Kretzschmar Lab

Kretzschmar Lab October 2014
Front row: Silvia Plascencia, Marlène Cassar
Back row: Doris Kretzschmar, Elizabeth Sunderhaus, Sudeshna Dutta


CURRENT LAB MEMBERS

Dr. Doris Kretzschmar, Principal Investigator

 

Doris Kretzschmar

email Dr. Kretzschmar

 

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.

Neurodegenerative Fly Brain

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. Marlène Cassar Postdoctoral Fellow

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Graduate School: University of Pierre and Marie Curie, Paris, FranceMariene Cassar

Marlène's Project:

A key factor in Alzheimer's pathogenesis is the generation of the small Aß peptide, which is processed from Amyloid Precursor Proteins (APPs).  However, APP processing also results in several other fragments, including soluble N-terminal ectodomains (sAPPs) and C-terminal intracellular domains (AICD). Despite the fact that APP is extensively studied, little is known about its normal function. Previous studies in our laboratory suggested that APPL (the fly ortholog of APP), signalling through its intracellular domain, is protective in a fly mutant that induces progressive neurodegeneration called AMPK/loe. Like in the human AICD, the Drosophila AICD contains several putative interaction domains, including a binding site for the G-protein Goα. In Drosophila, Goα proteins are widely expressed in the brain and are required for learning processes. My project is to identify whether Goα signalling is involved in the protective function of APPL previously observed in the AMPK/loe mutant.

 

Marlenefigweb

Figure: Pan-neuronal inhibition of Goα induces an enhancement in loe mutant neurodegenerative phenotype.  Arrows show neurodegenerative vacuoles in brain from 7 days old flies in the loe mutant (A).  In aged matched flies, bigger and numerous vacuoles are observed when Goα is inhibited in all neurons in the loe mutant genetic background (B)


DR. SUDESHNA DUTTA, POSTDOCTORAL FELLOW

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Graduate School: University of Maryland, College ParkSudeshna Dutta

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.

 

Sudeshna figure

Figure: Brain degeneration in sws fly


Elizabeth Sunderhaus, Graduate Student

Liz Sunderhaus

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Undergraduate education at Cedar Crest College

Lizzy's Project

Investigating the cell type specific roles of Neuropathy Target Esterase in the nervous system and how specific mutations lead to a spectrum of disorders

Neuropathy Target Esterase (NTE) is a phospholipase that maintains lipid homeostasis and can regulate PKA activity. Mutations in NTE in humans have been shown to cause a spectrum of disorders with symptoms ranging from hypogonadism to cerebellar atrophy and blindness. Complete loss of NTE's ortholog, Swiss Cheese (SWS), in Drosophila melanogaster has been shown to cause age-dependent neurodegeneration, including the retina, similar to the degeneration seen in the brain-specific knockouts of mouse NTE when aged. However, SWS and NTE are also expressed in glia, and sws1 has glial defects and cell death. Using a construct with a mutation in the active site of the phospholipase domain of SWS, we found that expression of this construct in glia or neurons cannot rescue degeneration, but it can rescue retinal degeneration when induced in the eye. In contrast, a construct with a mutation in the PKA interaction domain cannot rescue the neuronal degeneration, including photoreceptors, but can rescue glial death. This data shows that different cell types have different requirements for the two functions of SWS, suggesting that disease-associated mutations in NTE specifically affect one of these functions, thereby causing specific phenotypes. To investigate how different mutations in NTE result in distinct phenotypes, we have created transgenic flies expressing wildtype and mutant human NTE (hNTE). Expressing wildtype NTE pan-neuronally in the genetic background of sws1 showed that hNTE can suppress the neurodegeneration and rescue the decreased phototaxis performance and lifespan of the sws1 mutant. Expressing hNTE in glia suppressed cell death, confirming that the human construct can replace SWS, and we can test the functional ability of the mutant constructs in flies. First result show that a hNTE construct without the phospholipase domain due to a frame shift mutation does not rescue degeneration when expressed in neurons, and we are currently testing its function in glia. In addition to the rescue ability, we will also test how the mutant hNTE constructs affect the phospholipase and PKA interaction domains' function. Drosophila can therefore provide a model to gain further insights into the functions of NTE and how specific mutations cause the spectrum of phenotypes seen in patients.


Droso Phila, Undercover investigator

fly head

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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....

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Past Members

 

  • Bonnie Bolkan
  • Scott Holbrook
  • 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
  • Mandy Cook