Structural components of nuclear integrity with gene regulatory potential

Nuclear structures and their emerging roles in cell differentiation and development

The nucleus, a highly organized and dynamic organelle, plays a crucial role in regulating cellular processes. During cell differentiation, profound changes occur in gene expression, chromatin organization, and nuclear morphology. This review explores the intricate relationship between nuclear architecture and cellular function, focusing on the roles of the nuclear lamina, nuclear pore complexes (NPCs), sub-nuclear bodies, and the nuclear scaffold. These components collectively maintain nuclear integrity, organize chromatin, and interact with key regulatory factors. The dynamic remodeling of chromatin, its interactions with nuclear structures, and epigenetic modifications work in concert to modulate gene accessibility and ensure precise spatiotemporal control of gene expression. The nuclear lamina stabilizes nuclear shape and is associated with inactive chromatin regions, while NPCs facilitate selective transport. Sub-nuclear bodies contribute to genome organization and gene regulation, often by influencing RNA processing. The nuclear scaffold provides structural support, impacting 3D genome organization, which is crucial for proper gene expression during differentiation. This review underscores the significance of nuclear architecture in regulating gene expression and guiding cell differentiation. Further investigation into nuclear structure and 3D genome organization will deepen our understanding of the mechanisms governing cell fate determination. [BMB Reports 2024; 57(9): 381-387].

Opticool: Cutting-edge transgenic optical tools

Only a few short decades have passed since the sequencing of GFP, yet the modern repertoire of transgenically encoded optical tools implies an exponential proliferation of ever improving constructions to interrogate the subcellular environment. A myriad of tags for labeling proteins, RNA, or DNA have arisen in the last few decades, facilitating unprecedented visualization of subcellular components and processes. Development of a broad array of modern genetically encoded sensors allows real-time, in vivo detection of molecule levels, pH, forces, enzyme activity, and other subcellular and extracellular phenomena in ever expanding contexts. Optogenetic, genetically encoded optically controlled manipulation systems have gained traction in the biological research community and facilitate single-cell, real-time modulation of protein function in vivo in ever broadening, novel applications. While this field continues to explosively expand, references are needed to assist scientists seeking to use and improve these transgenic devices in new and exciting ways to interrogate development and disease. In this review, we endeavor to highlight the state and trajectory of the field of in vivo transgenic optical tools.

Transgenic force sensors and software to measure force transmission across the mammalian nuclear envelope in vivo

Nuclear mechanotransduction is a growing field with exciting implications for the regulation of gene expression and cellular function. Mechanical signals may be transduced to the nuclear interior biochemically or physically through connections between the cell surface and chromatin. To define mechanical stresses upon the nucleus in physiological settings, we generated transgenic mouse strains that harbour FRET-based tension sensors or control constructs in the outer and inner aspects of the nuclear envelope. We knocked-in a published esprin-2G sensor to measure tensions across the LINC complex and generated a new sensor that links the inner nuclear membrane to chromatin. To mitigate challenges inherent to fluorescence lifetime analysis in vivo, we developed software (FLIMvivo) that markedly improves the fitting of fluorescence decay curves. In the mouse embryo, the sensors responded to cytoskeletal relaxation and stretch applied by micro-aspiration. They reported organ-specific differences and a spatiotemporal tension gradient along the proximodistal axis of the limb bud, raising the possibility that mechanical mechanisms coregulate pattern formation. These mouse strains and software are potentially valuable tools for testing and refining mechanotransduction hypotheses in vivo.