- Researchers have found
that not all non-coding regions of the DNA are devoid of functions.
- Certain regions of the junk DNA called enhancers play an
active role in heart health
- Scientists are creating a map
of heart enhancers which will provide a better understanding of diseases.
- The absence of heart enhancers found to lead to
Lawrence Berkeley National Laboratory's Department of Energy have found that
certain DNA segments that were considered 'junk', also called enhancers, were
now found to be associated with heart abnormalities. These DNA segments did not
code for any specific protein and hence were termed 'junk'.
The researchers found
80,000 DNA segments that were considered junk and they chose 2 of these
segments for their study. Senior staff and co-author of the study, Axel Visel,
said "The cardiac changes that we observed in knockout mice lacking these
enhancers highlight the role of non-coding
in processes that are
important in human disease. Identifying and interpreting sequence changes
affecting non-coding sequences is increasingly a challenge in human genetics.
The genome-wide catalog of heart enhancers provided through this study will
facilitate the interpretation of human genetic data sets."
‘Heart enhancers are present right in the human genome.’
When the entire human genome
sequenced, it was found that only 5% of the genome coded for a specific
protein. The rest of the DNA were considered junk.
- A considerable percentage of the
genome were considered junk
- These segments of the DNA were
initially not believed to have any influence.
- The ENCODE
(Encyclopedia of DNA elements) was a comprehensive study that looked at
functional elements in DNA sequences.
- The scientists involved
with ENCODE stated that nearly 805 of these segments had biochemical functions.
- Scientists believe that junk DNA were formed during
evolution when certain genes undergo random mutations that result in the loss
of ability to code for proteins. Since there are 2 copies of genes in every
organism, mutations in one gene copy will not have too deleterious effect.
- Certain junk DNA have
been found to influence certain other genes by switching them on.
non coding region of the DNA have been found to play a pivotal role during
early stages of development by regulating gene expression.
- Some sections of the junk DNA sequences have also been
found to act as 'enhancers', they have a direct influence over the rate of
expression of nearby gene sequences.
- Some junk DNA
sequences act as suppressors that suppress the transcription of certain genes
that are close.
80,000 DNA segments that
are considered to be heart enhancers have been found in the human genome.
Diane Dickel, who is the
lead author of the study said "In genetic studies, the way you establish
whether a gene is important is you delete it from the genome and see what
happens. In many cases, there are genes that, if disabled, make it difficult
for the organism to survive. For enhancers, it's less known what the
consequences are if they are damaged or missing. To use a car analogy, if we
took the battery out of a car, it wouldn't start. That's a critical component.
A missing or damaged enhancer could be essential like a battery, or more
similar to a missing passenger seat in the car. It's not as nice, but it's
still possible to drive the car."
Dr. Dickel and
colleagues created a map of heart enhancers in the genome using chromatin
immunoprecipitation sequencing. This, the scientists believe, will help people
understand the basis of diseases better.
In their study, the
researchers disabled these known heart enhancers and compared them with mice
with normal heart enhancer function. The scientists carried out an electrocardiogram of the heart
of mice from both the groups to understand the
The scientists found
that mice with disabled heart enhancers pumped blood less effectively, an
indication of cardiomyopathy
"Prior to this
work, no study had looked at what happens to heart function as a result of
knocking out the heart enhancers in the genome. What was surprising to me was
that outwardly, the knockout mice seemed fine. If you just looked at them, you
wouldn't necessarily see anything wrong," said Dr. Dickel, stressing the
significance of the study.
- The Case for Junk DNA - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4014423/)
- Junk DNA