Impaired cell adhesion and apoptosis in the novel CLN9 Batten disease variant

Objective: To identify a novel form of neuronal ceroid lipofuscinosis (NCL), CLN9, and to examine cell biology and sphingolipid metabolism in CLN9-deficient cells.

Methods: Genechip analysis, genomic sequencing, cell culture, cell growth curve, [³H]thymidine incorporation, PI staining, filipin staining, sphingolipid measurements

Results: A novel form of neuronal ceroid lipofuscinosis, CLN9, was diagnosed in four patients with a clinical history characteristic for the juvenile form of NCL. They show strikingly similar gene profiles by genechip analysis. The existence of this novel CLN9-deficient NCL variant is supported by the presence of curvilinear inclusions and granular osmiophilic deposits (GRODS) seen in neurons and other cells by electron microscopy. Enzyme screening and sequencing of the entire coding region of all known NCL genes was negative. CLN9-deficient cells have a distinctive phenotype. They have a rounded cell body and a prominent nucleolus. They do not attach well to the culture dish. They are sensitive to apoptosis, but show increased growth rates compared to controls. Gene expression of proteins involved in cell adhesion and apoptosis is upregulated in CLN9-deficient cells. Sphingolipid metabolism is perturbed in CLN9-deficient cells. They have decreased levels of ceramide and sphingomyelin and increased activity of serine palmitoyl transferase.

Conclusion: A novel form of neuronal ceroid lipofuscinosis, CLN9, has been identified. CLN9-deficient cells have impaired cell adhesion, increased apoptosis and perturbation of sphingolipid metabolism.

Keywords: neuronal ceroid lipofuscinosis, cell adhesion, apoptosis, sphingolipids