The Bardet-Biedl syndrome is a a syndrome characterized mainly by obesity, pigmentary retinopathy, polydactyly, mental retardation, hypogonadism, and renal failure in fatal cases.

The syndrome is named after Georges Bardet and Arthur Biedl.

Two forms have been identified:

Bardet-Biedl syndrome 1 (BBS1) has no linkage to chromosome 16
Bardet-Biedl syndrome 2 (BBS2) is mapped to markers on chromosome 16.

Laurence-Moon-Biedl syndrome and Laurence-Moon-Biedl-Bardet syndrome are no longer considered as valid terms in that patients of Laurence and Moon had paraplegia but no polydactyly and obesity which are the key elements of the Bardet-Biedl the syndrome. Laurence-Moon syndrome is a separate entity.

Major features

Eyes: Pigmentary retinopathy.
Hand and foot: Polydactyly.
Cardiovascular system: Hypertrophy of interventricular septum and left ventricle and dilated cardiomyopathy.
Gastrointestinal system: Fibrosis.
Urogenital system: Hypogonadism, renal failure, urogenital sinuses, ectopic urethra, uterus duplex, septate vagina, and hypoplasia of the uterus, ovaries, and fallopian tubes.
Growth and development: Mental and growth retardation.
Behavior and performance: Poor visual acuity and blindness.
Heredity: The syndrome is familial and is transmitted as an autosomal recessive trait. chromosome 3 locus appears to be linked to polydactyly of all four limbs, whereas chromosome 15 is associated with early-onset morbid obesity and is mostly confined to the hands, and chromosome 16 represents the "leanest" form.
Additional features: Obesity.

Cause

The detail biochemical mechanism that leads to BBS is still unclear. Recently, eight genes (BBS1 to BBS8) that are responsible for the disease when mutated have been cloned, and most of the gene products encoded by these BBS genes are located in the basal body and cilia of the cell. It has been postulated that these BBS gene products might involve in the cell signaling pathway in the cilia, and these signaling systems play an essential role in the normal development so that a malfunction in these systems causes the diverse pathological effects of the Syndrome.

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STARS PUT ON THEIR JEANS TO BACK GENE RESEARCH
From Evening Standard (London), 10/9/00 by ZOE MORRIS

THE SEARCH for the defective genes which cause a rare debilitating syndrome has led to a discovery which could also provide clues to how obesity and diabetes runs in families.

Doctors have found the first of seven genes responsible for Bardet- Biedl syndrome, (BBS) which is hereditary and results in a series of disabling conditions. Babies born with the syndrome frequently have extra fingers and toes, but it often goes undiagnosed for years.

Children go on to have learning difficulties, suffer obesity and eventually become blind. As adults they are prone to diabetes and renal failure.

The current research is just one genetic project which is being carried out at the Institute of Child Health. It is supported by the charity Jeans for Genes which encourages people to pay to wear denim to work to raise money. Singer Billie and band Precious are among the celebrities which supported a Jeans for Genes day last Friday.

Doctors at the Institute of Child Health at Great Ormond Street Hospital have been searching for the defective genes which cause the syndrome for almost a decade.

Working with colleagues in America and Canada, Dr Phil Beales, a leading authority on the syndrome, has identified one of the seven defective genes which causes the syndrome. Only around 500 families are in Britain have been identified as carries of the syndrome which is not always passed onto their children.

However, the breakthrough should not only lead to prenatal testing for the families with the syndrome, but will start to unlock the mystery of inherited obesity, Dr Beales hopes.

He told the Evening Standard: "I wanted to look at the way obesity and diabetes run in families. There is no doubt that there is a genetic component to obesity. We all know fami-

lies where parents and children are overweight. Some people think it is because they have the same poor diet, which is not necessarily true."

The gene which has been identified in Bardet-Biedl sufferers is responsible for folding proteins. If they are not properly folded, proteins cannot perform their designated function, leading to disease.

Dr Beales will now carry out research to discover if the same gene present in families which suffer from obesity and diabetes and may have a less serious version of BBS.

The discovery also holds hope for the families with the disease and could lead to a way of preventing blindness. Dr Beales added: "The discovery offers hope for BBS sufferers.

We may, for example, understand how their blindness occurs and be able to halt its progression in years to come."

Mother-of-three, Drina Parker has one son, Richard, who was diagnosed with BBS when he was three. Now 19, Richard is blind, but is studying for business qualifications at a special college. She went on to set up a charity to provide support for parents and encourage research.

Mrs Parker added: "This is too late for Richard, but hopefully by the time my sons have children there will be prenatal testing for the syndrome."

Mrs Parker helped to put Dr Beales in touch with families in America and in Newfoundland, Canada, where there is a cluster of families who originally emigrated from South-West England who carry the disease. Forty per cent of the BBS population in Newfoundland carry the defective gene which has been identified.

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