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Dmitri Serjanov, Galina Bachay, Dale d Hunter, William J Brunken; Laminin β2 and γ3 Chains Regulate Retinal Progenitor Cell Division Polarity and Cell Cycle Dynamic. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1685.
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© ARVO (1962-2015); The Authors (2016-present)
Basement membranes are highly organized extracellular matrices that are important sources of developmental cues. Laminin, a heterotrimeric molecule, is an indispensable organizational component of basement membranes, and mutations in laminin genes lead to dysgenesis of the brain and eye in mice and humans. This study investigates the role of two constituents of CNS laminins, laminin β2 and γ3 chains in the regulation of the retinal progenitor cell polarity and cell cycle dynamics.
Retinae from P3 and P5 WT, laminin β2-/-, laminin γ3-/- and laminin β2-/- γ3-/- mice were used in this study. Immunohistochemistry was performed using centrosomal and mitotic markers. Retinal progenitor cell angles of division were visualized through 3D-reconstruction of the dividing nuclei. Cell cycle lengths were calculated using cumulative EdU saturation method allowing for a determination of the lengths of the cell cycle (TC) and the S phase (TS).
It has been previously shown that deletion of the laminin β2 and γ3 chains results in alteration of the cell cycle of retinal progenitor cells, retinal ganglion cell development, Müller glial cell polarity and photoreceptor development. Here, we demonstrate different cell division dynamics between developmentally older and younger regions of the retina as well as a disruption in laminin mutants. In WT retinae, cell divisions in younger regions are preferentially symmetrical and gradually become more asymmetric as the retina becomes older. In laminin β2-/- and γ3-/- retinae, the divisions in all regions are skewed, with noticeable division abnormalities. There is also a high incidence of centrosomal abnormalities in laminin β2-/-retinae, such as multipolar cells and centrosomes with multiple centrioles. Cell cycle studies in the WT mice revealed longer cell cycle length in the temporal crescent relative to the nasal one. Laminin β2 and γ3 deletions result in alteration of cell cycle progression as shown by lengthening or shortening of TC and TS.
Together with our previous findings, these data suggest that the ILM provides orientation cues and that laminin deletions lead to premature progenitor pool depletion, resulting in overproduction of early-born cells at the expense of later-born ones.
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