Biology subjects

Sharkova, M.

Publications and source records attributed to Sharkova, M..

2 recordsLinked to original sources

bioRxiv2023

Development and characteristics of photoreceptor actin-based apical processes in zebrafish (Danio rerio)

Vertebrate photoreceptors detect light through a large cilium-based outer segment, which is filled with photopigment-laden membranous discs. Surrounding the base of the outer segment are microvilli-like calyceal processes (CPs). While CP disruption has been associated with altered outer segment morphology and photoreceptor degeneration, the role of the processes remains elusive. Here, we used zebrafish as a model to characterize CPs. We quantified CP parameters and report a strong disparity in outer segment coverage between photoreceptor subtypes. CP length is stable across light and dark conditions, while heat shock inducible expression of tagged actin revealed rapid turnover of the CP actin core. Detailed imaging of the embryonic retina uncovered substantial remodeling of the developing photoreceptor apical surface, including a transition from dynamic tangential processes to vertically-oriented CPs immediately prior to outer segment formation. Remarkably, we also found a direct connection between apical extensions of the Muller glia and retinal pigment epithelium, arranged as bundles around the ultraviolet sensitive cones. In summary, our data characterize the structure, development, and surrounding environment of photoreceptor microvilli in the zebrafish retina.

cell biology↗

bioRxiv2020

Myogenin controls via AKAP6 non-centrosomal microtubule organizing center formation at the nuclear envelope

Non-centrosomal microtubule organizing centers (MTOC) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in myoblasts for the localization of MTOC proteins to the nuclear envelope. Moreover, myogenin is sufficient in fibroblasts for nuclear envelope MTOC (NE-MTOC) formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated NE-MTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and NE-MTOC-specific isoforms of Akap6 and Syne1, which encodes nesprin-1, the NE-MTOC anchor protein in muscle cells. Overexpression of AKAP6{beta} and nesprin-1 was sufficient to recruit endogenous MTOC proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an NE-MTOC and identify AKAP6 as a novel NE-MTOC component in muscle cells.

cell biology↗