The basis of cellular architecture is the cytoskeleton, a collection of specialized and dynamic “building blocks” that act as a cell’s scaffolding. Our investigations into the cytoskeleton focus on structural elements known as actin and myosin filaments, with an emphasis on how these nanoscale components generate microscale cellular architecture and macroscale tissue and organ function. We are interested in how the cytoskeleton provides mechanical stability and produces contractile forces that shape membrane curvature and confer mechanical resilience during cell differentiation, morphogenesis and aging. Our approaches include biochemistry, biophysics, super-resolution fluorescence microscopy, mouse genetics and physiology, and analysis of human cells from patients with congenital diseases.​

2.  Red Blood Cell Formation

Biogenesis of mammalian RBCs (erythropoiesis) is a highly orchestrated process of terminal differentiation in which regulated gene expression directs a series of cell divisions coupled to dramatic changes in cell and nuclear morphology, culminating in cell cycle exit and nuclear expulsion (enucleation). While enucleation has been described morphologically for decades, the molecular mechanisms that drive the process remain unclear. We study erythroblast enucleation in hematopoietic organs (bone marrow, spleen, and fetal liver) from transgenic mice and in human hematopoietic stem cells with actin cytoskeleton mutations. We identify critical components by genetics, proteomics and biochemistry, analyze 3D cell shape and cytoskeleton architecture using confocal and super-resolution fluorescence microscopy, observe dynamics of fluorescent-tagged cellular components using time-lapse microscopy of living erythroblasts, and determine enucleation forces using computational modeling. These studies will elucidate molecular mechanisms of human congenital anemias due to defects in erythropoiesis and enucleation and provide strategies for optimizing RBC production in vitro for future applications in transfusion medicine.

Read more about the actin cytoskeleton and enucleation.

3.  Eye Lens Function

The lens functions to fine focus light onto the retina to produce a clear image. For proper functioning, the lens not only has to be clear but also must be an appropriate size, shape, and mechanical stiffness. Age-associated conditions of the lens include cataracts (lens cloudiness) and presbyopia (difficulty to focus on close objects). Despite decades of study, the exact mechanisms underpinning these aging conditions remain unclear. Using transgenic mice and other mammalian model systems combined with genomic, proteomic, and biochemical approaches, we aim to identify the actin cytoskeleton components that determine lens growth, cell sizes and shapes, and their microstructural mechanical responses. We utilize electron microscopy and high-and super-resolution fluorescence confocal microscopy to evaluate the complex 3-dimensional shapes and structures of lens cells. Additionally, by utilizing specialized equipment we mechanically compress or stretch lenses to evaluate biomechanical properties, and collaborate with engineers and computational biologists to model forces within the lens. This will enable us to understand how the actin cytoskeleton establishes lens size, shape, and biomechanical properties, and how cytoskeleton dysfunction may contribute to cataracts and/or presbyopia. ​​​