Adhesion molecules are expressed by both adult and embryonic stem cells, with different classes of adhesion molecules involved in cell-membrane and intercellular contacts. In this study the expression of the adhesion molecule claudin-8 (CLDN8), a tight-junction protein, was investigated as a potential marker for undifferentiated spermatogonia in the bovine testis. We found that CLDN8 was expressed by both spermatogonia and a subset of Sertoli cells in the bovine testis. We also showed co-expression of GFRα1 in testis cells with CLDN8 and with 'Dolichos biflorus' agglutinin-fluorescein isothiocyanate (DBA-FITC) staining. We observed co-enrichment of spermatogonia and CLDN8-expressing Sertoli cells in DBA-FITC-assisted magnetic-activated cell sorting (MACS), an observation supported by results from fluorescence-activated cell sorting analysis, which showed CLDN8-expressing cells were over-represented in the MACS-positive cell fraction, leading to the hypothesis that CLDN8 may play a role in the spermatogonial stem-cell niche.

Profilin is a ubiquitously expressed protein involved in the regulation of cell proliferation, apoptosis and motility. In vitro, it is essential in the coordination of actin filament assembly and disassembly. However, the dynamics of profilin in live cells is still largely unknown. The epithelial breast cancer cell line MDA-MB-231 was transfected with wild type GFP-profilin, or GFP-profilin mutants R88A, R88E/R136D, H119E or H133S. These mutations affect the binding of profilin to phosphoinositide lipids, phosphoinositide lipids and actin, actin, or poly-proline rich domains respectively.

Image stacks of the cell membrane were acquired by TIRF microscopy and analysed using image mean square displacement (iMSD) analysis to determine if the diffusion modes (isotropic, confined or transiently confined) and diffusion rates were altered by the perturbation of profilin interactions by the different mutations. The cells were further perturbed by treatment by the actin filament disrupting drugs Cytochalasin D and Latrunculin A, by removal of cholesterol in membrane by methyl-cyclodextrin or by serum starvation.

The diffusion of wild type profilin and the profilin mutations respond in different ways to treatments, giving information not only on profilin dynamics in the cell membrane but also on the structure and organisation of the membrane itself.