?Keratinous? state ofEledone cirrhosa sperm cells and their special nuclear protein

Evolution of octopod sperm I: Comparison of nuclear morphogenesis in Eledone and Octopus

“…This apparent contradiction can be explained from the composition and chemical behavior of the DNA-interacting basic protein (protamine) in Eledone spermiogenesis. In the previous work (Gimenez-Bonafé et al, 1999), we demonstrated two main characteristics for this protein (Table 1). On the one hand, E. cirrhosa protamine displays a lower chemical basicity than does Octopus protamine (arginine þ lysine ¼ 54 mol% in E. cirrhosa, 75 mol% in O. vulgaris).…”

“…This implies that chromatin is still plastic in these stages. On the other hand, the observations of Maxwell (1974), Selmi (1996), andGimenez-Bonafé et al (1999) indicate beyond all doubt that the ripe sperm nucleus in E. cirrhosa is a very rigid, corkscrew-like structure. This apparent contradiction can be explained from the composition and chemical behavior of the DNA-interacting basic protein (protamine) in Eledone spermiogenesis.…”

“…It comprises 43 turns, with a pitch of 1 mm (Maxwell, 1974;Selmi, 1996). Spermiogenic chromatin condensation in Eledone is a more complex process than in decapods and Octopus (Maxwell, 1975), and is driven by a peculiar protamine that is very rich in cysteine residues (Gimenez-Bonafé et al, 1999). Comparing Eledone and Octopus, a situation similar to that described between Octopus and decapods is obtained: the first steps of Eledone spermiogenesis are practically identical to the complete process of spermiogenesis in Octopus.…”

“…It was used for the first time in sperm research by Lin et al (1995). In a previous work (Gimenez-Bonafé et al, 1999), we have demonstrated by MMNA labeling that free thiol groups disappear in E. cirrhosa ripe sperm nuclei. During these experiments, we observed that when the original procedure of Lin et al (1995) is slightly modified by limiting the labelling conditions, MMNA is an excellent marker for microtubules due to the large number of free sulfydryl (ÀSH) groups on cysteine residues of a and b tubulin.…”

“…A set of perinuclear microtubules appears transiently during spermiogenesis that, as in decapods, is not present in the ripe sperm cell (Longo and Anderson, 1970). Chromatin is condensed into thin fibres by a protamine that displays an amino acid composition similar to that of decapods (Gimenez-Bonafé et al, 1999).…”