Uncovering the Role of GIT Proteins in Encoding Acoustic Information.

• Applicant: Dr. Christian Keine, Ph.D.
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2018 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420075000

The auditory perception of the world relies on the transformation of sound pressure waves into temporally precise and rapid action potential (AP) signaling between neurons. The localization of a sound source is fundamental for binaural perception, to localize objects in space (e.g. approaching cars) and crucial for understanding speech in noise. Unlike in the visual or somatosensory system in which spatial information is represented at the level of the sensory epithelium, the location of a sound source has to be reconstructed by neuronal computations in the brain. These neuronal computations require the highest temporal resolution in the mammalian nervous system. Neuronal communication, however, relies on the release of neurotransmitters from a limited number of synaptic vesicles (SV) from the presynaptic terminal. The dynamics of SV release critically determine the timing and efficacy of AP signaling. To understand how temporal precise and efficient AP generation is established it is crucial to identify which molecular mechanisms control SV dynamics in the presynaptic terminal. A critical synapse for the first stages of binaural sound processing is the calyx of Held/MNTB synapse located in the auditory brainstem. The calyx of Held/MNTB synapse has extraordinary fidelity and reliability of synaptic transmission up to hundreds of Hertz firing rate. Recently, it was shown, that G protein-coupled receptor kinase-interacting proteins (GITs) control synaptic strength by regulation SV release probability. However, the GIT proteins’ role in enabling temporally precise and sustained auditory signaling is unknown. A combination of molecular, cellular, as well as behavioral methods will be used to generate novel insights into the molecular mechanisms that are required for encoding acoustic information. First, GIT proteins will be selectively ablated in the calyx of Held by combining novel viral vector technology with transgenic mouse lines circumventing the embryonal lethality of conventional knock-out animals. Whole-cell patch-clamp recordings will be performed in acute brain slices to measure the impact of GIT proteins on SV dynamics. To mimic the environment of an impact nervous system, all experiments will be performed at near-physiological conditions on functionally fully developed synapses. The ability to ensure precise and reliable AP firing will be assessed under stimulus conditions which mimic the neuronal response to natural sounds such as speech. Finally, the ability to localize sounds after deletion of GIT proteins will be tested using a passive behavioral paradigm. The project is expected to generate novel insights into the molecular mechanism of GIT proteins in regulating SV dynamics and their role in encoding acoustic information.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Samuel M. Young, Ph.D.