1
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Grelet C, Larsen T, Crowe MA, Wathes DC, Ferris CP, Ingvartsen KL, Marchitelli C, Becker F, Vanlierde A, Leblois J, Schuler U, Auer FJ, Köck A, Dale L, Sölkner J, Christophe O, Hummel J, Mensching A, Fernández Pierna JA, Soyeurt H, Calmels M, Reding R, Gelé M, Chen Y, Gengler N, Dehareng F. Prediction of key milk biomarkers in dairy cows through milk mid-infrared spectra and international collaborations. J Dairy Sci 2024; 107:1669-1684. [PMID: 37863287 DOI: 10.3168/jds.2023-23843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 09/23/2023] [Indexed: 10/22/2023]
Abstract
At the individual cow level, suboptimum fertility, mastitis, negative energy balance, and ketosis are major issues in dairy farming. These problems are widespread on dairy farms and have an important economic impact. The objectives of this study were (1) to assess the potential of milk mid-infrared (MIR) spectra to predict key biomarkers of energy deficit (citrate, isocitrate, glucose-6 phosphate [glucose-6P], free glucose), ketosis (β-hydroxybutyrate [BHB] and acetone), mastitis (N-acetyl-β-d-glucosaminidase activity [NAGase] and lactate dehydrogenase), and fertility (progesterone); (2) to test alternative methodologies to partial least squares (PLS) regression to better account for the specific asymmetric distribution of the biomarkers; and (3) to create robust models by merging large datasets from 5 international or national projects. Benefiting from this international collaboration, the dataset comprised a total of 9,143 milk samples from 3,758 cows located in 589 herds across 10 countries and represented 7 breeds. The samples were analyzed by reference chemistry for biomarker contents, whereas the MIR analyses were performed on 30 instruments from different models and brands, with spectra harmonized into a common format. Four quantitative methodologies were evaluated to address the strongly skewed distribution of some biomarkers. Partial least squares regression was used as the reference basis, and compared with a random modification of distribution associated with PLS (random-downsampling-PLS), an optimized modification of distribution associated with PLS (KennardStone-downsampling-PLS), and support vector machine (SVM). When the ability of MIR to predict biomarkers was too low for quantification, different qualitative methodologies were tested to discriminate low versus high values of biomarkers. For each biomarker, 20% of the herds were randomly removed within all countries to be used as the validation dataset. The remaining 80% of herds were used as the calibration dataset. In calibration, the 3 alternative methodologies outperform the PLS performances for the majority of biomarkers. However, in the external herd validation, PLS provided the best results for isocitrate, glucose-6P, free glucose, and lactate dehydrogenase (coefficient of determination in external herd validation [R2v] = 0.48, 0.58, 0.28, and 0.24, respectively). For other molecules, PLS-random-downsampling and PLS-KennardStone-downsampling outperformed PLS in the majority of cases, but the best results were provided by SVM for citrate, BHB, acetone, NAGase, and progesterone (R2v = 0.94, 0.58, 0.76, 0.68, and 0.15, respectively). Hence, PLS and SVM based on the entire dataset provided the best results for normal and skewed distributions, respectively. Complementary to the quantitative methods, the qualitative discriminant models enabled the discrimination of high and low values for BHB, acetone, and NAGase with a global accuracy around 90%, and glucose-6P with an accuracy of 83%. In conclusion, MIR spectra of milk can enable quantitative screening of citrate as a biomarker of energy deficit and discrimination of low and high values of BHB, acetone, and NAGase, as biomarkers of ketosis and mastitis. Finally, progesterone could not be predicted with sufficient accuracy from milk MIR spectra to be further considered. Consequently, MIR spectrometry can bring valuable information regarding the occurrence of energy deficit, ketosis, and mastitis in dairy cows, which in turn have major influences on their fertility and survival.
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Affiliation(s)
- C Grelet
- Walloon Agricultural Research Center (CRA-W), Gembloux, Belgium, 5030
| | - T Larsen
- Department of Animal and Veterinary Sciences, Aarhus University, Tjele, Denmark, DK-8830
| | - M A Crowe
- University College Dublin (UCD), Dublin, Ireland, D04 C1P1
| | - D C Wathes
- Royal Veterinary College (RVC), London, United Kingdom, CM24 1RW
| | - C P Ferris
- Agri-Food and Biosciences Institute (AFBI), Belfast, Northern Ireland, BT9 5PX
| | - K L Ingvartsen
- Department of Animal and Veterinary Sciences, Aarhus University, Tjele, Denmark, DK-8830
| | - C Marchitelli
- Research Center for Animal Production and Aquaculture (CREA), Roma, Italy, 00184
| | - F Becker
- Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany, 18196
| | - A Vanlierde
- Walloon Agricultural Research Center (CRA-W), Gembloux, Belgium, 5030
| | - J Leblois
- EEIG European Milk Recording (EMR), Ciney, Belgium, 5590
| | | | - F J Auer
- LKV-Austria, Vienna, Austria, A-1200
| | - A Köck
- ZuchtData, Vienna, Austria, A-1200
| | - L Dale
- LKV Baden Württemberg, Stuttgart, Germany, D-70190
| | - J Sölkner
- University of Natural Resources and Life Sciences, Vienna, Austria, A-1180
| | - O Christophe
- Walloon Agricultural Research Center (CRA-W), Gembloux, Belgium, 5030
| | - J Hummel
- University of Göttingen, Göttingen, Germany, D-37075
| | - A Mensching
- University of Göttingen, Göttingen, Germany, D-37075
| | | | - H Soyeurt
- University of Liège, Gembloux Agro-Bio Tech (Ulg-GxABT), Gembloux, Belgium, 5030
| | - M Calmels
- Seenovia, Saint Berthevin, France, 53940
| | - R Reding
- Convis, Ettelbruck, Luxembourg, 9085
| | - M Gelé
- Idele, Paris, France, 75012
| | - Y Chen
- University of Liège, Gembloux Agro-Bio Tech (Ulg-GxABT), Gembloux, Belgium, 5030
| | - N Gengler
- University of Liège, Gembloux Agro-Bio Tech (Ulg-GxABT), Gembloux, Belgium, 5030
| | - F Dehareng
- Walloon Agricultural Research Center (CRA-W), Gembloux, Belgium, 5030.
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2
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Trevers KE, Lu HC, Yang Y, Thiery AP, Strobl AC, Anderson C, Pálinkášová B, de Oliveira NMM, de Almeida IM, Khan MAF, Moncaut N, Luscombe NM, Dale L, Streit A, Stern CD. A gene regulatory network for neural induction. eLife 2023; 12:73189. [PMID: 36867045 PMCID: PMC10038663 DOI: 10.7554/elife.73189] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 03/02/2023] [Indexed: 03/04/2023] Open
Abstract
During early vertebrate development, signals from a special region of the embryo, the organizer, can redirect the fate of non-neural ectoderm cells to form a complete, patterned nervous system. This is called neural induction and has generally been imagined as a single signalling event, causing a switch of fate. Here, we undertake a comprehensive analysis, in very fine time course, of the events following exposure of competent ectoderm of the chick to the organizer (the tip of the primitive streak, Hensen's node). Using transcriptomics and epigenomics we generate a gene regulatory network comprising 175 transcriptional regulators and 5614 predicted interactions between them, with fine temporal dynamics from initial exposure to the signals to expression of mature neural plate markers. Using in situ hybridization, single-cell RNA-sequencing, and reporter assays, we show that the gene regulatory hierarchy of responses to a grafted organizer closely resembles the events of normal neural plate development. The study is accompanied by an extensive resource, including information about conservation of the predicted enhancers in other vertebrates.
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Affiliation(s)
- Katherine E Trevers
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Hui-Chun Lu
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Youwen Yang
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Alexandre P Thiery
- Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom
| | - Anna C Strobl
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Claire Anderson
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Božena Pálinkášová
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Nidia M M de Oliveira
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Irene M de Almeida
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Mohsin A F Khan
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Natalia Moncaut
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Nicholas M Luscombe
- The Francis Crick Institute, London, United Kingdom
- UCL Genetics Institute, Department of Genetics, Environment and Evolution, University College London, London, United Kingdom
| | - Leslie Dale
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Andrea Streit
- Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom
| | - Claudio D Stern
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
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3
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Meriwether K, Krashin J, Kim-Fine S, Ablove T, Dale L, Orejuela F, Mazloomdoost D, Beckham A, Probst K, Crisp C, Winkelman W, Florian-Rodriguez M, Grimes C, Turk J, Ollendorff A, Ros S, Chang O, Horvath S, Iglesia C. Trainee opinions regarding the effect of the dobbs v. jackson women’s health organization supreme court decision on obstetrics and gynecology training. Am J Obstet Gynecol 2023. [DOI: 10.1016/j.ajog.2022.12.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
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4
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Standish LJ, Sweet E, Kim E, Dowd F, McLaughlin R, Chiang P, Dale L, Gaul M, Andersen MR. Recurrence of Breast Cancer After Primary Treatment: A Matched Comparison Study of Disease-Free Survival in Women Who Do and Do Not Receive Adjunctive Naturopathic Oncology Care. Integr Cancer Ther 2021; 20:15347354211058404. [PMID: 34894812 PMCID: PMC8671681 DOI: 10.1177/15347354211058404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Purpose: To compare disease free survival experienced by women who received usual
oncologic care compared to a cohort of women who received naturopathic
oncology care in addition to usual care. Methods: Women with breast cancer who received naturopathic oncology (NO) care in
Western Washington State (WA) (N = 176) were recruited to a prospective
study of clinical health-related quality of life outcomes and then matched
to women who received usual care (UC) only (N = 334). Results: Among 510 women with breast cancer stages 1 to 3, a total of 50 women (10%)
experienced a disease-free survival (DFS) ending event within the
observation period; 23 (6.8% of those in the UC cohort, and 27 (15.3% of
those in the NO cohort (P < .05). Although, women in the
2 cohorts received similar surgical, chemotherapy, and radiation treatment,
women with breast cancer who received naturopathic oncology adjunctive care
were less likely to use anti-estrogen therapy, and experienced poorer DFS
(logrank test, P < .05). However, differences in DFS
could not be shown to be due to cohort differences in anti-estrogen therapy,
baseline HRQOL, or naturopathic oncology therapies prescribed. The stage 3
women in the naturopathic oncology group had more advanced disease at
diagnosis. They were more likely to have 5 or more metastatic lymph nodes at
baseline (18.5%) compared to their usual care matched control group (13%).
Women in the naturopathic oncology group also had higher grade tumors at
diagnosis. Conclusions: Results show that recurrence of breast cancer was associated with more
advanced malignant lymph node involvement; and that naturopathic oncology
services provided in 2009-2015 did not improve disease-free survival in
these high-risk breast cancer patients.
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Affiliation(s)
- L J Standish
- Bastyr University, Kenmore, WA, USA.,University of Washington, Seattle, WA, USA
| | - E Sweet
- Bastyr University, Kenmore, WA, USA
| | | | - F Dowd
- Bastyr University, Kenmore, WA, USA
| | | | - P Chiang
- Bastyr University, Kenmore, WA, USA
| | - L Dale
- Bastyr University, Kenmore, WA, USA
| | - M Gaul
- Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - M R Andersen
- University of Washington, Seattle, WA, USA.,Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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5
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Abstract
ADP-ribosyl cyclases are multifunctional enzymes involved in the metabolism of nucleotide derivatives necessary for Ca2+ signalling such as cADPR and NAADP. Although Ca2+ signalling is a critical regulator of early development, little is known of the role of ADP-ribosyl cyclases during embryogenesis. Here we analyze the expression, activity and function of ADP-ribosyl cyclases in the embryo of the sea urchin - a key organism for study of both Ca2+ signalling and embryonic development. ADP-ribosyl cyclase isoforms (SpARC1-4) showed unique changes in expression during early development. These changes were associated with an increase in the ratio of cADPR:NAADP production. Over-expression of SpARC4 (a preferential cyclase) disrupted gastrulation. Our data highlight the importance of ADP-ribosyl cyclases during embryogenesis.
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Affiliation(s)
- Latha Ramakrishnan
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT UK
| | - Kevin Uhlinger
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0202 USA
| | - Leslie Dale
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT UK
| | - Amro Hamdoun
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0202 USA
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT UK
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6
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Nalesso G, Thomas BL, Sherwood JC, Yu J, Addimanda O, Eldridge SE, Thorup AS, Dale L, Schett G, Zwerina J, Eltawil N, Pitzalis C, Dell'Accio F. WNT16 antagonises excessive canonical WNT activation and protects cartilage in osteoarthritis. Ann Rheum Dis 2016; 76:218-226. [PMID: 27147711 PMCID: PMC5264226 DOI: 10.1136/annrheumdis-2015-208577] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 03/21/2016] [Accepted: 03/23/2016] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Both excessive and insufficient activation of WNT signalling results in cartilage breakdown and osteoarthritis. WNT16 is upregulated in the articular cartilage following injury and in osteoarthritis. Here, we investigate the function of WNT16 in osteoarthritis and the downstream molecular mechanisms. METHODS Osteoarthritis was induced by destabilisation of the medial meniscus in wild-type and WNT16-deficient mice. Molecular mechanisms and downstream effects were studied in vitro and in vivo in primary cartilage progenitor cells and primary chondrocytes. The pathway downstream of WNT16 was studied in primary chondrocytes and using the axis duplication assay in Xenopus. RESULTS WNT16-deficient mice developed more severe osteoarthritis with reduced expression of lubricin and increased chondrocyte apoptosis. WNT16 supported the phenotype of cartilage superficial-zone progenitor cells and lubricin expression. Increased osteoarthritis in WNT16-deficient mice was associated with excessive activation of canonical WNT signalling. In vitro, high doses of WNT16 weakly activated canonical WNT signalling, but, in co-stimulation experiments, WNT16 reduced the capacity of WNT3a to activate the canonical WNT pathway. In vivo, WNT16 rescued the WNT8-induced primary axis duplication in Xenopus embryos. CONCLUSIONS In osteoarthritis, WNT16 maintains a balanced canonical WNT signalling and prevents detrimental excessive activation, thereby supporting the homeostasis of progenitor cells.
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Affiliation(s)
- Giovanna Nalesso
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Bethan Lynne Thomas
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Joanna Claire Sherwood
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK.,Institute of Experimental Musculoskeletal Medicine, University Hospital Muenster, Muenster, Germany
| | - Jing Yu
- Department of Cell Biology, The Center for Immunity, Inflammation and Regenerative Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Olga Addimanda
- Department of Medicine & Rheumatology Unit, Rizzoli Orthopaedic Institute, Bologna, Italy.,Department of Biomedical & Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Suzanne Elizabeth Eldridge
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Anne-Sophie Thorup
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Leslie Dale
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Georg Schett
- Department of Internal Medicine 3, Institute of Clinical Immunology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Jochen Zwerina
- Department of Internal Medicine 3, Institute of Clinical Immunology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Noha Eltawil
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK.,Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
| | - Costantino Pitzalis
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Francesco Dell'Accio
- Barts and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London, UK
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7
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Geach TJ, Faas L, Devader C, Gonzalez-Cordero A, Tabler JM, Brunsdon H, Isaacs HV, Dale L. An essential role for LPA signalling in telencephalon development. Development 2014. [DOI: 10.1242/dev.112391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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Geach TJ, Faas L, Devader C, Gonzalez-Cordero A, Tabler JM, Brunsdon H, Isaacs HV, Dale L. An essential role for LPA signalling in telencephalon development. Development 2014; 141:940-9. [PMID: 24496630 DOI: 10.1242/dev.104901] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Lysophosphatidic acid (LPA) has wide-ranging effects on many different cell types, acting through G-protein-coupled receptors such as LPAR6. We show that Xenopus lpar6 is expressed from late blastulae and is enriched in the mesoderm and dorsal ectoderm of early gastrulae. Expression in gastrulae is an early response to FGF signalling. Transcripts for lpar6 are enriched in the neural plate of Xenopus neurulae and loss of function caused forebrain defects, with reduced expression of telencephalic markers (foxg1, emx1 and nkx2-1). Midbrain (en2) and hindbrain (egr2) markers were unaffected. Foxg1 expression requires LPAR6 within ectoderm and not mesoderm. Head defects caused by LPAR6 loss of function were enhanced by co-inhibiting FGF signalling, with defects extending into the hindbrain (en2 and egr2 expression reduced). This is more severe than expected from simple summation of individual defects, suggesting that LPAR6 and FGF have overlapping or partially redundant functions in the anterior neural plate. We observed similar defects in forebrain development in loss-of-function experiments for ENPP2, an enzyme involved in the synthesis of extracellular LPA. Our study demonstrates a role for LPA in early forebrain development.
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Affiliation(s)
- Timothy J Geach
- Department of Cell and Developmental Biology, University College London, Anatomy Building, Gower Street, London, WC1E 6BT, UK
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9
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Churamani D, Geach TJ, Ramakrishnan L, Prideaux N, Patel S, Dale L. The signaling protein CD38 is essential for early embryonic development. J Biol Chem 2012; 287:6974-8. [PMID: 22223651 DOI: 10.1074/jbc.c111.323618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
CD38 is a multifunctional protein possessing ADP-ribosyl cyclase activity responsible for both the synthesis and the degradation of several Ca(2+)-mobilizing second messengers. Although a variety of functions have been ascribed to CD38, such as immune responses, insulin secretion, and social behavior in adults, nothing is known of its role during embryonic development when Ca(2+) signals feature prominently. Here, we report the identification and functional expression of CD38 from Xenopus laevis, a key model organism for the study of vertebrate development. We show that CD38 expression and endogenous ADP-ribosyl cyclase activity are developmentally regulated during cellular differentiation. Chemical or molecular inhibition of CD38 abolished ADP-ribosyl cyclase activity and disrupted elongation of the anterior-posterior axis and differentiation of skeletal muscle, culminating in embryonic death. Our data uncover a previously unknown role for CD38 as an essential regulator of embryonic development.
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Affiliation(s)
- Dev Churamani
- Department of Cell and Developmental Biology, University College London, Anatomy Building, Gower Street, London WC1E 6BT, United Kingdom
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10
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Lal A, Dale L, Lucas T, Chakraborty B, Banerjee D, Brocklebank D. P206 Compliance with CPAP: subjective versus objective methods of assessment and regional variations. Thorax 2010. [DOI: 10.1136/thx.2010.151068.7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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11
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Ramakrishnan L, Muller-Steffner H, Bosc C, Vacquier VD, Schuber F, Moutin MJ, Dale L, Patel S. A single residue in a novel ADP-ribosyl cyclase controls production of the calcium-mobilizing messengers cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate. J Biol Chem 2010; 285:19900-9. [PMID: 20385553 DOI: 10.1074/jbc.m110.105312] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate are ubiquitous calcium-mobilizing messengers produced by the same family of multifunctional enzymes, the ADP-ribosyl cyclases. Not all ADP-ribosyl cyclases have been identified, and how production of different messengers is achieved is incompletely understood. Here, we report the cloning and characterization of a novel ADP-ribosyl cyclase (SpARC4) from the sea urchin, a key model organism for the study of calcium-signaling pathways. Like several other members of the ADP-ribosyl cyclase superfamily, SpARC4 is a glycoprotein targeted to the plasma membrane via a glycosylphosphatidylinositol anchor. However, unlike most other members, SpARC4 shows a remarkable preference for producing cyclic ADP-ribose over nicotinic acid adenine dinucleotide phosphate. Mutation of a single residue (tyrosine 142) within a noncanonical active site reversed this striking preference. Our data highlight further diversification of this unusual enzyme family, provide mechanistic insight into multifunctionality, and suggest that different ADP-ribosyl cyclases are fine-tuned to produce specific calcium-mobilizing messengers.
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Affiliation(s)
- Latha Ramakrishnan
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom
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12
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Abstract
Xld (Xolloid) is a member of the Tolloid family of metalloproteases found in embryos of the frog Xenopus laevis. It cleaves Chordin, an inhibitory binding protein for BMP2/4, releasing fragments with reduced affinity for these important ventralizing signals. As a consequence, increasing Xld activity ventralizes Xenopus embryos. We have used this phenotype as an assay to determine the requirement for the C-terminal, nonprotease component of Xld for in vivo activity. This part of the protein is composed of five complement C1r/C1s-sea urchin epidermal growth factor-BMP1 (CUB) and two epidermal growth factor domains, which are thought to be involved in protein-protein interactions and may confer substrate specificity. Our results show that the protease coupled to CUB1 and CUB2 is the minimum domain structure required to ventralize Xenopus embryos and to block the dorsal axis-inducing activity of Chordin. Xld-CUB1-CUB2 cleaves Chordin, and a protease-inactive version co-precipitates Chordin. Our results indicate that the first and second CUB domains bind Chordin and present it to the protease domain. Protease-inactive Xld blocks the cleavage of Chordin by wild-type Xld and dorsalizes injected Xenopus embryos. We find that protease-inactive Xld-CUB1-CUB2 does not share this activity and that all of the C-terminal domains are required to generate the dorsalized phenotype.
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Affiliation(s)
- Timothy J Geach
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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13
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Devader C, Drew CM, Geach TJ, Tabler J, Townsend-Nicholson A, Dale L. A novel nucleotide receptor in Xenopus activates the cAMP second messenger pathway. FEBS Lett 2007; 581:5332-6. [PMID: 17977530 DOI: 10.1016/j.febslet.2007.10.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Accepted: 10/12/2007] [Indexed: 10/22/2022]
Abstract
We describe a Xenopus P2Y receptor that shares only weak homology with members of the mammalian P2Y family, being most similar to human P2Y(11). When activated by nucleotide analogs, it stimulates both calcium and cAMP mobilization pathways, a feature unique, among mammalian P2Y receptors, to P2Y(11). Activity can be blocked by compounds known to act as antagonists of mammalian P2Y(11). Genomic synteny between Xenopus and mammals suggests that the novel gene is a true ortholog of P2Y(11). Xenopus P2Y(11) is transcribed during embryonic development, beginning at gastrulation, and is enriched in the developing nervous system.
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Affiliation(s)
- Christelle Devader
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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14
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Churamani D, Boulware MJ, Geach TJ, Martin AC, Moy GW, Su YH, Vacquier VD, Marchant JS, Dale L, Patel S. Molecular characterization of a novel intracellular ADP-ribosyl cyclase. PLoS One 2007; 2:e797. [PMID: 17726527 PMCID: PMC1949048 DOI: 10.1371/journal.pone.0000797] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 08/02/2007] [Indexed: 11/22/2022] Open
Abstract
Background ADP-ribosyl cyclases are remarkable enzymes capable of catalyzing multiple reactions including the synthesis of the novel and potent intracellular calcium mobilizing messengers, cyclic ADP-ribose and NAADP. Not all ADP-ribosyl cyclases however have been characterized at the molecular level. Moreover, those that have are located predominately at the outer cell surface and thus away from their cytosolic substrates. Methodology/Principal Findings Here we report the molecular cloning of a novel expanded family of ADP-ribosyl cyclases from the sea urchin, an extensively used model organism for the study of inositol trisphosphate-independent calcium mobilization. We provide evidence that one of the isoforms (SpARC1) is a soluble protein that is targeted exclusively to the endoplasmic reticulum lumen when heterologously expressed. Catalytic activity of the recombinant protein was readily demonstrable in crude cell homogenates, even under conditions where luminal continuity was maintained. Conclusions/Significance Our data reveal a new intracellular location for ADP-ribosyl cyclases and suggest that production of calcium mobilizing messengers may be compartmentalized.
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Affiliation(s)
- Dev Churamani
- Department of Physiology, University College London, London, United Kingdom
| | - Michael J. Boulware
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Timothy J. Geach
- Department of Anatomy and Developmental Biology, University College London, London, United Kingdom
| | - Andrew C.R. Martin
- Department of Biochemistry and Molecular Biology, University College London, London, United Kingdom
| | - Gary W. Moy
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, United States of America
| | - Yi-Hsien Su
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, United States of America
| | - Victor D. Vacquier
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, United States of America
| | - Jonathan S. Marchant
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Leslie Dale
- Department of Anatomy and Developmental Biology, University College London, London, United Kingdom
| | - Sandip Patel
- Department of Physiology, University College London, London, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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15
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Devader C, Webb RJ, Thomas GMH, Dale L. Xenopus apyrase (xapy), a secreted nucleotidase that is expressed during early development. Gene 2005; 367:135-41. [PMID: 16314051 DOI: 10.1016/j.gene.2005.10.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Accepted: 10/04/2005] [Indexed: 10/25/2022]
Abstract
We have characterized a cDNA encoding a Xenopus laevis apyrase (XAPY) that is expressed during embryogenesis. XAPY is highly homologous to two recently described mammalian apyrases, human SCAN-1 and rat Ca2+-NDPase, and to a lesser extent the salivary apyrase of the blood-feeding arthropod Cimex lectularis. RT-PCR analysis shows that Xapy is expressed at all the developmental stages tested, from oocytes through to tadpoles. Xapy transcripts are widely distributed in the embryo, but from late neurulae through to late tailbud stages they are highly enriched in the cement gland, an adhesive organ in the epidermis of the head. When expressed in HEK 293 cells, XAPY is largely retained in the endoplasmic reticulum, although some is also secreted. XAPY conditioned media hydrolyses UDP and UTP, confirming that it is a functional apyrase.
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MESH Headings
- Amino Acid Sequence
- Animals
- Apyrase/chemistry
- Apyrase/genetics
- Apyrase/metabolism
- Base Sequence
- Bedbugs/enzymology
- Cell Line
- Codon
- Codon, Initiator
- Conserved Sequence
- Culture Media, Conditioned/pharmacology
- DNA, Complementary/genetics
- Embryo, Nonmammalian
- Endoplasmic Reticulum/enzymology
- Endoplasmic Reticulum/metabolism
- Fluorescein
- Fluorescent Antibody Technique, Indirect
- Fluorescent Dyes
- Gene Expression Regulation, Developmental
- Humans
- In Situ Hybridization
- Metamorphosis, Biological
- Microscopy, Fluorescence
- Molecular Sequence Data
- Nucleotidases/chemistry
- Nucleotidases/genetics
- Nucleotidases/metabolism
- Protein Structure, Tertiary
- RNA, Messenger/analysis
- Rats
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, RNA
- Sequence Homology, Amino Acid
- Tissue Distribution
- Transcription, Genetic
- Uridine Diphosphate/metabolism
- Uridine Triphosphate/metabolism
- Xenopus/embryology
- Xenopus/genetics
- Xenopus/metabolism
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Affiliation(s)
- Christelle Devader
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
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16
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Abstract
Lysyl oxidase (Lox) is a copper-dependent amine oxidase that catalyzes the cross-linking of collagen and elastin fibers in the extracellular matrix (ECM). In mammals, four closely related Lox-like enzymes have been described that share a highly conserved catalytic domain with Lox. We have characterized Xenopus laevis cDNAs for Lox, Loxl-1, and Loxl-3, and show that they are expressed during early embryonic development. Using RT-PCR we detected maternal transcripts for Xloxl-1, but levels remained low until tailbud stages. Transcripts for Xlox and Xloxl-3 were not detected until early neurulae, although transcripts for Xlox remained at low levels until tailbud stages. Whole mount in situ hybridization showed that transcripts for Xloxl-1 and Xloxl-3 are localized in the notochord, while transcripts for Xlox are found in the notochord, somites, and head. X. laevis Lox-like enzymes were inhibited by incubating embryos, from cleavage stages to tadpole stages, in beta-aminopropionitrile, a specific inhibitor of the catalytic domain. The resulting embryos appeared to differentiate normally but suffered from poor collagen fiber formation. Defects included kinks in the notochord, a posterior shift of the somites, abnormal gut coiling, and the formation of edemas. Our data suggest that Lox-related enzymes are required for the proper formation of the ECM during X. laevis development.
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Affiliation(s)
- Timothy J Geach
- Department of Anatomy and Developmental Biology University College London Gower Street London WC1E 6BT, U.K
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17
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Abstract
We have identified a novel Tolloid-like metalloprotease, called Xolloid-related (Xlr), that is expressed during early Xenopus development. Transcripts for xlr are localized to the marginal zone of mid-gastrulae and are most abundant in ventral and lateral sectors. At neurula stages xlr is strongly expressed around the blastopore and in the pharyngeal endoderm, and more weakly expressed throughout the ventral half of the embryo. Transcripts are detected in the nervous system, particularly the hindbrain and spinal cord, and tailbud of tailbud stage embryos, with weaker expression in the anterior nervous system, otic vesicle, heart, and pronephric duct. Transcription of xlr is increased by BMP4 and decreased by Noggin and tBR, indicating that xlr is regulated by BMP signalling. Injection of xlr mRNA inhibits dorsoanterior development and the dorsal axis inducing ability of coinjected chordin, but not noggin or tBR, mRNA. Xlr conditioned media cleaves Chordin in vitro, indicating that this protease may regulate the availability of Chordin in vivo.
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Affiliation(s)
- Leslie Dale
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
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18
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Rosu-Myles M, Gallacher L, Murdoch B, Hess DA, Keeney M, Kelvin D, Dale L, Ferguson SS, Wu D, Fellows F, Bhatia M. The human hematopoietic stem cell compartment is heterogeneous for CXCR4 expression. Proc Natl Acad Sci U S A 2000; 97:14626-31. [PMID: 11121064 PMCID: PMC18969 DOI: 10.1073/pnas.97.26.14626] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The chemokine stromal derived factor-1alpha (SDF-1alpha) has been implicated recently in the chemotaxis of primitive human hematopoietic cells, suggesting that pluripotent human stem cells express the SDF-1alpha receptor, CXCR4. By using flow cytometry and confocal microscopy, we have identified and isolated primitive subsets of human CXCR4(+) and CXCR4(-) cells. Distinctions in the progenitor content and response to SDF-1alpha in vitro indicate that CXCR4(+) and CXCR4(-) cells represent discrete populations of primitive blood cells. The i.v. transplantation of these subfractions into immune-deficient mice established that both possess comparable engraftment capacity in vivo. Human myeloid, lymphoid, and primitive CD34(+) CXCR4(+) cells were present in chimeric animals transplanted with either subset, indicating that CXCR4(+) and CXCR4(-) stem cells have equivalent proliferative and differentiative abilities. Our study indicates that the human stem cell compartment is heterogeneous for CXCR4 expression, suggesting that the relationship between CXCR4 expression and stem cell repopulating function is not obligatory.
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Affiliation(s)
- M Rosu-Myles
- The John P. Robarts Research Institute, Developmental Stem Cell Biology, 100 Perth Drive, London, ON, Canada N6A 5K8, UK
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19
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Abstract
Dorsal-ventral patterning in Xenopus and Drosophila embryos involves BMP family signalling molecules. Twisted Gastrulation has now been added to the list of proteins that regulate the activity of these molecules, providing new insights into how BMPs are made available to their signalling receptors.
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Affiliation(s)
- L Dale
- Department of Anatomy and Developmental Biology, University College London, Gower Street, WC1E 6BT, London, UK.
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20
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Angerer LM, Oleksyn DW, Logan CY, McClay DR, Dale L, Angerer RC. A BMP pathway regulates cell fate allocation along the sea urchin animal-vegetal embryonic axis. Development 2000; 127:1105-14. [PMID: 10662649 DOI: 10.1242/dev.127.5.1105] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To examine whether a BMP signaling pathway functions in specification of cell fates in sea urchin embryos, we have cloned sea urchin BMP2/4, analyzed its expression in time and space in developing embryos and assayed the developmental consequences of changing its concentration through mRNA injection experiments. These studies show that BMP4 mRNAs accumulate transiently during blastula stages, beginning around the 200-cell stage, 14 hours postfertilization. Soon after the hatching blastula stage, BMP2/4 transcripts can be detected in presumptive ectoderm, where they are enriched on the oral side. Injection of BMP2/4 mRNA at the one-cell stage causes a dose-dependent suppression of commitment of cells to vegetal fates and ectoderm differentiates almost exclusively as a squamous epithelial tissue. In contrast, NOGGIN, an antagonist of BMP2/4, enhances differentiation of endoderm, a vegetal tissue, and promotes differentiation of cells characteristic of the ciliated band, which contains neurogenic ectoderm. These findings support a model in which the balance of BMP2/4 signals produced by animal cell progeny and opposing vegetalizing signals sent during cleavage stages regulate the position of the ectoderm/ endoderm boundary. In addition, BMP2/4 levels influence the decision within ectoderm between epidermal and nonepidermal differentiation.
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Affiliation(s)
- L M Angerer
- Department of Biology, University of Rochester, Rochester, NY 14627, USA.
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21
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Ladher RK, Church VL, Allen S, Robson L, Abdelfattah A, Brown NA, Hattersley G, Rosen V, Luyten FP, Dale L, Francis-West PH. Cloning and expression of the Wnt antagonists Sfrp-2 and Frzb during chick development. Dev Biol 2000; 218:183-98. [PMID: 10656762 DOI: 10.1006/dbio.1999.9586] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The Wnt genes are known to play fundamental roles during patterning and development of a number of embryonic structures. Receptors for Wnts are members of the Frizzled family of proteins containing a cysteine-rich domain (CRD) that binds the Wnt protein. Recently several secreted frizzled-related proteins (Sfrps) that also contain a CRD have been identified and some of these can both bind and antagonise Wnt proteins. In this paper we report the expression patterns of the chick homologues of Frzb, a known Wnt antagonist, and Sfrp-2. Both genes are expressed in areas where Wnts are known to play a role in development, including the neural tube, myotome, cartilage, and sites of epithelial-mesenchymal interactions. Initially, Sfrp-2 and Frzb are expressed in overlapping areas in the neural plate and neural tube, whereas later, they have distinct patterns. In particular Sfrp-2 is associated with myogenesis while Frzb is associated with chondrogenesis, suggesting that they play different roles during development. Finally, we have used the early Xenopus embryo as an in vivo assay to show that Sfrp-2, like Frzb, is a Wnt antagonist. These results suggest that Sfrp-2 and Frzb may function in the developing embryo by modulating Wnt signalling.
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Affiliation(s)
- R K Ladher
- Department of Craniofacial Development, Guy's, King's and St. Thomas' School of Dentistry, Guy's Tower, Floor 27, Guy's Hospital, London, SE1 9RT, United Kingdom.
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22
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Abstract
Recent results support a two-step model for endoderm formation in amphibian embryos, in which endoderm is initially specified by localised maternal factors, including the transcription factor VegT, but is then maintained by extracellular signalling molecules of the transforming growth factor-beta family.
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Affiliation(s)
- L Dale
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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23
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Abstract
Bone morphogenetic proteins (BMPs) are typically members of the transforming growth factor beta (TGF-beta) family with diverse roles in embryonic development. At least five genes with homology to BMPs are expressed during Xenopus development, along with their receptors and intracellular signalling pathways. The evidence suggests that BMPs have roles to play in both mesoderm induction and dorsoventral patterning. Studies in Xenopus have also identified a number of inhibitory binding proteins for the classical BMPs, encoded by genes such as chordin and noggin. These proteins appear to be responsible for establishing a morphogen gradient of BMP4 activity, which specifies different dorsoventral fates in early gastrulae. An emerging theme is that inhibition of BMP signalling is an important mechanism regulating cell fate decisions in early development.
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Affiliation(s)
- L Dale
- Department of Anatomy and Developmental Biology, University College London, London WC1E 6BT, UK.
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24
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Abstract
Bone morphogenetic protein 1 (BMP1) is a metalloprotease that ventralises dorsal mesoderm when overexpressed in early Xenopus embryos. Here we show that Xenopus BMP1 blocks the dorsalising activity of chordin, but not noggin or DeltaxBMPR, when coexpressed in the ventral marginal zone and degrades chordin protein in vitro. We also show that a dominant-negative mutation for XBMP1 (dnBMP1) dorsalises ventral mesoderm in vivo, and blocks degradation of chordin by both XBMP1 and Xolloid, a closely related Xenopus metalloprotease, in vitro. dnBMP1 does not dorsalise ventral mesoderm in UV-irradiated embryos, demonstrating that this activity is dependent upon a functional organiser--the natural source of chordin in Xenopus gastrulae. Our results suggest that XBMP1 may regulate the availability of chordin during vertebrate embryogenesis.
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Affiliation(s)
- F C Wardle
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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25
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Aaltonen J, Laitinen MP, Vuojolainen K, Jaatinen R, Horelli-Kuitunen N, Seppä L, Louhio H, Tuuri T, Sjöberg J, Bützow R, Hovata O, Dale L, Ritvos O. Human growth differentiation factor 9 (GDF-9) and its novel homolog GDF-9B are expressed in oocytes during early folliculogenesis. J Clin Endocrinol Metab 1999; 84:2744-50. [PMID: 10443672 DOI: 10.1210/jcem.84.8.5921] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Growth differentiation factor 9 (GDF-9) is a transforming growth factor-beta family member that is required for normal folliculogenesis in female mice, but its role as a regulator of human fertility is still unclear. We determined here by in situ hybridization and immunohistochemical analyses the localization of the GDF-9 messenger ribonucleic acid (mRNA) and protein during human folliculogenesis. The GDF-9 transcripts were not detected in primordial follicles, but they are abundantly expressed in primary follicles in frozen sections of ovarian cortical tissue material obtained at laparoscopic surgery. We raised antipeptide antibodies against GDF-9 and showed by immunohistochemical studies on paraffin sections of whole human ovaries that the GDF-9 protein is most abundantly expressed in primary follicles. We recently demonstrated that a novel GDF-9-related factor, GDF-9B, is coexpressed with GDF-9 during murine folliculogenesis. We now isolated human GDF-9B complementary DNA and genomic clones and report the unusually restricted expression pattern of human GDF-9B. The human GDF-9B transcript can be detected only in the gonads by RT-PCR analysis, and in situ hybridization studies indicate that it is not expressed in small primary follicles but, rather, in the oocytes of late primary follicles. Functional studies using the Xenopus laeuis embryo model indicate that unlike the transforming growth factor-beta family members activin and bone morphogenetic protein-4, neither GDF-9 nor GDF-9B affects mesoderm induction, suggesting that they may use signaling pathways distinct from those well defined for activin and bone morphogenetic protein-4. We conclude that 1) both GDF-9 mRNA and protein are abundantly expressed in oocytes of primary follicles in human ovary, suggesting that the GDF-9 transcript is translated at this early stage of folliculogenesis; 2) human GDF-9B is specifically expressed in gonads at low levels; and 3) the expression of GDF-9 mRNA begins slightly earlier than that of GDF-9B in the human oocytes during follicular development. Our results are consistent with the suggestion that GDF-9 and GDF-9B may regulate human folliculogenesis in a manner specific to the ovary.
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Affiliation(s)
- J Aaltonen
- Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Finland.
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26
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Newton I, Wyllie I, Dale L. Trends in the numbers and mortality patterns of sparrowhawks (Accipiter nisus) and kestrels (Falco tinnunculus) in Britain, as revealed by carcass analyses. J Zool (1987) 1999. [DOI: 10.1111/j.1469-7998.1999.tb01190.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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27
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Affiliation(s)
- L Dale
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
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28
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Abstract
BMP-4 is an extracellular signalling molecule belonging to the TGF-beta superfamily that plays a central role in dorsoventral patterning in vertebrate gastrulae. We review the evidence indicating that BMP-4 acts as a morphogen, specifying dorsoventral positional values in a concentration-dependent manner. An activity gradient of BMP-4 is established not by simple diffusion from a localised source, but by diffusion of inhibitory binding proteins that act on a uniform level of BMP-4 protein. These in turn are regulated by the activity of tolloid-related metalloproteases, such as Xenopus xolloid and zebrafish tolloid.
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Affiliation(s)
- L Dale
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
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29
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Abstract
We have used the Xenopus embryo as a test system for analyzing the activity of SpAN, a sea urchin metalloprotease in the astacin family containing BMP1 and tolloid. Embryos expressing SpAN initiated gastrulation on a time scale indistinguishable from controls, but invagination of the vegetal pole was subsequently delayed by several hours. At tailbud stages the most severely affected embryos were completely ventralized, lacking all dorsal structures. Molecular analysis of injected embryos, using probes for both dorsal (xgsc and xnot) and ventral (xhox3 and xwnt8) mesoderm, indicates that SpAN ventralizes dorsal mesoderm during gastrula stages. These results mirror those previously obtained with BMP4, suggesting that SpAN may enhance the activity of this ventralizing factor. Consistent with this suggestion, we have shown that SpAN blocks the dorsalizing activity of noggin and chordin, two inhibitory binding proteins for BMP4, but not that of a dominant-negative receptor for BMP4. In contrast, a dominant-negative SpAN, in which the metalloprotease domain has been deleted, dorsalizes ventral mesoderm, a phenotype that can be rescued by coexpressing either SpAN or XBMP1. This suggests that SpAN is mimicking a Xenopus metalloprotease responsible for regulating the activity of Xenopus BMPs during gastrulation. Moreover, our results raise the possibility that SpAN may function to facilitate BMP signaling in early sea urchin embryos.
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Affiliation(s)
- F C Wardle
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
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30
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Douglass RL, Torres RE, Surfus P, Krinke B, Dale L. Health care needs and services utilization among sheltered and unsheltered Michigan homeless. J Health Care Poor Underserved 1999; 10:5-18. [PMID: 9989003 DOI: 10.1353/hpu.2010.0755] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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31
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Goodman SA, Albano R, Wardle FC, Matthews G, Tannahill D, Dale L. BMP1-related metalloproteinases promote the development of ventral mesoderm in early Xenopus embryos. Dev Biol 1998; 195:144-57. [PMID: 9520331 DOI: 10.1006/dbio.1997.8840] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bone morphogenetic protein 1 (BMP1) is a metalloproteinase closely related to Drosophila Tolloid (Tld). Tld regulates dorsoventral patterning in early Drosophila embryos by enhancing the activity of Dpp, a member of the TGF-beta family most closely related to BMP2 and BMP4. In Xenopus BMP4 appears to play an essential role in dorsoventral patterning, promoting the development of ventral fates during gastrula stages. To determine if BMP1 has a role in regulating the activity of BMP4, we have isolated cDNAs for Xenopus BMP1 and a novel closely related gene that we have called xolloid (xld). Whereas xbmp1 is uniformly expressed at all stages tested, the initial uniform expression of xld becomes localized to two posterior ectodermal patches flanking the neural plate and later to the inner ectoderm of the developing tailbud. xld is also expressed in dorsal regions of the brain during tailbud stages and is especially abundant in the ventricular layer of the dorsal hindbrain caudal to the otic vesicle. Overexpression of either gene inhibits the development of dorsoanterior structures in whole embryos and ventralizes activin-induced dorsal mesoderm in animal caps. Since ventralization of activin-induced animal caps can be blocked by coinjecting a dominant-inhibitory receptor for BMP2 and BMP4, we suggest a role for BMP1 and Xld in regulating the ventralizing activity of these molecules.
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Affiliation(s)
- S A Goodman
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
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32
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Abstract
Activin has long-range effects in Xenopus development, inducing the mesodermally expressed brachyury gene up to 10 cell diameters from a localised source. Recent experiments show that activin diffuses through tissues to establish a morphogen gradient, and that the long-range effects are a direct result of activin signalling.
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Affiliation(s)
- L Dale
- Department of Anatomy and Developmental Biology, University College London, UK
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33
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Piccolo S, Agius E, Lu B, Goodman S, Dale L, De Robertis EM. Cleavage of Chordin by Xolloid metalloprotease suggests a role for proteolytic processing in the regulation of Spemann organizer activity. Cell 1997; 91:407-16. [PMID: 9363949 PMCID: PMC3070600 DOI: 10.1016/s0092-8674(00)80424-9] [Citation(s) in RCA: 317] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The Xolloid secreted metalloprotease, a tolloid-related protein, was found to cleave Chordin and Chordin/BMP-4 complexes at two specific sites in biochemical experiments Xolloid mRNA blocks secondary axes caused by chordin, but not by noggin, follistatin, or dominant-negative BMP receptor, mRNA injection. Xolloid-treated Chordin protein was unable to antagonize BMP activity. Furthermore, Xolloid digestion released biologically active BMPs from Chordin/BMP inactive complexes. Injection of dominant-negative Xolloid mRNA indicated that the in vivo function of Xolloid is to limit the extent of Spemann's organizer field. We propose that Xolloid regulates organizer function by a novel proteolytic mechanism involving a double inhibition pathway required to pattern the dorsoventral axis: [formula in text].
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Affiliation(s)
- S Piccolo
- Howard Hughes Medical Institute, Department of Biological Chemistry, University of California, Los Angeles 90095-1662, USA
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34
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Abstract
Extracellular ATP functions as a neurotransmitter and neuromodulator in the adult nervous system, and a signaling molecule in non-neural tissue, acting either via ligand-gated ion channels (P2X) or G-protein-coupled receptors (P2Y). ATP can cause an increase in intracellular Ca2+ (Ca2+i) in embryonic cells and so regulate cell proliferation, migration, and differentiation. We have isolated a Xenopus cDNA encoding a novel P2Y receptor, XlP2Y, which is expressed abundantly in developing embryos. Recombinant XlP2Y responds equally to all five naturally occurring nucleoside triphosphates (ATP, UTP, CTP, GTP, and ITP), which elicit a biphasic Ca2+-dependent Cl- current (ICl,Ca) where the second phase persists for up to 60 min. XlP2Y also causes a continuous release of Ca2+i and a low level persistent activation of ICl,Ca in Xenopus oocytes through the spontaneous efflux of ATP. mRNAs for XlP2Y are expressed transiently in the neural plate and tailbud during Xenopus development, coincident with neurogenesis. This restricted pattern of expression and novel pharmacological features confer unique properties to XlP2Y, which may play a key role in the early development of neural tissue.
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Affiliation(s)
- Y D Bogdanov
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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35
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Abstract
A pilot study was administered to determine if stroke caregivers felt they were adequately educated, trained, and prepared to care for their stroke survivor upon discharge. The convenience sample consisted of 26 stroke caregivers from four Indiana facilities with established therapy/rehabilitation units and two Indiana stroke clubs. Subjects were divided into groups according to the amount of time after discharge in the caregiver role (1-3 days, 10-14 days, greater than 3 months). Survey results were obtained by phone interviews and by self-administration. Compilation of data occurred over 5 months, and interpretation involved visual inspection and frequency distributions. Overall preparedness for the newer caregivers was a 4 (prepared); whereas, the more experienced caregivers' average score was a 3 (somewhat prepared). This study can help rehabilitation staff in their efforts to prepare caregivers for assisting stroke survivors at home.
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Affiliation(s)
- L Dale
- University of Indianapolis, Indianapolis, IN
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Cusimano RJ, Dale L, Butany JW. Minimally invasive cardiac surgery for removal of the greater saphenous vein. Can J Surg 1996; 39:386-8. [PMID: 8857986 PMCID: PMC3949958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
OBJECTIVE To determine if saphenous vein required for coronary bypass could be quickly, easily and safely removed with a minimally invasive technique. DESIGN A consecutive series. SETTING A university centre. MATERIAL AND METHODS In cadavers, a standard mediastinoscope was used to remove segments of the greater saphenous vein. Thigh segments, superior leg segments and ankle segments were removed. Fifteen minutes were allowed for removal of a segment. RESULTS Segments of vein 15 to 17 cm long could be removed. One segment could not be removed within 15 minutes. Thigh segments were easy to remove, calf segments were the most difficult. There were no avulsed side branches. All incisions were less than 5 cm long. CONCLUSIONS Saphenous vein can be harvested quickly and safely by a minimally invasive method. Lower extremity complications may be reduced and long-term patency improved with this in-situ technique of vein removal.
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Affiliation(s)
- R J Cusimano
- Division of Candiovascular Surgery, Toronto Hospital, Ont
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Jones CM, Dale L, Hogan BL, Wright CV, Smith JC. Bone morphogenetic protein-4 (BMP-4) acts during gastrula stages to cause ventralization of Xenopus embryos. Development 1996; 122:1545-54. [PMID: 8625841 DOI: 10.1242/dev.122.5.1545] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Injection of RNA encoding BMP-4 into the early Xenopus embryo suppresses formation of dorsal and anterior cell types. To understand this phenomenon, it is necessary to know the stage at which BMP-4 acts. In this paper, we present three lines of evidence showing that BMP-4 misexpression has no effect on the initial steps of mesoderm induction, either dorsal or ventral, but instead causes ventralization during gastrulation. Firstly, activation of organizer-specific genes such as goosecoid, Xnot, pintallavis and noggin occurs normally in embryos injected with BMP-4 RNA, but transcript levels are then rapidly down-regulated as gastrulation proceeds. Similarly, BMP-4 does not affect the initial activation of goosecoid by activin in animal caps, but expression then declines precipitously. Secondly, embryos made ventral by injection with BMP-4 RNA cannot be rescued by grafts of Spemann's organizer at gastrula stages. Such embryos therefore differ from those made ventral by UV-irradiation, where the defect occurs early and rescue can be effected by the organizer. Finally, the dorsalizing effects of the organizer, and of the candidate dorsalizing signal noggin, both of which exert their effects during gastrulation, can be counteracted by BMP-4. Together, these experiments demonstrate that BMP-4 can act during gastrulation both to promote ventral mesoderm differentiation and to attenuate dorsalizing signals derived from the organizer.
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Affiliation(s)
- C M Jones
- Division of Developmental Biology, National Institute for Medical Research, London, UK
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Dale L. Nursing overseas. A lesson in litigation. Nurs Times 1996; 92:40-1. [PMID: 8710576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Abstract
A novel operative technique for postinfarction ventricular septal defect has been used in 44 consecutive patients. The operation consists of excluding rather than excising the infarcted septum and ventricular walls. This is accomplished by performance of a left ventriculotomy through the infarcted muscle and securing a glutaraldehyde-fixed bovine pericardium patch to the endocardium of the left ventricle all around the infarcted myocardium. The ventriculotomy is simply closed over the pericardial patch. There were 21 men and 23 women whose mean age was 69 +/- 7 years. Twenty-nine patients were in cardiogenic shock at the time of operation. All patients had Doppler echocardiography and coronary angiography before operation. All but two patients were operated on during the acute phase of the myocardial infarction. There were six operative deaths. Postoperative complications included renal failure in 10 patients and respiratory failure in 18. Severe right ventricular dysfunction was the only independent predictor of operative mortality. Patients have been followed up for a mean of 40 +/- 34 months. There have been six late deaths and three of these were because of cardiac problems. The actuarial survival at 6 years was 66% +/- 7%. Only one patient had a small residual ventricular septal defect. Late postoperative assessment of ventricular function by echocardiography revealed that most patients had normal or mild impairment of right ventricular function and mild or moderate impairment of left ventricular function. Repair of acute postinfarction ventricular septal defect by endocardial patch with infarct exclusion of the left ventricule probably avoids additional damage to the right ventricle, remodels the acutely infarcted left ventricle, and enhances survival.
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Affiliation(s)
- T E David
- Division of Cardiovascular Surgery, Toronto Hospital, Ontario, Canada
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Schulte-Merker S, Smith JC, Dale L. Effects of truncated activin and FGF receptors and of follistatin on the inducing activities of BVg1 and activin: does activin play a role in mesoderm induction? EMBO J 1994; 13:3533-41. [PMID: 8062830 PMCID: PMC395257 DOI: 10.1002/j.1460-2075.1994.tb06660.x] [Citation(s) in RCA: 115] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activin and Vg1, two members of the TGF-beta family, are believed to play roles in mesoderm induction and axis formation in the amphibian embryo. Both molecules are provided maternally, either as protein (activin) or as RNA and protein (Vg1), and experiments with a truncated form of a type IIB activin receptor have led to the conclusion that activin is required for induction of mesoderm in vivo. In this paper we first show that truncated versions of two different Xenopus activin receptors also have severe effects on the activity of the mature region of Vg1, suggesting that such receptors may block the function of several members of the TGF-beta family. We go on to demonstrate that follistatin, a secreted protein which binds activin and blocks its activity, does not interfere with Vg1 signalling. Furthermore, overexpression of follistatin mRNA in Xenopus embryos does not perturb mesoderm formation. Taken together, our data show that the effects of truncated activin receptors on Xenopus development can be explained by the inhibition of Vg1 activity, while the lack of effect of follistatin argues against a function for activin in mesoderm induction.
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Affiliation(s)
- S Schulte-Merker
- Laboratory of Developmental Biology, National Institute for Medical Research, London, UK
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Abstract
Vg1 is a maternal mRNA localized to the vegetal hemisphere of Xenopus embryos during blastula stages, a region responsible for the induction of mesoderm in the adjacent marginal zone. Its homology to the transforming growth factor-beta family, which includes several proteins with mesoderm-inducing activity, suggests a role for Vg1 as an endogenous mesoderm-inducing factor. However, expression of Vg1 protein in the animal hemisphere, following injection of synthetic mRNA, has no effect on development, and isolated animal caps are not mesodermalized. It is shown that Vg1 protein fails to form dimers and is not processed to release the putative bioactive domain. Furthermore it is shown that the N-terminal signal peptide of Vg1 is not cleaved following translocation into the ER, which may explain the failure of this protein to dimerize. To explore the role of Vg1 in amphibian development, a fusion protein has been made of the preproregion of Xenopus bone morphogenetic protein-4 and the putative bioactive C-terminal domain of Vg1. This fusion protein forms dimers and the C-terminal domain of Vg1 is secreted. Injection of this construct into Xenopus embryos induces the formation of a second dorsal axis and isolated animal caps are mesodermalized. The results are consistent with a role for Vg1 in mesoderm induction during Xenopus development.
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Affiliation(s)
- L Dale
- School of Biochemistry, University of Birmingham, UK
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Abstract
The mesoderm of amphibian embryos such as Xenopus laevis arises through an inductive interaction in which cells of the vegetal hemisphere of the embryo act on overlying equatorial and animal pole cells. Three classes of 'mesoderm-inducing factor' (MIF) that might be responsible for this interaction in vivo have been discovered. These are members of the transforming growth factor type beta (TGF-beta), fibroblast growth factor (FGF) and Wnt families. Among the most potent MIFs are the activins, members of the TGF-beta family, but RNA for activin A and B is not detectable in the Xenopus embryo until neurula and late blastula stages, respectively, and this is probably too late for the molecules to act as natural inducers. In this paper, we use the polymerase chain reaction to clone additional members of the TGF-beta family that might possess mesoderm-inducing activity. We show that transcripts encoding Xenopus bone morphogenetic protein 4 (XBMP-4) are detectable in the unfertilized egg, and that injection of XBMP-4 RNA into the animal hemisphere of Xenopus eggs causes animal caps isolated from the resulting blastulae to express mesoderm-specific markers. Surprisingly, however, XBMP-4 preferentially induces ventral mesoderm, whereas the closely related activin induces axial tissues. Furthermore, the action of XBMP-4 is 'dominant' over that of activin. In this respect, XBMP-4 differs from basic FGF, another ventral inducer, where simultaneous treatment with FGF and activin results in activin-like responses. The dominance of XBMP-4 over activin may account for the ability of injected XBMP-4 RNA to 'ventralize' whole Xenopus embryos. It is interesting, however, that blastopore formation in such embryos can occur perfectly normally. This contrasts with embryos ventralized by UV-irradiation and suggests that XBMP-4-induced ventralization occurs after the onset of gastrulation.
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Affiliation(s)
- L Dale
- School of Biochemistry, University of Birmingham, UK
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Abstract
Like its vertebrate homologues, Xenopus wnt-8 and murine wnt-1, we find that Drosophila wingless (wg) protein causes axis duplication when overexpressed in embryos of Xenopus laevis after mRNA injection. In many cases, the secondary axes contain eyes and cement glands, which reflect the induction of the most dorsoanterior mesodermal type, prechordal mesoderm. We show that the extent of axis duplication is dependent on the embryonic site of expression, with ventral expression leading to a more posterior point of axis bifurcation. The observed duplications are due to de novo generation of new axes as shown by rescue of UV-irradiated embryos. The true dorsal mesoderm-inducing properties of wg protein are indicated by its ability to generate extensive duplications after mRNA injection into D-tier cells of 32-cell embryos. As revealed by lineage mapping, the majority of these D cell progeny populate the endoderm; injections into animal blastomeres at this stage are far less effective in inducing secondary axes. However, when expressed in isolated animal cap explants, wg protein induces only ventral mesoderm, unless basic fibroblast growth factor is added, whereupon induction of muscle and occasionally notochord is seen. We conclude that in intact embryos, wg acts in concert with other factors to cause axis duplication. Immunolocalisation studies in embryos indicate that wg protein remains localised to the blastomeres synthesizing it and has a patchy, often perinuclear distribution within these cells, although some gets to the surface. In oocytes, the pool of wg protein is entirely intracellular and relatively unstable. When the polyanion suramin is added, most of the intracellular material is recovered in the external medium.
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Affiliation(s)
- A Chakrabarti
- School of Biochemistry, University of Birmingham, UK
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Abstract
Vg1 is a maternal mRNA localized in the vegetal cortex of Xenopus laevis oocytes, that encodes a protein homologous to the mammalian growth factor TGF-beta. Using a polyclonal antibody to a T7-Vg1 fusion protein, we have identified the native protein. We find that a single protein of Mr 40 kd is immunoprecipitated following in vitro translation of oocyte poly(A)+ RNA, whilst two proteins of Mr 45 and 43.5 kd are immunoprecipitated from oocyte and embryo extracts. Synthesis of at least the 40 kd, in vitro, and 45 kd, in vivo, proteins is specifically inhibited following treatment of the respective systems with antisense Vg1 (but not histone H4) oligodeoxynucleotides. Tunicamycin treatment reveals the in vivo proteins to be glycosylated versions of a 40 kd protein, modified by the addition of either two or three N-linked oligosaccharide side chains. Both proteins are sensitive to digestion by the enzyme endoglycosidase-H, and are segregated within a membrane fraction from which they can be released by high pH treatment. Their synthesis is first detectable in stage IV oocytes and continues throughout early embryogenesis until the late gastrula. During embryogenesis the relative proportions of the two proteins change, the 45 kd protein being predominant in early embryogenesis and the 43.5 kd protein in late embryogenesis. Synthesis only occurs in the vegetal hemisphere at all stages; however, in the large oocyte diffusion of both proteins into the animal hemisphere occurs.
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Affiliation(s)
- L Dale
- School of Biochemistry, University of Birmingham, UK
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Dale L. All together now. Nurs Times 1989; 85:42-4. [PMID: 2928226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Shuttleworth J, Matthews G, Dale L, Baker C, Colman A. Antisense oligodeoxyribonucleotide-directed cleavage of maternal mRNA in Xenopus oocytes and embryos. Gene X 1988; 72:267-75. [PMID: 2468567 DOI: 10.1016/0378-1119(88)90152-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We have investigated the effect of specific antisense oligodeoxynucleotides (oligos) on endogenous histone H4 mRNA in Xenopus oocytes, eggs and embryos. In unfertilised eggs and non-matured oocytes, one 20-mer oligo (H4-1) mediated the RNAse H-like cleavage of up to 95% of H4 mRNA (which included polysomal mRNA), and cleavage was still obtained when the size of the oligo was reduced to a 10-mer; no cleavage was observed with 6- and 8-mers. The residual uncleaved mRNA appeared to be completely inaccessible to H4-1 since a second injection caused no further cleavage. A second 20-mer (H4-2) directed against a different region of H4 mRNA was much less effective (less than 5% cleavage). In fertilised embryos, injections of H4-1 and an oligo directed against the localised Vg1 mRNA caused less cleavage than in oocytes and also showed signs of inducing localised, non-specific mRNA cleavage. However we have been able to prepare fertilised embryos devoid of Vg1 mRNA by maturing and fertilising oligo-injected oocytes in vitro.
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Collocott SJ, Driver R, Dale L, Dou SX. Schottky anomaly in the heat capacity of the high-Tc superconductor YBa2Cu. Phys Rev B Condens Matter 1988; 37:7917-7919. [PMID: 9944111 DOI: 10.1103/physrevb.37.7917] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Abstract
A prospective, controlled study was performed to compare side effect incidences after lumbar iohexol myelography (n = 97) and diagnostic lumbar puncture (n = 85). No significant side effect incidence differences (iohexol vs. controls) were found regarding number of patients with any side effect (63 vs. 73%), headache (44 vs. 54%), nausea, dizziness, visual, auditory, or psychic symptoms. Early-onset headache occurred significantly more often in the iohexol group (17 vs 5%), while postural headache occurred most frequently after lumbar puncture (25 vs. 41%). These results suggest that apart from the slight early-onset headache, most side effects after lumbar iohexol myelography are related to the puncture per se, not to the contrast agent.
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Abstract
We have further analysed the roles of mesoderm induction and dorsalization in the formation of a regionally specified mesoderm in early embryos of Xenopus laevis. First, we have examined the regional specificity of mesoderm induction by isolating single blastomeres from the vegetalmost tier of the 32-cell embryo and combining each with a lineage-labelled (FDA) animal blastomere tier. Whereas dorsovegetal (D1) blastomeres induce 'dorsal-type' mesoderm (notochord and muscle), laterovegetal and ventrovegetal blastomeres (D2-4) induce either 'intermediate-type' (muscle, mesothelium, mesenchyme and blood) or 'ventral-type' (mesothelium, mesenchyme and blood) mesoderm. No significant difference in inductive specificity between blastomeres D2, 3 and 4 could be detected. We also show that laterovegetal and ventrovegetal blastomeres from early cleavage stages can have a dorsal inductive potency partially activated by operative procedures, resulting in the induction of intermediate-type mesoderm. Second, we have determined the state of specification of ventral blastomeres by isolating and culturing them in vitro between the 4-cell stage and the early gastrula stage. The majority of isolates from the ventral half of the embryo gave extreme ventral types of differentiation at all stages tested. Although a minority of cases formed intermediate-type and dorsal-type mesoderms we believe these to result from either errors in our assessment of the prospective DV axis or from an enhancement, provoked by microsurgery, of some dorsal inductive specificity. The results of induction and isolation experiments suggest that only two states of specification exist in the mesoderm of the pregastrula embryo, a dorsal type and a ventral type. Finally we have made a comprehensive series of combinations between different regions of the marginal zone using FDA to distinguish the components. We show that, in combination with dorsal-type mesoderm, ventral-type mesoderm becomes dorsalized to the level of intermediate-type mesoderm. Dorsal-type mesoderm is not ventralized in these combinations. Dorsalizing activity is confined to a restricted sector of the dorsal marginal zone, it is wider than the prospective notochord and seems to be graded from a high point at the dorsal midline. The results of these experiments strengthen the case for the three-signal model proposed previously, i.e. dorsal and ventral mesoderm inductions followed by dorsalization, as the simplest explanation capable of accounting for regional specification within the mesoderm of early Xenopus embryos.
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Affiliation(s)
- L Dale
- Imperial Cancer Research Fund, Developmental Biology Unit, University of Oxford, UK
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