Background

John V. Brigande's introduction to neuroscience formally began in Thomas N. Seyfried's lab at Boston College where his Master's work focused on reactive astrocytosis in a mouse model of human temporal lobe epilepsy. Brigande then transitioned to developmental neurobiology for his doctoral work again with Dr. Seyfried studying glycosphinogolipid biosynthesis in the organogenesis-stage mouse embryo. His doctoral studies ignited a passion for mammalian development that was fostered by postdoctoral training in developmental genetics with Karen Artzt at the University of Texas at Austin and in auditory development with Donna M. Fekete at Purdue University. Brigande began his assistant professorship in the Oregon Hearing Research Center in July 2003 and was promoted to associate professor in 2009. Brigande joined the Hearing Health Foundation's Hearing Restoration Project in 2011 and works on the definition of mouse model systems to test candidate genes for hair cell regeneration

Summary of current research

We study the development of the mammalian inner ear using mouse as a model system. Our approach involves experimental embryology, a palette of surgical, micromanipulation, and gene transfer techniques that enables interrogation of developmental processes in vivo. Our long term goal is to apply what we learn about the genetic mechanisms governing inner ear sensory organ development to define and validate efficacious gene and cell therapies to treat hearing loss and balance disorders.

Retroviral lineage analysis enables us to understand the types of cell fate choices an otic progenitor makes and the timing of those choices during sensory organ formation. We have shown by transuterine microinjection of lineage virus at embryonic day 11.5 (E11.5) that both auditory and vestibular hair cells are lineally related to their supporting cells and that spiral ganglion neurons, interdental cells, and Claudius’ cells are lineally related to cells of the same type. We have also identified clonal relationships between organ of Corti cell types that reside on opposite sides of the tunnel of Corti. The extensive clonal dispersion detected and the observation of clonally related cells that span the tunnel suggest that progenitors integrating lineage label at ~E12 do not respect anatomical boundaries during convergent extension of the nascent cochlea. Correlating these observations with single cell transcriptomics of inner ear sensory cells may give us insight into the gene expression profiles required to specify individual sensory lineages and perhaps serve as the basis for new strategies to regenerate the sensory patch for therapeutic benefit.

Fetal pharmacotherapy for congenital deafness involves the use of gene replacement or drug strategies to restore wild type gene function during formation of the inner ear in utero. Our proof of concept for gene replacement focuses on the vesicular glutamate transporter 3 (VGLUT3) knockout mouse which is deaf at birth. Remarkably, adeno-associated virus (AAV)-mediated gene transfer of VGLUT3 into the E12.5 otocyst can restore auditory brainstem response thresholds (ABR) to near wild type levels. Our proof of concept for drug therapy focuses on the Usher 1c knockout mouse which is also deaf at birth. Transuterine microinjection of antisense oligonucleotide designed to correct mRNA slicing of harmonin incompletely but significantly restores ABR thresholds after a single dose to the E12.5 otocyst. These studies represent an exciting new experimental path for our lab that is refreshingly translational in perspective. 

Our lab is a member of the Hearing Health Foundation’s Hearing Restoration Project (HRP). The organizing principle of the HRP is that strategic collaborations among participating labs will more efficiently advance the science needed to define efficacious therapies for treating hearing loss and tinnitus. Our specific role is to devise mouse model systems required to test candidate hair cell regeneration genes in the postnatal, deafened mouse inner ear. Our HRP affiliation has led to intellectually engaging and productive ongoing collaborations that leave us excited about future prospects for treating inner ear disease.

Major Milestones and Significant Discoveries

Misexpression of the transcription factor atonal homolog 1 in the developing mouse inner ear generates functional auditory hair cells The in utero gene transfer technique premits gain and loss-of-function experiments in the developing mouse inner ear