RESEARCH
RESEARCH
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Research in our laboratory focuses on the cellular and molecular processes underlying differentiation of the mechanosensory hair cells of the inner ear, and on the innervation of these cells by axons of the eighth cranial nerve. The aquatic amphibians,Xenopus laevis and Xenopus tropicalis, are being used as a model system for these investigations. The broad objective of this research is to gain an integrated view of the development and proliferation of sensory hair cells of the inner ear by using multidisciplinary approaches that draw on techniques from biophysics, anatomy, tissue culture, and molecular biology. A major long term goal of our research is to understand the genetic basis of hair cell function, differentiation, and regeneration. As part of this effort we seek to gain an integrated view of sensory organ formation during inner ear development, and to identify novel genes expressed in the developing auditory and vestibular system.Experiments underway in the laboratory are testing several hypotheses about the expression of ion channel genes during development, and about the mechanisms that produce functionally heterogeneous hair cells in mature inner ears. For example, in some experiments, we are determining whether endorgans of the inner ear that are responsive to stimuli of different frequencies have hair cells with different types and complements of ion channels for calcium and potassium ions. A new line of investigation will study the role of cell adhesion molecules and myelination during innervation of hair cells by efferent and afferent axons.
Our research uses molecular approaches to clone the genes for calcium and potassium channels, cytoskeletal proteins, and cell adhesion molecules expressed in the ear. An emerging body of data indicate that these types of proteins may interact in novel and complex ways in cells of the nervous system. We rely on RT-PCR methods to clone genes expressed in the inner ear, and use antibodies to confirm protein expression using methods that rely on immunodetection. As part of this effort, gene expression patterns in the developing auditory and vestibular system are visualized in sectioned and whole mount tissue with in situ hybridization and immunohistohemical techniques. Furthermore, multi-photon and confocal fluorescence microscopy are being used to gather information about cell structure and gene expression. The digitized data can be processed to render tridimensional images of developing inner ear endorgans. Presently an in vitro culture system is being developed that will be used to test hypotheses about hair cell differentiation and regeneration.
The knowledge gained from this research should prove useful in developing treatments for hearing and balance disorders based on hair cell and eighth nerve dysfunction, particularly those caused by trauma, or those with a genetic basis.
PROJECTSNIH( NIDCD): ION CHANNEL EXPRESSION DURING XENOPUS INNER EAR DEVELOPMENT (1998-2003). AbstractWe are using PCR-based approaches to amplify sequences for potassium and calcium channels from whole inner ears and from individual auditory and vestibular organs. The presence of transcripts for cloned sequences is detected with in situ hybridization procedures in sectioned tissue, while antibodies are used to detect the presence of ion channel proteins. Physiological data will be gathered from isolated hair cells via electrical recordings using the patch clamp method. A main goal of this research is to determine the developmental pattern of ion channel expression in hair cells and the sensory ganglion cells of the inner ear, with the ultimate goal of understanding the regulation of ion channels in developing auditory and vestibular organs. Xenopus tropicalis and Xenopus laevis are being used as experimental models.
NIH( NIGMS): ORGAN FORMATION AND GENE EXPRESSION DURING INNER EAR DEVELOPMENT (2000-2004). Abstract
This project focuses on cell proliferation and organ formation duirng inner ear development. Confocal microscopy is being used to image the inner ear and its individual organs during development both in sectioned tissue and in intact sensory organs. Immunohistochemistical approaches are being used to study the differentiation of hair cells and sensory ganglion cell during development. One goal of this research is to identify novel genes expressed during inner ear and CNS development in Xenopus tropicalis and Xenopus laevis.
NASA: XENOPUS INNER EAR ORGAN FORMATION IN AN ALTERED GRAVITY ENVIRONMENT (1999-2002). Abstract
The impact of altered gravity on organismal development is of great interest to space life science investigators. A main objective of this research is to determine the role of gravity in the development of the nervous system, particularly the vestibular system responsible for balance and orientation. The effect of hypergravity exposure during the development of Xenopus tropicalis and Xenopus laevis is being assessed by examining morphogenesis, cell structure, and gene expression. As part of this research, we are designing and constructing modules that can hold Xenopus life support systems (habitats) suitable for exposure to altered gravity conditions.
Project photos NASA 03/00 NASA 05/00 NASA 03/01
Diaz de Lodron, ME, Varela-Ramirez, A., and Serrano, E. E. (1995) Quantity, bundle types and distribution of hair cells in the sacculus of Xenopus laevis during development. Hearing Research 91: 33-42
Lopez, V.L., Lopez, D.,and Serrano, E. E. (1997) Development of the Xenopus laevis eighth cranial nerve: Increase in number and area of axons of the saccular and papillar branches. Journal of Morphology 234:263-276.
Varela-Ramirez, A, Trujillo-Provencio, C, and Serrano, EE (1998) Detection of transcripts for delayed rectifier potassium channels in the Xenopus laevis inner ear. Hearing Research 119:125-134
Serrano, E.E. and Quick QA (2000) Confocal laser scanning microscopy of Xenopus inner ear organs during larval development. Developmental Biology 222:248
Serrano, E. E., Trujillo-Provencio, C., Sultemeier, D., Bullock, M., and Quick. Q. A. (2001) "Identification of genes expressed in the Xenopus inner ear" Cellular and Molecular Biology Journal (in press)
Williams, C, Trujillo-Provencio, C, Gladden, J.M., and Serrano, EE (in preparation) RT-PCR analysis of actin expression in the Xenopus laevis inner ear.
Cicero, S.A., Doyon, W.M, and Serrano, E. E. (in preparation) Development of the Xenopus laevis VIIIth cranial nerve: Increase in number, area and myelination of vestibular axons of the anterior branch.
Serrano, E. E. and Narins, P.M. (1989) Membrane currents in dissociated hair cells from the inner ear of Ranapipiens. Neurosci. Abstr. 15:207.
Trujillo-Provencio, C.,Varela-Ramirez, A., Williams, C.E., Gladden, J.N., and Serrano,E.E.(1997) RT-PCR analysis of gene expression in the Xenopus laevis inner ear: Actin and delayed rectifier potassium channels ARO Abstr. 20:855
López-Anaya, V.L. and E.E. Serrano (1997) Comparative SEM of Xenopus laevis auditory hair cell stereociliary bundles Neurosci. Abstr. 23:180.13
Cicero, S.A., Lopez-Anaya, V.L., Quick, Q.A., Doyon W.M., and Serrano, E.E. (1999) Developmental innervation patterns and morphology of the utricle in Xenopus laevis ARO. Abstr. 22:759
Gladden, J.M. and Serrano, E.E. (1999) Identification of actin gene family members in the Xenopus laevis inner ear with 3’RACE. ARO. Abstr. 22:62
Lopez-Anaya, V.L. and Serrano, E.E. (1999) Development of the Xenopus laevis amphibian papilla: Scanning electron microscopy of the sensory epithelia ARO. Abstr. 22:61
Quick,Q.A. and Serrano, E.E. (1999) Formation of the sensory epithelium of the inner ear during Xenopus laevis larval development. Neurosci.Abstr.25:297.9
Begay, A.J., Jefferson, D., Khawaja, H., and Serrano, EE. (2000) Construction of an aquatic habitat for hypergravity research. AAAS SWARM
Quick,Q.A and Serrano, EE (2000) Cell proliferation during early inner ear development in Xenopus laevis. Neurosci. Abstr.
Serrano, E.E. and Quick QA (2001) Confocal laser scanning microscopy of the inner ears of Xenopus tropicalis and Xenopus laevis ARO. Abstr. 0872
H.M. Khawaja, U.A. Brown-Glaberman, E.E. Serrano (2001) Determination Of Gene Copy Number For Delayed Rectifier Potassium (Kv2) Channels In Xenopus Laevis And Xenopus Tropicalis. Neurosci.Abstr. 27:812.20.
Richard Baird, Central Institute for the Deaf
David Corey, Harvard University
Robin Davis, Rutgers University
A. James Hudspeth, Rockefeller University
Cesar Fermin, Tulane University
Ruth Ann Eatock, Baylor College of Medicine
Peter Dallos, Northwestern University
Jonathan Art, University of llinois
William Roberts, University of Oregon;
Peter Narins, University of California, Los Angeles
Jeff Corwin, University Of Virginia
Paul Fuchs, Johns Hopkins University
Robert Fettiplace, University of Wisconsin
Peter Steyger, Oregon Health Sciences University
Andrea Simmons,Brown University
Sigrid Reinsch, NASA AmesTo be included on this list of links please email neurolab@biology-web.nmsu.edu/serrano
Kresge Laboratory, Louisiana State University
Association for Research in Otolaryngology
Central institute for the Deaf
House Ear InstituteUpdated January 16th, 2001
RBM
