could you suggest a reason to have neutrons in the nucleus shell
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Abstract
Over the past two decades, the biomechanical properties of cells have emerged as key players in a broad range of cellular functions, including migration, proliferation, and differentiation. Although much of the attention has focused on the cytoskeletal networks and the cell’s microenvironment, relatively little is known about the contribution of the cell nucleus. Here, we present an overview of the structural elements that determine the physical properties of the nucleus and discuss how changes in the expression of nuclear components or mutations in nuclear proteins can affect not only nuclear mechanics but also modulate cytoskeletal organization and diverse cellular functions. These findings illustrate that the nucleus is tightly integrated into the surrounding cellular structure. Consequently, changes in nuclear structure and composition are highly relevant to normal development and physiology and can contribute to many human diseases, such as muscular dystrophy, dilated cardiomyopathy, (premature) aging, and cancer.
Keywords: nucleus, biophysics, cancer, muscular dystrophy, lamins, migration
INTRODUCTION
The nucleus is the hallmark of eukaryotic cells. It is generally the largest subcellular organelle (~5–20 µm in diameter) and houses the genetic information that directs the activity of the entire cell. The structural organization of the nucleus and its mechanical properties are critical for a variety of cellular functions and processes. The nuclear envelope, in particular the nuclear lamina, protects the nuclear interior in cells subjected to physical stress (e.g., in muscle tissues) (1, 2); the nuclear envelope can also modulate important signaling pathways by interacting with transcription factors that shuttle between the nucleus and the cytoplasm (3–7). In the nuclear interior, DNA and chromatin occupy well-defined chromosome territories that are often conserved over several generations (8, 9), and the localization of genes within the nucleus can determine their transcriptional activity (10). Importantly, the influence of nuclear structure and mechanics extends beyond the nucleus: Nuclear envelope proteins that physically interface with the cytoskeleton can affect cytoskeletal organization, cell polarization, adhesion, and migration (11–13). The importance of nuclear composition and organization has recently received increasing prominence as mutations in nuclear envelope proteins, such as lamins or emerin, were identified as causing a perplexing number of human diseases, including Emery-Dreifuss muscular dystrophy (EDMD), dilated cardiomyopathy, familial partial lipodystrophy (FPLD), and the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS) (14). In the following, we provide a concise overview of normal nuclear structure and mechanics and the physical interplay between the nucleus and the surrounding cytoskeleton. Subsequently, we discuss how changes in nuclear structure and composition, such as those resulting from mutations in nuclear envelope proteins or changes in expression, can contribute to a variety of human diseases and pathological conditions.