Comparative transcriptomics reveals mechanisms underlying cln3-deficiency phenotypes in Dictyostelium

Area of Science:

• Cell Biology
• Molecular Genetics
• Biochemistry

Background:

• Mutations in CLN3 cause juvenile neuronal ceroid lipofuscinosis (Batten disease), a severe neurological disorder.
• The precise physiological role of CLN3 protein remains poorly understood, hindering treatment development.
• Research in Dictyostelium discoideum offers new insights into CLN3 function, linking it to cellular adhesion and development.

Purpose of the Study:

• To explore the molecular mechanisms behind the abnormal starvation response in cln3-deficient Dictyostelium cells.
• To identify genes and pathways affected by the loss of CLN3 function.
• To elucidate the role of CLN3 in cellular homeostasis and lysosomal function.

Main Methods:

• Comparative transcriptomics (RNA-seq) to analyze gene expression changes in cln3-deficient cells versus wild-type cells during starvation.
• Bioinformatic analyses including STRING and Gene Ontology (GO) term enrichment.
• Biochemical assays to assess lysosomal enzyme activity, endo-lysosomal pH, and nitric oxide homeostasis.
• Microscopic observation of autofluorescent storage bodies.

Main Results:

• 1153 genes were differentially expressed in cln3-deficient cells during starvation, including homologs of other human NCL genes.
• GO term analysis indicated enrichment of genes involved in metabolic, biosynthetic, and catalytic processes.
• Loss of CLN3 function led to altered lysosomal enzyme expression and activity, increased endo-lysosomal pH, and disrupted nitric oxide homeostasis.
• Autofluorescent storage bodies accumulated in cln3-deficient cells, suggesting a link to impaired lysosomal function.

Conclusions:

• CLN3 plays a crucial role in regulating gene expression, metabolic processes, and lysosomal function in Dictyostelium during starvation.
• The study provides evidence linking CLN3 function to the activity of specific lysosomal enzymes like Tpp1 and CtsD.
• Understanding CLN3's molecular mechanisms in this model organism advances knowledge of Batten disease pathogenesis.