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PI, Amy S. Gladfelter
Associate Professor of Biological Sciences
Ph.D. Duke University 2001
B.A. Princeton University 1996
   
 
amy gladfelter  
 
Samantha Roberts
Graduate Student
 
Huaiying Zhang
Postdoctoral Fellow
sam
 

 

Huaiying

Progression through the cell cycle is known to be regulated by cytoplasmic factors, yet there are examples of nuclei cohabitating in a common cytoplasm and maintaining cell cycle autonomy. This is the case in the multinucleate filamentous fungus Ashbya gossypii, in which nuclei only a few microns from each other in the same cytoplasm divide independently. Asynchronous mitosis in the syncytium requires highly regulated microtubule dynamics and non-random nuclear spacing, as well as nuclear-autonomous transcriptional activity for cell cycle regulators. We are using this system to gain a better understanding of cytoplasmic organization and its influence on transcriptional regulation and cell cycle progression.

 

Despite their functional roles in RNA post transcription modification, many RNA binding proteins with disordered domains are associated with neurodegenerative diseases because they form pathological aggregates. We have found that the polglutamine tract in an RNA binding protein called Whi3 works together with the RNA-bind motif to perform a biological function. PolyQ works by helping Whi3 form aggregates in the multinucleate fungus Ashbya gossypii. Heterogeneously localized Whi3 aggregates, bound to cyclin transcripts, result in transcript clustering around nuclei and therefore create cytoplasm compartmentalization that allows nuclear division autonomy in a common cytoplasm. This leads to the hypothesis that polyQ tracts in RNA binding proteins have important biological function involving physiological aggregation, yet under other circumstances have the ability to form pathological aggregates like those observed in polyQ diseases. My research focus is to use Whi3 as a model protein to study the assembly mechanism of physiological RNA-protein complexes and their phase transition into pathological aggregates.

     
 
Anum Khan
Graduate Student

 

 

 

Andrew Bridges
Graduate Student
Anum   Drew

Septins are the fourth cytoskeletal element. These are filament-forming proteins involved in cytokinesis and other cellular processes. Similar to actin (ATP) and microtubules (GTP) septins can bind GTP and hydrolyze it. One of the unsettled questions in septin literature is the role of this GTP binding and hydrolysis for their function. While all the septins have a central conserved domain with the potential to bind GTP only a subset of them have the ability to hydrolyze it. I use biochemical and microscopy approaches to understand how GTP binding and hydrolysis might be playing a role in septin filament formation, recruitment and function.

 

Dynamic transitions between soluble and assembled states lend cytoskeletal polymers many of their functional properties, from force generation and motility to contraction and scaffolding. Septins are far less understood than other cytoskeletal elements such as actin and microtubules, yet they have a conserved function acting as scaffolds at cell membranes and are implicated in cancers, neurodegenerative diseases, and microbial pathogenesis. We have defined a key role of the plasma membrane in directing septin filament formation in live cells and reconstituted dynamic septin polymerization using purified septin and lipid components. We find that septins grow into filaments and form higher order structures by diffusing, colliding and annealing on the plasma membrane. Currently, I am interested in membrane properties that direct septin filament formation, how septin interacting proteins regulate their assembly and structure, and how alternate septin subunits influence higher-order structure and function. 

     
 
Patricia Occhipinti
Lab Manager
 
Molly McQuilken
Graduate Student
pat    McQuilken

 

 

Many cell structures are on the scale of microns, but must be built from the nanometer scale protein building blocks. It has been challenging to study how cells address these scaling problems. One group of proteins whose assembled structure has eluded researchers is the septins. Polarization microscopy is a technique that can be used to assess the structural order of cellular components using linearly polarized light. The questions pertaining to septin assembly that I am able to address through polarization microscopy are as follows: a) what regulated higher order structure formation of septins; b) how the organization of septins in higher order structures changes in the cell cycle; and c) how septin filaments are oriented relative to the membrane.

 
Steven Chen
Undergraduate Researcher
   
Maximilian Jentzsch
Undergraduate Researcher
     
 
Steven Chen
Undergraduate Researcher
   
Courtney Kelly
Undergraduate Researcher
     
 
Ittai Eres
Undergraduate Researcher
   
Joshua Cox
Undergraduate Researcher
     
     
     

Last Updated: 11/14/13