In collaboration with international researchers, a study led by scientists from the RIKEN Center for Integrative Medical Sciences, Japan, discovered that recombinations of specific genome sequences repeated millions of times in the genomes of human cells are found in both normal and disease states.
Identifying the mechanisms that lead to numerous recombinations involving DNA sequences previously believed to be junk may be crucial to further understanding how cells develop and what makes them unhealthy.
Identifying the Mechanisms of DNA Recombinations
Following the discovery of DNA, it was believed that all the cells in the human body shared the same genetic material, safely guarded by the nucleus. On the other hand, modern advances in DNA sequencing techniques have challenged this view. Now, we know that mutations accumulate in the genomic code of single cells starting from the earliest stages of their development.
But, the magnitude of the phenomenon and how it contributes to diseases is not well known.
In the recent study published in the journal Cell, titled "Recombination of repeat elements generates somatic complexity in human genomes." scientists analyzed specific repeated genomic sequences, Alu and L1, and developed a novel method to study specific DNA sequences that are repeated millions of times in each cell's genome.
It is common knowledge that these sequences recombine, generating mutations such as those commonly found in cancer and other genetic disorders.
By studying the DNA of donors unaffected by diseases, the team identified millions of DNA mutations caused by recombining the repeated sequences and discovered that different recombination signatures characterize different bodily tissues, reports EurekAlert.
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Healthy vs. Diseased Cells and Their Genomic Recombination
Researchers also identified the differentiation of human stem cells into neuronal cells joined by distinct changes in repeat sequences' recombination. Indicating that the specific DNA mutation may be a physiological phenomenon involved in the development of humans.
Finally, the tea looked into the recombination of repeated samples from donors affected with Alzheimer's and Parkinson's disorders, the two most prominent neurodegenerative disorders across the globe. Researchers found signatures of recombinations that were specific to each of the diseases. This suggests that genomic recombination caused by repeated sequences was also involved in brain diseases.
Giovanni Pascarella, the first author of the study, says that the team has demonstrated that the recombination of the repeat sequences in the human genome is a widespread phenomenon contributing to the complex constellation of genomic variants that make up the human genome.
Piero Carninci, principal investigator and co-corresponding author, explains that researchers hypothesize that it is plausible for random recombination of the repeat sequences in somatic cells to occasionally prime the genome cells of the individual at vulnerable sites driving the transition from healthy to pathological states.
He adds that it is difficult to know, at this point, whether the recombination of diseases is causative or if they are effects of the cell's diseased states.
The authors note that more investigation into the phenomenon is needed to understand the underlying mechanisms.
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