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Investigators from the Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Cantabria and the University of Harvard (United States) have discovered new clues about the origin of the focomelia, a rare disease that causes a deficient development of the long bones of the extremities, making them shorter than normal and, in extreme cases, the hands, feet or fingers directly arising from the trunk. The findings, which allows a better understanding of how they.

The focomelia is a very rare malformation, which affects about one in 20,000 newborns and is caused by genetic or environmental causes. In the 60 years its incidence has increased dramatically due to the prescription of thalidomide to relieve the nausea of pregnancy, drug later was shown to cause focomelia. Although easily detected during pregnancy, no treatment and those affected have a high mortality.

Researchers have produced X-ray focomelia chick embryos and have carried out an analysis of molecular and cell lineage to see how to produce disease. So far, it is believed that the disease originated on the model of the 'progress zone': reducing the size of the limb due to loss of cells (caused by the death, in this case, by irradiation) the surviving cells remain longer in the area of achievement, becoming increasingly distant destinations (from the center of the body). Ie, cells that normally give rise to newly formed humerus fingers.

Marian Ros, CSIC researcher at the Institute of Biomedicine and Biotechnology, Cantabria, says: "Our results show that this is not true since, as indicated by molecular markers available, the next three segments of the distal-end ( arm, forearm and hand) are properly only if they are to form the fingers. These findings are consistent with the predictions of the model of the progress zone. "

"The research also shows that irradiation prevents condensation of the skeletal elements that are being formed at the time the damage occurs, indicating that focomelia is primarily the result of a defect in cell differentiation," concludes the researcher. This means that the skeletal-precursor cells that form skeletal tissues, which have just begun their differentiation into cartilage and are greatly affected, although they received instructions to do it, do not reach the critical mass to do so.

The discovery, which clarifies the causes of this malformation is an important step towards understanding of limb development, a process not yet fully known. "Know it would explain not only the focomelia but many other malformations occurring during development," concludes Ros.