Deciphering the thalamic reticular functions of phospholamban

The National Institute of Mental Health (NIMH) awarded a 3-year, $413,681 Project Grant (CFDA 93.242 - Mental Health Research Grants) to the University of Dayton Research Institute to study the role of phospholamban (PLN), a critical calcium regulatory protein, in the thalamic reticular nucleus (TRN) of the brain. The research aims to decipher the cellular and molecular mechanisms by which PLN regulates the signaling properties of TRN neurons and influences behavioral outcomes like locomotor activity and motor impulsivity. The project will leverage a combination of transgenic mouse models, transcriptomics, neurochemical analyses, and in vivo calcium imaging to uncover the TRN-specific functions of the PLN/SERCA2 calcium-handling pathway. This work is expected to provide novel insights into the neurobiology of TRN circuits and their involvement in neurodevelopmental disorders. The award will also support the research training of over 10 undergraduate and 1 graduate student at the University of Dayton.

Abstract

The thalamic reticular nucleus (TRN) is a poorly understood structure of the mammalian forebrain that is deeply involved in regulating complex behaviors such as sensory processing, attention, and sleep. TRN dysfunction has been recently proposed to comprise a circuit endophenotype in neurodevelopmental disorders, including autism, schizophrenia and attention-deficit/hyperactivity disorder (adhd). Notably, a specialized sarco-endoplasmic reticulum calcium (CA2+) atpase 2 (SERCA2)-dependent CA2+-cycling network operates in the dendrites of thalamic reticular neurons to regulate their burst-firing activity. Phospholamban (PLN) is a critical regulator of the SERCA2, and well-known for preserving CA2+ homeostasis in the heart. Findings from our lab indicate that the role of PLN extends beyond the cardiovascular system to influence the brain's thalamic reticular neurocircuitry. Specifically, we have found PLN protein to be selectively expressed in the inhibitory TRN neurons of the mouse brain, while conditional loss of PLN function in the TRN (i.e., plncko) results in aberrant behaviors that map onto thalamic reticular circuits, including locomotor hyperactivity and motor impulsivity. The studies outlined in the current 3-year area (R15) project will test the specific hypotheses that: i) PLN is a prominent CA2+-handling player in the TRN with an important role in regulating the signaling properties of TRN neurons, and II) that dysfunctional neuronal responses in the TRN underlie the hyperactive and impulsive behavioral phenotypes observed in plncko mice. In order to address these hypotheses, this project will use a combination of novel TRN-specific plncko transgenic mouse models, and high-throughput RNA-sequencing (RNA-SEQ) transcriptomics, neurochemical and in vivo CA2+ fiber photometry imaging approaches to unveil the intricate cellular and molecular mechanisms orchestrated by the PLN/SERCA2 pathway in the TRN neurocircuit. The studies outlined in this proposal have high potential to decipher the cellular and molecular dynamics of a novel thalamic reticular CA2+-handling regulator involved in fine-tuning locomotor activity and motor impulsivity at the organismal level. Importantly, this area (R15) award will support a neuroscience research team at the university of dayton composed primarily of undergraduate student researchers and will provide an outstanding opportunity for students to gain a solid understanding of a wide spectrum of cutting-edge neuroscience methodologies. Over the project period, over ten undergraduate students and one graduate student will be involved in the proposed research. Specialized upper-level undergraduate neurobiology laboratory courses (i.e., 20-24 students per year), as well as introductory biology core laboratory courses required by all science majors (i.e., 450 students per year) will utilize antibodies, reagents, mouse models and experimental protocols developed in this project. This project will therefore meet area (R15) goals by increasing scientific literacy of more than 1,400 students at the university of dayton through exposure to meritorious research.