UNIVERSITY OF COLOGNE

Charcot-Marie-Tooth (CMT) disease, also known as hereditary motor and sensory neuropathy, describes a heterogeneous group of inherited peripheral nervous system disorders affecting 1 in 2500 people worldwide. The CMT clinical phenotype is the muscle weakness and decreased sensation, arising as the consequence of impaired synaptic transmission due to a progressive degeneration of preferentially long-range axons. More than 80 genes have been identified in CMT, and the majority of them are involved in the regulation of intracellular membrane trafficking (Bucci et al., 2012). This highlights membrane trafficking as a crucial process underlying axonal health and maintenance. Among these genes is Fgd4 that encodes the FGD1-related actin filament-binding protein (Frabin). Mutations in Fgd4 cause early-onset recessively inherited CMT4H (Rajan et al., 2015), but the synaptic function of FGD4 is currently unkown. Equally unkown are the mechanisms regulating the FGD4 abundance in neurons. Our preliminary data indicate that autophagy regulates FGD4 levels in neurons and that this function of autophagy is important to maintain the presynaptic membrane trafficking. Because CMT4H is a recessively inherited disease caused by loss-of-function mutations, our preliminary data implicate autophagy-dependent membrane recycling impairment as a potential pathogenic mechanism in long-range axons neuropathy, a hypothesis which will be addressed in the currently research project.  

Research groups of Kononenko and Rugarli will join forces to elucidate the role of autophagy in regulation of FGD4 levels in neurons. The group of Kononenko has extensive expertise in molecular and cellular analysis of membrane trafficking in neurons, as well as in characterization of synaptic physiology. The group of Rugarli has a longstanding interest and expertise in analysis of distal axonopathies in hereditary spastic paraplegias (HSP).

The major aim of this proposal is to understand how autophagy regulates FGD4 levels in neurons and test the role of this interaction for synaptic physiology and axonal maintenance in-vitro and in-vivo.

Specific goals are:
1. To define the precise molecular and cellular mechanism by which autophagy regulates FGD4 levels in neurons.
2. To understand the exact membrane recycling pathway, which requires the FGD4 and autophagy at the synapse.
3. To elucidate the consequences of autophagy/FGD4 loss-of-function for synaptic function and axon maintenance in-vivo.

Molecular and cellular biology (including CRISPR/Cas9 technology), animal mouse models, in-vivo neuroanatomy techniques, state-of-the-art live imaging, FACS analysis, multiple OMICS techniques and neurophysiology.

The candidate should have a good knowledge of molecular and cellular neuroscience and/or cell biology, experience with mouse work is an advantage. We expect an open-minded and very enterprising personality, capable of working in a collaborative research group. Ideal candidates should possess a good scientific appetite and a willingness to succeed!

1. Torres-Benito L, Schneider S, Rombo R., Ling KK, Grysko V, Upadhyay A, Kononenko NL, Rigo FW, Bennett CF, Wirth B. NCALD antisense oligonucleotide-based therapy additionally to low-dose Nusinersen further ameliorates spinal muscular atrophy in mice. AJHG, 105, 221-230 (2019).

2. Soykan T, Kaempf N, Vollweiter D, Sakaba T, Goerdeler F, Puchkov D, Kononenko NL, Haucke V. Synaptic vesicle endocytosis occurs on a timescale of seconds and is mediated by formins independent of clathrin. Neuron 93, 854-866 (2017).

3. Kononenko NL*, Claßen GA, Kuijpers M, Puchkov D, Maritzen T, Tempes A, Malik AR, Skalecka A, Jaworski J, Haucke V.* Retrograde transport of TrkB-containing autophagosomes via the adaptor AP-2 mediates neuronal complexity and prevents neurodegeneration. Nat. Commun. 7;8: 14819 (2017). *-co-corresponding author.

4. Kaempf N, Kochlamazashvili G, Puchkov D, Maritzen T, Bajjalieh SM, Kononenko NL*, Haucke V*. Overlapping functions of stonin 2 and SV2 in sorting of the calcium sensor synaptotagmin 1 to synaptic vesicles. PNAS 112, 7297-302 (2015). *-co-corresponding author.

5. Kononenko NL, Puchkov D, Classen GA, Walter AM, Pechstein A, Sawade L, Kaempf N, Trimbuch T, Lorenz D, Rosenmund C, Maritzen T, Haucke V. Clathrin/AP-2 Mediate Synaptic Vesicle Reformation from Endosome-like Vacuoles but Are Not Essential for Membrane Retrieval at Central Synapses. Neuron 82, 981-988 (2014).

6. Sakaba T, Kononenko NL, Bacetic J, Perchstein A, Schmoranzer J, Yao L, Barth H, Schupljakov O, Kobler O, Aktories K, Haucke V. et al. Fast neurotransmitter release regulated by the endocytic scaffold intersectin.  PNAS 110, 8266-8271 (2013).

7. Kononenko NL, Diril MK, Puchkov D, Kintscher M, Koo SJ, Pfuhl G, Winter Y, Wienisch M, Klingauf J, Breustedt J, Schmitz D, Maritzen T, Haucke V. Compromised fidelity of endocytic synaptic vesicle protein sorting in the absence of stonin 2. PNAS 110, (2013).