Ambrosio L, Schedl P
Dev Biol. 1985 Sep;111(1):220-31. doi: 10.1016/0012-1606(85)90447-6.
We have used in situ hybridization to ovarian tissue sections to study the pattern of histone gene expression during oogenesis in Drosophila melanogaster. Our studies suggest that there are two distinct phases of histone gene expression during oogenesis. In the first phase, which occurs during early to middle oogenesis (stages 5-10A), we observe a mosaic pattern of histone mRNA in the 15 nurse cells of the egg chamber: some cells have very high levels of mRNA, while others have little or no mRNA. Our analysis suggests that there is a cyclic accumulation and subsequent degradation of histone mRNA in the egg chamber and that very little histone mRNA is transported into the growing oocyte. Moreover, since the endomitotic replication cycles of the nurse cells are asynchronous during this period, the mosaic distribution of histone message would suggest that the expression of the histone genes in each nurse cell nucleus is probably coupled to DNA replication as in most somatic cells. The second phase begins at stage 10B. During this period, histone gene expression appears to be "induced" in all 15 nurse cells of the egg chamber, and instead of a mosaic pattern, high levels of histone mRNA are found in all cells. Unlike the earlier phase, this expression is apparently uncoupled from the endomitotic replication of the nurse cells (which are completed by the end of stage 10A). Moreover, much of the newly synthesized histone mRNA is transported from the nurse cells into the oocyte where it accumulates and is stored for use during early embryogenesis. Finally, we have also observed tightly clustered grains within nurse cell nuclei in non-denatured tissue sections. As was the case with cytoplasmic histone mRNA, there is a mosaic distribution of nuclear grains from stages 5 to 10A, while at stage 10B, virtually all nurse cell nuclei have grain clusters. These grain clusters appear to be due to the hybridization of nurse cell histone gene DNA to our probe, and are localized in specific regions of the nucleus.
我们运用原位杂交技术对果蝇卵巢组织切片进行研究，以探究黑腹果蝇卵子发生过程中组蛋白基因的表达模式。我们的研究表明，卵子发生过程中组蛋白基因的表达存在两个不同阶段。在第一阶段，即卵子发生的早期至中期（5-10A阶段），我们在卵室的15个滋养细胞中观察到组蛋白mRNA的镶嵌模式：一些细胞具有非常高的mRNA水平，而其他细胞则几乎没有或没有mRNA。我们的分析表明，卵室内组蛋白mRNA存在周期性积累并随后降解，并且极少有组蛋白mRNA转运到正在生长的卵母细胞中。此外，由于在此期间滋养细胞的核内有丝分裂复制周期是异步的，组蛋白信息的镶嵌分布表明每个滋养细胞核中组蛋白基因的表达可能如大多数体细胞一样与DNA复制相关联。第二阶段始于10B阶段。在此期间，卵室的所有15个滋养细胞中组蛋白基因表达似乎被“诱导”，并且与镶嵌模式不同，所有细胞中都发现了高水平的组蛋白mRNA。与早期阶段不同，这种表达显然与滋养细胞的核内有丝分裂复制（在10A阶段结束时完成）无关。此外，许多新合成的组蛋白mRNA从滋养细胞转运到卵母细胞中，在那里积累并储存起来以供早期胚胎发育期间使用。最后，我们还在未变性的组织切片中观察到滋养细胞核内紧密聚集的颗粒。与细胞质组蛋白mRNA的情况一样，从5到10A阶段核颗粒存在镶嵌分布，而在10B阶段，几乎所有滋养细胞核都有颗粒簇。这些颗粒簇似乎是由于滋养细胞组蛋白基因DNA与我们的探针杂交所致，并且定位于细胞核的特定区域。
