Featured Research

from universities, journals, and other organizations

Fertilized oocytes digest paternal mitochondria

Date:
November 3, 2011
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
During fertilization, the entire spermatozoon enters the oocyte. However, most of its organelles, including mitochondria, are not transmitted to the offspring. A new study demonstrates for the first time how the spermatozoon organelles are digested by the oocyte shortly after fertilization. These findings could improve cloning and medically-assisted reproductive technology and help to better understand the evolutionary origin of the elimination of paternal mitochondria.

Autophagosomes (green) forming after fertilization to degrade organelles from the sperm during the first divisions of the embryo (mitotic spindle in red).
Credit: © V.Galy/S. Al Rawi

During fertilization, the entire spermatozoon enters the oocyte. However, most of its organelles, including mitochondria, are not transmitted to the offspring. A Franco-American study involving scientists from CNRS, Inserm, Institut Pasteur, Université Paris-Sud and UPMC(1) demonstrates for the first time how the spermatozoon organelles are digested by the oocyte shortly after fertilization.

Published in the journal Science on October 28, 2011, these findings could improve cloning and medically-assisted reproductive technology and help to better understand the evolutionary origin of the elimination of paternal mitochondria.

Mitochondria, the cellular organelles that specialize in the production of energy, possess their own genome. However, in most organisms, including mammals, mitochondrial DNA from the father is not transmitted to the offspring. Only maternal mitochondria, already present in the oocyte, remain. Yet, it was not known how and when the paternal mitochondria were degraded until this study provided the answer, using as a model the nematode C. elegans, a 1-mm long transparent worm well-known to biologists.

The researchers demonstrated that, within minutes after fertilization, the oocyte triggers an autophagic process involving the sequestration in vesicles of sperm components and their subsequent elimination by enzymatic degradation. Using a DNA analysis technique called PCR(2), they could confirm that the entire genetic material from the paternal mitochondria is rapidly degraded after fertilization.

Then, the researchers inactivated the cellular machinery involved in spermophagy and observed that paternal mitochondria remained in the embryo. To determine whether this process is conserved in mammals, they analyzed newly-fertilized mouse oocytes for the presence of specific markers for the initial steps of autophagy. They observed that the autophagy proteins of the oocyte clustered around the mid-piece of the spermatozoon, where the mitochondria are located, suggesting that a similar degradation mechanism does occur in mammals.

Owing to their very high metabolism, spermatozoa could possibly undergo frequent mutations of their mitochondrial DNA. By eliminating this DNA, the oocyte would prevent such mutations from being passed on to and affecting the offspring. This work paves the way for new experiments to test this hypothesis. Indeed, by inactivating spermophagy, organisms containing both paternal and maternal mitochondria could be created and studied for ensuing effects. Finally, these findings raise the issue of the fate of paternal mitochondria in embryos created by cloning or through advanced assisted reproductive technologies. Would these techniques allow the autophagic response of the oocyte and the subsequent degradation of paternal mitochondria, potentially responsible for diseases? The issue is up for discussion.

Notes:

1 -- This study was conducted by teams led by Vincent Galy at the Laboratoire de biologie du développement (CNRS/UPMC) and by Renaud Legouis au Centre de génétique moléculaire (CNRS).

2 -- PCR: Polymerase Chain Reaction, a molecular biology technique for in vitro DNA amplification.


Story Source:

The above story is based on materials provided by CNRS (Délégation Paris Michel-Ange). Note: Materials may be edited for content and length.


Journal Reference:

  1. S. Al Rawi, S. Louvet-Vallee, A. Djeddi, M. Sachse, E. Culetto, C. Hajjar, L. Boyd, R. Legouis, V. Galy. Postfertilization Autophagy of Sperm Organelles Prevents Paternal Mitochondrial DNA Transmission. Science, 2011; DOI: 10.1126/science.1211878

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "Fertilized oocytes digest paternal mitochondria." ScienceDaily. ScienceDaily, 3 November 2011. <www.sciencedaily.com/releases/2011/11/111103143515.htm>.
CNRS (Délégation Paris Michel-Ange). (2011, November 3). Fertilized oocytes digest paternal mitochondria. ScienceDaily. Retrieved August 22, 2014 from www.sciencedaily.com/releases/2011/11/111103143515.htm
CNRS (Délégation Paris Michel-Ange). "Fertilized oocytes digest paternal mitochondria." ScienceDaily. www.sciencedaily.com/releases/2011/11/111103143515.htm (accessed August 22, 2014).

Share This




More Plants & Animals News

Friday, August 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Newsy (Aug. 21, 2014) — An experimental drug used to treat Marburg virus in rhesus monkeys could give new insight into a similar treatment for Ebola. Video provided by Newsy
Powered by NewsLook.com
Terrifying City-Dwelling Spiders Are Bigger And More Fertile

Terrifying City-Dwelling Spiders Are Bigger And More Fertile

Newsy (Aug. 21, 2014) — According to a new study, spiders that live in cities are bigger, fatter and multiply faster. Video provided by Newsy
Powered by NewsLook.com
Lost Brain Cells To Blame For Sleep Problems Among Seniors

Lost Brain Cells To Blame For Sleep Problems Among Seniors

Newsy (Aug. 21, 2014) — According to a new study, elderly people might have trouble sleeping because of the loss of a certain group of neurons in the brain. Video provided by Newsy
Powered by NewsLook.com
Ramen Health Risks: The Dark Side of the Noodle

Ramen Health Risks: The Dark Side of the Noodle

AP (Aug. 21, 2014) — South Koreans eat more instant ramen noodles per capita than anywhere else in the world. But American researchers say eating too much may increase the risk of diabetes, heart disease and stroke. (Aug. 21) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins