BRACHYDACTYLY, PECULIAR FACIES AND MENTAL RETARDATION

The transcriptional coactivator and histone acetyltransferase CBP regulates neural precursor cell development and migration

CREB (cyclic AMP response element binding protein) binding protein (CBP, CREBBP) is a ubiquitously expressed transcription coactivator with intrinsic histone acetyltransferase (KAT) activity. Germline mutations within the CBP gene are known to cause Rubinstein-Taybi syndrome (RSTS), a developmental disorder characterized by intellectual disability, specific facial features and physical anomalies. Here, we investigate mechanisms of CBP function during brain development in order to elucidate morphological and functional mechanisms underlying the development of RSTS. Due to the embryonic lethality of conventional CBP knockout mice, we employed a tissue specific knockout mouse model (hGFAP-cre::CBP^Fl/Fl, mutant mouse) to achieve a homozygous deletion of CBP in neural precursor cells of the central nervous system.

Our findings suggest that CBP plays a central role in brain size regulation, correct neural cell differentiation and neural precursor cell migration. We provide evidence that CBP is both important for stem cell viability within the ventricular germinal zone during embryonic development and for unhindered establishment of adult neurogenesis. Prominent histological findings in adult animals include a significantly smaller hippocampus with fewer neural stem cells. In the subventricular zone, we observe large cell aggregations at the beginning of the rostral migratory stream due to a migration deficit caused by impaired attraction from the CBP-deficient olfactory bulb. The cerebral cortex of mutant mice is characterized by a shorter dendrite length, a diminished spine number, and a relatively decreased number of mature spines as well as a reduced number of synapses.

In conclusion, we provide evidence that CBP is important for neurogenesis, shaping neuronal morphology, neural connectivity and that it is involved in neuronal cell migration. These findings may help to understand the molecular basis of intellectual disability in RSTS patients and may be employed to establish treatment options to improve patients’ quality of life.

Surgical treatment of scoliosis in Rubinstein-Taybi syndrome type 2: a case report

INTRODUCTION

Rubinstein-Taybi syndrome is an autosomal dominant disorder resulting in congenital craniofacial deformities, and divided into types 1 and 2. Scoliosis has not been reported as one of the extra-cranial manifestations of Rubinstein-Taybi syndrome type 2.

CASE PRESENTATION

We present a 14-year-old British Caucasian girl with Rubinstein-Taybi type 2 syndrome who developed a severe double thoracic scoliosis measuring 39° and 68° respectively. Her scoliosis was associated with thoracic hypokyphosis, causing a marked reduction in the anteroposterior diameter of her chest and consequent severe restrictive lung disease. The deformity was noted by her local pediatrician as part of a chest infection assessment when she was aged 13 years, and gradually progressed as the result of spinal growth. Our patient underwent a posterior spinal arthrodesis using a single concave pedicle hook and screw rod construct and locally harvested autologous graft supplemented by allograft bone. This spinal fixation technique was selected because of our patient's low body weight to avoid prominence of the instrumentation causing skin healing problems and pain. Her scoliosis was corrected to 18° and 30° and we achieved a balanced spine in the coronal and sagittal planes. An underarm spinal jacket was provided for six months after surgery. During her latest follow-up at skeletal maturity, our patient had an excellent cosmetic outcome with no loss of deformity correction or detected pseudoarthrosis and a normal level of activities.

CONCLUSION

Scoliosis can develop in young children with Rubinstein-Taybi syndrome type 2, with the deformity deteriorating around the pubertal growth spurt. Surgical treatment can correct the deformity, balance the spine and prevent mechanical back pain. It can also stabilize the chest area and avoid respiratory complications developing as the scoliosis progresses, which can result in severe restrictive pulmonary disease. The use of single concave instrumentation is indicated in very slim patients with poor muscle bulk; in our patient, this produced satisfactory deformity correction and a favorable outcome at completion of growth. Peri-operative care in this group of patients can be very challenging because of associated co-morbidities as well as the presence of severe behavioral issues that result in poor patient compliance.

Glaucoma and findings simulating glaucoma in the Rubinstein-Taybi syndrome

Information is reviewed on the ophthalmologic findings in 614 individuals with Rubinstein-Taybi syndrome (RTS). The data were collected from the world literature, from communication with colleagues and with families of individuals with RTS, and from personal observations. Particular emphasis is given in this article to the association of RTS with glaucoma and five other findings that may be confused with glaucoma (corneal lesions, megalocornea, colobomatous or cystic optic nerve, excavation of papilla, and large cup-to-disc ratio). A case report is presented including autopsy results on a 5-year-old black female with RTS, corneal lesions, colobomas of the optic nerves, and normal intraocular pressure.

Rubinstein-Taybi syndrome

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The Rubinstein-Taybi syndrome: a report of two cases

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The Rubinstein-Taybi syndrome

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