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Giffen KP, Liu H, Yamane KL, Li Y, Chen L, Kramer KL, Zallocchi M, He DZ. Molecular Specializations Underlying Phenotypic Differences in Inner Ear Hair Cells of Zebrafish and Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.24.595729. [PMID: 38826418 PMCID: PMC11142236 DOI: 10.1101/2024.05.24.595729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Hair cells (HCs) are the sensory receptors of the auditory and vestibular systems in the inner ears of vertebrates that selectively transduce mechanical stimuli into electrical activity. Although all HCs have the hallmark stereocilia bundle for mechanotransduction, HCs in non-mammals and mammals differ in their molecular specialization in the apical, basolateral and synaptic membranes. HCs of non-mammals, such as zebrafish (zHCs), are electrically tuned to specific frequencies and possess an active process in the stereocilia bundle to amplify sound signals. Mammalian cochlear HCs, in contrast, are not electrically tuned and achieve amplification by somatic motility of outer HCs (OHCs). To understand the genetic mechanisms underlying differences among adult zebrafish and mammalian cochlear HCs, we compared their RNA-seq-characterized transcriptomes, focusing on protein-coding orthologous genes related to HC specialization. There was considerable shared expression of gene orthologs among the HCs, including those genes associated with mechanotransduction, ion transport/channels, and synaptic signaling. For example, both zebrafish and mouse HCs express Tmc1, Lhfpl5, Tmie, Cib2, Cacna1d, Cacnb2, Otof, Pclo and Slc17a8. However, there were some notable differences in expression among zHCs, OHCs, and inner HCs (IHCs), which likely underlie the distinctive physiological properties of each cell type. Tmc2 and Cib3 were not detected in adult mouse HCs but tmc2a and b and cib3 were highly expressed in zHCs. Mouse HCs express Kcna10, Kcnj13, Kcnj16, and Kcnq4, which were not detected in zHCs. Chrna9 and Chrna10 were expressed in mouse HCs. In contrast, chrna10 was not detected in zHCs. OHCs highly express Slc26a5 which encodes the motor protein prestin that contributes to OHC electromotility. However, zHCs have only weak expression of slc26a5, and subsequently showed no voltage dependent electromotility when measured. Notably, the zHCs expressed more paralogous genes including those associated with HC-specific functions and transcriptional activity, though it is unknown whether they have functions similar to their mammalian counterparts. There was overlap in the expressed genes associated with a known hearing phenotype. Our analyses unveil substantial differences in gene expression patterns that may explain phenotypic specialization of zebrafish and mouse HCs. This dataset also includes several protein-coding genes to further the functional characterization of HCs and study of HC evolution from non-mammals to mammals.
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Affiliation(s)
- Kimberlee P. Giffen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
- Augusta University/University of Georgia Medical Partnership, Athens, GA, USA
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, USA
| | - Kacey L. Yamane
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, USA
| | - Yi Li
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, USA
- Department of Otorhinolaryngology, Beijing Tongren Hospital, Beijing Capital Medical University, Beijing, China
| | - Lei Chen
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Ken L. Kramer
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, USA
| | - Marisa Zallocchi
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, USA
| | - David Z.Z. He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, USA
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Xu W, Zhu C, Gao X, Wu B, Xu H, Hu M, Zeng H, Gan X, Feng C, Zheng J, Bo J, He LS, Qiu Q, Wang W, He S, Wang K. Chromosome-level genome assembly of hadal snailfish reveals mechanisms of deep-sea adaptation in vertebrates. eLife 2023; 12:RP87198. [PMID: 38134226 PMCID: PMC10746142 DOI: 10.7554/elife.87198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2023] Open
Abstract
As the deepest vertebrate in the ocean, the hadal snailfish (Pseudoliparis swirei), which lives at a depth of 6,000-8,000 m, is a representative case for studying adaptation to extreme environments. Despite some preliminary studies on this species in recent years, including their loss of pigmentation, visual and skeletal calcification genes, and the role of trimethylamine N-oxide in adaptation to high-hydrostatic pressure, it is still unknown how they evolved and why they are among the few vertebrate species that have successfully adapted to the deep-sea environment. Using genomic data from different trenches, we found that the hadal snailfish may have entered and fully adapted to such extreme environments only in the last few million years. Meanwhile, phylogenetic relationships show that they spread into different trenches in the Pacific Ocean within a million years. Comparative genomic analysis has also revealed that the genes associated with perception, circadian rhythms, and metabolism have been extensively modified in the hadal snailfish to adapt to its unique environment. More importantly, the tandem duplication of a gene encoding ferritin significantly increased their tolerance to reactive oxygen species, which may be one of the important factors in their adaptation to high-hydrostatic pressure.
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Affiliation(s)
- Wenjie Xu
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Chenglong Zhu
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Xueli Gao
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Baosheng Wu
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Han Xu
- Institute of Deep-Sea Science and Engineering, Chinese Academy of SciencesSanyaChina
| | - Mingliang Hu
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Honghui Zeng
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of SciencesWuhanChina
| | - Xiaoni Gan
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of SciencesWuhanChina
| | - Chenguang Feng
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Jiangmin Zheng
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Jing Bo
- Institute of Deep-Sea Science and Engineering, Chinese Academy of SciencesSanyaChina
| | - Li-Sheng He
- Institute of Deep-Sea Science and Engineering, Chinese Academy of SciencesSanyaChina
| | - Qiang Qiu
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Wen Wang
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
| | - Shunping He
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
- Institute of Deep-Sea Science and Engineering, Chinese Academy of SciencesSanyaChina
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of SciencesWuhanChina
| | - Kun Wang
- School of Ecology and Environment, Northwestern Polytechnical UniversityXi'anChina
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New Insights into the Identity of the DFNA58 Gene. Genes (Basel) 2022; 13:genes13122274. [PMID: 36553541 PMCID: PMC9777997 DOI: 10.3390/genes13122274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/21/2022] [Accepted: 11/28/2022] [Indexed: 12/12/2022] Open
Abstract
Hearing loss is the most common sensory deficit, affecting 466 million people worldwide. The vast and diverse genes involved reflect the complexity of auditory physiology, which requires the use of animal models in order to gain a fuller understanding. Among the loci with a yet-to-be validated gene is the DFNA58, in which ~200 Kb genomic duplication, including three protein-coding genes (PLEK, CNRIP1, and PPP3R1's exon1), was found to segregate with autosomal dominant hearing loss. Through whole genome sequencing, the duplication was found to be in tandem and inserted in an intergenic region, without the disruption of the topological domains. Reanalysis of transcriptomes data studies (zebrafish and mouse), and RT-qPCR analysis of adult zebrafish target organs, in order to access their orthologues expression, highlighted promising results with Cnrip1a, corroborated by zebrafish in situ hybridization and immunofluorescence. Mouse data also suggested Cnrip1 as the best candidate for a relevant role in auditory physiology, and its importance in hearing seems to have remained conserved but the cell type exerting its function might have changed, from hair cells to spiral ganglion neurons.
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Mauduit O, Aure MH, Delcroix V, Basova L, Srivastava A, Umazume T, Mays JW, Bellusci S, Tucker AS, Hajihosseini MK, Hoffman MP, Makarenkova HP. A mesenchymal to epithelial switch in Fgf10 expression specifies an evolutionary-conserved population of ionocytes in salivary glands. Cell Rep 2022; 39:110663. [PMID: 35417692 PMCID: PMC9113928 DOI: 10.1016/j.celrep.2022.110663] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 01/21/2022] [Accepted: 03/21/2022] [Indexed: 12/21/2022] Open
Abstract
Fibroblast growth factor 10 (FGF10) is well established as a mesenchyme-derived growth factor and a critical regulator of fetal organ development in mice and humans. Using a single-cell RNA sequencing (RNA-seq) atlas of salivary gland (SG) and a tamoxifen inducible Fgf10CreERT2:R26-tdTomato mouse, we show that FGF10pos cells are exclusively mesenchymal until postnatal day 5 (P5) but, after P7, there is a switch in expression and only epithelial FGF10pos cells are observed after P15. Further RNA-seq analysis of sorted mesenchymal and epithelial FGF10pos cells shows that the epithelial FGF10pos population express the hallmarks of ancient ionocyte signature Forkhead box i1 and 2 (Foxi1, Foxi2), Achaete-scute homolog 3 (Ascl3), and the cystic fibrosis transmembrane conductance regulator (Cftr). We propose that epithelial FGF10pos cells are specialized SG ionocytes located in ducts and important for the ionic modification of saliva. In addition, they maintain FGF10-dependent gland homeostasis via communication with FGFR2bpos ductal and myoepithelial cells. Mauduit et al. identified unique FGF10-expressing ionocytes in salivary glands. FGF10 expression shifts from fibroblasts to epithelial ionocytes during postnatal development. Ionocytes play a dual role in salivary gland homeostasis; they maintain specific ion composition in saliva and act as niche cells, providing growth factor support for other epithelial cells.
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Affiliation(s)
- Olivier Mauduit
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Marit H Aure
- Matrix and Morphogenesis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | - Vanessa Delcroix
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Liana Basova
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Amrita Srivastava
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Takeshi Umazume
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jacqueline W Mays
- Oral Immunobiology Unit, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | - Saverio Bellusci
- Cardio-Pulmonary Institute (CPI) and Department of Pulmonary and Critical Care Medicine and Infectious Diseases, Universities of Giessen and Marburg Lung Center (UGMLC), The German Center for Lung Research (DZL), Justus-Liebig University Giessen, 35392 Giessen, Germany
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, King's College London, London WC2R 2LS, UK
| | | | - Matthew P Hoffman
- Matrix and Morphogenesis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Helen P Makarenkova
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Giffen KP, Li Y, Liu H, Zhao XC, Zhang CJ, Shen RJ, Wang T, Janesick A, Chen BB, Gong SS, Kachar B, Jin ZB, He DZ. Mutation of SLC7A14 causes auditory neuropathy and retinitis pigmentosa mediated by lysosomal dysfunction. SCIENCE ADVANCES 2022; 8:eabk0942. [PMID: 35394837 PMCID: PMC8993119 DOI: 10.1126/sciadv.abk0942] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 02/22/2022] [Indexed: 05/13/2023]
Abstract
Lysosomes contribute to cellular homeostasis via processes including macromolecule degradation, nutrient sensing, and autophagy. Defective proteins related to lysosomal macromolecule catabolism are known to cause a range of lysosomal storage diseases; however, it is unclear whether mutations in proteins involved in homeostatic nutrient sensing mechanisms cause syndromic sensory disease. Here, we show that SLC7A14, a transporter protein mediating lysosomal uptake of cationic amino acids, is evolutionarily conserved in vertebrate mechanosensory hair cells and highly expressed in lysosomes of mammalian cochlear inner hair cells (IHCs) and retinal photoreceptors. Autosomal recessive mutation of SLC7A14 caused loss of IHCs and photoreceptors, leading to presynaptic auditory neuropathy and retinitis pigmentosa in mice and humans. Loss-of-function mutation altered protein trafficking and increased basal autophagy, leading to progressive cell degeneration. This study implicates autophagy-lysosomal dysfunction in syndromic hearing and vision loss in mice and humans.
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Affiliation(s)
- Kimberlee P. Giffen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University/University of Georgia Medical Partnership, Athens, GA 30602, USA
| | - Yi Li
- Beijing Institute of Otorhinolaryngology, Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Xiao-Chang Zhao
- Beijing Institute of Otorhinolaryngology, Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Chang-Jun Zhang
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Ren-Juan Shen
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Tianying Wang
- Beijing Institute of Otorhinolaryngology, Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Amanda Janesick
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305, USA
| | - Bo-Bei Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Wenzhou 325027, China
| | - Shu-Sheng Gong
- Department of Otorhinolaryngology-Head and Neck Surgery, Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Bechara Kachar
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zi-Bing Jin
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - David Z. He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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Riley SE, Feng Y, Hansen CG. Hippo-Yap/Taz signalling in zebrafish regeneration. NPJ Regen Med 2022; 7:9. [PMID: 35087046 PMCID: PMC8795407 DOI: 10.1038/s41536-022-00209-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 12/14/2021] [Indexed: 12/29/2022] Open
Abstract
The extent of tissue regeneration varies widely between species. Mammals have a limited regenerative capacity whilst lower vertebrates such as the zebrafish (Danio rerio), a freshwater teleost, can robustly regenerate a range of tissues, including the spinal cord, heart, and fin. The molecular and cellular basis of this altered response is one of intense investigation. In this review, we summarise the current understanding of the association between zebrafish regeneration and Hippo pathway function, a phosphorylation cascade that regulates cell proliferation, mechanotransduction, stem cell fate, and tumorigenesis, amongst others. We also compare this function to Hippo pathway activity in the regenerative response of other species. We find that the Hippo pathway effectors Yap/Taz facilitate zebrafish regeneration and that this appears to be latent in mammals, suggesting that therapeutically promoting precise and temporal YAP/TAZ signalling in humans may enhance regeneration and hence reduce morbidity.
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Affiliation(s)
- Susanna E Riley
- University of Edinburgh Centre for Inflammation Research, Institute for Regeneration and Repair, Queen's Medical Research Institute, Edinburgh bioQuarter, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Yi Feng
- University of Edinburgh Centre for Inflammation Research, Institute for Regeneration and Repair, Queen's Medical Research Institute, Edinburgh bioQuarter, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Carsten Gram Hansen
- University of Edinburgh Centre for Inflammation Research, Institute for Regeneration and Repair, Queen's Medical Research Institute, Edinburgh bioQuarter, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.
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7
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Arendt D. Animal evolution: Of flame and collar cells. Curr Biol 2021; 31:R1003-R1006. [PMID: 34428408 DOI: 10.1016/j.cub.2021.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Nephridia are small excretory organs that function in waste disposal and osmoregulation in a wide range of animals but differ in type and germ-layer origin. A new comparison of gene expression in disparate species supports homology of nephridia across bilaterian animals, and their origin from ciliated epidermal cells.
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Wilkerson BA, Zebroski HL, Finkbeiner CR, Chitsazan AD, Beach KE, Sen N, Zhang RC, Bermingham-McDonogh O. Novel cell types and developmental lineages revealed by single-cell RNA-seq analysis of the mouse crista ampullaris. eLife 2021; 10:e60108. [PMID: 34003106 PMCID: PMC8189719 DOI: 10.7554/elife.60108] [Citation(s) in RCA: 7] [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: 06/16/2020] [Accepted: 05/17/2021] [Indexed: 12/16/2022] Open
Abstract
This study provides transcriptomic characterization of the cells of the crista ampullaris, sensory structures at the base of the semicircular canals that are critical for vestibular function. We performed single-cell RNA-seq on ampullae microdissected from E16, E18, P3, and P7 mice. Cluster analysis identified the hair cells, support cells and glia of the crista as well as dark cells and other nonsensory epithelial cells of the ampulla, mesenchymal cells, vascular cells, macrophages, and melanocytes. Cluster-specific expression of genes predicted their spatially restricted domains of gene expression in the crista and ampulla. Analysis of cellular proportions across developmental time showed dynamics in cellular composition. The new cell types revealed by single-cell RNA-seq could be important for understanding crista function and the markers identified in this study will enable the examination of their dynamics during development and disease.
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Affiliation(s)
- Brent A Wilkerson
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Institute for Stem Cells and Regenerative Medicine, University of WashingtonSeattleUnited States
| | - Heather L Zebroski
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Institute for Stem Cells and Regenerative Medicine, University of WashingtonSeattleUnited States
| | - Connor R Finkbeiner
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Institute for Stem Cells and Regenerative Medicine, University of WashingtonSeattleUnited States
| | - Alex D Chitsazan
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Institute for Stem Cells and Regenerative Medicine, University of WashingtonSeattleUnited States
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Kylie E Beach
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Institute for Stem Cells and Regenerative Medicine, University of WashingtonSeattleUnited States
| | - Nilasha Sen
- Department of Biological Structure, University of WashingtonSeattleUnited States
| | - Renee C Zhang
- Department of Biological Structure, University of WashingtonSeattleUnited States
| | - Olivia Bermingham-McDonogh
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Institute for Stem Cells and Regenerative Medicine, University of WashingtonSeattleUnited States
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Unlocking the Secrets of the Regenerating Fish Heart: Comparing Regenerative Models to Shed Light on Successful Regeneration. J Cardiovasc Dev Dis 2021; 8:jcdd8010004. [PMID: 33467137 PMCID: PMC7830602 DOI: 10.3390/jcdd8010004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/11/2021] [Accepted: 01/12/2021] [Indexed: 01/01/2023] Open
Abstract
The adult human heart cannot repair itself after injury and, instead, forms a permanent fibrotic scar that impairs cardiac function and can lead to incurable heart failure. The zebrafish, amongst other organisms, has been extensively studied for its innate capacity to repair its heart after injury. Understanding the signals that govern successful regeneration in models such as the zebrafish will lead to the development of effective therapies that can stimulate endogenous repair in humans. To date, many studies have investigated cardiac regeneration using a reverse genetics candidate gene approach. However, this approach is limited in its ability to unbiasedly identify novel genes and signalling pathways that are essential to successful regeneration. In contrast, drawing comparisons between different models of regeneration enables unbiased screens to be performed, identifying signals that have not previously been linked to regeneration. Here, we will review in detail what has been learnt from the comparative approach, highlighting the techniques used and how these studies have influenced the field. We will also discuss what further comparisons would enhance our knowledge of successful regeneration and scarring. Finally, we focus on the Astyanax mexicanus, an intraspecies comparative fish model that holds great promise for revealing the secrets of the regenerating heart.
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