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Department of Physiology and Biophysics

University of Colorado Department of Physiology and Biophysics
 

Angeles B. Ribera, PhD

Professor and Interim Chair
 

Department of Physiology & Biophysics
Neuroscience Program

UCD Anschutz Medical Campus
C-1 North Tower, P18-7117
Mail Stop 8307
Tel (303) 724-4517
Fax (303) 724-4501

E-mail:
Angie.Ribera@ucdenver.edu

BNAT program member
Neuroscience Program


RESEARCH


Our laboratory is interested in determining the mechanisms that direct differentiation of electrical excitability in neurons, and, in turn, how activity regulates neuronal development. Our studies span the period from when neurons exit the cell cycle and begin terminal differentiation and to when synaptic interactions emerge. In order to have access to the relevant early stages of development, we use two classic vertebrate embryological systems - the frog, Xenopus laevis [In the movie to the left, the embryo develops from a 1-cell animal to a 2-day larva.], and zebrafish, Danio rerio. Studies using the Xenopus system concern stages of development prior to synapse formation. In contrast, studies using the zebrafish model focus on stages when synaptic interactions occur and behaviors are evident at the level of the organism.  Below, we first discuss current work using the Xenopus model and then turn to on-going studies using the zebrafish embryo.


REVIEWS:

Ribera AB (1998) Potassium currents in developing neurons. NYAS 868:399-405. pdf

Spitzer NC, Ribera AB (1998) Development of electrical excitability in embryonic neurons: mechanisms and roles. J. Neurobiol 37:190-197. pdf

Ribera AB (1998) Perspective: Ion channel activity drives ion channel expression. J. Physiol. 511.3:645.pdf

Novak AE, Ribera AB (2005) The zebrafish embryo as an integrative physiology model system. In: Integrative physiology: In the Proteomics and Post-Genomics Age. W. Walz, Editor. Humana Press: Totawa, N.J.

Pineda RH, Ribera AB (2007) Evolution of the action potential. In Evolution of Nervous Systems, Elsevier, pp. 211-238.

Gravagna NG, Ribera AB (2007) Regulation of Kv1 and Kv2 Potassium Channels. In Encyclopedia of Neuroscience.

Wright MA, Ribera AB (2007) Studying Electrical Activity in Development: Challenges and Solutions Using the Zebrafish Model. Global Science Books, in press.

Developmental regulation and function of potassium current in developing spinal neurons (Xenopus laevis).

Potassium currents play a major role in determining the emerging properties of excitability in amphibian embryonic spinal neurons. The overall goal of research in this area is to identify molecular mechanisms that regulate potassium channel function and its contribution to electrical excitability during initial stages of neuronal differentiation. Embryonic amphibian spinal neurons acquire electrical excitability a few hours after they exit the cell cycle, prior to neurite extension. At this time, impulses are of long duration and provide transient elevations of intracellular calcium that trigger developmental signaling cascades. During the next 24 hours, voltage-dependent potassium current (IKv) density gradually triples, leading to decreases in the duration of the action potential and the associated calcium influx. By the time synapses begin to form, impulse durations have undergone profound developmental regulation and are now brief, as is characteristic of adult neurons. During the next day, no further increase in IKv density occurs, indicating establishment of a set point for this current.

We are identifying potassium channel genes that are essential for proper development of excitability. Using molecular, physiological and embryological methods, we manipulate functional expression of these potassium channel genes and uncover underlying mechanisms. Our data so far suggest that transcriptional mechanisms contribute to the rapid initial increase in potassium current density. However, post-translational and post-transcriptional mechanisms determine the set points for potassium current density in mature neurons. A combination of physiological, molecular, histochemical and embryological methods are used for these studies.

[The picture depicts in situ hybridization for the Xenopus Kv1.1a gene in the developing spinal cord. A transverse section through the spinal cord of a 2-day embryo is shown and the blue-purple signal represent the hybridization signal hat is found specifically in dorsal spinal sensory neurons known as Rohon-Beard cells.]


Vanessa Carmean
Graduate Student

E-mail: Vanessa.Carmean@ucdenver.edu

Vanessa Carmean is studying a touch-insensitive zebrafishmutant (macho) in zebrafish to learn more about the development of Rohon-Beard cells, which are responsible for touch in the first few days after fertilization.

Chris Knoeckel
Graduate Student

E-mail: Christopher.Knoeckel@ucdenver.edu

Tara Martin
Graduate Student

E-mail: Tara.Martin@ucdenver.edu

Tara Martin is investigating the role of synchronous electrical activity via gap junctional communication between nascent neurons of the developing spinal cord in zebrafish embryos.

Rosa Moreno, PhD
Research Instructor

E-mail: Rosa.Moreno@ucdenver.edu

Rosa Moreno's research is identifying the intrinsic genetic programs that allow neurons to develop early electrical properties in a subtype specific manner.

Michelle Perales
Professional Research Assistant

E-mail: Michelle.Perales@ucdenver.edu

Michelle Perales maintains the Ribera Lab zebrafish colony and co manages the zebrafish facility.

Jason Santiago
Professional Research Assistant

E-mail: Jason.Santiago@ucdenver.edu
​​​​

Selected Publications

Lazaroff MA, Taylor AD and Ribera AB (2002) In vivo analysis of Kvb2 function in Xenopus embryonic myocytes. J Physiol 541.3: 673-683. pdf

Kukuljan M, Taylor A, Chouinard H, Olguín P, Rojas, CV and Ribera AB (2003) Selective regulation of xSlo splice variants during Xenopus embryogenesis. J Neurophysiol  90: 3352-3360. pdf

Blaine JT, Taylor AD and Ribera AB (2004) The carboxyl tail region of the Kv2.2 subunit mediates novel developmental regulation of channel density. 92: 3446-3454. pdf (Perspectives and Highlights)

Pineda RH, Ribera AB (2008) Dorsal-Ventral Gradient for Neuronal Plasticity in the Embryonic Spinal Cord. J Neurosci 28: 3824-3834. pdf

Gravagna NG, Knoeckel CS, Taylor AD, Hultgren B, Ribera AB (2008) Localization of Kv2.2 protein in Xenopus laevis embryos and tadpoles. J Comp Neur 510: 508-524. pdf

Pineda RH, Knoeckel CS, Taylor AD, Estrada-Bernal A, Ribera AB (2008) Kv1 potassium channel complexes in vivo require Kvβ2 subunits and drive developmental changes in potassium current in dorsal spinal neurons. J Neurophysiol 100:  2125-2136. pdf

Electrical excitability in wild type and mutant zebrafish (Danio rerio).

Forward genetic strategies uncover genes with irreplaceable functions. Because ion channel activity is developmentally-regulated and essential for generation of organismal behavior, zebrafish motility mutants in which specific behaviors fail to appear may exhibit abnormal developmental expression/function of ion channels. For example, one group of mutants does not respond to touch, although these embryos are motile and can swim (Granato et al., 1996). The specific behavioral phenotype suggests that the defect may originate in mechanosensory Rohon-Beard (RB) neurons. In wildtype embryos, the action potential of RB cells undergoes developmental regulation while the embryo acquires touch sensitivity. The changes in action potential waveform are due to underlying changes in voltage-gated sodium (INa) and potassium currents (Ribera and Nüsslein-Volhard, 1998). The INa of RB cells of the mao touch-insensitive mutant have reduced amplitudes and action potentials are not generated. Further, although the normal developmental changes in potassium current occur, upregulation of INa is absent. These data suggest that developmental regulation of RB INa may underlie stage-specific acquisition of touch sensitivity. We will identify functional, pharmacological and molecular properties of RB INa that are developmentally regulated. In addition, our preliminary data indicate that RB cells of mao mutants exhibit abnormal morphology. Accordingly, we will quantify differences in RB morphology of touch-insensitive and touch-sensitive fish to assess possible contributions of changes in peripheral innervation and central projections to normal developmental acquisition of touch sensitivity. We have recently found that activity of RB cells regulates their programmed cell death. A combination of genetic, molecular, anatomical and physiological methods will be used in these studies.

In related work, we have collaborated with Dr. Winfried Denk (MPI Heidelberg) to examine the appearance of spontaneous calcium transients in the developing zebrafish embryo (/physiology/abr2/movie.htm). Future work will test the possibility that these spontaneous evens influence subsequent development of spinal neurons.

Over the long-term, the studies will provide a framework for analysis of other behavioral mutants and identification of ion channels with essential functions during embryonic development of the nervous system and emergence of stage-specific behaviors.

Representative Publications

Ribera, A.B. and Nüsslein-Volhard, C. (1998) Zebrafish touch-insensitive mutants reveal an essential role for developmental regulation of sodium current. J. Neurosci. 18:9181-9191. pdf

Svoboda, K.R., Linares, A.E., and Ribera, A.B. (2001) Activity regulates programmed cell death of zebrafish Rohon-Beard neurons. Development 128(18):3511-3520. pdf

Novak AE and Ribera AB. (2003) Immunocytochemistry as a tool for zebrafish developmental neurobiology. Methods Cell Sci 25: 79-83. pdf

Pineda, RH, Heiser RA and Ribera AB (2005) Molecular determinants of INa in vivo in embryonic zebrafishsensory neurons. J Neurophysiol 93: 3582-3593. pdf

Novak AE, Jost MC, Lu Y, Taylor AD, Zakon HH and Ribera AB (2006) Gene duplications and evolution of vertebrate voltage-gated sodium channels. J Mol Evol 63:208-221. pdf

Novak AE, Taylor AD, Pineda RH, Lasda EL, Wright MA and Ribera AB (2006) Embryonic and larval expression of zebrafish voltage-gated sodium channel a-subunit genes. Dev Dyn 235: 1962-1973. pdf

Pineda RH, Svoboda KR, Wright MA, Wright MA, Taylor AD, Novak AE, Gamse J, Eisen JS and Ribera AB. (2006) Knock-down of Nav1.6a sodium channels affects zebrafish motor neuron development. Development 133: 3827-3836. pdf

Yonkers MA, Ribera AB (2008) Sensory neuron sodium current requires nongenomic actions of thyroid hormone during development.  J Neurophysiol 100:  2719-2725 pdf

Fein AJ, Wright MA, Slat EA, Ribera AB, Isom LL (2008) scn1bb, a zebrafish ortholog of SCN1B expressed in excitable and nonexcitable cells, affects motor neuron axon morphology and touch sensitivity.  J Neurosci 28:  12510-12522. pdf


PubMed search (Ribera AB)