Center for Human Genetics and Laboratory Diagnostics, Dr. Klein, Dr. Rost and Colleagues

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Scientific Background

The Joubert syndrome (JBTS) is an autosomal recessive disease, characterized by congenital malformations of the brainstem as well as agenesis/hypoplasia of the cerebellar vermis (molar tooth sign during magnet resonance imaging). Common signs during the neonatal period include tachy/dyspnoea, nystagmus, vertical gaze palsy and muscular hypotonia. Later on, cerebellar ataxia with a delay in the motor development is frequently seen. The cognitive development of the patients may range from normal intelligence to severe deficits. In some cases, JBTS may be associated with nephronophthisis (17-27% of all cases), optic nerve coloboma, liver fibrosis and polydactyly. The frequency of JBTS is approx. 1 in 100,000.

JBTS shows a high locus heterogeneity. So far, mutations have been found in multiple genes; mutation analysis is therefore extensive. Along with nephronophthisis, the Joubert syndrome belongs to the group of ciliopathies. Cilia are cell organelles and serve as mechano, chemo and osmotic sensors. Furthermore, they play a vital part in numerous pathways and are crucial for appropriate development of the organs, maintenance of tissue homeostasis and for general developmental processes.