Renal and Extra Renal Manifestations in Adult Zebrafish Model of Cystinosis

Abstract

Cystinosis is a rare, incurable, autosomal recessive disease caused by mutations in the CTNS gene. This gene encodes the lysosomal cystine transporter cystinosin, leading to lysosomal cystine accumulation in all cells of the body, with kidneys being the first affected organs. The current treatment with cysteamine decreases cystine accumulation, but does not reverse the proximal tubular dysfunction, glomerular injury or loss of renal function. In our previous study, we have developed a zebrafish model of cystinosis through a nonsense mutation in the CTNS gene and have shown that zebrafish larvae recapitulate the kidney phenotype described in humans. In the current study, we characterized the adult cystinosis zebrafish model and evaluated the long-term effects of the disease on kidney and extra renal organs through biochemical, histological, fertility and locomotor activity studies. We found that the adult cystinosis zebrafish presents cystine accumulation in various organs, altered kidney morphology, impaired skin pigmentation, decreased fertility, altered locomotor activity and ocular anomalies. Overall, our data indicate that the adult cystinosis zebrafish model reproduces several human phenotypes of cystinosis and may be useful for studying pathophysiology and long-term effects of novel therapies.

Fertility in Cystinosis

“…In an attempt to find a more suitable animal model for cystinosis, zebrafish were proposed as an alternative [ 37 , 38 ]. In a study by Berlingerio et al, the authors found that both male and female Ctns −/− zebrafish were fertile.…”

“…In a study by Berlingerio et al, the authors found that both male and female Ctns −/− zebrafish were fertile. However, female Ctns −/− zebrafish showed reduced egg production and percentage of fertilized eggs compared to wild-type zebrafish [ 38 ]. In addition, a histological analysis of the testicular tissue showed the accumulation of spermatozoa in the spermatogenic cysts when compared to wild-type zebrafish [ 38 ].…”

“…However, female Ctns −/− zebrafish showed reduced egg production and percentage of fertilized eggs compared to wild-type zebrafish [ 38 ]. In addition, a histological analysis of the testicular tissue showed the accumulation of spermatozoa in the spermatogenic cysts when compared to wild-type zebrafish [ 38 ]. Interestingly, the accumulation of spermatozoa in the spermatogenic cysts could be a sign of obstruction, which potentiate the hypothesis that azoospermia in male infantile cystinosis patients is obstructive in origin.…”

In Vitro and In Vivo Models to Study Nephropathic Cystinosis

“…Follow-on analysis of adult ctns -/- zebrafish found that the highest level of cystine accumulation was in the kidney [ 98 ]. This result differs from C57BL/6 Ctns -/- mice where greatest cystine loading is seen in the liver and spleen.…”

“…However, the zebrafish mesonephric kidney is also the site of hematopoiesis, which may explain the species difference [ 95 ]. Surprisingly, adult ctns -/- zebrafish do not show podocyte foot process effacement and only a mild enlargement of Bowman’s capsule and the glomerular tuft [ 98 ]. This difference compared to the larval mutants may be related to differences in glomerular filtration rates, as larval zebrafish have a single glomerulus that may operate under greater stress compared to adult glomeruli.…”