Thiex Lab Research

The Thiex Lab investigates the molecular mechanisms that govern macrophage biology — how these key immune cells sense, internalize and process their environment. Our goal is to uncover fundamental principles of cellular regulation using a mechanistic and technology-driven approach.

We combine forward genetic strategies (such as CRISPR/Cas9 whole-genome screening) with quantitative cell biology, biochemistry and advanced microscopy to identify critical genes and dissect their molecular functions. This integrative approach allows us to move from discovery to mechanistic understanding.

Current Research Focuses

• Macropinocytosis: how macrophages nonspecifically internalize extracellular material through large-scale reorganization of the plasma membrane.
• Cholesterol and lipid droplet dynamics: how lipid metabolism supports macrophage function in healthy and disease states.
• Macrophage fitness: identification of essential genes for macrophage survival.

Macrophages are essential for tissue homeostasis, host defense and inflammation, making these questions highly relevant to both health and disease.

Over the years, our lab community has included graduate, undergraduate and high school students, postdoctoral fellows, and research technicians. Alumni from the Thiex Lab have gone on to academic postdocs, biotechnology and pharmaceutical positions, and professional programs.

CRISPR/Cas9 Whole-Genome Screens

We use CRISPR/Cas9-based forward genetic screens to identify genes that control key macrophage processes. In these experiments, we apply a library of ~80,000 small guide RNAs targeting all ~20,000 mouse genes, enabling systematic disruption of gene function.

For example, in our macropinocytosis screen, macrophages were sorted based on uptake of a fluorescent dye. Cells showing reduced fluorescence reveal genes required for macropinocytosis, while those with enhanced fluorescence identify potential negative regulators.

This unbiased discovery strategy has been instrumental in generating mechanistic hypotheses that we test using complementary biochemical and imaging approaches.

This work led to the surprising discovery that fluorescent dextran, a reagent widely used to measure macropinocytosis, is also internalized via receptor-mediated endocytosis in macrophages (Wollman et al., Molecular Biology of the Cell, 2024).

Advanced 3D Microscopy

Our lab leverages state-of-the-art live-cell imaging platforms, including Lattice Light Sheet Microscopy and Oblique Plane Illumination Microscopy, to visualize macrophage behavior in unprecedented detail. We combine cross-disciplinary expertise in molecular cloning, protein engineering and image analysis.

Specifically, by expressing fluorescently tagged proteins and probes for signaling lipids, we capture the spatiotemporal organization of signaling events and membrane remodeling in real time.

In a recent study, we revealed how PI3K-dependent synthesis of 3-phosphoinositides organizes macropinocytic cup formation and membrane sealing, using integrated volumetric reconstructions of plasma membrane topology and lipid distribution (Quinn et al., Nature Communications, 2021).

About Natalie Thiex

Natalie Thiex is a tenured associate professor of biology at South Dakota State University, where she leads a research program focused on uncovering the molecular mechanisms of macrophage biology, including macropinocytosis, membrane trafficking and lipid dynamics.

A native of Volga, South Dakota, Thiex earned her Ph.D. at the University of Michigan before returning to South Dakota to establish her lab, which combines CRISPR/Cas9-based functional genomics, advanced microscopy and biochemical approaches to investigate how macrophages internalize and process their environment. Her group has developed and implemented whole-genome CRISPR screens in primary macrophages, leading to the identification of key genes and pathways regulating macropinocytosis. The lab’s discoveries have refined fundamental understanding of macrophage signaling and membrane organization.

Thiex’s laboratory has also assembled a powerful experimental toolbox that includes molecular probes for live-cell imaging of membrane remodeling, actin polymerization and phosphoinositide signaling, along with automated pipelines for quantitative image analysis. This integrative, technology-driven approach enables precise dissection of molecular mechanisms underlying immune cell function.

Her research has been supported by a NIH R15 grant, COBRE funding and awards from the South Dakota GOED. As a COBRE research project leader, she has built a collaborative and highly productive team environment, providing exceptional training for undergraduate and graduate students pursuing careers in cellular biology.