Research Finds Shared DNA Signature of Identical Twins

Identical siblings are used to sharing a lot with their twin, including their DNA. But new research suggests that they also share a distinct marker of their twin status, not encoded within their DNA, but rather on it. This marker is found within the epigenome, consisting of chemical tags along the DNA that regulate gene activity without changing the genetic sequence. Researchers discovered that identical twins universally exhibit a common set of these markers, which remains consistent from birth through adulthood. 

The shared epigenetic markers can help identify individuals who were conceived as identical twins but lost their sibling in the womb or were separated at birth. This research lays the groundwork for understanding the process of monozygotic twinning, which remains a mystery despite its long-standing fascination. Identical twins form when a fertilized egg splits into two embryos, a process with unknown triggers. Jenny van Dongen, an epigeneticist at Vrije Universiteit Amsterdam, says the biological process that generates twins “is an enigma.”

During early development, both twins and non-twins undergo numerous epigenetic changes that activate or deactivate genes as the embryo forms. Some of these changes might explain minor distinctions between identical twins. So to better understand what makes a zygote split to form identical twins, “it makes sense to look at epigenetics,” van Dongen says.

By analyzing over 450,000 genomic sites in nearly 6,000 monozygotic and dizygotic twins, they compared identical twins with fraternal ones, eliminating influences from shared womb experiences. They identified 834 spots where identical twins exhibited remarkable similarity in epigenetic marks, particularly in centromere and telomere regions and near genes governing early developmental processes, like cell adhesion regulation. The health implications of these differences remain uncertain. These shared epigenetic patterns were consistent across twins of various ages and geographical locations- and even in different cell types. The researchers developed a test with an 80 percent accuracy rate to identify identical twins, including those affected by vanishing twin syndrome or separated at birth.

“This is a very, very important finding that opens up a lot of avenues of inquiry,” says Segal, the developmental psychologist. For example, identical twins are predisposed for a variety of conditions, from left-handedness to certain congenital disorders such as spina bifida, where the spine fails to develop properly. Perhaps, for some portion of people, these conditions stem from being an unknown identical twin, she says. 

Genetic research, and quite frankly all research, regarding twins always seems so interesting! It's quite cool how twins have piqued interest across cultures and traditions throughout history- and it’s even cooler to see how science develops deeper into understanding twins and the biological mechanisms behind it. 

Sources: 

https://www.nature.com/articles/s41467-021-25583-7

https://www.sciencenews.org/article/identical-twin-siblings-common-set-chemical-markers-dna-epigenetics

Wheat Epigenome Created for First Time

For the first time, scientists at the University of Liverpool created a survey of heritable molecular changes that regulate gene activity in wheat, according to a Science Daily article. They used epigenetic marks and DNA methylation to study the complex wheat genome. The changes in methylation displayed an association with changes in gene-expression and in the end, affect the phenotype. 

The leader of the study, professor Anthony Hall, said, "With the ability to characterize genome-wide patterns of methylation we can now address fundamental questions in wheat, such as the role of epigenetics in the domestication of crops and the stability and long-term function of methylation." He also added that by observing methylation changes in the wheat genome, important traits such as disease resistance and yield variability can be manipulated to benefit farmers. 

This is a significant breakthrough in agriculture genomics because of how highly in demand wheat is and the the complexity of its genome. If geneticists are able to accurately and consistently break down this genome, crops can be improved and produce higher yields. This can lower the price for wheat consumers and increase the profits farmers are making. Most importantly, diseases and mutations found in the wheat genome can be isolated and prevented from reproducing into other generations. Overall, this advancement in genetics will help agriculture and farmers in the future if continuing studies are conducted on the wheat genome.  

Blood from Children Contain Evidence of Prenatal Smoking

Researchers at John Hopkins University Bloomberg School of Public Health led a study where the blood of 531 children up to five years old were tested  to see if they could find any evidence that shows that their mother's smoked during pregnancy. In a previous study, there were presences of epigenetic marks, which include DNA methylation, in the DNA of a newborn's umbilical cord at 26 locations of the genome. The epigenetic markers are molecules not part of the DNA sequence and regulate the turning on and off of genes.

This new study took this even further, by finding that when the 26 epigenetic markers were looked at in the children, 81%  of the time the researchers could correctly predict that there was prenatal smoking. Although, in some cases it could be from exposure to secondhand smoke after birth. This study overall found that not only is the DNA marked in newborns, but it is still shows the epigenetic markers even five years after the children are born. This is known as an epigenetic memory. Prenatal smoking causes many health problems for children down the line and finding out if their mother's smoked during pregnancy can at least get a head start in preventing or treating these problems. I never knew that you can actually tell if a woman smoked during pregnancy, especially in the DNA of their child even after five years of being born.

Original article