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The function of the junk jumping gene (LINE1) uncovered

Posted in Biological Networks, Biological Networks, Gene Regulation and Evolution, Clinical Genomics, Developmental biology, Gene Regulation, Gene Regulation and Evolution, Genetics & Innovations in Treatment, Genome Biology, Population genetics, Population Health Management, Genetics & Pharmaceutical, Reproductive Andrology, Embryology, Genomic Endocrinology, Preimplantation Genetic Diagnosis and Reproductive Genomics, tagged development, Dux, embryo, jumping gene, LINE1, transposons on July 21, 2018| Leave a Comment »

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

Long interspersed nuclear elements 1 (LINE1) is repeated half a million times in the human genome, making up nearly a fifth of the DNA in every cell. But nobody cared to study it and may be the reason to call it junk DNA. LINE1, like other transposons (or “jumping genes”), has the unusual ability to copy and insert itself in random places in the genome. Many other research groups uncovered possible roles in early mouse embryos and in brain cells. But nobody quite established a proper report about the functions of LINE1.

Geneticists gave attention to LINE1 when it was found to cause cancer or genetic disorders like hemophilia. But researchers at University of California at San Francisco suspected there was more characteristics of LINE1. They suspected that if it can be most harmless then it can be worst harmful also.

Many reports showed that LINE1 is especially active inside developing embryos, which suggests that the segment actually plays a key role in coordinating the development of cells in an embryo. Researchers at University of California at San Francisco figured out how to turn LINE1 off in mouse embryos by blocking LINE1 RNA. As a result the embryos got stuck in the two-cell stage, right after a fertilized egg has first split. Without LINE1, embryos essentially stopped developing.

The researchers thought that LINE1 RNA particles act as molecular “glue,” bringing together a suite of molecules that switch off the two-cell stage and kick it into the next phase of development. In particular, it turns off a gene called Dux, which is active in the two-cell stage.

LINE1’s ability to copy itself, however, seems to have nothing to do with its role in embryonic development. When LINE1 was blocked from inserting itself into the genome, the embryonic stem cells remained unaffected. It’s possible that cells in embryos have a way of making LINE1 RNA while also preventing its potentially harmful “jumping” around in the genome. But it’s unlikely that every one of the thousands of copies of LINE1 is actually being used to regulate embryonic development.

LINE1 is abundant in the genomes of almost all mammals. Other transposons, also once considered junk DNA, have turned out to have critical roles in development in human cells too. There are differences between mice and humans, so, the next obvious step is to study LINE1 in human cells, where it makes up 17 percent of the genome.

References:

https://www-theatlantic-com.cdn.ampproject.org/c/s/www.theatlantic.com/amp/article/563354/

https://www.ncbi.nlm.nih.gov/pubmed/29937225

https://www.nature.com/scitable/topicpage/transposons-the-jumping-genes-518

https://www.sciencedaily.com/releases/2018/06/180621141038.htm

https://www.ncbi.nlm.nih.gov/pubmed/16015595