75% of the genes in the human body are garbage?

"Junk DNA" has been studied by a large number of scientists, and the results of these studies continue to show that "junk DNA" is by no means a "useless" role in our body, on the contrary, it may play an important role in many ways

When it comes to garbage, our first reaction is usually useless stuff

A recent study published in Cell Stem Cell found that a previously overlooked part of DNA, so-called "junk DNA", is responsible for the differences between humans and chimpanzees

"One thing is certain, 'junk DNA' is by no means junk

There are stages in the research on human genes.

"Junk DNA" cognition and "technology" advance

"Junk DNA" is a literal translation from the English "Junk DNA", originally proposed by Japanese geneticist Ono Miyuki to describe the DNA sequences in the genome that cannot encode proteins

Gu Chaojiang introduced that according to the early definition, the number of genes responsible for encoding proteins in human genes is only 40,000, accounting for only 2% of the genome, and the other 98% are classified as "junk DNA"

With the advancement of scientific research, the definition of "junk DNA" is also changing

Not only is the definition of "junk DNA" changing, but scientists are also divided on how much "junk DNA" we have in our bodies

In 2003, the ENCODE (The Encyclopedia of DNA Elements) program was launched, involving more than 400 scientists worldwide

However, Dan Graul, a professor of biology and biochemistry at the University of Houston in the United States, published a paper in the journal Genome Biology and Evolution, saying that using a new model to count the functional genes in the human genome, it was found that functional genes accounted for only 25% at most.

Gu Chaojiang believes that this study "overturns" ENCODE's conclusion and will guide researchers to refocus on human genome research

The cognition of "junk DNA" keeps pace with "technology", so where does it come from?

Studies have shown that some "junk DNA" originates from viruses and can regulate the human immune system

A document published in Science in 2017 believes that "junk DNA" originates from the asymmetric distribution of chromosomes

Functionality is the tip of the iceberg

"Junk DNA" has been studied by a large number of scientists, and the results of these studies continue to show that "junk DNA" is by no means a "useless" role in our body, on the contrary, it may play an important role in many ways

Gu Chaojiang introduced that some "junk DNA" can be regarded as molecular switches of genes

American scientists analyzed 330 exons derived from the Alu (highly repetitive sequence) genome in 11 human tissues and identified many interesting exons
.
Alu is a primate-specific retrotransposon, through which exon production may contribute to the unique properties of primates
.

"Junk DNA" can function by synthesizing regulatory RNA
.
They can be transcribed into small RNAs, control protein expression, activate or repress gene expression, and assist in very complex cell division, differentiation, and more
.
According to Gu Chaojiang, if this method is applied to medicine, cancer genes can be silenced, which is of great significance
.

Other studies have shown that "junk DNA" has the potential to change the way genes are assembled
.
Previously, researchers from the University of North Carolina found that small fragments of genetic sequences in some "junk DNA" tell genes how to splicing, or can increase or inhibit the splicing process, thereby changing the way genes are assembled
.

The impact of "junk DNA" on humans doesn't stop there
.

Scientists from Germany and the United Kingdom have found that after chemotherapy, hematopoietic stem cells in the bone marrow will use "junk DNA" to transcribe and generate RNA molecules to enhance activation, generate fresh cells, and promote blood regeneration
.

The researchers also found that with the rapid increase in the number of individuals who have their genomes sequenced, nearly a hundred potential breast and prostate cancers have recently been identified in regions of "junk DNA" when deciphering mutations in their genomes, especially in noncoding regions.
fuse", which indicates that "junk DNA" may be a potential source of cancer
.
Other studies have demonstrated in Hodgkin lymphoma under what conditions "junk DNA" can remain active, thereby accelerating tumor growth
.

Contrary to the above point of view, researchers from the University of Bath and the University of Cambridge in the United Kingdom found that "junk DNA" located between genes can be transcribed to form non-coding RNA, and this process can block cancerous cells
.

In addition, researchers in the United States have developed a new bioinformatics method to identify and determine de novo tandem repeat mutations (referred to as de novo TR mutations) from sequencing data, and for pre-existing ASD (autism spectrum disorder) Genome-wide characterization of de novo TR mutations in afflicted and unaffected hands and feet
.
A large number of de novo TR mutations were found to be genome-wide in ASD probands, enriched in regulatory regions of the fetal brain, and predicted to be evolutionarily more harmful
.

"Junk DNA" may also affect the nervous system
.
Studies have found that the retrotransposon LINE-1, considered to be "junk DNA", is at high levels in the brains of schizophrenia patients and can modify the expression of schizophrenia-related genes
.
Therefore, researchers speculate that it may be the main cause of schizophrenia
.
At the same time, this part of "junk DNA" was placed under the genetic factors that cause schizophrenia, and the researchers found that in patients with schizophrenia, LINE-1 can be inserted into genes related to synaptic function, making it function normally It is destroyed, so it can be considered that this "junk DNA" may be the culprit in causing schizophrenia
.

According to Gu Chaojiang, in the study of molecular mechanisms of development, foreign research teams have found that microRNAs transcribed from "junk DNA" play an important role in the process of cell and germ layer allocation during development
.
Using next-generation gene sequencing and sophisticated computer analysis, researchers at the Centennial Institute in Sydney have revealed how specific white blood cells use non-coding DNA to regulate the activity of a range of genes that control shape and function
.

"Junk DNA" may even affect our appearance
.
Some American researchers have found that there are some sequence fragments in "junk DNA" that can affect facial genes like switches or amplifiers
.
The size of the eyes, the uprightness of the nose, the shape of the skull, etc.
, may all be inseparable from these sequence segments called enhancers
.

Clear the clouds and see the fog, more mysteries to be solved

What questions still need to be answered in the face of "junk DNA"?

Gu Chaojiang said that with the advent of the post-genome era, advances in sequencing technology have benefited the interpretation of "junk DNA"
.
The second and third generation sequencing technologies have greatly improved the sequencing throughput, and can complete the sequencing of DNA molecules ranging from hundreds of thousands to millions at one time, making the deep sequencing of the genome and transcriptome of a species convenient and feasible.
"Junk DNA" interpretation provides technical support
.

As more and more functional "junk DNA" is recognized and identified, there will be less and less "junk DNA" in the actual sense
.

Gu Chaojiang believes that in the future, we may continue to deeply analyze the functions of "junk DNA" in the following 10 directions, namely the regulation of DNA replication, transcriptional regulation, marking sites for the programmed rearrangement of genetic material, and affecting the normal folding of chromosomes.
and maintenance, controls the interaction of chromosomes with the nuclear envelope, controls RNA processing, editing and splicing, modulates translation, regulates embryonic development, DNA repair and helps fight disease
.

The era of "junk DNA" is over, according to a paper published in Genome Biology and Evolution
.
At the same time, with the continuous development of life sciences, people have gradually realized that "junk DNA" is not garbage
.

"With technological updates and in-depth research, more and more functional sequences will be generated in 'junk DNA',
" Gu Chaojiang said firmly
.