Bio

Professional Education


  • Doctor of Philosophy, Eberhard Karls Universitat Tubingen (2010)

Stanford Advisors


Publications

Journal Articles


  • Changes in the regulation of the Notch signaling pathway are temporally correlated with regenerative failure in the mouse cochlea. Frontiers in cellular neuroscience Maass, J. C., Gu, R., Basch, M. L., Waldhaus, J., Lopez, E. M., Xia, A., Oghalai, J. S., Heller, S., Groves, A. K. 2015; 9: 110-?

    Abstract

    Sensorineural hearing loss is most commonly caused by the death of hair cells in the organ of Corti, and once lost, mammalian hair cells do not regenerate. In contrast, other vertebrates such as birds can regenerate hair cells by stimulating division and differentiation of neighboring supporting cells. We currently know little of the genetic networks which become active in supporting cells when hair cells die and that are activated in experimental models of hair cell regeneration. Several studies have shown that neonatal mammalian cochlear supporting cells are able to trans-differentiate into hair cells when cultured in conditions in which the Notch signaling pathway is blocked. We now show that the ability of cochlear supporting cells to trans-differentiate declines precipitously after birth, such that supporting cells from six-day-old mouse cochlea are entirely unresponsive to a blockade of the Notch pathway. We show that this trend is seen regardless of whether the Notch pathway is blocked with gamma secretase inhibitors, or by antibodies against the Notch1 receptor, suggesting that the action of gamma secretase inhibitors on neonatal supporting cells is likely to be by inhibiting Notch receptor cleavage. The loss of responsiveness to inhibition of the Notch pathway in the first postnatal week is due in part to a down-regulation of Notch receptors and ligands, and we show that this down-regulation persists in the adult animal, even under conditions of noise damage. Our data suggest that the Notch pathway is used to establish the repeating pattern of hair cells and supporting cells in the organ of Corti, but is not required to maintain this cellular mosaic once the production of hair cells and supporting cells is completed. Our results have implications for the proposed used of Notch pathway inhibitors in hearing restoration therapies.

    View details for DOI 10.3389/fncel.2015.00110

    View details for PubMedID 25873862

  • Inner Ear Hair Cell-Like Cells from Human Embryonic Stem Cells STEM CELLS AND DEVELOPMENT Ronaghi, M., Nasr, M., Ealy, M., Durruthy-Durruthy, R., Waldhaus, J., Diaz, G. H., Joubert, L., Oshima, K., Heller, S. 2014; 23 (11): 1275-1284

    Abstract

    In mammals, the permanence of many forms of hearing loss is the result of the inner ear's inability to replace lost sensory hair cells. Here, we apply a differentiation strategy to human embryonic stem cells into cells of the otic lineage using chemically-defined attached-substrate conditions. Generation of human otic progenitor cells was dependent on FGF signaling and protracted culture led to the upregulation of markers indicative of differentiated inner ear sensory epithelia. Using a transgenic embryonic stem cell reporter line based on a murine Atoh1 enhancer, we show that differentiated hair cell-like cells express multiple hair cell markers simultaneously. Hair cell-like cells displayed protrusions reminiscent of stereociliary bundles, but failed to fully mature into cells with typical hair cell cytoarchitecture. We conclude that optimized defined conditions can be used in vitro to attain otic progenitor specification and sensory cell differentiation.

    View details for DOI 10.1089/scd.2014.0033

    View details for Web of Science ID 000336959800011

    View details for PubMedID 24512547

  • Reconstruction of the Mouse Otocyst and Early Neuroblast Lineage at Single-Cell Resolution CELL Durruthy-Durruthy, R., Gottlieb, A., Hartman, B. H., Waldhaus, J., Laske, R. D., Altman, R., Heller, S. 2014; 157 (4): 964-978

    Abstract

    The otocyst harbors progenitors for most cell types of the mature inner ear. Developmental lineage analyses and gene expression studies suggest that distinct progenitor populations are compartmentalized to discrete axial domains in the early otocyst. Here, we conducted highly parallel quantitative RT-PCR measurements on 382 individual cells from the developing otocyst and neuroblast lineages to assay 96 genes representing established otic markers, signaling-pathway-associated transcripts, and novel otic-specific genes. By applying multivariate cluster, principal component, and network analyses to the data matrix, we were able to readily distinguish the delaminating neuroblasts and to describe progressive states of gene expression in this population at single-cell resolution. It further established a three-dimensional model of the otocyst in which each individual cell can be precisely mapped into spatial expression domains. Our bioinformatic modeling revealed spatial dynamics of different signaling pathways active during early neuroblast development and prosensory domain specification. PAPERFLICK:

    View details for DOI 10.1016/j.cell.2014.03.036

    View details for Web of Science ID 000335765500022

  • Stemness of the Organ of Corti Relates to the Epigenetic Status of Sox2 Enhancers PLOS ONE Waldhaus, J., Cimerman, J., Gohlke, H., Ehrich, M., Mueller, M., Loewenheim, H. 2012; 7 (5)

    Abstract

    In the adult mammalian auditory epithelium, the organ of Corti, loss of sensory hair cells results in permanent hearing loss. The underlying cause for the lack of regenerative response is the depletion of otic progenitors in the cell pool of the sensory epithelium. Here, we show that an increase in the sequence-specific methylation of the otic Sox2 enhancers NOP1 and NOP2 is correlated with a reduced self-renewal potential in vivo and in vitro; additionally, the degree of methylation of NOP1 and NOP2 is correlated with the dedifferentiation potential of postmitotic supporting cells into otic stem cells. Thus, the stemness the organ of Corti is related to the epigenetic status of the otic Sox2 enhancers. These observations validate the continued exploration of treatment strategies for dedifferentiating or reprogramming of differentiated supporting cells into progenitors to regenerate the damaged organ of Corti.

    View details for DOI 10.1371/journal.pone.0036066

    View details for Web of Science ID 000305343400010

    View details for PubMedID 22570694

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