As the world scrambles to control the growing Covid-19 pandemic, a new study shows viruses also play a key evolutionary role in mammals' ability to reproduce and survive.
According to the study, published in the journal Nature Structural & Molecular Biology, scientists in the Cincinnati Children's Perinatal Institute (CCPI) and at Azabu University in Japan obtained their data by studying laboratory mice and human germline cells.
In two separate papers appearing in the same edition of the journal, they revealed two distinct and fundamental processes underlying germline transcriptomes. They also show that species-specific transcriptomes are fine-tuned by endogenous retroviruses in the mammalian germline.
Germline transcriptomes include all the messenger RNA in germline cells, which contain either the male or female half of chromosomes passed on as inherited genetic material to offspring when species mate.
This means that germline transcriptomes define the unique character of sperm and egg to prepare for the next generation of life.
"Although the studies are separate they complement one another. One paper explores super-enhancers, which are robust and evolutionally conserved gene regulatory elements in the genome," said study researcher Satoshi Namekawa of CCPI.
They fuel a tightly regulated burst of essential germline genes as sperm start to form," Namekawa added.The second study involves endogenous retroviruses that act as another type of enhancer - gene regulatory elements in the genome - to drive the expression of newly evolved genes.
This helps fine-tune species-specific transcriptomes in mammals like humans, mice, and so on, the ream said.
The study, combined biological testing of mouse models and human germline cells with computational biology, including genome-wide profiling of gene regulatory elements in germline cells.Those tests revealed that the genome-wide reorganisation of super-enhancers drives bursts of germline gene expression after germ cells enter meiosis, a specialised form of cell division that produces the haploid genome of germ cells.The study further demonstrated the molecular process through which super-enhancer switching takes place in germ cells.
Super-enhancers are regulated by two molecules that act as gene-burst control switches - the transcription factor A-MYB and SCML2, a critical silencing protein in sperm formation, according to the team."What we learn from our study is that, in general, viruses have major roles in driving evolution. In the long-term, viruses have positive impacts on our genome and shape evolution," Namekawa explained.
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