Investigating mechanisms of neuronal growth and synapse formation

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The formation of neuronal connections (synapses) between nerve cells (neurons) is a fundamental hallmark in the nervous system. Synapses are critical for brain function as they mediate cognitive processes. Synapses form by the coordinated actions of signaling molecules that carryout structural and functional changes to promote growth and maturation. Our long-term goal is to uncover novel signaling mechanisms regulating mammalian synapse formation, to better understand how the nervous system develops. Typically, only a single isoform of a given protein is studied within a signaling pathway. However, proteins can have multiple isoforms that have very different activities in neurons. Therefore, our understanding of whether different isoforms of the same protein family have distinct or similar signaling networks is significantly under developed. This knowledge would strenghthen our basic understanding of nervous system development . Therefore in the short term, we are studying a member of the Ste family of kinases with multiple isoforms that have been poorly studied during synapse development, to identify isoform-specific signaling mechanisms. Our previously work on the Ste family member, thousand and one amino acid 2 (TAOK2) revealed that mice lacking TAOK2 have structural and functional defects in cortical excitatory synapses. However, TAOK2 has two predominant protein isoforms (alpha and beta), but the details of when and how these isoforms regulate synapse development, maturation and plasticity are unknown. We have generated proteomics reagents to study this problem and identify binding partners of each TAOK2 isoform using BioID, a method for screening protein-protein interactions. We will use proteomic data in combination with our TAOK2 mouse model to perform functional studies to understand how the novel TAOK2 isoform-specific signaling pathways regulate synapse development. Our functional studies include the use of state-of-the-art approaches including electrophysiology on individual neurons, and electrophysiology on populations of neurons with new multielectrode array technology. Our program will address previous limitations and provide novel mechanistic insight into how kinases regulate synapse development. The novel and unbiased proteomic techniques will reveal unappreciated details into how a kinase with multiple isoforms controls different aspects of synapse formation and maturation. If we are successful, our future program will perform isoform-specific proteomics and functional validation experiments on other synaptic proteins, including the novel TAOK2-interacting proteins, which will significantly advance our fundamental understanding of neuronal signaling. Lastly, our program will make use of emerging and state-of-the-art experimental approaches including molecular and cellular biology, proteomics, biochemistry, gene editing and electrophysiology, providing HQP a cutting-edge and dynamic training environment.