PR87490

REYKJAVIK, Iceland, January 7, 2021, /PRNewswire=KYODO JBN/--

By sequencing the germline genomes of twins and comparing them to those of

close relatives, scientists at deCODE genetics found mutations that are present

in just one of the monozygotic twins and traced them back to the first days

after conception.

In the article, Differences between germline genomes of monozygotic twins,

published in Nature Genetics today scientists at deCODE genetics searched for

mutations that were present in only one of monozygotic twins.  

In the study of human genetics the genomes of monozygotic twins are often

assumed to be identical, and differences between them have been pinned on the

environment rather than genetics. This assumption has been used throughout the

centuries to disentangle the contribution of genetics and environment to

disease and other phenotypes.

The scientists found two groups of twin pairs, one where twins share mutations

and another where the developmental mutations are only present in one of them

at high frequency.

"Mutations can be formed when cells divide and the daughter cells may carry a

mutation that marks the descendants of the mutated cell within an individual.

Mutations that are present in only one of the twins allow us therefore to

backtrack to the cell divisions that lead to the development of the twins."

says Hákon Jónsson scientist at deCODE Genetics and author on the paper.

Remarkably this backtracking of the mutations that differ between twins

suggests that the mutations are formed in the first days of embryonic

development when the embryo consists of several cells.  

"These two groups of monozygotic twins give insight into development of the

embryo only few divisions after conception when the embryo consists of several

cells," says Kari Stefansson CEO of deCODE genetics. "These are exciting times

that allows us to use mutations to shed light on the development of humans at

these first stages of development."

Hákon Jónsson and colleagues sequenced the genomes of 387 pairs of identical

twins and their parents, spouses and children to track mutation divergence. The

authors found that twins differ by 5.2 early developmental mutations, on

average. In approximately 15% of twin pairs, one twin carries a high number of

these mutations that the other twin does not have.

Physical or behavioral differences between identical twins are usually

attributed to environmental factors, according to the assumption that genetic

differences between the pair are minimal. However, autism and other

developmental disorders—which one twin in a pair might have—are linked to

genetic mutations. The authors conclude that the role of genetic factors in

shaping such phenotypic differences has been underestimated.

Thora Kristin Asgeirsdottir, PR and Communications deCODE genetics, 00354 -570

1909, 00354 -894 1909, thoraa@decode.is

Photo - https://mma.prnewswire.com/media/1395021/deCODE_twins.jpg

SOURCE: deCODE genetics Inc