Cystinosis (ctns) zebrafish mutant shows pronephric glomerular and tubular dysfunction

Abstract

The human ubiquitous protein cystinosin is responsible for transporting the disulphide amino acid cystine from the lysosomal compartment into the cytosol. In humans, Pathogenic mutations of CTNS lead to defective cystinosin function, intralysosomal cystine accumulation and the development of cystinosis. Kidneys are initially affected with generalized proximal tubular dysfunction (renal Fanconi syndrome), then the disease rapidly affects glomeruli and progresses towards end stage renal failure and multiple organ dysfunction. Animal models of cystinosis are limited, with only a Ctns knockout mouse reported, showing cystine accumulation and late signs of tubular dysfunction but lacking the glomerular phenotype. We established and characterized a mutant zebrafish model with a homozygous nonsense mutation (c.706 C > T; p.Q236X) in exon 8 of ctns. Cystinotic mutant larvae showed cystine accumulation, delayed development, and signs of pronephric glomerular and tubular dysfunction mimicking the early phenotype of human cystinotic patients. Furthermore, cystinotic larvae showed a significantly increased rate of apoptosis that could be ameliorated with cysteamine, the human cystine depleting therapy. Our data demonstrate that, ctns gene is essential for zebrafish pronephric podocyte and proximal tubular function and that the ctns-mutant can be used for studying the disease pathogenic mechanisms and for testing novel therapies for cystinosis.

Cysteamine-bicalutamide combination treatment restores alpha-ketoglutarate and corrects proximal tubule phenotype in cystinosis

“…To extend our knowledge on the beneficial effect of the combination treatment and bring the therapy one step closer to clinical application, we evaluated the safety and efficacy in patient- phenotype, allowing to develop a personalized medicine 28 . The ctns −/− zebrafish, on the other hand, is a robust and versatile model of cystinosis with early phenotypic characteristics of the disease that can be used for the in vivo screening of novel therapeutic agents 29,30 . The fact that the improved cystine lowering-efficacy of the combination treatment could be reproduced in tubuloids from two different patients and in cystinotic zebrafish, underlines the robustness of these findings and increases the likelihood that this treatment can be successfully extrapolated to cystinosis patients in general.…”

“…improves survival of cystinotic zebrafish. Finally, we assessed the combination therapy in cystinotic zebrafish, a well-characterized in vivo model of cystinosis 29,30 . Cystinotic zebrafish displayed significantly increased levels of cystine, dysmorphic features, delayed hatching, and reduced survival compared to the controls ( Fig.…”

Molecular Basis of Cystinosis: Geographic Distribution, Functional Consequences of Mutations in the <b><i>CTNS</i></b> Gene, and Potential for Repair

“…Carrying the homozygous nonsense mutation in exon 8 of the ctns, zebrafish larvae demonstrated early cystine accumulation, enhanced deformity, apoptosis and increased mortality, which are partially responsive to cysteamine treatment [48]. Furthermore, the model is characterized by impaired glomerular permselectivity and defective tubular reabsorption.…”

“…A comparison of cystinosis in humans, mice, yeast and zebrafish is presented in Table 3 (adapted from [48]). …”

“…Hence, the zebrafish larval model closely copies the human kidney phenotype for cystinosis and is superior to all model organisms currently available. Therefore, it will be useful to further unravel the pathophysiological aspects of cystinosis and for the in vivo screening of novel therapeutic agents [48].…”