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El seguimiento completo de los cinetocoros revela una biorientación cromosómica homóloga propensa a errores en los
Tomoya S Kitajima1, Miho Ohsugi, Jan Ellenberg
1Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, Heidelberg D-69117, Germany.
Cell
|August 23, 2011
Resumen
La división celular fiel requiere la biorientación cromosómica. Las imágenes de los ovocitos de ratón revelan un proceso de biorientación propenso a errores, lo que explica la aneuploidía en los huevos.
Área de la Ciencia:
- Biología celular Biología celular.
- Genética La genética.
- Biología del desarrollo Biología del desarrollo.
Sus antecedentes:
- La segregación cromosómica precisa es crucial para la fidelidad de la división celular.
- Los mecanismos que coordinan la alineación cromosómica y la fijación del eje no se comprenden completamente.
Objetivo del estudio:
- Para dilucidar la dinámica 3D de la biorientación cromosómica durante la meiosis I en ovocitos de ratón.
- Identificar eventos clave y mecanismos de corrección de errores en el establecimiento de anexos cromosómicos estables.
Principales métodos:
- Imágenes en vivo de alta resolución de la meiosis I en ovocitos de ratón.
- Rastreo 3D de cinetocoros a lo largo de la división celular.
- Análisis de la congestión cromosómica y las interacciones del eje.
Principales resultados:
- Se identificó un intermediario del "cinturón de prometafase" durante la alineación cromosómica en ovocitos acentrosomales.
- Se demostró que casi el 90% de los cromosomas se someten a la corrección de errores de las fijaciones cinetocoro-microtubulares.
- Se demostró que la biorientación cromosómica homóloga es inherentemente propensa a errores, dependiendo de la actividad de la aurora quinasa.
Conclusiones:
- La biorientación cromosómica es un proceso complejo y propenso a errores que implica configuraciones intermedias y una extensa corrección de errores.
- Los mecanismos identificados proporcionan información sobre las altas tasas de aneuploidía observadas en los huevos de mamíferos.
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01:29Nondisjunction
During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.
02:57Attachment of Sister Chromatids
As cells progress into mitosis, the nuclear envelope breaks down, and the condensed chromosomes are exposed to the array of bipolar microtubules of the mitotic spindle. The kinetochore, a large, disc-shaped protein complex, is present at the centromere region of the sister chromatids and acts as a binding site for the microtubules. Usually, the plus-end of a single microtubule is embedded within the kinetochore. However, some kinetochores first establish lateral contact with the side-wall of a...
02:11Forces Acting on Chromosomes
During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis.
Microtubules and motor proteins exert two types of forces on...
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02:19The Spindle Assembly Checkpoint
The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
02:02Meiosis II
Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
02:57Meiosis vs. Mitosis
Cell division is necessary for growth and reproduction in organisms. Mitosis aids cell growth and development by dividing somatic cells. In contrast, meiosis causes the division of germ cells and plays an essential role in sexual reproduction. Due to their unique functional requirements, mitosis and meiosis differ from each other in multiple aspects.
Before the start of mitosis and meiosis I, the cell synthesizes DNA, resulting in two homologous copies of each chromosome. DNA synthesis is...
Before the start of mitosis and meiosis I, the cell synthesizes DNA, resulting in two homologous copies of each chromosome. DNA synthesis is...