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Kwan GT, Andrade LR, Prime KJ, Tresguerres M. Immunohistochemical and ultrastructural characterization of the inner ear epithelial cells of splitnose rockfish ( Sebastes diploproa). Am J Physiol Regul Integr Comp Physiol 2024; 326:R277-R296. [PMID: 38189166 DOI: 10.1152/ajpregu.00223.2023] [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] [Received: 09/18/2023] [Revised: 12/01/2023] [Accepted: 01/01/2024] [Indexed: 01/09/2024]
Abstract
The inner ear of teleost fish regulates the ionic and acid-base chemistry and secretes protein matrix into the endolymph to facilitate otolith biomineralization, which is used to maintain vestibular and auditory functions. The otolith is biomineralized in a concentric ring pattern corresponding to seasonal growth, and this calcium carbonate (CaCO3) polycrystal has become a vital aging and life-history tool for fishery managers, ecologists, and conservation biologists. Moreover, biomineralization patterns are sensitive to environmental variability including climate change, thereby threatening the accuracy and relevance of otolith-reliant toolkits. However, the cellular biology of the inner ear is poorly characterized, which is a hurdle for a mechanistic understanding of the underlying processes. This study provides a systematic characterization of the cell types in the inner ear of splitnose rockfish (Sebastes diploproa). Scanning electron microscopy revealed the apical morphologies of six inner ear cell types. In addition, immunostaining and confocal microscopy characterized the expression and subcellular localization of the proteins Na+-K+-ATPase, carbonic anhydrase, V-type H+-ATPase, Na+-K+-2Cl--cotransporter, otolith matrix protein 1, and otolin-1 in six inner ear cell types bordering the endolymph. This fundamental cytological characterization of the rockfish inner ear epithelium illustrates the intricate physiological processes involved in otolith biomineralization and highlights how greater mechanistic understanding is necessary to predict their multistressor responses to future climate change.
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Affiliation(s)
- Garfield T Kwan
- Wildlife, Fish and Conservation Biology, University of California Davis, Davis, California, United States
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States
| | - Leonardo R Andrade
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, California, United States
| | - Kaelan J Prime
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States
| | - Martin Tresguerres
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States
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Kwan GT, Smith TR, Tresguerres M. Immunological characterization of two types of ionocytes in the inner ear epithelium of Pacific Chub Mackerel (Scomber japonicus). J Comp Physiol B 2020; 190:419-431. [PMID: 32468089 DOI: 10.1007/s00360-020-01276-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 01/20/2020] [Accepted: 03/30/2020] [Indexed: 12/14/2022]
Abstract
The inner ear is essential for maintaining balance and hearing predator and prey in the environment. Each inner ear contains three CaCO3 otolith polycrystals, which are calcified within an alkaline, K+-rich endolymph secreted by the surrounding epithelium. However, the underlying cellular mechanisms are poorly understood, especially in marine fish. Here, we investigated the presence and cellular localization of several ion-transporting proteins within the saccular epithelium of the Pacific Chub Mackerel (Scomber japonicus). Western blotting revealed the presence of Na+/K+-ATPase (NKA), carbonic anhydrase (CA), Na+-K+-2Cl--co-transporter (NKCC), vacuolar-type H+-ATPase (VHA), plasma membrane Ca2+ ATPase (PMCA), and soluble adenylyl cyclase (sAC). Immunohistochemistry analysis identified two distinct ionocytes types in the saccular epithelium: Type-I ionocytes were mitochondrion-rich and abundantly expressed NKA and NKCC in their basolateral membrane, indicating a role in secreting K+ into the endolymph. On the other hand, Type-II ionocytes were enriched in cytoplasmic CA and VHA, suggesting they help transport HCO3- into the endolymph and remove H+. In addition, both types of ionocytes expressed cytoplasmic PMCA, which is likely involved in Ca2+ transport and homeostasis, as well as sAC, an evolutionary conserved acid-base sensing enzyme that regulates epithelial ion transport. Furthermore, CA, VHA, and sAC were also expressed within the capillaries that supply blood to the meshwork area, suggesting additional mechanisms that contribute to otolith calcification. This information improves our knowledge about the cellular mechanisms responsible for endolymph ion regulation and otolith formation, and can help understand responses to environmental stressors such as ocean acidification.
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Affiliation(s)
- Garfield T Kwan
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA
| | - Taylor R Smith
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA.
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Di Santo V. Ocean acidification and warming affect skeletal mineralization in a marine fish. Proc Biol Sci 2020; 286:20182187. [PMID: 30963862 DOI: 10.1098/rspb.2018.2187] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ocean acidification and warming are known to alter, and in many cases decrease, calcification rates of shell and reef building marine invertebrates. However, to date, there are no datasets on the combined effect of ocean pH and temperature on skeletal mineralization of marine vertebrates, such as fishes. Here, the embryos of an oviparous marine fish, the little skate ( Leucoraja erinacea), were developmentally acclimatized to current and increased temperature and CO2 conditions as expected by the year 2100 (15 and 20°C, approx. 400 and 1100 µatm, respectively), in a fully crossed experimental design. Using micro-computed tomography, hydroxyapatite density was estimated in the mineralized portion of the cartilage in jaws, crura, vertebrae, denticles and pectoral fins of juvenile skates. Mineralization increased as a consequence of high CO2 in the cartilage of crura and jaws, while temperature decreased mineralization in the pectoral fins. Mineralization affects stiffness and strength of skeletal elements linearly, with implications for feeding and locomotion performance and efficiency. This study is, to my knowledge, the first to quantify a significant change in mineralization in the skeleton of a fish and shows that changes in temperature and pH of the oceans have complex effects on fish skeletal morphology.
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Affiliation(s)
- Valentina Di Santo
- Museum of Comparative Zoology, Harvard University , 26 Oxford Street, Cambridge, MA , USA
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Cruz S, Shiao JC, Liao BK, Huang CJ, Hwang PP. Plasma membrane calcium ATPase required for semicircular canal formation and otolith growth in the zebrafish inner ear. J Exp Biol 2009; 212:639-47. [DOI: 10.1242/jeb.022798] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
SUMMARY
Fish otoliths consist of >90% calcium carbonate, the accretion of which depends on acellular endolymph. This study confirms the presence of plasma membrane calcium ATPase 1a isoform (Atp2b1a) in the auditory and vestibular system of a teleost fish. As shown by in situ hybridization,zebrafish atp2b1a is expressed mainly in larval otic placode and lateral-line neuromast as well as in the hair cells within the adult zebrafish inner ear chamber. Zebrafish atp2b1a knockdown by antisense morpholinos reduced the number of hair cells and produced malformation of semicircular canals and smaller otoliths. These defects coincide with unbalanced body orientation. The formation of smaller otoliths in atp2b1a morphants may stem from an impairment of calcium supply in the endolymph. However, otolith formation persists in most morphants,suggesting that other zebrafish Atp2b isoforms or paracellular pathways may also transport calcium into the endolymph. These results suggest that Atp2b1a plays an important role for normal development of the auditory and vestibular system as well as calcium transport in the inner ear of zebrafish.
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Affiliation(s)
- Shelly Cruz
- Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan
| | - Jen-Chieh Shiao
- Institute of Oceanography, College of Science, National Taiwan University,Taipei, Taiwan
| | - Bo-Kai Liao
- Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan
| | - Chang-Jen Huang
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei,Taiwan
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang,Taipei, Taiwan
| | - Pung-Pung Hwang
- Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang,Taipei, Taiwan
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Anken RH. On the role of the central nervous system in regulating the mineralisation of inner-ear otoliths of fish. PROTOPLASMA 2006; 229:205-8. [PMID: 17180502 DOI: 10.1007/s00709-006-0219-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 11/20/2005] [Indexed: 05/13/2023]
Abstract
Stato- or otoliths are calcified structures in the organ of balance and equilibrium of vertebrates, the inner ear, where they enhance its sensitivity to gravity. The compact otoliths of fish are composed of the calcium carbonate polymorph aragonite and a small fraction of organic molecules. The latter form a protein skeleton which determines the morphology of an otolith as well as its crystal lattice structure. This short review addresses findings according to which the brain obviously plays a prominent role in regulating the mineralisation of fish otoliths and depends on the gravity vector. Overall, otolith mineralisation has thus been identified to be a unique, neuronally guided biomineralisation process. The following is a hypothetical model for regulation of calcification by efferent vestibular neurons: (1) release of calcium at tight junctions in the macular epithelia, (2) macular carbonic anhydrase activity (which in turn is responsible for carbonate deposition), (3) chemical composition of matrix proteins. The rationale and evidence that support this model are discussed.
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Affiliation(s)
- Ralf H Anken
- Zoological Institute, University of Hohenheim, Stuttgart, Federal Republic of Germany.
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Tohse H, Murayama E, Ohira T, Takagi Y, Nagasawa H. Localization and diurnal variations of carbonic anhydrase mRNA expression in the inner ear of the rainbow trout Oncorhynchus mykiss. Comp Biochem Physiol B Biochem Mol Biol 2006; 145:257-64. [PMID: 16996283 DOI: 10.1016/j.cbpb.2006.06.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 03/24/2006] [Accepted: 03/26/2006] [Indexed: 10/24/2022]
Abstract
Physiological studies have suggested that carbonic anhydrase (CA) plays a central role in otolith biomineralization via ion transport. However, the presence and exact function of CA in the inner ear have not been determined. In the present study, to investigate the localization of CA and its involvement in otolith calcification, we cloned two cDNAs encoding CAs from the rainbow trout sacculus. These two cDNAs, designated rainbow trout CAa (rtCAa) and rtCAb, both had an open reading frame encoding 260 amino acids with a sequence identity of 78%. Remarkably, rtCAb has a high degree of homology (82%) with "high activity CA" in the zebrafish, and its mRNA expression showed variation in the range 1.9-11.4 x 10(4) copies/ng total RNA in the sacculus. In contrast, rtCAa mRNA was constantly expressed at approximately 3 x 10(4) copies/ng total RNA. In situ hybridization revealed that rtCAb mRNA was strongly expressed in the distal squamous epithelial cells and transitional epithelial cells, except the mitochondria-rich cells, whereas, rtCAa was localized in extrasaccular tissue. These results suggest that the rtCAb isozyme is involved in the daily increment formation and calcification of otoliths via phase and spatial differences of the bicarbonate supply to the endolymph.
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Affiliation(s)
- Hidekazu Tohse
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan.
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Lundberg YW, Zhao X, Yamoah EN. Assembly of the otoconia complex to the macular sensory epithelium of the vestibule. Brain Res 2006; 1091:47-57. [PMID: 16600187 DOI: 10.1016/j.brainres.2006.02.083] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 02/20/2006] [Accepted: 02/22/2006] [Indexed: 10/24/2022]
Abstract
In the inner ear, specificity of stimulus perception is achieved by associating the sensory epithelia of the three mechanoreceptor organs, the utricle/saccule, cristae, and cochlea, with distinct types of acellular matrices. Only the utricle and saccule have an extremely dense matrix, the otoconial complex, which overlies the sensory epithelium (macula) and provides inertial mass to generate shearing forces essential for the mechanoreceptors to sense gravity and linear acceleration. Such sensation is necessary for spatial orientation and balance. The importance of otoconia is clearly demonstrated by the impact of balance disorders upon the elderly population that involve otoconia degeneration, as well as by canalithiasis and cupulolithiasis, in which otoconia are dislocated. This underscores the need to understand how otoconia are formed and maintained and how to prevent their degeneration. To date, a number of otoconia-related proteins have been identified mostly in mice and bony fish. Although most of these proteins are also present in other structures of the inner ear, a distinct collection of proteins in the macula plus the unique ionic microenvironment of the endolymph near its epithelium likely contribute to the site-specific calcification of otoconia. Based on the current literature and ongoing research, this mini-review postulates a working model of how the otoconia complex is assembled specifically above the macular sensory epithelium of the vestibule. The central hypothesis of this model is that proteins are critical in sequestering calcium for crystallization in the calcium-poor endolymph. The review also sets forth some issues that need to be resolved in the future.
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Affiliation(s)
- Yunxia Wang Lundberg
- Department of Genetics, Boys Town National Research Hospital, Omaha, NE 68131, USA.
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