The Loss of Vacuolar Protein Sorting 11 (vps11) Causes Retinal Pathogenesis in a Vertebrate Model of Syndromic Albinism

Abstract

PURPOSE.To establish the zebrafish platinum mutant as a model for studying vision defects caused by syndromic albinism diseases such as Chediak-Higashi syndrome, Griscelli syndrome, and Hermansky-Pudlak syndrome (HPS). METHODS. Bulked segregant analysis and candidate gene sequencing revealed that the zebrafish platinum mutation is a single-nucleotide insertion in the vps11 (vacuolar protein sorting 11) gene. Expression of vps11 was determined by RT-PCR and in situ hybridization. Mutants were analyzed for pigmentation defects and retinal disease by histology, immunohistochemistry, and transmission electron microscopy. RESULTS. Phenocopy and rescue experiments determined that a loss of Vps11 results in the platinum phenotype. Expression of vps11 appeared ubiquitous during zebrafish development, with stronger expression in the developing retina and retinal pigmented epithelium (RPE). Zebrafish platinum mutants exhibited reduced pigmentation in the body and RPE; however, melanophore development, migration, and dispersion occurred normally. RPE, photoreceptors, and inner retinal neurons formed normally in zebrafish platinum mutants. However, a gradual loss of RPE, an absence of mature melanosomes, and the subsequent degradation of RPE/photoreceptor interdigitation was observed. CONCLUSIONS. These data show that Vps11 is not necessary for normal retinal development or initiation of melanin biosynthesis, but is essential for melanosome maturation and healthy maintenance of the RPE and photoreceptors. (Invest Ophthalmol Vis Sci. 2011;52:3119 -3128)

Maintenance of Melanophore Morphology and Survival Is Cathepsin and vps11 Dependent in Zebrafish

“…Fine mapping analysis, narrowed the region to 53kilobases, containing the ift46 , vps11 and hyou1 genes (Figure 2A). Previous studies examining vps11 medaka and zebrafish ( platinum ) mutants indicated hypopigmentation phenotypes very similar to the integrity mutant [10], [11]. Based on these previous findings, we sequenced the vps11 gene in mutant larvae.…”

“…The following alleles were used: vps11 w66 , kit w34 [15] and WIK for mapping. platinum zebrafish were used for complementation and zVAD-fmk melanophore quantification analysis [11].…”

“…vps11 null mutations cause endosomal/vacuolar (homologous to mammalian lysosomes) delivery defects in yeast [9]. vps11 function has also been analyzed in model organisms, Oryzias latipes medaka [10] and most recently, in Danio rerio zebrafish [11]. Although vps11 mutations are lethal in both organisms, larvae live long enough to examine pigmentation defects.…”

Hypomyelination and developmental delay associated withVPS11mutation in Ashkenazi-Jewish patients

“…The fourth spaced cysteine residue is the mutated residue in our patients. Loss of Vps11 in zebrafish manifests by oculocutaneous albinism, pericardial oedema, hepatomegaly and premature death underscoring Vps11 role in the fish melanosome maturation 20. Studies in various yeast mutants revealed that Vps11 is an essential component of the endosomal system;21 vps11 Δ null mutants exhibited defects in endosomal and vacuolar delivery and in late endosome and vacuole fusion.…”

The vacuole within

“…Here we benefited from previous work that identified several mutants in genes encoding members of the HOPS (homotypic fusion and vacuole protein sorting) complex and V-H + -ATPase complexes. [7][8][9] We found that both the HOPS complex genes vps11 and vps18, Another area of interest is investigating how vacuole expansion and final size are determined. The rigid ECM encasing the notochord ultimately restricts the expansion of the single vacuole within inner cells.…”