The Genetics Of Psoriasis

A new gene associated with a variant of psoriasis and seborrheic dermatitis has been identified by a research group led by Dr. Ohad Birk at the Morris Kahn Laboratory of Human Genetics at Ben Gurion University and Soroka Medical Center. The gene discovered by the Israeli researchers is of much interest as it allows the first major molecular insight into why the specific skin cells proliferate excessively, causing these two common skin diseases. Psoriasis and seborrheic dermatitis affect 2-3% of the population worldwide and 85% of AIDS patients. Both skin diseases are caused by excessive proliferation of specific cells (keratinocytes) in the skin. To date, there is only very limited understanding as to the molecular mechanisms causing these two common disorders. The two-and-a-half-year study examined an Israeli Moroccan Jewish family with 44 members over five generations who showed signs characteristic of psoriasis and seborrheic dermatitis. By using advanced techniques to analyze DNA samples of the affected members of the family and comparing them to normal, unmutated DNA, Ramon Birnbaum, a doctoral student at Birk's laboratory, has succeeded in pinning the beginning of the molecular pathway on a mutation in a gene that is normally expressed, or "turned on" in the keratinocytes. The gene is believed to suppress or regulate cell proliferation and is thought to be a transcription factor, meaning that it switches on other genes, which may also play a role in the disease. When mutated, this regulation malfunctions, enabling excessive proliferation of skin cells and calling in cells of the immune system. The findings, to be reported in this month's issue of Nature Genetics, allow new insights into the mechanism of disease in psoriasis and seborrheic dermatitis. In turn, these insights are likely to assist pharmaceutical companies in developing "smart drugs" for these two common skin diseases.