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Studies Why children of older mothers are more often born with Down syndrome
With the age of the mother increases the risk that your child has a chromosome defect such as the Down syndrome (trisomy 21). Researchers from Austria have come a little closer to the question of why this is so.
Average age of mothers is increasing more and more
The average age of mothers continues to rise. This brings with it some health risks. For example, it increases the risk of miscarriage, gestational diabetes and the transmission of genetic defects. The risk of chromosomal abnormality in the baby, such as the one causing Down's syndrome (trisomy 21), increases with the age of the mother. The fear of trisomy is great, although experts repeatedly point out that children with Down syndrome are not sick but only slower. It helps to learn more about the chromosomal defects and how they are passed on. Austrian scientists have gained new insights here.
Image: Photographee.eu - fotolia Only one chromosome is too much
Down syndrome is the most common genetic mental disability. Only one chromosome is too much in the genome of those affected. Years ago, the mechanisms of Down's syndrome were decoded. Researchers at the Institute of Molecular Biotechnology (IMBA) of the Austrian Academy of Sciences have now found out more about the relationships. As the news agency APA reports, the Viennese scientists have discovered that the division of oocytes in mammals depends on a protein complex that encloses the chromosomes before birth and may be lost over the years. This may explain why children of older mothers are more likely to suffer from Down syndrome.
Very long-lived protein complex
Although this cohesin complex is remarkably long-lasting, it may be lost irreversibly from the chromosomes over the years. It is said that the inability of the egg cells to renew the annular band holding the chromosomes together could contribute to the age-related occurrence of defective chromosome partitioning. In a trisomy, a single chromosome is present in addition to the usual set of chromosomes. The most important risk factor for the development of trisomies in children, such as Down syndrome, where there are three copies of chromosome 21, is the mother's age, according to the APA report. The loss of cohesin could be a cause here. Several years ago it had been observed that cohesin becomes unstable in aging oocytes.
First proof in earlier investigation
"My team and I want to find out how the chromosomes in the ovum are held together by the cohesin complex from birth to ovulation," said first author Kikuë Tachibana-Konwalski of the study published in the journal Current Biology. The study is based on Tachibana-Konwalski's work as a postdoctoral fellow (Post-Doc) at the University of Oxford (UK). There the scientist investigated whether Cohesin is renewed in egg cells during a period of two to three weeks before ovulation (ovulation) and found no evidence for it. It was reported that this provided the first evidence that cohesin is remarkably persistent in oocytes.
Age-related loss is likely to be irreversible
In general, proteins in most cells of the body are renewed within a few hours. However, the IMBA research team found that cohesin is maintained in adult mice for at least four months and does not renew itself. As stated in the APA message, this means to humans that cohesin may hold together the chromosomes in women's ova for decades without renewal. According to the scientists, the age-related loss of cohesin from the chromosomes is probably irreversible. The next step is to find out the molecular causes of this loss. (Ad)