The fraction of Americans 65 and older is expected to double by 2060.13 Unless significant progress is made in the treatment of age-related diseases, this fundamental demographic shift will herald drastic economic and social challenges. The study of aging in S. cerevisiae has revealed fundamental insights into the most common causes of mortality including cancer, cardiovascular disease, neurodegeneration, and diabetes.14?16 Using a microfluidic device, we can monitor the yeast aging process at single-cell resolution via time-lapse microscopy. This device also allows us to study environmental perturbations of aged cells. Microfluidic trapping is a rare validated method for collection of longitudinal, dynamic, in situ aging data at single-cell resolution. I will exploit this device to perform whole-lifespan monitoring of yeast cell towards the following specific aims:
Aim 1 : Determine mechanism of iron starvation response in age-related mitochondrial dysfunction Mitochondrial dysfunction has been implicated as a driver of multiple age-related diseases,17 and changes in mitochondrial phenotype have been mechanistically tied to yeast RLS.18 Previous research has linked an early life loss of vacuolar acidity to later mitochondrial dysfunction.19 Preliminary data indicates that an iron starvation response mediates this process. I will affirm the links between vacuolar acidity, iron regulation, and mitochondrial dysfunction and determine the causal mechanism of these connections.
Aim 2 : Determine mechanism of age-related loss of mother-daughter lifespan asymmetry Asymmetric cell division is a hallmark of metazoan life, with important implications in both development and age-related pathology.20,21 Contrary to popular assumption in the yeast aging field, I have observed a progressive age-dependent decline in mother-daughter lifespan asymmetry that begins early in life. I hypothesize that this decline is due to a progressive decline in the septin-mediated cortical and membrane diffusion barrier. I will investigate the kinetics and the mechanism of this loss of asymmetry.
Aim 3 : Define role of age-related loss of fidelity in MSN2 glucose-sensing signal transduction Aging is characterized by a reduced ability to maintain homeostasis in response to environmental change.22,23 Our microfluidic device makes it possible to perturb and observe aged cells. I have found that MSN2 signaling differs between young and old cells in the same environment. Moreover, I have found that cells exposed to temporally varying environments as they age have shorter lifespans. I hypothesize that the MSN2 loses glucose-signaling transmission fidelity due to its role in reporting of increased oxidative stress with age. I will characterize this loss of information transfer and determine whether it is responsible for an age-related loss of resilience.

Public Health Relevance

Lay statement: The aging process drives development of neurodegeneration, cancer, cardiovascular disease and many other diseases. We will learn more about the molecular mechanisms of aging by trapping and monitoring single yeast cells as they age. Specifically, we will learn about changes in mitochondrial health and coordination of protein expression during aging.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Individual Predoctoral NRSA for M.D./Ph.D. Fellowships (ADAMHA) (F30)
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Special Emphasis Panel (ZRG1)
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Fridell, Yih-Woei
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University of Washington
Schools of Medicine
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Chen, Kenneth L; Crane, Matthew M; Kaeberlein, Matt (2017) Microfluidic technologies for yeast replicative lifespan studies. Mech Ageing Dev 161:262-269