Choosing
the best eggs for IVF
BROWN
(US) - Gathering genetic information without harming the eggs will help us
identify which eggs will possibly become the most viable embryos for in vitro
fertilization states a new procedure
Based on the findings published in the Journal of Biological Chemistry,
it appears that a team of biologists and physicians, in a scientific first, were
able to sequence mRNA or the transcribed genetic material in egg cells in smaller structures pinched off from
them called “polar bodies.”
The
finding also states that the researchers were able to determine the genetic
activity of host eggs was faithfully reflected in their respective polar bodies
by comparing the gene expression sequences of both.
The
director of the Center for Reproduction and Infertility at Women & Infants
Hospital, Sandra Carson who is also a co-author and professor of obstetrics and
gynecology at Brown University says that they can now consider
the polar body a natural cytoplasmic biopsy
The cells
dispense with the second copies of chromosomes they don’t need as sex cells in
the polar bodies. Egg’s mRNA is the genetic material when a cell is set to make
proteins based on genetic instructions after the genes have been transcribed
whose microcosm is captured by the polar bodies nevertheless.
Pairs of genes
Just after
becoming the first to find mRNA in human polar bodies last year, the team has
now established that what is in the polar bodies is a good proxy for what is in
the eggs after transcribing it in 22 pairs of human eggs and their polar
bodies.
Gary
Wessel, professor of biology, says that the task wasn’t easy given that only
little mRNA is present in polar bodies. Lead author and graduate student Adrian
Reich and second author Peter Klatsky’s combination of clever amplification and
analysis techniques helped the team to get it done.
Wessel
says that because there was so little material this should not have worked. He
further adds that single-cell sequencing is very challenging.
The samples were analyzed in two pools of 10 cells each, comparing mRNA
in 10 eggs with mRNA in the 10 related polar bodies by the team to be cautious.
And they were surprised when they were able to directly sequence two individual
eggs and polar bodies.
The genes expressed in the eggs surpass the count of 14,000. The rate of
genes detected in the polar bodies which were also detected in the eggs was
more than 90%. The 460 were also the most abundant genes in the eggs out of the
700 most abundant genes which were found in the polar bodies.
Nearing clinical use
Carson says that what’s in the egg is reflected in the polar body. He
further states that we can get a clue into what is happening during the first
three days of human embryo development by what we are finding in the polar body
as the egg is the major driver during that time.
The next major step would be finding which genes impact embryo viability
for which a clinically useful tool will be created requiring more research.
We could track the progress of the resulting embryos with the new
knowledge and developed techniques in their study by analyzing the mRNA from
the polar bodies of the eggs.
After knowing the key genes, the clinicians and patients would be able
to pick the best eggs as they could create fast assays to look for those genes
in the polar bodies. In order to choose which eggs to bank for later use we may
also take the help of efficient developed technology.
Carson says they have the words, but not the sentences while explaining
that they can’t find out what those messages are doing or comprehend the
purpose of them in the cell function which they are hoping to resolve in the
future.
Sigma-Aldrich, a research reagent supplier and see grants from Brown
University office of the
Provost, the Center of Excellence in Women’s Health of Women & Infants
Hospital funded the research.