Galynn Zitnik, PhD

My research interests include:

• Neurodegenerative diseases such as Alzheimer's disease
• The intracellular trafficking of amyloid precursor protein (APP) and its secretase products in neuroblastoma cells, neural progenitor cells and mature neurons. 
• Interactions of these proteins and peptides with the cytoskeleton and other cytoplasmic organelles, interactions with the cell nucleus and possible functions during mitosis.

 I collaborate in these studies with George M. Martin (Dept. of Pathology)

 

• Cataract as a function of oxidative damage and aging
• DNA damage associated with X-irradiation and aging in the lens epithelial cells. 
• Identification and culture of stem cells of the lens epithelium.

I collaborate in these studies with Norman S Wolf (Dept. of Pathology).

　

When DNA is damaged, part of the response to that damage is mobilization of gamma-H2AX.  In this picture an unirradiated cell (human neuroblastoma SK-N-SH) has been fixed in 3.7% paraformaldehyde, then stained with mouse anti-gamma-H2AX (red) and rabbit anti-gamma-H2AX (green).  Dapi was used to stain DNA blue. 

Levels of gamma-H2AX protein are low.

　

This SK-N-SH cell was irradiated with 11 Gy X-irradiation for 5.5 minutes.  After 30 minutes of recovery the cell was fixed with PAF then stained for gamma-H2AX as described before.

 

Note that the signal from mouse anti-gamma-H2AX (red) is now prominent in large protein clusters.  The signal from rabbit anti-gamma-H2AX (green) has also increased but as smaller aggregates.  Why do the two signals not colocalize? 

We speculate that the mouse antibody and the rabbit antibody are specific for different epitopes on the gamma-H2AX protein.  When the protein is in one configuration (=I) the mouse antibody has access to its epitope while the epitope specific for the rabbit antibody is hidden.  When the protein is in a different configuration (=II) the rabbit antibody has access to its epitope while that of the mouse antibody is hidden.

Assuming that the large aggregate indicate sites of DNA damage due to irradiation, configuration I may occur when gamma-H2AX is active at sites of damage, while configuration II may occur when the protein is inactive.