Actin Cytoskeleton and Nucleus Interaction

Subject: Science
Type: Exploratory Essay
Pages: 3
Word count: 853
Topics: Biology, Chemistry, Standardized Testing, Stem Cell
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Introduction

Whenever we talk of a nucleus in the cytoskeleton, an extension of Endoplasmic Reticulum linked to the nucleus which compartmentalizes it comes in our mind.

The cytoskeleton in interphase appears to be an extremely high complex multipolymer matrix and multiprotein.

The Endoplasmic Reticulum is seen to provide in large context a physical rigidity to the nucleus, organizing the chromatin, and lastly playing a role in the meiotic pairing of chromosomes.

The interaction between the Cytoskeleton and the nucleus is mandatory, and serves as a central factor in controlling all these functions. Similar molecular mechanisms however, are used to transfer the generated forces in the cytoskeleton to the inside nucleus components.

Nonetheless, I am going to review that the interaction between the cytoskeleton and the nucleus as stipulated by the hypothesis is true.

Analysis

Just before the prophase, the multipolymer matrix usually possesses an array of polar microtubules that is usually disassembled and it’s during mitosis that is replaced by a mitotic spindle-a more dynamic structure.

The blue dyed cells (alive cells) were composed mainly of centrosome nucleated microtubules and are regulated by the MAPs which apparently seem to control all events occurring during mitosis. This was observed in the image below obtained from the fluorescence microscopy, after accounting for the viability of BR Green and BR Blue.

After we stained the actin dapi with Actin Green-488 dye, there was an indication of the inter-connective bridges which were starting to form as shown in fig.1.This was a result of the KASHSUN protein complex which had already started being in effect as a result of the membrane protein of the inner and outer membrane.

The bridge however was not formed until after the first phase of mitosis was merely in its course way. As we saw from fig.2, the cells appeared to be moving close to each other arranged in opposite fashions. Not only was Fig.1 showing the nuclear bridge but it was a complementary image of what the latter image was signifying (that is the dawn of interphase).

A good image of what shown to be spindle fibers formation at the interphase stage.

Scientifically, centrosomes have been considered to play a vital role in spindle fiber assembly due to their spindle poles and their microtubule nucleating activity.

Nonetheless, as we continued to observe our images, apparently what seems to be a nuclear-envelope bridge is seen. It is these bridges that permit the interaction between the nucleus and the actin cytoskeleton.

These bridges were as a result of two vital proteins; SUN (Sad1 and UNC-84) and KASH (Klarischt, ANC1, and Syne homology) proteins (Illustrated by the yellow arrows in the picture below).

These combinations serve to connect the microtubules, centrosomes, the intermediate/actin filaments to the nuclear surface.

(The yellow arrows point at what was anticipated to having been the bridges)

This first image was taken in a fluorescence microscopy of previously stained cells.as compared to the latter.

These proteins however, apart from their vital role they were noted to be responsible in mispositioning the nuclei as seen below; Fig 6  shows the nucleus in position, Fig 7 shows it being mispositioned.

Nucleus was in position initially.

Nucleus is misplaced from its original position.

In the formation of the connective bridge, it was known that the nucleus has an inner and outer membrane, which seems to be contiguous to the nuclear pores. Membrane proteins from the Endoplasmic Reticulum membrane are either trafficked to the inner nuclear membrane or outer nuclear membrane of the live cells to interact with the cytoskeleton. To completely furnish up the inter-connective nuclear bridge, the Outer Nuclear Membrane and Inner Nuclear Membrane proteins intermingle with each other in the perinuclear space.

Future Recommendations

During mitotic cell division, necessarily there are cases which arise when spindle fibers necessarily form but not from the centrioles. Therefore, it is best if apart from the HeLa cells, for the experiments are carried out in wide contexts using samples of Drosophila which relay this principle, as well as extracts of Xenopus eggs. Alternatively, since more researches have been done using C.elegans , it will sound best if we take the same line so as to be certain with the results obtained in the lab when we compare them to what other scientists have done.

Scientists should come up with a full complete full array of the nucleoplasmic that correspondingly interact with KASH and SUN proteins, and their respective functions.

Researchers should work on how the switch model of the proteins do work during nuclear anchorage and migration.

Possible Questions

Since it was anticipated that forces are generated and relayed outside ,what could these forces help in the interaction?

Is this interaction beneficial all way ,or to some extent is harmful and might cause harm?

Possible Answers

These forces trigger the action of the KASH and SUN proteins to initiate.

Since the interaction is as a result of KASH and SUN proteins, it is observed that their defects might lead to cancer, progeria, ataxia, and muscular dystrophy.

Also it could affect the global organization of the cytoskeleton

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  1. COOPER, Geoffrey M. 2000. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates.
  2. DA, Starr. 2009. A nuclear-envelope bridge positions nuclei and moves chromosomes. J Cell Science. 1(6), pp.577-586.
  3. FRIDOLFSSON, Daniel A. Starr and Heidi N. 2014. Interactions Between Nuclei and the Cytoskeleton Are Mediated by SUN-KASH Nuclear-Envelope Bridges. US National Library of Medicine National Institutes of Health. 3(2), pp.421-444.
  4. GIENI RS, Hendzel MJ. 2009. Actin dynamics and functions in the interphase nucleus: moving toward an understanding of nuclear polymeric actin. Biochemistry Cell Biology. 1(87), pp.283-306.
  5. HÉLDERMAIATO, PaulaSampaio & Claudio E.Sunkel. 2004. Microtubule-Associated Proteins and Their Essential Roles During Mitosis. International Review of Cytology. 241(12), pp.53-153.
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