Saperas N, Ribes E, Buesa C, García-Hegart F, Chiva M
Institut de Ciències del MAR, CSIC, Barcelona (N.S.), Spain.
J Exp Zool. 1993 Feb 1;265(2):185-94. doi: 10.1002/jez.1402650210.
The sperm cells of Mullus surmuletus (family Mullidae, order Perciformes) and Dicentrarchus labrax (family Percichthyidae, order Perciformes) belong respectively to "type I" and "type II" spermiogenesis categorized by Mattei ('70). The protein content in their sperm nuclei consists of two histone-like proteins (Mullus surmuletus) and one typical protamine (D. labrax). In order to correlate the molecular characteristics of these proteins with their function, we have analyzed the molecules in detail and studied at the ultrastructural level the condensation of chromatin during the spermiogenesis in both species. D. labrax has a true protamine of 34 amino acid residues and its sequence (PR4QASRPVR5TR2STAER5V2R4) contains four arginine clusters. The sperm proteins of M. surmuletus contain 110 and 115 amino acid residues and , by their composition (23-24% Lys, 21-22% Arg, 11-12% Ala), they are similar to protamine-like molecules from sperm of molluscs. During the spermiogenesis of D. Labrax, chromatin condensation progresses from small fibro-granular structures (25 +/- 5 nm in diameter), to larger granules (150 +/- 50 nm diameter). M. surmuletus accumulates 25 +/- 5 nm diameter structures in the basal pole of the nucleus; these structures grow till they reach a diameter of 50 +/- 10 nm and finally go through a process of fusion that changes the condensation of chromatin in sperm nuclei, acquiring a homogeneous aspect. These observations show that during spermiogenesis in the studied types, the last stages of chromatin condensation are dependent on the type of nuclear proteins.
灰鳍鲷（鲷科，鲈形目）和欧洲鲈（鲈科，鲈形目）的精子细胞分别属于马泰（1970年）分类的“ I型”和“ II型”精子发生类型。它们精子细胞核中的蛋白质成分分别由两种组蛋白样蛋白（灰鳍鲷）和一种典型的鱼精蛋白（欧洲鲈）组成。为了将这些蛋白质的分子特征与其功能联系起来，我们详细分析了这些分子，并在超微结构水平上研究了这两个物种精子发生过程中染色质的凝聚情况。欧洲鲈有一种由34个氨基酸残基组成的真正鱼精蛋白，其序列（PR4QASRPVR5TR2STAER5V2R4）包含四个精氨酸簇。灰鳍鲷的精子蛋白含有110和115个氨基酸残基，从其组成来看（23 - 24%的赖氨酸、21 - 22%的精氨酸、11 - 12%的丙氨酸），它们类似于软体动物精子中的类鱼精蛋白分子。在欧洲鲈精子发生过程中，染色质凝聚从小的纤维颗粒结构（直径25±5纳米）发展到较大的颗粒（直径150±50纳米）。灰鳍鲷在细胞核的基部积累直径为25±5纳米的结构；这些结构不断生长，直到直径达到50±10纳米，最终经历一个融合过程，这个过程改变了精子细胞核中染色质的凝聚状态，使其呈现出均匀的外观。这些观察结果表明，在所研究的精子发生类型中，染色质凝聚的最后阶段取决于核蛋白的类型。
