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Conover CA, Oxvig C. The Pregnancy-Associated Plasma Protein-A (PAPP-A) Story. Endocr Rev 2023; 44:1012-1028. [PMID: 37267421 DOI: 10.1210/endrev/bnad017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/01/2023] [Accepted: 05/31/2023] [Indexed: 06/04/2023]
Abstract
Pregnancy-associated plasma protein-A (PAPP-A) was first identified in the early 1970s as a placental protein of unknown function, present at high concentrations in the circulation of pregnant women. In the mid-to-late 1990s, PAPP-A was discovered to be a metzincin metalloproteinase, expressed by many nonplacental cells, that regulates local insulin-like growth factor (IGF) activity through cleavage of high-affinity IGF binding proteins (IGFBPs), in particular IGFBP-4. With PAPP-A as a cell surface-associated enzyme, the reduced affinity of the cleavage fragments results in increased IGF available to bind and activate IGF receptors in the pericellular environment. This proteolytic regulation of IGF activity is important, since the IGFs promote proliferation, differentiation, migration, and survival in various normal and cancer cells. Thus, there has been a steady growth in investigation of PAPP-A structure and function outside of pregnancy. This review provides historical perspective on the discovery of PAPP-A and its structure and cellular function, highlights key studies of the first 50 years in PAPP-A research, and introduces new findings from recent years.
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Affiliation(s)
- Cheryl A Conover
- Division of Endocrinology, Mayo Clinic, Rochester, MN 55905, USA
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
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2
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Barrett LM, Mitchell DM, Meighan PC, Varnum MD, Stenkamp DL. Dynamic functional and structural remodeling during retinal regeneration in zebrafish. Front Mol Neurosci 2022; 15:1070509. [PMID: 36533135 PMCID: PMC9748287 DOI: 10.3389/fnmol.2022.1070509] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 11/14/2022] [Indexed: 12/03/2022] Open
Abstract
Introduction Zebrafish regenerate their retinas following damage, resulting in restoration of visual function. Here we evaluate recovery of retinal function through qualitative and quantitative analysis of the electroretinogram (ERG) over time following retinal damage, in correlation to histological features of regenerated retinal tissue. Methods Retinas of adult zebrafish were lesioned by intravitreal injection of 10 μM (extensive lesion; destroys all neurons) or 2 μM (selective lesion; spares photoreceptors) ouabain. Unlesioned contralateral retinas served as controls. Function of retinal circuitry was analyzed at selected timepoints using ERG recordings from live zebrafish, and whole eyes were processed for histological analyses immediately thereafter. Results Qualitative and quantitative assessment of waveforms during retinal regeneration revealed dynamic changes that were heterogeneous on an individual level within each sampling time, but still followed common waveform recovery patterns on a per-fish and population-level basis. Early in the regeneration period (13-30 days post injury; DPI), for both lesion types, b-waves were essentially not detected, and unmasked increased apparent amplitudes, implicit times, and half-widths of a-waves (vs. controls). In control recordings, d-waves were not obviously detected, but apparent d-waves (OFF-bipolar responses) from regenerating retinas of several fish became prominent by 30DPI and dominated the post-photoreceptor response (PPR). Beyond 45DPI, b-waves became detectable, and the ratio of apparent d- to b-wave contributions progressively shifted with most, but not all, fish displaying a b-wave dominated PPR. At the latest timepoints (extensive, 90DPI; selective, 80DPI), recordings with measurable b-waves approached a normal waveform (implicit times and half-widths), but amplitudes were not restored to control levels. Histological analyses of the retinas from which ERGs were recorded showed that as regeneration progressed, PKCa + ON-bipolar terminals and parvalbumin + amacrine cell processes became more stereotypically positioned within the deep sublaminae of the INL over recovery time after each lesion type, consistent with the shift in PPR seen in the ERG recordings. Discussion Taken together, these data suggest that photoreceptor-OFF-bipolar component/connectivity may functionally recover and mature earlier during regeneration compared to the photoreceptor-ON-bipolar component, though the timeframe in which such recovery happens is heterogeneous on a per-fish basis. Collectively our studies suggest gradual restoration of ON-bipolar functional circuitry during retinal regeneration.
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Affiliation(s)
- Lindsey M. Barrett
- Department of Biological Sciences, University of Idaho, Moscow, ID, United States
| | - Diana M. Mitchell
- Department of Biological Sciences, University of Idaho, Moscow, ID, United States
| | - Peter C. Meighan
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, United States
| | - Michael D. Varnum
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, United States
| | - Deborah L. Stenkamp
- Department of Biological Sciences, University of Idaho, Moscow, ID, United States,*Correspondence: Deborah L. Stenkamp,
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Yoon B, Yeung P, Santistevan N, Bluhm LE, Kawasaki K, Kueper J, Dubielzig R, VanOudenhove J, Cotney J, Liao EC, Grinblat Y. Zebrafish models of alx-linked frontonasal dysplasia reveal a role for Alx1 and Alx3 in the anterior segment and vasculature of the developing eye. Biol Open 2022; 11:bio059189. [PMID: 35142342 PMCID: PMC9167625 DOI: 10.1242/bio.059189] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 01/28/2022] [Indexed: 11/18/2022] Open
Abstract
The cellular and genetic mechanisms that coordinate formation of facial sensory structures with surrounding skeletal and soft tissue elements remain poorly understood. Alx1, a homeobox transcription factor, is a key regulator of midfacial morphogenesis. ALX1 mutations in humans are linked to severe congenital anomalies of the facial skeleton (frontonasal dysplasia, FND) with malformation or absence of eyes and orbital contents (micro- and anophthalmia). Zebrafish with loss-of-function alx1 mutations develop with craniofacial and ocular defects of variable penetrance, likely due to compensatory upregulation in expression of a paralogous gene, alx3. Here we show that zebrafish alx1;alx3 mutants develop with highly penetrant cranial and ocular defects that resemble human ALX1-linked FND. alx1 and alx3 are expressed in anterior cranial neural crest (aCNC), which gives rise to the anterior neurocranium (ANC), anterior segment structures of the eye and vascular pericytes. Consistent with a functional requirement for alx genes in aCNC, alx1; alx3 mutants develop with nearly absent ANC and grossly aberrant hyaloid vasculature and ocular anterior segment, but normal retina. In vivo lineage labeling identified a requirement for alx1 and alx3 during aCNC migration, and transcriptomic analysis suggested oxidative stress response as a key target mechanism of this function. Oxidative stress is a hallmark of fetal alcohol toxicity, and we found increased penetrance of facial and ocular malformations in alx1 mutants exposed to ethanol, consistent with a protective role for alx1 against ethanol toxicity. Collectively, these data demonstrate a conserved role for zebrafish alx genes in controlling ocular and facial development, and a novel role in protecting these key midfacial structures from ethanol toxicity during embryogenesis. These data also reveal novel roles for alx genes in ocular anterior segment formation and vascular development and suggest that retinal deficits in alx mutants may be secondary to aberrant ocular vascularization and anterior segment defects. This study establishes robust zebrafish models for interrogating conserved genetic mechanisms that coordinate facial and ocular development, and for exploring gene--environment interactions relevant to fetal alcohol syndrome.
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Affiliation(s)
- Baul Yoon
- Departments of Integrative Biology and Neuroscience, University of Wisconsin, Madison, WI 53706, USA
- Genetics Ph.D. Training Program, University of Wisconsin, Madison, WI 53706, USA
| | - Pan Yeung
- Center for Regenerative Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, 02114, USA
| | - Nicholas Santistevan
- Departments of Integrative Biology and Neuroscience, University of Wisconsin, Madison, WI 53706, USA
- Genetics Ph.D. Training Program, University of Wisconsin, Madison, WI 53706, USA
| | - Lauren E. Bluhm
- Departments of Integrative Biology and Neuroscience, University of Wisconsin, Madison, WI 53706, USA
| | - Kenta Kawasaki
- Center for Regenerative Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, 02114, USA
| | - Janina Kueper
- Center for Regenerative Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, 02114, USA
- Institute of Human Genetics, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Richard Dubielzig
- Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW), University of Wisconsin, Madison, WI 53706, USA
| | - Jennifer VanOudenhove
- University of Connecticut School of Medicine, Department of Genetics and Genome Sciences, Farmington, CT 06030, USA
| | - Justin Cotney
- University of Connecticut School of Medicine, Department of Genetics and Genome Sciences, Farmington, CT 06030, USA
| | - Eric C. Liao
- Center for Regenerative Medicine, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, 02114, USA
| | - Yevgenya Grinblat
- Departments of Integrative Biology and Neuroscience, University of Wisconsin, Madison, WI 53706, USA
- Genetics Ph.D. Training Program, University of Wisconsin, Madison, WI 53706, USA
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Onesto MM, Short CA, Rempel SK, Catlett TS, Gomez TM. Growth Factors as Axon Guidance Molecules: Lessons From in vitro Studies. Front Neurosci 2021; 15:678454. [PMID: 34093120 PMCID: PMC8175860 DOI: 10.3389/fnins.2021.678454] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 04/26/2021] [Indexed: 11/13/2022] Open
Abstract
Growth cones at the tips of extending axons navigate through developing organisms by probing extracellular cues, which guide them through intermediate steps and onto final synaptic target sites. Widespread focus on a few guidance cue families has historically overshadowed potentially crucial roles of less well-studied growth factors in axon guidance. In fact, recent evidence suggests that a variety of growth factors have the ability to guide axons, affecting the targeting and morphogenesis of growth cones in vitro. This review summarizes in vitro experiments identifying responses and signaling mechanisms underlying axon morphogenesis caused by underappreciated growth factors.
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Affiliation(s)
| | | | | | | | - Timothy M. Gomez
- Neuroscience Training Program and Cell and Molecular Biology Program, Department of Neuroscience, University of Wisconsin–Madison, Madison, WI, United States
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LIM Homeobox 4 (lhx4) regulates retinal neural differentiation and visual function in zebrafish. Sci Rep 2021; 11:1977. [PMID: 33479361 PMCID: PMC7820405 DOI: 10.1038/s41598-021-81211-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 01/04/2021] [Indexed: 01/29/2023] Open
Abstract
LIM homeobox 4 (LHX4) is expressed in the photoreceptors (PRs) of the outer nuclear layer (ONL) and bipolar cells (BCs) of the inner nuclear layer (INL) in mouse and chicken retina. It regulates the subtype-specific development of rod BCs and cone BCs in the mouse retina. However, no report has been published on its expression and function in the zebrafish retina. In this study, we assessed the expression of Lhx4 using in situ hybridization (ISH) technique and explored its role in zebrafish (Danio rerio) retinal development via morpholino (MO) technology. We found that the expression of lhx4 in the zebrafish retina begins 48 h post-fertilization (hpf) and is continuously expressed in the ONL and INL. A zebrafish model constructed with lhx4 knockdown in the eyes through vivo-MO revealed that: lhx4 knockdown inhibits the differentiation of Parvalbumin+ amacrine cells (ACs) and Rhodopsin+ rod photoreceptors (RPs), enhances the expression of visual system homeobox 2 (vsx2); and damages the responses of zebrafish to light stimulus, without affecting the differentiation of OFF-BCs and rod BCs, and apoptosis in the retina. These findings reveal that lhx4 regulates neural differentiation in the retina and visual function during zebrafish embryonic development.
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Liu C, Li S, Noer PR, Kjaer-Sorensen K, Juhl AK, Goldstein A, Ke C, Oxvig C, Duan C. The metalloproteinase Papp-aa controls epithelial cell quiescence-proliferation transition. eLife 2020; 9:e52322. [PMID: 32293560 PMCID: PMC7185994 DOI: 10.7554/elife.52322] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 04/11/2020] [Indexed: 02/06/2023] Open
Abstract
Human patients carrying PAPP-A2 inactivating mutations have low bone mineral density. The underlying mechanisms for this reduced calcification are poorly understood. Using a zebrafish model, we report that Papp-aa regulates bone calcification by promoting Ca2+-transporting epithelial cell (ionocyte) quiescence-proliferation transition. Ionocytes, which are normally quiescent, re-enter the cell cycle under low [Ca2+] stress. Genetic deletion of Papp-aa, but not the closely related Papp-ab, abolished ionocyte proliferation and reduced calcified bone mass. Loss of Papp-aa expression or activity resulted in diminished IGF1 receptor-Akt-Tor signaling in ionocytes. Under low Ca2+ stress, Papp-aa cleaved Igfbp5a. Under normal conditions, however, Papp-aa proteinase activity was suppressed and IGFs were sequestered in the IGF/Igfbp complex. Pharmacological disruption of the IGF/Igfbp complex or adding free IGF1 activated IGF signaling and promoted ionocyte proliferation. These findings suggest that Papp-aa-mediated local Igfbp5a cleavage functions as a [Ca2+]-regulated molecular switch linking IGF signaling to bone calcification by stimulating epithelial cell quiescence-proliferation transition under low Ca2+ stress.
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Affiliation(s)
- Chengdong Liu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Shuang Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
- College of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Pernille Rimmer Noer
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | | | - Anna Karina Juhl
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Allison Goldstein
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Caihuan Ke
- College of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Cunming Duan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
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Alassaf M, Daykin EC, Mathiaparanam J, Wolman MA. Pregnancy-associated plasma protein-aa supports hair cell survival by regulating mitochondrial function. eLife 2019; 8:47061. [PMID: 31205004 PMCID: PMC6594750 DOI: 10.7554/elife.47061] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 06/14/2019] [Indexed: 12/18/2022] Open
Abstract
To support cell survival, mitochondria must balance energy production with oxidative stress. Inner ear hair cells are particularly vulnerable to oxidative stress; thus require tight mitochondrial regulation. We identified a novel molecular regulator of the hair cells’ mitochondria and survival: Pregnancy-associated plasma protein-aa (Pappaa). Hair cells in zebrafish pappaa mutants exhibit mitochondrial defects, including elevated mitochondrial calcium, transmembrane potential, and reactive oxygen species (ROS) production and reduced antioxidant expression. In pappaa mutants, hair cell death is enhanced by stimulation of mitochondrial calcium or ROS production and suppressed by a mitochondrial ROS scavenger. As a secreted metalloprotease, Pappaa stimulates extracellular insulin-like growth factor 1 (IGF1) bioavailability. We found that the pappaa mutants’ enhanced hair cell loss can be suppressed by stimulation of IGF1 availability and that Pappaa-IGF1 signaling acts post-developmentally to support hair cell survival. These results reveal Pappaa as an extracellular regulator of hair cell survival and essential mitochondrial function.
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Affiliation(s)
- Mroj Alassaf
- Department of Integrative Biology, University of Wisconsin, Madison, United States.,Neuroscience Training Program, University of Wisconsin, Madison, United States
| | - Emily C Daykin
- Department of Integrative Biology, University of Wisconsin, Madison, United States
| | - Jaffna Mathiaparanam
- Department of Integrative Biology, University of Wisconsin, Madison, United States
| | - Marc A Wolman
- Department of Integrative Biology, University of Wisconsin, Madison, United States
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Angueyra JM, Kindt KS. Leveraging Zebrafish to Study Retinal Degenerations. Front Cell Dev Biol 2018; 6:110. [PMID: 30283779 PMCID: PMC6156122 DOI: 10.3389/fcell.2018.00110] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 08/20/2018] [Indexed: 12/11/2022] Open
Abstract
Retinal degenerations are a heterogeneous group of diseases characterized by death of photoreceptors and progressive loss of vision. Retinal degenerations are a major cause of blindness in developed countries (Bourne et al., 2017; De Bode, 2017) and currently have no cure. In this review, we will briefly review the latest advances in therapies for retinal degenerations, highlighting the current barriers to study and develop therapies that promote photoreceptor regeneration in mammals. In light of these barriers, we present zebrafish as a powerful model to study photoreceptor regeneration and their integration into retinal circuits after regeneration. We outline why zebrafish is well suited for these analyses and summarize the powerful tools available in zebrafish that could be used to further uncover the mechanisms underlying photoreceptor regeneration and rewiring. In particular, we highlight that it is critical to understand how rewiring occurs after regeneration and how it differs from development. Insights derived from photoreceptor regeneration and rewiring in zebrafish may provide leverage to develop therapeutic targets to treat retinal degenerations.
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Affiliation(s)
- Juan M. Angueyra
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD, United States
| | - Katie S. Kindt
- Section on Sensory Cell Development and Function, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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