Overexpression of Flii during Murine Embryonic Development Increases Symmetrical Division of Epidermal Progenitor Cells.

Gink N Yang,Xanthe L Strudwick,Allison J Cowin,Zlatko Kopecki,Parinaz Ahangar

doi:10.3390/ijms22158235

Gink N Yang, Xanthe L Strudwick + Show 3 more

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https://doi.org/10.3390/ijms22158235

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Abstract

Epidermal progenitor cells divide symmetrically and asymmetrically to form stratified epidermis and hair follicles during late embryonic development. Flightless I (Flii), an actin remodelling protein, is implicated in Wnt/β-cat and integrin signalling pathways that govern cell division. This study investigated the effect of altering Flii on the divisional orientation of epidermal progenitor cells (EpSCs) in the basal layer during late murine embryonic development and early adolescence. The effect of altering Flii expression on asymmetric vs. symmetric division was assessed in vitro in adult human primary keratinocytes and in vivo at late embryonic development stages (E16, E17 and E19) as well as adolescence (P21 day-old) in mice with altered Flii expression (Flii knockdown: Flii+/−, wild type: WT, transgenic Flii overexpressing: FliiTg/Tg) using Western blot and immunohistochemistry. Flii+/− embryonic skin showed increased asymmetrical cell division of EpSCs with an increase in epidermal stratification and elevated talin, activated-Itgb1 and Par3 expression. FliiTg/Tg led to increased symmetrical cell division of EpSCs with increased cell proliferation rate, an elevated epidermal SOX9, Flap1 and β-cat expression, a thinner epidermis, but increased hair follicle number and depth. Flii promotes symmetric division of epidermal progenitor cells during murine embryonic development.

Highlights

To investigate if Flightless I (Flii) plays a role in the division orientation of proliferative keratinocytes, the division pattern of primary keratinocytes isolated from Flii+/−, WT and FliiTg/Tg epidermis were characterized by BrdU-cytochalasin D (cytD) assay
A significantly increased percentage of symmetric cell division (SCD) was found in FliiTg/Tg primary keratinocytes when compared to Flii+/− and WT counterparts (Figure 1C)
Previous studies have described a role for Sex-Determining Region Y-Box 9 Protein (SOX9) in promoting cell proliferation, so we investigated if proliferating cell nuclear antigen expression (PCNA) expression was different between Flii mice genotypes during epidermal development (Figure 5A,C)

Summary

Introduction

The formation of the epidermis begins at E9.5 and from E14 onwards, asymmetric basal cell division occurs with cells dividing perpendicular to the basement membrane and this is maintained until birth when the epidermis is fully mature [6] Established through this stratification of the developing epidermis, the skin barrier is formed at E16.5 in Balb/c mice [8]. Beginning at E14.5, ACD is adopted by developing EpSCs in the basal layer to form hair placodes while generating progenies retaining the adult stem cell features [7] These placodes interact with the dermal papilla, which develops into hair pegs that continue to mature into hair follicles at E18.5 and become fully functional with the ability to produce hair fibre at P21 in rodents [9,10]

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