1. Research Background

Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and Huntington’s disease are age-dependent brain disorders that are becoming increasingly prevalent in our aging society, but remain incurable. At the cellular level, these diseases are characterized by progressive dysfunction and ultimate loss of neurons in defined brain regions. Another common hallmark of neurodegenerative disorders is misfolding and aggregation of certain proteins such as Aβ, Tau, α-synuclein or mutant Huntingtin. The appearance of aggregates is a result of impairments in the protein homeostasis (proteostasis) network, which maintains the integrity of the cellular proteome. However, it remains unclear why certain populations of neurons are particularly vulnerable to degeneration, while other neurons remain largely intact. Furthermore, we lack understanding of how the demise of the vulnerable neuronal cell types affects the function of neural circuits, and how these changes are linked to the disease-specific behavioral defects. The overall goal of our research is to identify molecular pathways and neural circuit impairments that play a role in disease pathogenesis, and could provide promising targets for new therapeutic approaches.

2. Research questions addressed by the group:

• How is neuronal proteostasis affected in different neurodegenerative disorders?
  We have recently generated a new reporter mouse that allows visualizing neuronal proteostasis in the mouse brain (Blumenstocket al., 2021). Taking advantage of the proteostasis reporter, we are now investigating the effects of different types of protein aggregates on the protein quality control system. With the help of single-cell sequencing and imaging methods, we compare proteostasis in vulnerable and resistant neuronal populations, in order to uncover the molecular underpinnings of neuronal vulnerability. We furthermore plan to determine whether and to what extent proteostasis changes in the brain are reversible and if improving neuronal proteostasis is sufficient to ameliorate disease symptoms.
• How are neural circuits altered in neurodegeneration?
  Another research direction in the lab is devoted to deciphering neural circuit impairments and their impact on the mouse behavior. Using in vivo two-photon calcium imaging, we have demonstrated early disturbances of cortical circuits in Huntington’s disease, a hereditary neurodegenerative movement disorder (Burgold et al., 2019). Current work in the labcombines in vivo microscopy with behavioral tracking, and aims to understand the role of individual genetically targeted cortical cell types in the cortical circuit defects (Voelkl et al., 2022). In the future, we plan to investigate how cortical changes are linked to the impairments in other connected brain regions.
• How can affected molecular pathways and circuit elements be targeted for potential therapeutic strategies?
  Based on the identified molecular pathways and circuit elements affected in disease, we aim to design targeted strategies to increase neuronal resilience and ameliorate disease symptoms. To this end, we use gain- and loss-of-function manipulations in cell culture and mouse disease models (Voelkl et al., 2023). In addition, we plan to modulate the activity of specific neuronal cell types with opto- or chemogenetic approachesin order to normalize neural circuit function and rescue behavioral defects.

3. Possible project(s):

Possible projects include molecular and cell biological investigations of the effects of aggregating proteins in neurons. Thus, we are currently assessing the impact of aggregates on nucleocytoplasmic transport and on the proteostasis machinery, including the autophagy- lysosomal system (Riera-Tur et al., 2022). Mechanistic studies in primary neuronal cultures are complemented with histological, molecular and behavioral analyses in genetic mouse models.

Another possible direction is characterizing neural circuit defects in neurodegeneration. Here, in vivo two-photon calcium imaging will be combined with neuroanatomical viral tracings and unbiased behavioral tracking methods to assess changes in connectivity and function of specific neuronal cell types. Potential projects involve functional analysis of individual cell types in Huntington’s disease, as well as chronic simultaneous in vivo imaging of neuronal activity and proteostasis alterations in single neurons.

4. Applied Methods and model organisms:

We integrate in vitro studies in cell lines and murine primary neuronal cultures with in vivo investigations in mouse models. Our range of methods includes mouse genetics, histology, cell biology, biochemistry, behavioral assays, stereotactic brain surgeries, in vivo two-photon microscopy in anesthetized and awake behaving mice.

5. Desirable skills and qualifications:

We are looking for enthusiastic candidates with a background in neurobiology and experience in at least one of the following areas: molecular biology, cell culture, brain histology, in vivo imaging, behavioral tests. Willingness to work with mice is essential, previous experience is a plus.

6. References and key publications:

1. Voelkl K, Gutiérrez-Ángel S, Keeling S, Koyuncu S, da Silva Padilha M, Feigenbutz D, Arzberger T, Vilchez D,Klein R, Dudanova I (2023) Neuroprotective effects of hepatoma-derived growth factor in models of Huntington's disease. Life Sci Alliance, in press. doi: 10.26508/lsa.202302018
2. Saha I, Yuste-Checa P, Da Silva Padilha M, Guo Q, Körner R, Holthusen H, Trinkaus V, Dudanova I, Fernández-Busnadiego R, Baumeister W, Sanders DW, Gautam S, Diamond MI, Hartl FU, Hipp MS (2023) The AAA+ chaperone VCP disaggregates Tau fibrils and generates aggregate seeds. Nat Commun 14(1): 560. doi: 10.1038/s41467-023-36058-2
3. Voelkl K, Schulz-Trieglaff EK, Klein R, Dudanova I (2022) Distinct histological alterations of cortical interneuron types in mouse models of Huntington’s disease. Front Neurosci 16. doi: 10.3389/fnins.2022.1022251
4. Blumenstock S, Dudanova I (2022) Balancing neuronal circuits. Science 377: 1383-1384.
5. Dudanova I (2022) Biosensors for studying neuronal proteostasis. Front Mol Neurosci 15. doi: 10.3389/fnmol.2022.829365.
6. Riera-Tur I, Schaefer T, Hornburg D, Mishra A, da Silva Padilha M, Fernández-Mosquera L, Feigenbutz D, Auer P, Mann M, Baumeister W, Klein R, Meissner F, Raimundo N, Fernández- Busnadiego R*, Dudanova I* (2022) Amyloid-like aggregating proteins cause lysosomal defects in neurons via gain-of-function toxicity. Life Sci Alliance 5(3) e202101185. doi: 10.26508/lsa.202101185. PMID: 34933920 *equal contribution
7. Blumenstock S, Schulz-Trieglaff EK, Voelkl K, Bolender A-L, Lapios P, Lindner J, Hipp MS, Hartl FU, Klein R, Dudanova I (2021) Fluc-EGFP reporter mice reveal differential alterations of neuronal proteostasis in aging and disease. EMBO J, e107260. doi: 10.15252/embj.2020107260
8. Yuste-Checa P, Trinkaus VA, Riera-Tur I, Imamoglu R, Schaller T, Wang H, Dudanova I, Hipp MS, Bracher A, Hartl FU (2021) The extracellular chaperone Clusterin enhances Tau aggregate seeding in a cellular model. Nat Commun 12(1): 4863. doi: 10.1038/s41467-021-25060-1
9. Trinkaus VA, Riera-Tur I, Martínez-Sánchez A, Bäuerlein FJB, Guo Q, Arzberger T, Baumeister W, Dudanova I, Hipp MS, Hartl FU, Fernández-Busnadiego R (2021) In situ architecture of neuronal α- Synuclein inclusions. Nat Commun 12(1):2110. doi: 10.1038/s41467-021-22108-0
10. Blumenstock S, Dudanova I (2020) Cortical and striatal circuits in Huntington’s disease. Front Neurosci 14:82; doi: 10.3389/fnins.2020.00082
11. Burgold J, Schulz-Trieglaff EK, Voelkl K, Gutiérrez-Ángel S, Bader JM, Hosp F, Mann M, Arzberger T, Klein R*, Liebscher S*, Dudanova I* (2019) Cortical circuit alterations precede motor impairments in Huntington’s disease mice. Sci Rep 9(1):6634. doi: 10.1038/s41598-019-43024-w *equal contribution
12. Hosp F, Gutiérrez-Ángel S, Schaefer MH, Cox J, Meissner F, Hipp MS, Hartl FU, Klein R, Dudanova I^#, Mann M^#(2017) Spatiotemporal profiling of Huntington’s disease inclusions reveals widespread loss of protein function. Cell Rep 21: 2291-2303. ^#co-corresponding authors
13. Bäuerlein FJB, Saha I, Mishra A, Kalemanov M, Martinez-Sanchez A, Klein R, Dudanova I, Hipp MS, Hartl FU, Baumeister W, Fernández-Busnadiego R (2017) In situ architecture and cellular interactions of polyQ inclusions. Cell 171: 179-187.