The gene coding for centrosomal protein 290 (CEP290), a large multidomain protein, is the most frequently mutated gene underlying the non-syndromic blinding disorder Leber's congenital amaurosis (LCA). CEP290 has also been implicated in several cilia-related syndromic disorders including Meckel–Gruber syndrome, Joubert syndrome, Senor–Loken syndrome and Bardet–Biedl syndrome (BBS). In this study, we characterize the developmental and functional roles of cep290 in zebrafish. An antisense oligonucleotide [Morpholino (MO)], designed to generate an altered cep290 splice product that models the most common LCA mutation, was used for gene knockdown. We show that cep290 MO-injected embryos have reduced Kupffer's vesicle size and delays in melanosome transport, two phenotypes that are observed upon knockdown of bbs genes in zebrafish. Consistent with a role in cilia function, the cep290 MO-injected embryos exhibited a curved body axis. Patients with LCA caused by mutations in CEP290 have reduced visual perception, although they present with a fully laminated retina. Similarly, the histological examination of retinas from cep290 MO-injected zebrafish revealed no gross lamination defects, yet the embryos had a statistically significant reduction in visual function. Finally, we demonstrate that the vision impairment caused by the disruption of cep290 can be rescued by expressing only the N-terminal region of the human CEP290 protein. These data reveal that a specific region of the CEP290 protein is sufficient to restore visual function and this region may be a viable gene therapy target for LCA patients with mutations in CEP290.
Force loss in skeletal muscle exposed to eccentric contraction is often attributed to injury. We show that EDL muscles from dystrophin-deficient mdx mice recover 65% of lost force within 120 min of eccentric contraction and exhibit minimal force loss when the interval between contractions is increased from 3 to 30 min. A proteomic screen of mdx muscle identified an 80% reduction in the antioxidant peroxiredoxin-2, likely due to proteolytic degradation following hyperoxidation by NADPH Oxidase 2. Eccentric contraction-induced force loss in mdx muscle was exacerbated by peroxiredoxin-2 ablation, and improved by peroxiredoxin-2 overexpression or myoglobin knockout. Finally, overexpression of γcyto- or βcyto-actin protects mdx muscle from eccentric contraction-induced force loss by blocking NADPH Oxidase 2 through a mechanism dependent on cysteine 272 unique to cytoplasmic actins. Our data suggest that eccentric contraction-induced force loss may function as an adaptive circuit breaker that protects mdx muscle from injurious contractions.
The highly similar cytoplasmic β- and γ-actins differ by only four functionally similar amino acids, yet previous in vitro and in vivo data suggest that they support unique functions due to striking phenotypic differences between and null mouse and cell models. To determine whether the four amino acid variances were responsible for the functional differences between cytoplasmic actins, we gene edited the endogenous mouse locus to translate γ-actin protein. The resulting mice and primary embryonic fibroblasts completely lacked β-actin protein, but were viable and did not present with the most overt and severe cell and organismal phenotypes observed with gene knockout. Nonetheless, the edited mice exhibited progressive high-frequency hearing loss and degeneration of actin-based stereocilia as previously reported for hair cell-specific knockout mice. Thus, β-actin protein is not required for general cellular functions, but is necessary to maintain auditory stereocilia.
Both gene- and transcript-targeted ablations of Actb expression demonstrate that βcyto-actin is more disruptive than γcyto-actin to primary fibroblast function. This is evident via a decrease in cell proliferation and cellular ATP and an increase in myofibroblast differentiation signaling and protein expression in Actb-null primary cells.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common genetic defect and enzymopathy worldwide, affecting approximately 400 million people and causing acute hemolysis in persons exposed to prooxidant compounds such as menthol, naphthalene, anti-malarial drugs, and fava beans. Mouse models have not been useful because of a lack of significant response to oxidative challenge. We turned to zebrafish (Danrio rerio) embryos, which develop ex utero and are transparent, allowing visualization of hemolysis. We designed morpholinos to zebrafish g6pd that were effective in reducing gene expression as shown by Western blot and G6PD enzyme activity, resulting in a brisk hemolysis and pericardial edema secondary to anemia. Titration of the g6pd knockdown allowed us to generate embryos that displayed no overt phenotype until exposed to the prooxidant compounds 1-naphthol, menthol, or primaquine, after which they developed hemolysis and pericardial edema within 48–72 hours. We were also able to show that g6pd morphants displayed significant levels of increased oxidative stress compared with controls. We anticipate that this will be a useful model of G6PD deficiency to study hemolysis as well as oxidative stress that occurs after exposure to prooxidants, similar to what occurs in G6PD-deficient persons.
In mammals, stromal cell-derived factor-1 (SDF-1) promotes hematopoietic cell mobilization and migration. Although the zebrafish, Danio rerio, is an emerging model for studying hematopoietic cell transplantation (HCT), the role of SDF-1 in the adult zebrafish has yet to be determined. We sought to characterize sdf-1 expression and function in the adult zebrafish in the context of HCT. In situ hybridization of adult zebrafish organs shows sdf-1 expression in kidney tubules, gills, and skin. Radiation up-regulates sdf-1 expression in kidney to nearly 4-fold after 40 Gy. Assays indicate that zebrafish hematopoietic cells migrate toward sdf-1, with a migration ratio approaching 1.5 in vitro. A sdf-1a:DsRed2 transgenic zebrafish allows in vivo detection of sdf-1a expression in the adult zebrafish. Matings with transgenic reporters localized sdf-1a expression to the putative hematopoietic cell niche in proximal and distal renal tubules and collecting ducts. Importantly, transplant of hematopoietic cells into myelosuppressed recipients indicated migration of hematopoietic cells to sdf-1a-expressing sites in the kidney and skin. We conclude that sdf-1 expression and function in the adult zebrafish have important similarities to mammals, and this sdf-1 transgenic vertebrate will be useful in characterizing the hematopoietic cell niche and its interactions with hematopoietic cells. (Blood. 2011;118(3):766-774) IntroductionThe zebrafish, Danio rerio, is emerging as a useful model organism for the study of hematopoietic cell transplantation (HCT). 1,2 Its fecundity makes high experimental sample numbers logistically feasible, it is amenable to high-throughput chemical screens for hematopoietic effects of drugs and small molecules, 3 and its optical transparency offers excellent opportunities for direct visualization of cell migration events and in vivo fluorescence detection of donor-derived hematopoietic reconstitution. The true extent to which the zebrafish will prove useful for experimental HCT studies, however, will ultimately depend on the degree to which the mechanisms that result in HCT success in mammals are conserved in the zebrafish.In mammals, the chemokine stromal cell-derived factor-1 (SDF-1; CXCL12) and its cognate receptor CXCR4 have been strongly implicated in the homing and reconstitution that that occurs during HCT. 4-6 SDF-1 is expressed in many organs throughout the body, including the spleen, thymus, skin, heart, lung, kidney, and bone marrow. 7,8 The widespread anatomic distribution of SDF-1 expression has been shown to play roles in diverse migration and retention events of a wide array of hematopoietic cells, including migration of mast cell precursors in the skin, 9 retention of myeloid cells in extramedullary locations, 10 migration of megakaryocytes in the bone marrow after radiation, 11 migration of hematopoietic stem cells (HSCs) to regions of injury, 12 and HSC migration to bone marrow both during homeostasis as well as during HCT. 13,14 In the bone marrow cavity, cells expressing high levels o...
There is accumulating evidence that mesenchymal stem cells (MSC) have their origin as perivascular cells (PVC) in vivo, but precisely identifying them has been a challenge, as they have no single definitive marker and are rare. We have developed a fluorescent transgenic vertebrate model in which PVC can be visualized in vivo based upon sdf1 expression in the zebrafish. Prospective isolation and culture of sdf1DsRed PVC demonstrated properties consistent with MSC including prototypical cell surface marker expression; mesodermal differentiation into adipogenic, osteogenic and chondrogenic lineages; and the ability to support hematopoietic cells. Global proteomic studies performed by 2-dimensional liquid chromatography and tandem mass spectrometry revealed a high degree of similarity to human MSC and discovery of novel markers (CD99, CD151 and MYOF) that were previously unknown to be expressed by hMSC. Dynamic in vivo imaging during fin regeneration showed that PVC may arise from undifferentiated mesenchyme providing evidence of a PVC – MSC relationship. This is the first model, established in zebrafish, in which MSC can be visualized in vivo and will allow us to better understand their function in a native environment.
Objective The goal of this study was to determine if we could establish a mesenchymal stromal line from zebrafish that would support hematopoietic cells. Such a co-culture system would be a great benefit to study the hematopoietic cell-stromal cell interaction in both the in vitro and in vivo environments. Methods Zebrafish stromal cells, ZStrC, were isolated from the “mesenchymal” tissue of the caudal tail and expanded in a specialized growth media. ZStrC were evaluated for phenotype, gene expression, and the ability to maintain zebrafish marrow cells in co-culture experiments. Results ZStrC showed mesenchymal and endothelial gene expression. Although ZStrC lacked the ability to differentiate into classic MSC lineages (osteocytes, adipocytes, chondrocytes), they did have the capacity for endotube formation on matrigel and LDL-uptake. ZStrC supported marrow cells for greater than 2 weeks in vitro. Importantly, the marrow cells were shown to retain homing ability in adoptive transfer experiments. ZStrC also were shown to improve hematopoietic recovery after sub-lethal irradiation after adoptive transfer. Conclusion As the zebrafish model grows in popularity and importance in the study of hematopoiesis, new tools to aid in our understanding of the hematopoietic cell-stromal cell interaction are required. ZStrC represent an additional tool in the study of hematopoiesis and will be useful to understand the factors that mediate the stromal cell-hematopoietic cell interaction that are important in hematopoietic maintenance.
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