A new study from Karolinska Institutet published in the scientific journal Nature Genetics shows how chromosome disorders can arise when sex cells are formed.
Sex cells contain a control station for monitoring the mechanism that ensures that the correct numbers of chromosomes are distributed during cell division. Scientists have now shown that there is an alternative distribution mechanism in female sex cells that cause chromosome disorders. Aberrant chromosomes orientate themselves like normal chromosomes, and this ability to adopt double identities protects them from detection by the control centre.
"We believe that this new fundamental mechanism can help to explain why chromosome disorders are so common in female sex cells," says Professor Christer Hg, leader of the study.
The research might eventually lead to new medical treatments able to reduce the risk of foetal damage.
Over 0.3 per cent of children are born with some kind of chromosome disorder. Most develop Downs Syndrome, or obtain the wrong number of sex chromosomes and develop Turner's or Klinefelter's syndrome. Turner's syndrome only occurs in females and is caused when one of the two X chromosomes is missing. Girls with Turner's have arrested development and if no treatment is given do not enter puberty. Klinefelter's syndrome affects males, who receive an extra X chromosome. Symptoms include concentration difficulties, poor motor skills and infertility.
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Malaria is caused by parasites of the genus Plasmodium, which are spread to humans through mosquito bites. A mosquito picks up the parasite via infected human blood. The parasite then embeds itself in the mosquito's gut wall and reproduces, eventually passing to the salivary glands. The mosquito then infects new people during subsequent bites.
The research group's French collaborators, using a Plasmodium species that infects rodents, previously determined that the gene for TEP1 occurs in two forms, or alleles. One, called TEP1r, occurs in mosquitoes that are resistant to malarial infection. Another, TEP1s, is found in mosquitoes that are vulnerable to infection.
The TEP1r and TEP1s proteins are 93 percent genetically identical, and the new study, in which TEP1r was structurally analyzed, shows that the differences cluster around the warhead area, Dr. Baxter said. This finding reinforces the theory that the warhead is a key element of the overall immune response to malaria in mosquitoes.
In future studies, the researchers will genetically manipulate the warhead to study its binding properties, Dr. Baxter said. In addition, further research is needed to determine what other elements of the mosquito's immune system are activated once TEP1 binds to an invader.
Other UT Southwestern researchers involved in the study were Dr. Chung-I Chang, a former postdoctoral researcher, and Yogarany Chelliah, an HHMI research specialist. Researchers from the Institut de Biologie Mol?©culaire et Cellulaire in Strasbourg, France, also participated.
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