Featured Research

from universities, journals, and other organizations

African pygmy mice: Females are XY ... researchers find out why

Date:
February 25, 2010
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
In a great majority of cases, the Y chromosome determines sex in mammals. The African pygmy mouse M. minutoides is an exception to this rule. In this species, which is a close relative of the house mouse, it is the X chromosome that determines sex. Researchers in France have just identified this unexpected case of sex determination. These scientists have demonstrated a particular chromosomal rearrangement on the X chromosome of this mouse. This work should provide a clearer understanding of how classic sex determination functions in mammals.

An XY female Mus minutoides.
Credit: Copyright Frédéric Veyrunes / CNRS 2009

In a great majority of cases, the Y chromosome determines sex in mammals. The African pygmy mouse M. minutoides is an exception to this rule. In this species, which is a close relative of the house mouse, it is the X chromosome that determines sex.

Related Articles


A team led by Frédéric Veyrunes, CNRS researcher at the Institut des Sciences de l'Evolution in Montpellier, working in collaboration with biologists from the Institut de Génomique Fonctionnelle in Lyon and the IRD, have just identified this unexpected case of sex determination. These scientists have demonstrated a particular chromosomal rearrangement on the X chromosome of this mouse. This work should provide a clearer understanding of how classic sex determination functions in mammals.

The research is published in the 7 April issue of the journal Proceedings of the Royal Society B.

In the great majority of mammals, sex determination follows a simple rule: an XX chromosome arrangement defines a female while an XY arrangement produces a male. However, some situations may deviate from this principle, in which case reference is made to chromosomal anomalies that most generally cause sterility. On the Y chromosome, sex is determined by the presence or absence of a single gene called Sry. Located in 1990, this gene initiates the development of male characteristics; without this gene, the gonads become ovaries.

However, some mammal species do not obey this rule. Until now, only seven cases of atypical sex determination had been observed, all in rodents. The team coordinated by Frédéric Veyrunes has just identified a new case, the first to be described for 30 years, in Mus minutoides, an African pygmy mouse species which is particularly interesting as it is very closely related to the house mouse, the principal mammal model used in biology. By studying different populations of African Mus minutoides, the researchers observed a very high proportion of fertile females carrying XY chromosomes (between 74% and 100%).

In order to better understand the situation at a genetic level, the scientists performed molecular and cytogenetic analyses, and revealed that sex reversion did not appear to be induced by a mutation on the Sry gene but by an as yet unknown chromosomal rearrangement on the X chromosome. Indeed, two morphologically indistinguishable X chromosomes were present in the females: X and X*. One of them, named X*, was invariably associated with females carrying the X*Y pair. It bore a mutation causing a reversion of sex. It was quite surprising that the mutation was carried by the X rather than the Y chromosome, which generally determines gender. But the X chromosome of mammals also carries numerous genes that control sexual and reproductive traits, some of which are expressed at spermatogenesis. One question remains: why have these XY mice not disappeared as a result of natural selection? Several hypotheses have been put forward to explain this evolutionary paradox and are now being explored in more detail.

These aberrant systems are a subject of little study, and the mechanisms that explain these anomalies and their functioning remain almost unknown. Greater knowledge of them might enable a clearer understanding of "classic" sex determination in mammals. Indeed, most of the major advances in this area have arisen from the analysis of variant sex systems and pathological sex reversions in humans and mice.


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. Frederic Veyrunes, Pascale Chevret, Josette Catalan, Riccardo Castiglia, Johan Watson, Gauthier Dobigny, Terence J. Robinson and Janice Britton-Davidian. A novel sex determination system in a close relative of the house mouse. Proceedings of The Royal Society B Biological Sciences, 2010; 277 (1684): 1049 DOI: 10.1098/rspb.2009.1925

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "African pygmy mice: Females are XY ... researchers find out why." ScienceDaily. ScienceDaily, 25 February 2010. <www.sciencedaily.com/releases/2010/02/100224134147.htm>.
CNRS (Délégation Paris Michel-Ange). (2010, February 25). African pygmy mice: Females are XY ... researchers find out why. ScienceDaily. Retrieved March 28, 2015 from www.sciencedaily.com/releases/2010/02/100224134147.htm
CNRS (Délégation Paris Michel-Ange). "African pygmy mice: Females are XY ... researchers find out why." ScienceDaily. www.sciencedaily.com/releases/2010/02/100224134147.htm (accessed March 28, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Saturday, March 28, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Lioness Has Rare Five-Cub Litter

Raw: Lioness Has Rare Five-Cub Litter

AP (Mar. 27, 2015) — A lioness in Pakistan has given birth to five cubs, twice the usual size of a litter. Queen gave birth to two other cubs just nine months ago. (March 27) Video provided by AP
Powered by NewsLook.com
Jockey Motion Tracking Reveals Racing Prowess

Jockey Motion Tracking Reveals Racing Prowess

Reuters - Innovations Video Online (Mar. 26, 2015) — Using motion tracking technology, researchers from the Royal Veterinary College (RVC) are trying to establish an optimum horse riding style to train junior jockeys, as well as enhance safety, health and well-being of both racehorses and jockeys. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Bear Cubs Tumble for the Media

Bear Cubs Tumble for the Media

Reuters - Light News Video Online (Mar. 26, 2015) — Two Andean bear cubs are unveiled at the U.S. National Zoo in Washington, D.C. Alicia Powell reports. Video provided by Reuters
Powered by NewsLook.com
Botswana Talks to End Illegal Wildlife Trade

Botswana Talks to End Illegal Wildlife Trade

AFP (Mar. 25, 2015) — Experts are gathering in Botswana to try to end the illegal wildlife trade that is decimating populations of elephants, rhinos and other threatened species. Duration: 01:05 Video provided by AFP
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:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

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