Dr Stuart Johnson

Royal Society University Research Fellow Department of Biomedical Science University of Sheffield Western Bank Sheffield S10 2TN United Kingdom Room: B1 220 Alfred Denny Tel: +44 (0)114 2223692 Email: s.johnson@sheffield.ac.uk

Career History

• 2011-present: Royal Society University Research Fellow, University of Sheffield, UK.
• 2009-2011: RNID Postdoctoral Fellow, University of Sheffield, UK.
• 2006-2009: Wellcome Trust Postdoctoral Fellow, University of Sheffield, UK.
• 2003-2005: MRC Postdoctoral Fellow, University of Sussex, UK.
• 1998-2003: D.Phil, University of Sussex, UK.
• 1995-1998: BSc Hons Biological Sciences (Animal Physiology), University of Leicester, UK.

Research interests

Signalling characteristics of cochlear hair cells

Mammalian cochlear inner hair cells (IHCs) are the primary sensory cells of the auditory pathway. Their job is to convert sound vibrations into an electrical signal that can be interpreted by the brain and it is vital that the information is transmitted with high fidelity and temporal precision. One of the major causes of hearing loss is associated with a loss of IHC function.

The aim of my research is to find out how IHCs accurately encode sounds over wide ranges of frequency and intensity, and how the information is processed on its way to the brain. Knowledge of how the ear processes sound will inform the development of hearing aids, including cochlear implants. An additional aspect of my research involves the physiological analysis of human stem cells that are being used to replace damaged nerve fibres to restore hearing (in collaboration with Dr Marcelo Rivolta).

In order to achieve this I will study IHCs in the isolated cochlea using a combination of electrophysiological, cell imaging and molecular biology techniques.

Funding

• The Royal Society
• The Wellcome Trust

Recent publications

1. Johnson SL, Beurg M, Marcotti W & Fettipplace R (2011)
   Prestin-driven cochlear amplification is not limited by the outer hair cell membrane time constant.
   Neuron 70: 1143-1154
2. Johnson SL, Eckrich T, Kuhn S, Zampini V, Franz C, Ranatunga KM, Roberts TP, Masetto S, Knipper M, Kros CJ & Marcotti W (2011)
   Position-dependent patterning of spontaneous action potentials in immature cochlear inner hair cells.
   Nature Neurosci 14: 711-717
3. Zampini V, Rüttiger L, Johnson SL, Franz C, Furness DN, Waldhaus J, Xiong H, Hackney CM, Holley MC, Offenhauser N, Di Fiore PP, Knipper M, Masetto S & Marcotti W (2011)
   Eps8 Regulates Hair Bundle Length and Functional Maturation of Mammalian Auditory Hair Cells.
   PloS Biology 9: e1001048.
4. Kuhn S, Johnson SL, Furness DN, Chen J, Ingham N, Hilton JM, Steffes G, Lewis MA, Zampini V, Hackney CM, Masetto S, Holley MC, Steel KP & Marcotti W (2011) miR-96 regulates the progression of differentiation in mammalian cochlear inner and outer hair cells.
   Proc Natl Acad Sci USA 108:2355-60.
5. Johnson SL, Franz C, Kuhn S, Furness DN, Rüttiger L, Münkner S, Rivolta MN, Seward EP, Herschman HR, Engel J, Knipper M & Marcotti W (2010)
   Synaptotagmin IV determines the linear calcium dependence of vesicle fusion at auditory ribbon synapses.
   Nature Neurosci 13: 45-52.