Scientists at The University of Toledo discovered new movement in sperm that
provides innovative avenues for diagnostics and therapeutic strategies for
male infertility.
The research published in Nature Communications finds that the atypical
centriole in the sperm neck acts as a transmission system that controls
twitching in the head of the sperm, mechanically synchronizing the sperm
tail movement to the new head movement.
The centriole has historically been considered a rigid structure that acts
like a shock absorber.
"We think the atypical centriole in the sperm's neck is an evolutionary
innovation whose function is to make your sperm move better," said Dr. Tomer
Avidor-Reiss, professor of biological sciences in the UToledo College of
Natural Sciences and Mathematics. "Reproductive success depends on the
ability of sperm to swim through female reproductive tract barriers while
out-competing their rivals to fertilize the egg."
The study led by Ph.D. candidate Sushil Khanal builds upon the lab's
previous groundbreaking discovery in human sperm that changed the dogma in
reproductive biology: A father donates not one but two centrioles through
the sperm during fertilization, and the newly discovered sperm structure
called the atypical centriole may contribute to infertility, miscarriages
and birth defects.
"Together, these studies call for a revision in our understanding of sperm
centrioles both in sperm movement and in the early embryo," Avidor-Reiss
said.
Avidor-Reiss believes this discovery can open the door to new possibilities
to help families understand why they may be having trouble getting pregnant.
If the head and tail of the sperm aren't moving together, the sperm isn't
going to move efficiently enough to get to the egg.
"If the centriole is defective, this coupling between the sperm tail and
head is going to be defective," Avidor-Reiss said. "In a patient when we
don't know what is wrong, potentially we can look at the way the sperm's
tail moves and reverse engineer it to determine centriole functionality to
determine couple's infertility."
He also said finding this movement can be used in the future to predict
which sperm have a good centriole that can support life.
"Right now, people don't know what to fix," Avidor-Reiss said. "We can
pinpoint the problem. This knowledge allows us to identify a subgroup of
infertile men that was not revealed before."
The new research shows that in the sperm of mammals there is a cascade of
internal sliding formations in the neck's atypical distal centriole, typical
proximal centriole and surrounding material that links tail beating with
asymmetric head kinking.
Using a STORM immunofluorescent microscope in the UToledo Instrumentation
Center, the researchers were able to show the left and right side of the
atypical centriole move about 300 nanometers relative to each other. Though
it's a small number, it marks dramatic movement in a cell considering the
average protein diameter is five nanometers.
Ph.D. student Luke Achinger, who recently graduated from UToledo with a
bachelor's degree in biology, sang bass in the University's premier choral
ensemble as an undergraduate and penned lyrics about his lab's new
discovery, explaining how the new movement works in a song called "Twitch,
Roll and Yaw."
"We love to promote science and art, and in this case, we are showing that
the sperm beats in unity. The head of the sperm is not isolated from the
tail. The neck including the atypical and typical centrioles may act as a
morphological computer, or sperm brain, that coordinates the sperm
movement," Avidor-Reiss said.
"The song is a creative way to understand a big change. The centriole always
looked the same over the last billion years. It's one of most conservative
structures in the cell. We found something different that functions in the
opposite manner, evolving from a shock absorber to a transmission system."
Reference:
“A dynamic basal complex modulates mammalian sperm movement” by Sushil
Khanal, Miguel Ricardo Leung, Abigail Royfman, Emily L. Fishman, Barbara
Saltzman, Hermes Bloomfield-Gadêlha, Tzviya Zeev-Ben-Mordehai and Tomer
Avidor-Reiss, 21 June 2021, Nature Communications.