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The Causes of Rubinstein Taybi Syndrome – Genetics, Epigenetics and RTS
Rubinstein Taybi syndrome (RTS) is a genetic condition associated with impaireded cognitive development. There is evidence that RTS involves both genetic and epigenetic factors.
The genetics of Rubinstein Taybi syndrome are heterogeneous. RTS is an autosomal dominant disorder. In approximately 55% of cases, RTS is attributed to a new mutation in the CREB-binding protein gene, CBP. In approximately 3% of patients the causative mutation is in the EP300 gene. In around 42% of cases, the genetic cause is unidentified.
These mutations can in theory give rise to epigenetic effects. Epigenetic effects are those that result from changes in gene expression rather than changes in DNA sequence. Over the past decade it has become clear that proper neurological function requires tightly controlled epigenetic processes. Gene expression is governed by many factors, including histone modification. One group of enzymes involved in histone modification are the histone acetyltransferases (HATs). It is believed that the genetic mutations seen in RTS result in dysfunctional HATs and hence dysfunctional histone modification.
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The Symptoms of Rubinstein Taybi Syndrome
As well as reduced cognitive function, a range of physical abnormalities are characteristic of RTS. These include:
- broad radially deviated thumbs
- feeding problems
- hearing, breathing and mobility problems
- deficiency in post-natal growth
- excessive weight gain during later childhood/puberty
- increased risk of tumors
- characteristic facial deformities
- grimacing expression/unusual smile
- Talon cusps on the incisors
Rubinstein-Taybi syndrome is rare, with an incidence of around 1 in 125,000 births in the US.
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Treatment and Care of Patients with Rubinstein Taybi Syndrome
Early diagnosis of RTS is important, allowing for treatment of specific problems in early childhood. Current medical care attempts to address feeding problems and constipation.
RTS infants are usually evaluated for heart defects and glaucoma. Since RTS patients have a higher risk of developing cancer, regular check-ups are indicated. This is to allow early detection of malignancy and hence maximize the chance of successful treatment.
The delayed motor and cognitive development requires long-term attention. Many patients do well in special schools for children with learning disabilities. RTS sufferers are usually friendly and happy, although some parents report sudden mood changes in RTS children. Generally, RTS individuals show no deficiencies in forming social and emotional bonds.
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Future Treatment of Rubinstein Taybi Syndrome
The genetics of Rubinstein taybi syndrome provide scope for future treatment. RTS involves epigenetic phenomenon which can, theoretically, provide therapeutic targets. As well as RTS, epigenetic factors are involved in disorders such as Alzheimer's disease, Huntington's disease and cancer. Drugs known as HDAC inhibitors, which are used widely in cancer therapy are being investigated as possible treatment for epigenetic cognitive disease.
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Epigenetic mechanisms in neurological diseases: genes, syndromes and therapies. R.Urdinguio, J.Sanchez-Mut, M.Estella. Lancet Neurology, 2009, Vol 8, P1056-72.
Epigenetic dysregulation in cognitive disorders. J.Graff & I.Mansuy. European Journal of Neuroscience, 2009, Vol 30, P1-8.