane-bound protein precursors, including cytokines and growth factors, are proteolytically shed to yield soluble intercellular regulatory ligands. The responsible protease, tumor necrosis factor-α converting enzyme (TACE/ADAM-17), is a transmembrane metalloprotease-disintegrin that cleaves multiple cell surface proteins, although it was initially identified for the enzymatic release of tumor necrosis factor-α (TNF-α). Mammalian lung growth and development are tightly controlled by cytokines and peptide growth factors. However, the biological function of the cell shedding mechanism during lung organogenesis is not understood. We therefore evaluated the role of TACE as a “sheddase” during lung morphogenesis by analyzing the developmental phenotypes of lungs in mice with an inactive TACE gene in both in vivo and ex vivo organ explant culture. Neonatal TACE-deficient mice had visible respiratory distress and their lungs failed to form normal saccular structures. These newborn mutant lungs had fewer peripheral epithelial sacs with deficient septation and thick-walled mesenchyme, resulting in reduced surface for gas exchange. At the canalicular stage of E16.5, the lungs of TACE mutant mice were impaired in branching morphogenesis, inhibited in epithelial cell proliferation and differentiation, and delayed in vasculogenesis. Embryonic TACE knockout mouse lungs (E12) branched poorly compared to wild-type lungs, when placed into serumless organ culture. Gene expression of both surfactant protein-C and aquaporin-5 were inhibited in cultured TACE-mutant embryonic lungs, indicating defects in both branching and peripheral epithelial cytodifferentiation in the absence of TACE protein. Furthermore, both the hypoplastic phenotype and the delayed cytodifferentiation in TACE-deficient lungs were rescued by exogenous addition of soluble stimulatory factors including either TNF-α or epidermal growth factor in embryonic lung culture. Thus, the impaired lung branching and maturation without TACE suggest a broad role for TACE in the processing of multiple membrane-anchored proteins, one or more of which is essential for normal lung morphogenesis. Taken together, our data indicate that the TACE-mediated proteolytic mechanism which enzymatically releases membrane-tethered proteins plays an indispensable role in lung morphogenesis, and its inactivation leads to abnormal lung development
Laminin-Induced Change in Conformation of Preexisting α7β1 Integrin Signals Secondary Myofiber Formation

AbstractTwo distinct populations of myoblasts, distinguishable by α7 integrin expression have been hypothesized to give rise to two phases of myofiber formation in embryonic limb development. We show here that α7 integrin is detectable far earlier than previously reported on both “primary” and “secondary” lineage myoblasts and myofibers. An antibody (1211) that recognizes an intracellular epitope allowed detection of α7 integrin previously missed using an antibody (H36) that recognizes an extracellular epitope. We found that when myoblasts were isolated and cultured from different developmental stages, H36 only detected α7 integrin that was in direct contact with its ligand, laminin. Moreover, α7 integrin detection by H36 was reversible and highly localized to subcellular points of contact between myoblasts and laminin-coated 2.8-μm microspheres. Prior to secondary myofiber formation in limb embryogenesis, laminin was present but not in close proximity to clusters of primary myofibers that expressed α7 integrin detected by antibody 1211 using deconvolution microscopy. These results suggest that the timing of the interaction of preexisting α7 integrin with its ligand, laminin, is a major determinant of allosteric changes that result in an activated form of α7 integrin capable of transducing signals from the extracellular matrix commensurate with secondary myofiber formation
The bHLH Factors Xath5 and XNeuroD Can Upregulate the Expression of XBrn3d, a POU-Homeodomain Transcription Factor

AbstractThe basic helix-loop-helix (bHLH) factor Xath5 promotes retinal ganglion cell differentiation when overexpressed and may do so by regulating the expression of factors involved in the differentiation of these cells. Potential candidates include the Brn3 POU-homeodomain transcription factors, which have been implicated in retinal ganglion cell development. Here we have identified a new member of the Brn3 gene subfamily in Xenopus, XBrn3d. In situ hybridization analysis shows XBrn3d expression in developing sensory neurons and developing ganglion cells of the retina. Using a hormone-inducible Xath5 fusion protein, we have shown that in animal caps Xath5 can directly regulate the expression of XBrn3d. Since XBrn3d is also expressed in sensory populations where Xath5 is not expressed, we examined the regulation of XBrn3d expression by the bHLH factor XNeuroD. A XNeuroD–hGR fusion protein is similarly able to directly induce the expression of XBrn3d in animal caps. In addition, overexpression of XBrn3d by RNA injection promotes the expression of ectopic sensory neuronal markers in the lateral ectoderm, suggesting a role in regulating neuronal development. Therefore, Xath5 and XNeuroD can directly regulate the expression of a neuronal subtype-specific factor, providing a link between neuronal differentiation and cell fate specification