RESUMO
The plasma membrane of the mature guinea pig sperm is segregated into at least four domains of different composition. Previous studies have shown that some proteins localized within these domains are free to diffuse laterally, suggesting that barriers to protein diffusion are responsible for maintaining the nonuniform distribution of at least some surface proteins in mature sperm. The different membrane domains appear sequentially during sperm morphogenesis in the testis and during later passage through the epididymis. To determine when diffusion barriers become functional during sperm development, we examined the diffusion of two proteins that are expressed on the cell surface of developing spermatids and become segregated to different plasma membrane domains during the course of spermiogenesis. Both proteins exhibited rapid lateral diffusion throughout spermiogenesis, even after they become localized to specific regions of the surface membrane. These results suggest that barriers to membrane diffusion form concomitantly with membrane domains during spermiogenesis.
Assuntos
Proteínas de Membrana/fisiologia , Espermatogênese/fisiologia , Espermatozoides/citologia , Espermatozoides/fisiologia , Proteínas ADAM , Animais , Anticorpos Monoclonais , Biotina , Membrana Celular/fisiologia , Difusão , Fertilinas , Cobaias , Fragmentos Fab das Imunoglobulinas , Imunoglobulina G , Masculino , Glicoproteínas de Membrana/análise , Proteínas de Membrana/análise , Metaloendopeptidases/análise , Microscopia de Fluorescência/métodos , Espermátides/citologia , Espermátides/fisiologia , Espermatócitos/citologia , Espermatócitos/fisiologia , TestículoRESUMO
Fluorescence microscopic examination coupled with digital videoimage analysis of 4',6-diamidino-2-phenylindole-stained sporulating cells of Bacillus megaterium or Bacillus subtilis revealed a striking condensation of the forespore nucleoid. While both mother cell and forespore compartments had equal amounts of DNA, the forespore nucleoid became greater than 2-fold more condensed than the mother cell nucleoid. The condensation of the forespore nucleoid began after only the first hour of sporulation, 2 to 3 h before expression of most forespore-specific genes including those for small, acid-soluble spore proteins, and was abolished in spo0 mutants but not in spoII or spoIII mutants. It is possible that this striking condensation of forespore DNA plays some role in modulating gene expression during sporulation.
