Spindle Checkpoint

Spindle Checkpoint

In order to preserve one cell's identity and its proper functioning, it is necessary to maintain constant the appropriate number of chromosomes after each cell division. Only one error generating cells with more or less chromosomes than expected (a situation termed aneuploidy), might lead in best cases to cell death, or alternatively it might generate catastrophic phenotypic results:

  • In humans, Down syndrome appears in children carrying in their cells one extra copy of chromosome 21, as a result of a defect in chromosome segregation during meiosis in one of the progenitors. This defect will generate a gamete (spermatozoide or oocyte) with an extra chromosome 21. After fecundation, this gamete will generate an embryo with three copies of chromosome 21.
  • In cancer cells, aneuploidy is a frequent event, indicating that these cells present a defect in the machinery involved in chromosome segregation, as well as in the mechanism ensuring that segregation is correctly performed.

The mechanisms verifying that all the requirements to pass to the next phase in the cell cycle have been fulfilled are called checkpoints. All along the cell cycle, there are different checkpoints. The checkpoint ensuring that chromosome segregation is correct is termed spindle assembly checkpoint (SAC), spindle checkpoint or mitotic checkpoint. During mitosis or meiosis, the spindle checkpoint prevents anaphase onset until all chromosomes are properly attached to the spindle. To achieve proper segregation, the two kinetochores on the sister chromatids must be attached to opposite spindle poles (bipolar orientation). Only this pattern of attachment will ensure that each daughter cell receives one copy of the chromosome.

Read more about Spindle CheckpointDiscovery of The Spindle Assembly Checkpoint (SAC), Metaphase To Anaphase Transition, Spindle Assembly Checkpoint Overview, Spindle Checkpoint Defects and Cancer

Other articles related to "spindle checkpoint, spindle, checkpoint":

Kinetochore Structure in Animal Cells
... network of resident and temporary proteins implicated in the spindle checkpoint, in MTs anchoring and in the regulation of chromosome behavior ... (as well as their target components ZW10 and ROD), and the spindle checkpoint proteins (such as Mad1, Mad2, BubR1 and Cdc20) ... Whereas the spindle checkpoint protein levels present in the outer plate diminish as MTs anchor, other components such as EB1, APC and proteins in the Ran pathway (RanGap1 ...
Spindle Checkpoint Defects and Cancer - Cancer Therapies That Target Aspects of The SAC
... Advances in this field have led to the introduction of development of some therapies targeted at spindle assembly defects ... Older treatments such as vinca alkaloids and taxanes target microtubules that accompany mitotic spindle formation via disruption of microtubule dynamics which engage the SAC ... kinetochore to microtubule attachment and abrogate the mitotic checkpoint as well ...
Anaphase-promoting Complex - Metaphase To Anaphase Transition
... As metaphase begins, the spindle checkpoint inhibits the APC/C until all sister-kinetochores are attached to opposite poles of the mitotic spindle, a process known as chromosome ... When all kinetochores are properly attached, the spindle checkpoint is silenced and the APC/C can become active ... In animal cells the spindle checkpoint system contributes to the delay if it needs to correct the bi-orientation of chromosomes ...
... gene encodes a cytoplasmic protein implicated in regulation of the mitotic spindle checkpoint, a regulatory pathway that monitors chromosome segregation during cell ... and in response to activation of the spindle checkpoint, and disappears when cells transition to G1 phase ... regulator, and its expression is required to efficiently activate the spindle checkpoint ...
Kinetochore Function - Spindle Checkpoint Activation
... The spindle checkpoint or SAC (for spindle assembly checkpoint), also known as mitotic checkpoint, is a cellular mechanism responsible for detection of correct assembly of the mitotic spindle ... just one chromosome (for any reason) remains lagging during congression, the spindle checkpoint machinery generates a delay in cell cycle progression the cell is arrested, allowing time for repair mechanisms to ... throughout mitosis (including telophase), the spindle checkpoint components are assembled on the kinetochore in high concentrations in absence of MTs ...