Krieser R J, MacLea K S, Longnecker D S, Fields J L, Fiering S, Eastman A
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, NH 03755, USA.
Cell Death Differ. 2002 Sep;9(9):956-62. doi: 10.1038/sj.cdd.4401056.
Deoxyribonuclease IIalpha (DNase IIalpha) is one of many endonucleases implicated in DNA digestion during apoptosis. We produced mice with targeted disruption of DNase IIalpha and defined its role in apoptosis. Mice deleted for DNase IIalpha die at birth with many tissues exhibiting large DNA-containing bodies that result from engulfed but undigested cell corpses. These DNA-containing bodies are pronounced in the liver where fetal definitive erythropoiesis occurs and extruded nuclei are degraded. They are found between the digits, where apoptosis occurs, and in many other regions of the embryo. Defects in the diaphragm appear to cause death of the mice due to asphyxiation. The DNA in these bodies contains 3'-hydroxyl ends and therefore stain positive in the TUNEL assay. In addition, numerous unengulfed TUNEL-positive cells are observed throughout the embryo. Apoptotic cells are normally cleared rapidly from a tissue; hence the persistence of the DNA-containing bodies and TUNEL-positive cells identifies sites where apoptosis occurs during development. These results demonstrate that DNase IIalpha is not required for the generation of the characteristic DNA fragmentation that occurs during apoptosis but is required for degrading DNA of dying cells and this function is necessary for proper fetal development.
脱氧核糖核酸酶IIα（DNase IIα）是凋亡过程中参与DNA消化的多种核酸内切酶之一。我们制备了DNase IIα靶向缺失的小鼠，并确定了其在凋亡中的作用。DNase IIα缺失的小鼠在出生时死亡，许多组织中出现大量含DNA的小体，这些小体是由被吞噬但未消化的细胞尸体形成的。这些含DNA的小体在发生胎儿期确定性红细胞生成且细胞核被挤出并降解的肝脏中尤为明显。它们出现在发生凋亡的趾间以及胚胎的许多其他区域。膈肌缺陷似乎导致小鼠因窒息而死亡。这些小体中的DNA含有3'-羟基末端，因此在TUNEL检测中呈阳性染色。此外，在整个胚胎中观察到大量未被吞噬的TUNEL阳性细胞。凋亡细胞通常会迅速从组织中清除；因此，含DNA小体和TUNEL阳性细胞的持续存在确定了发育过程中发生凋亡的部位。这些结果表明，DNase IIα对于凋亡过程中发生的特征性DNA片段化的产生不是必需的，但对于降解死亡细胞的DNA是必需的，并且该功能对于正常的胎儿发育是必要的。
