Expression of individual mammalian Sun1 isoforms depends on the cell type

Abstract

Mammalian Sun1 belongs to an evolutionarily conserved family of inner nuclear membrane proteins, which are known as SUN domain proteins. SUN domain proteins interact with KASH domain partners to form bridging complexes, so-called LINC complexes, that physically connect the nuclear interior to the cytoskeleton. LINC complexes are critical for nuclear integrity and play fundamental roles in nuclear positioning, shaping and movement. The mammalian genome codes for at least five different SUN domain proteins used for the formation of a number of different LINC complexes. Recently, we reported on the identification of several Sun1 isoforms, which tremendously enlarges the alternatives to form functional LINC complexes. We now confirmed that Sun1 actually exists in at least seven distinct splice variants. Besides that, we observed that expression of individual Sun1 isoforms remarkably depends on the cell type, suggesting a cell type-specific adaption of Sun1 dependent LINC complexes to specific cellular and physiological requirements.

This article refers to:

Acknowledgments

This study was supported by the German Research Foundation (DFG; grant Al 1090/1-1), the Graduate School GK 1048 of the University of Würzburg and by the funding programme Open Access Publishing of the DFG and the University of Würzburg.

Figures and Tables

Figure 1 Differential expression of murine Sun1 isoforms. (A) Presence of different Sun1 isoforms in selected mouse tissues was analyzed by RT-PCR. To amplify the recently described N-terminal Sun1 variants with deletions between exon 7 and 10, primers were selected which specifically annealed in exon 6 and exon 11 (forward: 5′-CAG CAA TGG ATA CAC TT G CCG TG-3′; reverse: 5′-CCA GAA GGT TCC CGA GGC TG-3′; annealing at 60°C; 30 cycles). Amplification of GAPDH served as control for RN A fidelity (forward: 5′-GGG CCC ACT TGA AGG GTG GAG C-3′; reverse: 5′-GGC ACC ATA AAG AAT GTT CTA TTT CCT TGG ATC C-3′; annealing at 58°C; 25 cycles). (B) Schematic illustration of the mouse Sun1 isoforms as yet identified. Triangles mark positions of deleted exons. INM , inner nuclear membrane; ONM outer nuclear membrane; AM acrosomal membrane; ZnF, zinc finger; H1, H2, H3, hydrophobic domains; TM , transmembranen domain; CC, coiled coil domain.

Addendum to: