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Combined DNA-RNA Fluorescent In situ Hybridization (FISH) to Study X Chromosome Inactivation in Differentiated Female Mouse Embryonic Stem Cells
Published on: June 14, 2014
X chromosome inactivation: when dosage counts
1Institut Curie, CNRS UMR3215, INSERM U934, 75724 Paris Cedex 05, France.
Cell
|December 1, 2009
Summary
Mammals ensure only one X chromosome is active by using Rnf12/RLIM. This protein triggers X chromosome inactivation when its levels exceed a threshold, which occurs with multiple active X chromosomes.
Area of Science:
- Genetics
- Epigenetics
- Mammalian biology
Background:
- Mammalian cells possess a unique mechanism for dosage compensation between sexes.
- X chromosome inactivation (XCI) silences one X chromosome in females to equalize gene expression with males.
Discussion:
- The study investigates the trigger for XCI initiation.
- Rnf12/RLIM, a protein encoded by an X-linked gene, is identified as a key regulator.
- XCI is induced only when Rnf12/RLIM levels surpass a critical threshold.
Key Insights:
- Rnf12/RLIM acts as a dose-sensitive inducer of X chromosome inactivation.
- The threshold mechanism ensures XCI occurs only when multiple X chromosomes are present.
- This finding clarifies how mammals count active X chromosomes.
Outlook:
- Further research can explore the precise molecular events at the threshold.
- Understanding Rnf12/RLIM regulation could offer insights into developmental disorders.
- Investigating variations in XCI mechanisms across different mammalian species.
Related Concept Videos
X-Inactivation
The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.
X-inactivation
The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.
Dosage Compensation
In animals, gender is determined by the number and type of sex chromosome. For example, human females have two X chromosomes, and males have one X and one Y chromosome, whereas C.elegans with one X chromosome is a male, and the one with two X chromosomes is a hermaphrodite.
In addition to sexual development, the X chromosome has genes involved in autosomal functions such as brain development and the immune system. Therefore, males and females with distinct numbers of X chromosomes will have...
In addition to sexual development, the X chromosome has genes involved in autosomal functions such as brain development and the immune system. Therefore, males and females with distinct numbers of X chromosomes will have...
Inheritance of Chromatin Structures
Epigenetics is the study of inherited changes in a cell's phenotype without changing the DNA sequences. It provides a form of memory for the differential gene expression pattern to maintain cell lineage, position-effect variegation, dosage compensation, and maintenance of chromatin structures such as telomeres and centromeres. For example, the structure and location of the centromere on chromosomes are epigenetically inherited. Its functionality is not dictated or ensured by the underlying DNA...
Heterochromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions that take up more dye are called heterochromatin. Heterochromatin is further classified into two forms – constitutive heterochromatin and facultative heterochromatin.
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
Euchromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions take up more dye, appearing darker, while the less-compact areas take up less dye and appear lighter. Based on the compaction level, chromatins are classified into two primary forms – euchromatin and heterochromatin.
Euchromatin is the less dense region of the chromatin and stains lighter. Euchromatin contains histone H3 extensively...
Euchromatin is the less dense region of the chromatin and stains lighter. Euchromatin contains histone H3 extensively...

