Selection pressure on human STR loci and its relevance in repeat expansion disease
| Autor: | Ranajit Chakraborty, Tadashi Imanishi, Makoto K. Shimada, Chisato Yamasaki, Yoshiyuki Suzuki, Yumi Yamaguchi-Kabata, Takashi Gojobori, Ryoko Sanbonmatsu |
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| Rok vydání: | 2015 |
| Předmět: |
0301 basic medicine
Neurogenesis Population Single-nucleotide polymorphism Biology Evolution Molecular 03 medical and health sciences 0302 clinical medicine Tandem repeat Sequence Analysis Protein Genetics Humans Disease Selection Genetic education Molecular Biology Gene education.field_of_study Genome Human General Medicine Sequence Analysis DNA Human genetics 030104 developmental biology Microsatellite Human genome Trinucleotide repeat expansion 030217 neurology & neurosurgery Microsatellite Repeats |
| Zdroj: | Molecular genetics and genomics : MGG. 291(5) |
| ISSN: | 1617-4623 |
| Popis: | Short Tandem Repeats (STRs) comprise repeats of one to several base pairs. Because of the high mutability due to strand slippage during DNA synthesis, rapid evolutionary change in the number of repeating units directly shapes the range of repeat-number variation according to selection pressure. However, the remaining questions include: Why are STRs causing repeat expansion diseases maintained in the human population; and why are these limited to neurodegenerative diseases? By evaluating the genome-wide selection pressure on STRs using the database we constructed, we identified two different patterns of relationship in repeat-number polymorphisms between DNA and amino-acid sequences, although both patterns are evolutionary consequences of avoiding the formation of harmful long STRs. First, a mixture of degenerate codons is represented in poly-proline (poly-P) repeats. Second, long poly-glutamine (poly-Q) repeats are favored at the protein level; however, at the DNA level, STRs encoding long poly-Qs are frequently divided by synonymous SNPs. Furthermore, significant enrichments of apoptosis and neurodevelopment were biological processes found specifically in genes encoding poly-Qs with repeat polymorphism. This suggests the existence of a specific molecular function for polymorphic and/or long poly-Q stretches. Given that the poly-Qs causing expansion diseases were longer than other poly-Qs, even in healthy subjects, our results indicate that the evolutionary benefits of long and/or polymorphic poly-Q stretches outweigh the risks of long CAG repeats predisposing to pathological hyper-expansions. Molecular pathways in neurodevelopment requiring long and polymorphic poly-Q stretches may provide a clue to understanding why poly-Q expansion diseases are limited to neurodegenerative diseases. |
| Databáze: | OpenAIRE |
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