The goal of B2 is to understand the role of RNP granules in the pathogenesis of amyotrophic lateral sclerosis (ALS).

Motor neurons (MNs) have very long axons that require local translation of mRNAs transported from the soma via ribonucleoprotein (RNP) granules. RNP granules are condensates that protect mRNA from degradation in a translationally arrested state¹. There are many different types of RNP granules found in MN axons, and MNs are able to disassemble individual granules at specific times and locations in order to support specialized functions such as metabolism or injury repair¹. Highlighting the importance of this process, alterations in RNP granules have been linked to ALS pathogenesis and MN degeneration^2,3. Thus, a better understanding of RNP granules could lead to novel therapeutics to protect MN axons against degeneration in ALS. To reach this objective, the Sterneckert team uses induced pluripotent stem cell (iPSC)-derived MNs^4-6 to investigate RNP granule dynamics in a physiological model. In collaboration with the Hyman and Alberti teams, we generated FUS-eGFP reporter iPSCs for live-cell imaging of RNP granules, facilitating compound screening to identify novel drugs for repurposing as ALS therapeutics⁴. We also generated a microfluidic device enabling the study of axonal RNP granules as well as the functionality of neuromuscular junctions⁶. Using this technology, we uncovered evidence that mutant FUS disrupts axonal RNP granules, leading to reduced translation of nuclear proteins required for axonal mitochondrial function (see figure). Here, we will use these technologies to answer fundamental questions about RNP granules in MNs and how this is impacted by ALS pathogenesis.

Project 1:

1. How are multiple different RNP granules with individualized mRNA cargo maintained in MN axons?
2. How much exchange of RNA-binding proteins occurs between different RNP granules within axons?
3. How do RNP granules regulate their size and prevent fusion in order to maintain separation of mRNAs?

Project 2:

1. How does ALS pathogenesis impact RNP granule maintenance and composition?

To answer these research questions, both projects will utilize dCas13d-mediated proximity labeling to identify the proteins binding specific axonal mRNAs. Pulse-chase experiments can be used to assess if proteins in RNP granules are exchanged over time. Project 2 will compare motor neurons derived from isogenic iPSCs to characterize the impact of ALS mutations. In addition, we will explore if specific oligonucleotides (“bait RNAs”) could offer an effective strategy for reversing ALS pathogenesis.

Understanding how human motor neuron axons maintain diverse RNP granule subtypes

The PhD students will be trained in iPSC culture, MN differentiation, confocal microscopy, live cell imaging, and image analysis. Collaborations with groups using alternative model systems, including theoretical groups, will further the acquisition of communication skills and interdisciplinary thinking.

• Candidates have a Masters degree in biology or related fields
• Candidates should have a sound basis in cell biology, neurology or closely related fields.
• Experience in microscopy and cell culture are expected