Dax A. Hoffman, Ph.D.

Senior Investigator

Section on Molecular Neurophysiology and Biophysics

NICHD/DIR

BG 35 RM 3C905
35 Convent Drive
Bethesda, MD 20814

301-402-6772

hoffmand@mail.nih.gov

Research Topics

Potassium Channels and Dendritic Function in Hippocampal Pyramidal Neurons

The central nervous system underlies all our experiences, actions, emotions, knowledge, and memories. With billions of neurons each firing hundreds of times per second, the complexity of the brain is stunning. To pare down the task of understanding something so complex, our research approach calls for studying the workings of a single central neuron—the pyramidal neuron from the CA1 region of the hippocampus. The hippocampus is essential for long-term memory in humans and is among the first brain regions affected by epilepsy and Alzheimer’s disease. To understand how the hippocampus stores and processes information, we focus on one of its principal cell types, the CA1 pyramidal neuron. Each pyramidal neuron in the CA1 region of the hippocampus receives tens of thousands of inputs onto its dendrites, and it is commonly thought that information is stored by altering the strength of individual synapses (synaptic plasticity). Recent evidence suggests that the regulation of synaptic surface expression of glutamate receptors can, in part, determine synaptic strength. However, the dendrites contain an abundance of ion channels that are involved in receiving, transforming, and relaying information in the dendrites, adding an additional layer of complexity to neuronal information processing.

We have found that the A-type potassium channel subunit Kv4.2 is highly expressed in the dendritic regions of CA1 neurons in the hippocampus and, as one of the primary regulators of dendritic excitability, plays a pivotal role in information processing. Kv4.2 is targeted for modulation during the types of plasticity thought to underlie learning and memory. Moreover, the functional expression level of Kv4.2 was found to regulate the subtype expression of the NMDA–type glutamate receptors, the predominate molecular devices controlling synaptic plasticity and memory. We are currently following up on these findings with more detailed investigations into the mechanisms of activity-dependent Kv4.2 regulation. In addition, we have begun investigating the role of dendritic voltage-gated channels in CNS disorders, including autism-spectrum disorder and Alzheimer’s disease, that exhibit profound changes in neuronal excitability along with learning and memory deficits.

Biography

Dr. Dax Hoffman received his B.S. in Genetics from the University of Minnesota in 1994 and his Ph.D. from Baylor College of Medicine in 1999, where he studied dendritic K+ channels with Dr. Dan Johnston. During a postdoctoral fellowship with Dr. Bert Sakmann at the Max Planck Institute for Medical Research in Heidelberg Germany, he investigated synaptic plasticity and Ca2+ signaling in transgenic and gene-targeted mice. Dr. Hoffman became head of the Molecular Neurophysiology and Biophysics Unit, NICHD in 2002. His laboratory explores dendritic signal processing in CA1 pyramidal neurons of the hippocampus.

Selected Publications

  1. Liu X, Campanac E, Cheung HH, Ziats MN, Canterel-Thouennon L, Raygada M, Baxendale V, Pang AL, Yang L, Swedo S, Thurm A, Lee TL, Fung KP, Chan WY, Hoffman DA, Rennert OM. Idiopathic Autism: Cellular and Molecular Phenotypes in Pluripotent Stem Cell-Derived Neurons. Mol Neurobiol. 2016.

  2. Hall AM, Throesch BT, Buckingham SC, Markwardt SJ, Peng Y, Wang Q, Hoffman DA, Roberson ED. Tau-dependent Kv4.2 depletion and dendritic hyperexcitability in a mouse model of Alzheimer's disease. J Neurosci. 2015;35(15):6221-30.

  3. Lin L, Long LK, Hatch MM, Hoffman DA. DPP6 domains responsible for its localization and function. J Biol Chem. 2014;289(46):32153-65.

  4. Sun W, Maffie JK, Lin L, Petralia RS, Rudy B, Hoffman DA. DPP6 establishes the A-type K(+) current gradient critical for the regulation of dendritic excitability in CA1 hippocampal neurons. Neuron. 2011;71(6):1102-15.

  5. Lin L, Sun W, Throesch B, Kung F, Decoster JT, Berner CJ, Cheney RE, Rudy B, Hoffman DA. DPP6 regulation of dendritic morphogenesis impacts hippocampal synaptic development. Nat Commun. 2013;4:2270.


This page was last updated on October 6th, 2017