New understanding of Joubert Syndrome

Joubert syndrome is a disease showing a clear brain malformation and is sometimes associated, to varying degrees, with liver fibrosis, nephronophthisis and retinal dystrophy. It is a ciliopathy disease, affecting the primary cilia present in several organs of the body. Joubert syndrome is particularly common in the Middle East, due to the relatively high rates of consanguinity.

A group of researchers, including Lihadh Al-Gazali from the Faculty of Medicine and Health Sciences, United Arab Emirates University, studied the genetic origins of the disease virus. Their study focused on the disease in two Emirati families, but was later expanded to include others from Egypt, Turkey and Italy.

Individuals with Joubert syndrome locus 1 (JBTS1) were found to have mutations in the INPP5E gene, which is responsible for producing an enzyme involved in hydrolysis of phosphotidylinositol (PtdIns).

INPP5E was found to be localized adjacent to or within the basal end of cilia, especially in organs affected by Joubert syndrome. In the presence of the mutated version of INPP5E, ciliary disassembly was more rapid when compared to the normal gene. Researchers concluded that the gene plays a mediating role for both cilia stability and cell-cycle dynamics.

Further clinical research is needed to determine whether the developmental defects seen in Joubert syndrome are a result of cilia-maintenance problems or disruption of PtdIns in general.

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