Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan, PR China.
Mol Reprod Dev. 2011 Feb;78(2):139-47. doi: 10.1002/mrd.21278.
The histone H3.3 chaperone HIRA is essential for chromatin assembly during male pronucleus formation in Drosophila. However, the role of HIRA during fertilization in vertebrates remains unclear. The gibel carp (Carassius auratus gibelio) is a unique gynogenetic crucian carp (gyno-carp). Heterologous sperm nuclei cannot decondense when incorporated in the egg, thus the eggs produce a clonal lineage of all females by typical gynogenesis. In contrast, after entering the egg, homologous sperm can undergo decondensation and sexual reproduction is activated, which may produce both female and male offspring. Therefore, this fish is a useful model for studying the mechanisms of fertilization. Herein, we first compared HIRA expression during embryogenesis between gyno-carp and the gonochoristic color crucian carp (Carassius auratus; gono-carp). In gono-carp, a dramatic reduction of HIRA protein occurs shortly after fertilization, whereas HIRA protein is consistently expressed during embryogenesis of gyno-carp. Next, we used immunodepletion and an in vitro sperm decondensation system, and found that complete removal of HIRA inhibited sperm decondensation in both of the fish. Immunofluorescence localization showed that in the condensed sperm nuclei of gono-carp incubated in gyno-carp egg extracts, HIRA was detected, but neither the histone H2A variant H2af1o nor acetylated histone H4 was observed. These results suggest that HIRA may be a critical factor required for sperm nucleus decondensation, while the defect in deposition of some maternal histones in the sperm nucleus could be one reason why heterologous sperm cannot decondense in the gibel carp egg.
组蛋白 H3.3 伴侣 HIRA 对于果蝇雄原核形成过程中的染色质组装是必不可少的。然而，HIRA 在脊椎动物受精过程中的作用尚不清楚。吉富罗非鱼（Carassius auratus gibelio）是一种独特的雌核发育鲫鱼（gyno-carp）。异源精子核不能在卵中去浓缩，因此卵通过典型的雌核发育产生完全雌性的克隆系。相比之下，同源精子进入卵后可以经历去浓缩并激活有性生殖，这可能产生雌性和雄性后代。因此，这种鱼是研究受精机制的有用模型。在此，我们首先比较了雌核发育的吉富罗非鱼和两性发育的彩鲫（Carassius auratus；gono-carp）胚胎发育过程中的 HIRA 表达。在 gono-carp 中，HIRA 蛋白在受精后不久急剧减少，而 HIRA 蛋白在雌核发育的吉富罗非鱼中持续表达。接下来，我们使用免疫耗竭和体外精子去浓缩系统，发现完全去除 HIRA 抑制了两种鱼精子的去浓缩。免疫荧光定位显示，在孵育于吉富罗非鱼卵提取物中的 gono-carp 浓缩精子核中，检测到 HIRA，但未检测到组蛋白 H2A 变体 H2af1o 或乙酰化组蛋白 H4。这些结果表明，HIRA 可能是精子核去浓缩所必需的关键因素，而精子核中某些母体组蛋白的沉积缺陷可能是异源精子不能在吉富罗非鱼卵中去浓缩的原因之一。
