Transvection

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In genetics, transvection describes an influence that an allele of a gene has on its homologous partner on another chromosome . Transvection can both weaken and increase the effects of a mutated allele on another chromosome. Transvection only occurs with paired chromosomes. It is counted among the epigenetic processes.

Transvection is completely different from transfection ; This can lead to confusion due to the similar spelling.

background

In diploid organisms, the chromosomes and thus the entire genetic information are available in two corresponding copies. The variants (the technical term for this is alleles ) can be identical to one another ( homozygous ) or each of the chromosomes carries a different allele of the same gene ( heterozygous ). In the heterozygous case, one allele can be dominant and thus determine the phenotype , recessive and then have no influence on the phenotype, or both have a certain effect (intermediate).

In some cases it is also observed that the phenotypic expression of a certain allele depends on whether it is (somatically) paired with its homologous partner on the other chromosome. For example, a certain mutation has less of an effect if there are paired chromosomes than if the same chromosomes are unpaired. The effect is not based on the genetic information as such (which is the same in all these cases), but purely on the spatial arrangement of the chromosomes. The first to observe and describe such an effect was the American geneticist Edward B. Lewis . He observed that the same (heterozygous) mutation of the Hox gene Ubx in the fruit fly Drosophila melanogaster could have a small or a large effect on the resulting phenotype, depending on the arrangement of the chromosomes. Since the effect originates from a different DNA strand, called "trans" by geneticists, he coined the term transvection for it.

Since Lewis' results in the 1950s, transvection has been detected in many other cases, mostly other mutated genes in the model organism Drosophila melanogaster , but now also in other organisms, including mice and humans. Their general significance for gene regulation is still insufficiently understood.

Mechanism of action

The explanation of transvection effects is now being sought in the mechanisms of gene regulation . The transcription of genes is controlled by other DNA segments, so-called cis elements , which are usually spatially adjacent on the DNA strand, but sometimes also at some distance from the regulated genes. The reinforcing ( enhancer ) or weakening ( repressor ) elements act via proteins formed as gene products, so-called transcription factors , which attach to the DNA strand at a specific point and thus influence gene expression. In the case of transvection, it is assumed that enhancers and repressors of one chromosome reach the other chromosome by diffusion and can intervene in gene regulation here. Since this is only effective in spatial proximity, paired chromosomes are a prerequisite for this. In the meantime, cases of reciprocal transvection have also been described in which enhancers of functional (i.e. not impaired by a mutation) genes of the wild type in Drosophila influence the gene expression on the other chromosome, even if the regulatory function on the same strand (called cis by geneticists) is not impaired is.

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  • C.-ting Wu: Transvection, Nuclear Structure, and Chromatin Proteins. In: Journal of Cell Biology. Vol. 120, Number 3, 1993, pp. 587-590.
  • David J. Mellert, James W. Truman: Transvection Is Common Throughout the Drosophila Genome. In: Genetics. vol. 191, no. 4, 2012, pp. 1129–1141. doi: 10.1534 / genetics.112.142893 (open access)

Individual evidence

  1. ↑ Howard D. Lipshitz: From fruit flies to fallout: Ed Lewis and his science. In: Journal of Genetics. Vol. 83, no. 2, 2004, pp. 201-218.
  2. ↑ EB Lewis: The Theory and Application of a New Method of Detecting Chromosomal Rearrangements in Drosophila melanogaster. In: American Naturalist. Vol. 88, No. 841, 1954, pp. 225-239. (Access via JSTOR )
  3. ↑ M. Rassoulzadegan, M. Magliano, F. Cuzin: Transvection effects involving DNA methylation during meiosis in the mouse. In: The EMBO Journal. 21, 2002, pp. 440-450. doi: 10.1093 / emboj / 21.3.440 (open access)
  4. ^ H. Liu, J. Huang, J. Wang, S. Jiang, AS Bailey, DC Goldman, M. Welcker, V. Bedell, ML Slovak, B. Clurman: Transvection mediated by the translocated cyclin D1 locus in mantle cell lymphoma . In: Journal of Experimental Medicine. 205, 2008, pp. 1843-1858. doi: 10.1084 / jem.20072102