Expression of the tetraspanin family members Tspan3, Tspan4, Tspan5 and Tspan7 during Xenopus laevis embryonic development.

Tetraspanins comprise a large family of integral membrane proteins involved in the regulation of cell adhesion, migration and fusion. In humans it consists of 33 members divided in four subfamilies. Here, we examined the spatial and temporal gene expression of four related tetraspanins during the embryonic development of Xenopus laevis by quantitative real-time PCR and in situ hybridization: Tspan3 (encoded by the gene Tm4sf8 gene) Tspan4 (encoded by the gene Tm4sf7), Tspan5 (encoded by the gene Tm4sf9) and Tspan7 (encoded by the gene Tm4sf2). These genes appeared first in the vertebrates during the evolution and are conserved across different species. In humans, they were associated with several diseases such as sclerosis, mental retardation and cancer; however their physiological role remained unclear. This work provides a comprehensive comparative analysis of the expression of these tetraspanins during the development of X. laevis. The more closely related tetraspanins Tspan3, Tspan4 and Tspan7 exhibited very similar spatial expression patterns, albeit differing in their temporal occurrence. The corresponding transcripts were found in the dorsal animal ectoderm at blastula stage. At early tailbud stages (stage 26) the genes were expressed in the migrating cranial neural crest located in the somites, developing eye, brain, and in otic vesicles. In contrast, Tspan5 appeared first at later stages of development and was detected prominently in the notochord. These data support close relatedness of Tspan3, Tspan4 and Tspan7. The expression of these tetraspanins in the cells with a high migratory potential, e.g. neural crest cells, suggests their role in the regulation of migration processes, characteristic for tetraspanin family members, during development. Similarity of the expression profiles might indicate at least partial functional redundancy, which is in concordance with earlier findings of tissue-limited or absent phenotypes in the knock-down studies of tetraspanins family members performed.