Sciurano Roberta B, De Luca Geraldine, Rahn I Mónica, Solari Alberto J
2da. U.A. Biología Celular, Histología, Embriología y Genética, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
Cytogenet Genome Res. 2017;152(3):137-147. doi: 10.1159/000479569. Epub 2017 Aug 25.
The heteromorphic X and Y chromosomes behave in a special way in mammalian spermatocytes; they form the XY body and synapse only partially. The aim of this article was to study the origin and the role of the special differentiations in the XY pair of the domestic cat during pachytene by analyzing its fine structural characteristics and the immunolocalization of the main meiotic proteins SYCP3, SYCP1, SYCE3, SMC3, γ-H2AX, BRCA1, H3K27me3, and MLH1. The cat XY body shows particularly striking structures: an extreme degree of axial fibrillation in late pachynema and a special location of SYCP3-containing fibrils, bridging different regions of the main X axis, as well as one bridge at the inner end of the pairing region that colocalizes with the single mandatory MLH1 focus. There are sequential changes, first bullous expansions, then subdivision into fibrils, all involving axial thickening. The chromatin of the XY body presents the usual features of meiotic sex chromosome inactivation. An analysis of the XY body of many eutherians and metatherians suggests that axial thickenings are primitive features. The sequential changes in the mass and location of SYCP3-containing fibers vary among the clades because of specific processes of axial assembly/disassembly occurring in different species.
异型的X和Y染色体在哺乳动物精母细胞中表现出特殊行为；它们形成XY体，且仅部分联会。本文旨在通过分析家猫粗线期XY染色体对的精细结构特征以及主要减数分裂蛋白SYCP3、SYCP1、SYCE3、SMC3、γ-H2AX、BRCA1、H3K27me3和MLH1的免疫定位，研究其特殊分化的起源和作用。猫的XY体呈现出特别显著的结构：粗线期末期轴向纤维极度纤维化，含SYCP3的纤维有特殊定位，横跨主X轴的不同区域，以及在配对区域内端有一个与单个必需的MLH1焦点共定位的桥。存在连续变化，先是大泡状扩张，然后细分为纤维，所有这些都涉及轴向增厚。XY体的染色质呈现出减数分裂性染色体失活的常见特征。对许多真兽类和后兽类XY体的分析表明，轴向增厚是原始特征。由于不同物种中发生的轴向组装/拆卸的特定过程，含SYCP3纤维的质量和位置的连续变化在不同类群中有所不同。
