# Mechanisms of nuclear size regulation

> **NIH NIH R35** · UNIVERSITY OF WYOMING · 2021 · $347,909

## Abstract

Project Summary: Organelle size control is a fundamental cell biological problem, and nuclear size is often
inappropriately enlarged in cancer cells in a ploidy-independent manner, a change used by pathologists in
cancer diagnosis and staging. It is not known if nuclear size changes in cancer are a cause or consequence of
disease due to a gap in our knowledge of the mechanisms that regulate nuclear size. My lab addresses
fundamental questions about nuclear size regulation using biochemically tractable cytoplasmic extracts that
reconstitute nuclear assembly and Xenopus embryos that allow for in vivo functional testing. (1) What
mechanisms control nuclear size? Recent progress from my lab has revealed how nuclear import and nuclear
lamins contribute to the regulation of nuclear size. To complement candidate approaches to identifying nuclear
size effectors, an imaging-based RNAi screen was performed. Results from this screen will be used to dissect
novel mechanisms of nuclear size control using Xenopus egg extracts and embryos, focusing on hits enriched
in the screen: nuclear structural proteins, regulators of histone and DNA methylation, and vesicular transport
proteins. (2) How does cytoplasmic volume influence nuclear size? Using microfluidic-based technologies to
encapsulate Xenopus extract in droplets of defined size and shape, my lab recently demonstrated that limiting
amounts of a histone chaperone contribute to developmental regulation of nuclear size. (3) What are the
physical forces that drive nuclear growth? Having identified multiple regulators of chromatin structure as
nuclear size effectors, we hypothesize that intranuclear pushing forces applied to the nuclear envelope allow
for protein incorporation into the nuclear lamina, thereby promoting nuclear growth. Using a variety of in vitro
approaches, we will test the relative contributions of chromatin structure and nuclear f-actin to nuclear growth
and whether intranuclear pushing forces are sufficient to drive nuclear expansion. (4) Elaborating on the
microfluidic extract encapsulation approach, we will introduce f-actin, natural cell cycling, and modifications to
the droplet cortex. This bottom-up approach to generating synthetic cells with increasingly complex and native
attributes will allow us to address questions at the intersection of size control, cytoskeletal organization, and
cell cycle timing. (5) How is nuclear size regulated during development and differentiation? To extend our work
on Xenopus development to mammalian cells, we have initiated studies with human induced pluripotent stem
cells (iPSCs). We find that nuclear morphology and lamin dynamics change significantly during iPSC
differentiation, and we will investigate the underlying mechanisms using information gained from the Xenopus
system. Our work is bolstered by ongoing productive collaborations that employ diverse interdisciplinary
techniques including high-resolution microscopy, RNAi screening, microfluidics, pr...

## Key facts

- **NIH application ID:** 10077485
- **Project number:** 5R35GM134885-02
- **Recipient organization:** UNIVERSITY OF WYOMING
- **Principal Investigator:** Daniel Leon Levy
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $347,909
- **Award type:** 5
- **Project period:** 2020-01-01 → 2024-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10077485

## Citation

> US National Institutes of Health, RePORTER application 10077485, Mechanisms of nuclear size regulation (5R35GM134885-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10077485. Licensed CC0.

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