Midnolin-dependent nuclear proteostasis in striatal circuits in Parkinson’s diseasedyskinesia and Huntington’s disease - Project Summary Recent work has identified the protein Midnolin (Midn) as a nuclear proteasome adaptor that targets proteins with β-strand–forming intrinsically disordered regions, including many immediate early gene (IEG) transcription factors, for ubiquitin-independent degradation. However, Midn’s physiological roles in defined neuronal populations, and its contribution to disease-relevant nuclear protein handling in vivo, remain largely unknown. My central hypothesis is that Midn can tune transcriptional homeostasis in striatal neurons, thereby potentially modifying both L-DOPA–induced dyskinesia (LID) in a PD context and mutant huntingtin (mHTT) driven pathology in HD. My preliminary data show that Midn is one of the most highly upregulated genes, along with several IEGs, in Drd1 (D1) expressing-direct pathway striatal medium spiny neurons (MSNs) in a mouse model of LID. Based on these data, Aim 1 will test whether Midn levels in D1-MSNs regulate LID severity. I will use Cre-dependent AAV-PHP.eB vectors in unilateral 6-OHDA lesioned D1-MSN conditional mice to overexpress or knockdown Midn specifically in D1-MSNs. I will quantify the resulting effects on LID (abnormal involuntary movements), therapeutic motor benefit, and LID-associated IEG protein levels (e.g. ΔFosB/FosB, Egr1, Arc, Pdyn, pERK) to determine whether Midn acts as a homeostatic regulator of IEG-driven maladaptive plasticity. Aim 2 will define how Midn loss and overexpression influence mHTT nuclear levels, transcriptional dysregulation, and behavioral symptoms in HD models. Using STHdhQ7/Q111 cells and both R6/2 and zQ175 HD model mice, I will perform AAV-delivered MSN-restricted Midn overexpression and knockdown. I will quantify Htt/mHTT levels, localization, and aggregation, as well as MSN gene expression and HD model behavioral outcomes. Together, these studies will establish whether augmenting a ubiquitin-independent nuclear degradation pathway is sufficient to ameliorate mHTT-associated nuclear stress in HD and alter LID in a PD context. This fellowship will provide integrated training in in vivo circuit-specific gene perturbation, quantitative imaging, and transcriptomic analysis, alongside formal and informal instruction in neurodegenerative disease mechanisms, molecular and systems neuroscience, and quantitative methods and computational tools. Under the mentorship of Dr. Heiman and my interdisciplinary thesis committee and within the highly collaborative environment of MIT’s Brain and Cognitive Sciences department, I will also receive structured training in grant writing, scientific communication, mentoring, and research ethics. The proposed project and training plan will position me to launch an independent career focused on nuclear proteostasis mechanisms in neurodegenerative disease contexts.
