Chromatin motion in interphase nuclei, its modulation and its potential role in gene expression

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Nuclear Rotation (NR) describes the in vitro rotatory motion of cell nuclei, measured by nucleoli displacement.
• NR occurs in cycling cells but is also observed in neurons, suggesting mitosis is not a prerequisite.
• NR involves saltatory movements of chromatin domains and nucleoli, independent of cytoplasmic structures, implying a stationary outer nuclear membrane.

Purpose of the Study:

• To investigate the functional significance of Nuclear Rotation (NR) in cellular processes.
• To test the hypothesis that NR facilitates gene expression by repositioning chromatin domains.
• To explore the relationship between NR, gene expression, and intracellular calcium levels.

Main Methods:

• Observation and measurement of nucleoli and chromatin domain displacement over time to quantify NR.
• Treatment of cells with Nerve Growth Factor (NGF) and GABA to assess their impact on NR and gene expression.
• Manipulation of intracellular calcium levels using ionophore A23187 and chelator EGTA to determine calcium's role in NR.

Main Results:

• NR involves complex 3D curvilinear trajectories of nucleoli and chromatin domains within the interphase nucleus.
• Nerve Growth Factor (NGF) and GABA, agents altering gene expression, increased NR.
• Calcium redistribution agents (A23187, EGTA) increased NR, with calcium restoration returning NR to control rates, suggesting calcium-dependent mechanisms.

Conclusions:

• Nuclear Rotation (NR) is a dynamic 3D chromatin motion within the nucleus.
• Evidence supports the hypothesis that NR functions in gene expression by translocating chromatin domains.
• NR modulation by agents altering gene expression and ion balance likely involves calcium-dependent pathways.