Kretzschmar Lab
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CURRENT LAB MEMBERS
Dr. Doris Kretzschmar, Principal Investigator
To analyze our "neurodegenerative" flies, we are using diverse imaging techniques ranging from live cell imaging to electron microscopy, in addition to molecular and behavioral assays.
For example, the picture on the left is a confocal image showing the localization of the Amyloid Precursor Protein and its proteolytic fragments (with green and red fluorescence tags at both ends) within an intact Drosophila brain whereas the picture in the middle is from a movie determining the trafficking of this protein in a living neuron in culture. The picture on the right shows an electron microscopic image from a nuclear aggregate (arrow) caused by the expression of a pathogenic Sca1 protein which is responsible for Machado-Joseph Disease.
Dr. Bonnie Bolkan, Postdoctoral Fellow
Graduate School: Cornell University
Bonnie's Project:
She has two related projects focusing on the normal functions of homologs of Alzheimer’s Disease (AD) related proteins dBACE and dTau. BACE-1 is the enzyme that cleaves Amyloid Precursor Protein creating the toxic Aß fragment found in AD plaques. Hyperphosphorylated tangles of Tau are one of the other pathological hallmarks of AD. Both BACE and Tau are highly conserved in Drosophila making it a good model to investigate their functions in normal neuronal function.
Figure : Knockdown of dBace in photoreceptor neurons results in progressive degeneration of the glia in the lamina cortex. GMR-GAL4 control flies show an intact lamina neuropil (la n), which mostly consists of neuronal fibers, and lamina cortex (la c), which houses the cell bodies of the neuronal monopolar cells and various glial cells. The basement membrane, which separates the retina (re) from the lamina, is indicated by the white line in the magnification in the right panels. Vacuoles have formed in the lamina cortex (arrowheads) of GMR-GAL4; UAS-dBACERNAi flies (arrowheads). 7µm thick paraffin sections of 28-day-old flies. Scale bar = 10μm.
Dr. Mandy Cook, Postdoctoral Fellow
Graduate School: University Würzburg, Germany
Mandy's Project:
The AMPK mutant loechrig
The Drosophila mutant loechrig, which lacks a neuronal isoform of the AMPK (AMP- activated protein kinase) γ subunit, shows progressive neurodegeneration, neuronal cell death of the adult nervous system and a lower cholesterol ester level.
In order to determine the correlation between the loe mutation, isoprenylation and the RHO1 pathway, we generated and analyzed flies with mutations in RHO and its downstream targets. Isoprenylation (which is negatively regulated by AMPK) is an important mechanism allowing intracellular proteins, like small G proteins (e.g. RHO) to associate with the membrane, which is then followed by activation of the protein. This step is critical for signal transduction of cellular hormones, growth factors, and cytokines from the cytoplasm to the nucleus and influences proliferation, differentiation and survival of the cell.
Figure: Paraffin section of the adult brain.
loe shows severe vacuolization
in the brain after 5 days
Figure: The sws fly has reduced walking and flying ability
The swiss cheese protein is the fly homologue of the human Neuropathy Target Esterase (NTE). Mutations in NTE cause a Hereditary Spastic Paraplegia called NTE- related Motor- Neuron Disorder. The sws mutant shows vacuolization due to apoptosis, which led to the name swiss cheese.
We are currently investigating the downstream targets of SWS and their role in neurodegeneration. Specifically we look into the role of cAMP activated protein kinase (PKA-C3) and we propose that SWS binds to PKA-C3 which leads to the inhibition of PKA-C3. For the dissociation of SWS and therefore activation of PKA- C3, cAMP/cGMP binding is required.
Dr. Sudeshna Dutta, Postdoctoral Fellow
Graduate School: University of Maryland, College Park
Sudeshna's Project:
The role of Swiss cheese, the Drosophila homologue of Neuropathy target esterase, in glia development
Neuropathy target esterase (NTE), a molecular target of organophosphates (OP) found in pesticides and nerve gases induce delayed neuropathy (OPIDN) in humans. OPIDN is characterized by axonal degeneration mainly of motoneurons. Similarly, loss of the Drosophila homologue of NTE, Swiss Cheese (SWS) causes progressive neurodegeneration in flies but also glial degeneration. Using both Drosophila and mouse model systems,we are trying to understand the importance of the SWS protein in glia, its regulation in axonal-glial interaction and its pathogenic function in inherited spastic paraplegia and in OPIDN in humans.
Figure: Braindegeneration in sws fly
Dr. Scott Holbrook, Postdoctoral Fellow
Graduation School: University of Oregon
Scott's Project:
My research focuses on the role of the endosomal sorting protein, GGA, in the processing of amyloid plaque precursor protein, (APP). Cleavage of APP at specific sites results in the generation of neurotoxic Aβ protein fragments, consequently, regulation of APP-cleaving proteins is paramount for nervous system integrity. Through the use of confocal microscopy, molecular biology, and Drosophila genetics I am figuring out the function of GGA in targeting APP and APP-cleaving proteins to specific subcellular compartments.
Figure: Cleavage of full length human APP expressed in the adult drosophila brain :
GFP labeled N-terminal APP and RFP-labeled C-terminal APP
Droso Phila, Undercover investigator
Droso Phila's Project:
I investigate human behavior. We like to observe scientists and document on their performance under stress. And we keep wondering why these poor creatures have not developed wings....
Past Members :
- Jill Wentzell
- Derek Musashe
- Alex Bettencourt da Cruz
- Jakob Tschaepe
- Jennifer Holliday
- Katia Carmine-Simmen
- Mahtab Niyyati
- Isabell Schwenkert
- Laura Reese
- Thomas Proctor
- Hanil Quirindongo
- Priya Mani
