Mammalian sperm head formation involves different polarization of two novel LINC complexes.
BACKGROUND
LINC complexes are nuclear envelope bridging protein structures formed by interaction of SUN and KASH proteins. They physically connect the nucleus with the peripheral cytoskeleton and are critically involved in a variety of dynamic processes, such as nuclear anchorage, movement and positioning and meiotic chromosome dynamics. Moreover, they are shown to be essential for maintaining nuclear shape.


RESULTS
Based on detailed expression analysis and biochemical approaches, we show here that during mouse sperm development, a terminal cell differentiation process characterized by profound morphogenic restructuring, two novel distinctive LINC complexes are established. They consist either of spermiogenesis-specific Sun3 and Nesprin1 or Sun1eta, a novel non-nuclear Sun1 isoform, and Nesprin3. We could find that these two LINC complexes specifically polarize to opposite spermatid poles likely linking to sperm-specific cytoskeletal structures. Although, as shown in co-transfection/immunoprecipitation experiments, SUN proteins appear to arbitrarily interact with various KASH partners, our study demonstrates that they actually are able to confine their binding to form distinct LINC complexes.


CONCLUSIONS
Formation of the mammalian sperm head involves assembly and different polarization of two novel spermiogenesis-specific LINC complexes. Together, our findings suggest that theses LINC complexes connect the differentiating spermatid nucleus to surrounding cytoskeletal structures to enable its well-directed shaping and elongation, which in turn is a critical parameter for male fertility.
Göb
Eva
E
Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany.
Schmitt
Johannes
J
Benavente
Ricardo
R
Alsheimer
Manfred
M
D000595:Amino Acid Sequence; D000818:Animals; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D008540:Meiosis; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D009928:Organ Specificity; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D013077:Sperm Head / Q000378:metabolism*; D013087:Spermatids / Q000378:metabolism; D013091:Spermatogenesis; D013737:Testis / Q000378:metabolism
D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; C485901:Syne1 protein, mouse; C507800:nesprin-3 protein, mouse