True polyploid meiosis in the human male

Abstract Polyploidy does not usually occur in germinal cells of mammals and other higher vertebrates. We describe a unique example of mosaic autotetraploidy in the meiosis of a human male. Although the original observations were made in the late 1960s, we did not publish them at that time, because we expected to detect further examples that could be described together. However, this did not occur and we have now decided to make the observations available to demonstrate that polyploidy in mammalian male meiosis can arise at a higher frequency than expected by random polyploidization of individual meiotic cells, by either DNA duplication or cell fusion prior to synapsis. This is the first description of a population of primary spermatocytes exhibiting multivalent formation at leptotene /diakinesis in human spermatogenesis, with ring, chain, frying pan and other types of quadrivalents, typical of autotetraploidy. As many of the polyploid configurations showed apoptotic breakdown, it is likely that diploid and/or aneuploid spermatozoa would have rarely or never resulted from this mosaic autotetraploid meiosis.

摘要 多倍体（Polyploidy）通常不会出现于哺乳动物及其他高等脊椎动物的生殖细胞（germinal cells）中。本文报道了一例罕见的人类男性减数分裂（meiosis）中的镶嵌式同源四倍体（autotetraploidy）现象。尽管原始观测工作于20世纪60年代末完成，但我们当时并未发表相关结果，因曾期望能找到更多可一并报道的类似案例。但后续并未发现更多此类案例，因此我们决定将本次观测结果公开发表，以证实哺乳动物雄性减数分裂中的多倍体现象，其发生频率高于随机多倍化（polyploidization）所致的预期水平；该随机多倍化指的是在联会（synapsis）前，经由DNA复制或细胞融合引发的单个减数分裂细胞的多倍化过程。这是首次在人类精子发生（spermatogenesis）过程中，报道一类在细线期（leptotene）/终变期（diakinesis）阶段呈现多价体形成（multivalent formation）的初级精母细胞（primary spermatocytes）群体，其包含环状、链状、煎锅状等典型同源四倍体特征的四价体（quadrivalents）结构。由于多数多倍体构型均发生了凋亡性降解（apoptotic breakdown），因此由该镶嵌式同源四倍体减数分裂所产生的二倍体（diploid）和/或非整倍体（aneuploid）精子（spermatozoa），极有可能极少甚至从未形成。