Qixuan Wang, Postdoctoral Scholar

I am a postdoctoral scholar in Dr. Qing Nie’s lab since 2012. My work includes developing multi-scale models for hair follicle growth and computational modeling on noise and cell sorting in the sharpening of gene expression boundaries. I did my PhD study in the school of mathematics, University of Minnesota, advised by Hans Othmer, my work was mostly on developing mathematical models and computational methods on cells swimming at low Reynolds number.

Multi-scale Modeling of HF Growth and the Spatio-temporal Patterns

The hair follicle (HF) is a skin mini-organ that undergoes cyclic bouts of regeneration throughout its lifetime. This ability is in part related to its distinct stem cell populations, making the HF a model to study the mechanisms of stem cell regulation and tissue regeneration. Cyclic growth is regulated both by signaling within the HF, and long-range interactions between neighboring HFs and other skin components. Correlations between hair cycle phases and various molecular activities suggest that coupling between the activator and inhibitor serves to jointly regulate hair growth timing, and the co-option of these signals into skin macro-environment produces wave-like coupled hair growth. We present a multi-scale mathematical model that accounts for the realistic HF morphology, where hair-to-hair growth coordination emerges based on shared signaling.

Noise and Cell Sorting in Gene Expression Boundary Sharpening

In many developing systems, chemical gradients control the formation of segmental domains of gene expression, specifying distinct domains that go on to form different tissues and structures, in a concentration-dependent manner. These gradients are noisy and it is crucial that developing systems be able to cope with stochasticity and generate well-defined boundaries between different segmented domains. Cells may physically sort but the effectiveness of sorting is unclear, while cellular plasticity in response to morphogens (e.g. RA, Fgf and Wnt) also promotes sharpening of segment boundaries. We developed a hybrid computational model to investigate the influences of gene expression noise and cell sorting in boundary sharpening. We use the sub-cellular element method (SCEM) to model the inter-cellular mechanical interactions such as cell-cell adhesion and repulsion, while the influence of morphogens and gene regulation on cell identity is described by a spatial stochastic model of cell fate regulation.

Computation and Analysis of Low Reynolds Number (LRN) Swimming Models

Locomotion of cells, both individually and collectively, is an important process in development, tissue regeneration, cancer metastasis, etc. Recent studies show that Dictyostelium discoideum (Dd) can swim by propelling themselves through a fluid using only fluid-cell interactions. We are interested in how complicated shape changes lead to locomotion in LRN flows which is governed by the Stokes equations. In 2-dimensional LRN swimming problem, we use techniques from complex analysis to analyze the swimming behavior of Dd cells. For 3-dimensional LRN swimming problems, we apply the reflection method on linked-sphere models to investigate the effect of higher-order hydrodynamic interactions on LRN swimming behaviors.

Publications

  • 1. Qixuan Wang and Hans G. Othmer (2016) Analysis of a model microswimmer with applications to blebbing cells and mini-robots. Under review.
  • 2. Qixuan Wang, Ji Won Oh, Hye-Lim Lee, Anukriti Dhar, Tao Peng, Raul Ramos, Christian Fernando Guerrero-Juarez, Xiaojie Wang, Jonathan Le, Melisa A. Fuentes, Shelby C. Jocoy, Antoni R. Rossi, Brian Vu, Kim Pham, Xiaoyang Wang, Nanda Maya Mali, Jung Min Park, Hyunsu Lee, Julien Legrand, Eve Kandyba, Jung Chul Kim, Moonkyu Kim, John Foley, Zhengquan Yu, Krzysztof Kobielak, Bogi Andersen, Kiarash Khosrotehrani, Qing Nie, Maksim V. Plikus (2016) A multi-scale model for the hair follicle reveals heterogeneous skin domains driving rapid spatiotemporal hair growth patterning. Under Review.
  • 3. Qixuan Wang, William R. Holmes, Julian Sosnik, Thomas Schilling, Qing Nie (2016) Cell sorting and noise-induced cell plasticity coordinate to sharpen boundaries between gene expression domains. Under Review.
  • 4. William R. Holmes, Nabora Soledad Reyes de Mochel, QixuanWang, Huijing Du, Michael Chiang, Olivier Cinquin, Ken W.Y. Cho and Qing Nie (2016 ) Interplay between Asymmetric Distribution of Noise and Timing of Cell Fate Specification Directs Early Embryonic Organization. Under Review.
  • 5. Qixuan Wang and Hans G. Othmer (2016) Computational analysis of amoeboid swimming at low Reynolds number. Journal of mathematical biology, Vol. 72, no. 7, 1893-1926.
  • 6. Qixuan Wang and Hans G. Othmer (2015) The performance of discrete models of low Reynolds number swimmers. Mathematical Biosciences and Engineering, Vol. 12, no. 6, 1303–1320.
  • 7. Qixuan Wang, Jifeng Hu and Hans G. Othmer (2012) Models of Low Reynolds Number Swimmers Inspired by Cell Blebbing. Natural Locomotion in Fluids and on Surfaces, Springer New York, 185-195.