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Regulation of melanosome number, shape and movement in the zebrafish retinal pigment epithelium by OA1 and PMEL.

Burgoyne T, O'Connor MN, Seabra MC, Cutler DF, Futter CE - J. Cell. Sci. (2015)

Bottom Line: We further show that PMEL, a key component of mammalian melanosome biogenesis, is required for the generation of cylindrical melanosomes in zebrafish, which in turn is required for melanosome movement into the apical processes and maintenance of photoreceptor integrity.Spherical and cylindrical melanosomes containing similar melanin volumes co-exist in the cell body but only cylindrical melanosomes enter the apical processes.Taken together, our findings indicate that melanosome number and shape are independently regulated and that melanosome shape controls a function in the RPE that depends on localisation in the apical processes.

View Article: PubMed Central - PubMed

Affiliation: UCL Institute of Ophthalmology, London EC1V 9EL, UK.

No MeSH data available.


Related in: MedlinePlus

Serial section electron microscopy analysis of tyrosinase MO-treated RPE reveals immature melanosomes that contain fibrils. (A–E) Serial section micrographs of the same immature melanosome in an RPE cell from a tyrosinase MO-treated zebrafish at 5 dpf. (F) 3D rendering of the micrograph data reveals fibrils running through the melanosome. Dotted lines indicate the position of the slice shown in the right-hand panel; arrowheads indicate fibrils running through the entire thickness of the melanosome. Scale bars: 100 nm.
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f03: Serial section electron microscopy analysis of tyrosinase MO-treated RPE reveals immature melanosomes that contain fibrils. (A–E) Serial section micrographs of the same immature melanosome in an RPE cell from a tyrosinase MO-treated zebrafish at 5 dpf. (F) 3D rendering of the micrograph data reveals fibrils running through the melanosome. Dotted lines indicate the position of the slice shown in the right-hand panel; arrowheads indicate fibrils running through the entire thickness of the melanosome. Scale bars: 100 nm.

Mentions: Successful MO-mediated tyrosinase depletion was readily identified through diluted skin colour of the embryos (supplementary material Fig. S1) but, at 2 dpf, fibrillar stage II melanosomes could still not be readily identified in the RPE. However, by 5 dpf, when the MO was becoming less effective, the presence of small amounts of melanin made immature melanosomes easy to identify. Within these immature melanosomes, melanin appeared to be deposited as dense spots within the MVB structures, rather than on fibrils (Fig. 3; supplementary material Fig. S3). Initially it was difficult to discern whether the spots were ILVs surrounded by melanin or PMEL fibrils running into the depth of the section. Utilising serial section electron microscopy, the dense melanin spots were revealed as fibrils running perpendicular to the plane of view (Fig. 3; supplementary material Fig. S3), suggesting that, as has been described in mammalian RPE, melanin is deposited on fibrils in immature melanosomes. Indeed, on the rare occasions when an immature melanosome was sectioned parallel to the longitudinal axis, fibrils on which melanin had been deposited could be discerned, and so these resembled stage III melanosomes (supplementary material Fig. S3). It is noteworthy that melanin in immature fibrillar melanosomes in mouse RPE appears as dense spots in melanosomes sectioned perpendicular to the fibrils (supplementary material Fig. S2).


Regulation of melanosome number, shape and movement in the zebrafish retinal pigment epithelium by OA1 and PMEL.

Burgoyne T, O'Connor MN, Seabra MC, Cutler DF, Futter CE - J. Cell. Sci. (2015)

Serial section electron microscopy analysis of tyrosinase MO-treated RPE reveals immature melanosomes that contain fibrils. (A–E) Serial section micrographs of the same immature melanosome in an RPE cell from a tyrosinase MO-treated zebrafish at 5 dpf. (F) 3D rendering of the micrograph data reveals fibrils running through the melanosome. Dotted lines indicate the position of the slice shown in the right-hand panel; arrowheads indicate fibrils running through the entire thickness of the melanosome. Scale bars: 100 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4379728&req=5

f03: Serial section electron microscopy analysis of tyrosinase MO-treated RPE reveals immature melanosomes that contain fibrils. (A–E) Serial section micrographs of the same immature melanosome in an RPE cell from a tyrosinase MO-treated zebrafish at 5 dpf. (F) 3D rendering of the micrograph data reveals fibrils running through the melanosome. Dotted lines indicate the position of the slice shown in the right-hand panel; arrowheads indicate fibrils running through the entire thickness of the melanosome. Scale bars: 100 nm.
Mentions: Successful MO-mediated tyrosinase depletion was readily identified through diluted skin colour of the embryos (supplementary material Fig. S1) but, at 2 dpf, fibrillar stage II melanosomes could still not be readily identified in the RPE. However, by 5 dpf, when the MO was becoming less effective, the presence of small amounts of melanin made immature melanosomes easy to identify. Within these immature melanosomes, melanin appeared to be deposited as dense spots within the MVB structures, rather than on fibrils (Fig. 3; supplementary material Fig. S3). Initially it was difficult to discern whether the spots were ILVs surrounded by melanin or PMEL fibrils running into the depth of the section. Utilising serial section electron microscopy, the dense melanin spots were revealed as fibrils running perpendicular to the plane of view (Fig. 3; supplementary material Fig. S3), suggesting that, as has been described in mammalian RPE, melanin is deposited on fibrils in immature melanosomes. Indeed, on the rare occasions when an immature melanosome was sectioned parallel to the longitudinal axis, fibrils on which melanin had been deposited could be discerned, and so these resembled stage III melanosomes (supplementary material Fig. S3). It is noteworthy that melanin in immature fibrillar melanosomes in mouse RPE appears as dense spots in melanosomes sectioned perpendicular to the fibrils (supplementary material Fig. S2).

Bottom Line: We further show that PMEL, a key component of mammalian melanosome biogenesis, is required for the generation of cylindrical melanosomes in zebrafish, which in turn is required for melanosome movement into the apical processes and maintenance of photoreceptor integrity.Spherical and cylindrical melanosomes containing similar melanin volumes co-exist in the cell body but only cylindrical melanosomes enter the apical processes.Taken together, our findings indicate that melanosome number and shape are independently regulated and that melanosome shape controls a function in the RPE that depends on localisation in the apical processes.

View Article: PubMed Central - PubMed

Affiliation: UCL Institute of Ophthalmology, London EC1V 9EL, UK.

No MeSH data available.


Related in: MedlinePlus