Sonnenfeld M J, Jacobs J R
Department of Biology, McMaster University, Hamilton, Ontario, Canada.
J Comp Neurol. 1995 Sep 4;359(4):644-52. doi: 10.1002/cne.903590410.
Cell death in the Drosophila embryonic central nervous system (CNS) proceeds by apoptosis, which is revealed ultrastructurally by nuclear condensation, shrinkage of cytoplasmic volume, and preservation of intracellular organelles. Apoptotic cells do not accumulate in the CNS but are continuously removed and engulfed by phagocytic haemocytes. To determine whether embryonic glia can function as phagocytes, we studied serial electronic microscopic sections of the Drosophila CNS. Apoptotic cells in the nervous system are engulfed by a variety of glia including midline glia, interface (or longitudinal tract) glia, and nerve root glia. However, the majority of apoptotic cells in the CNS are engulfed by subperineurial glia in a fashion similar to the microglia of the vertebrate CNS. A close proximity between macrophages and subperineurial glia suggests that glia may transfer apoptotic profiles to the macrophages. Embryos affected by the maternal-effect mutation Bicaudal-D have no macrophages. In the absence of macrophages, most apoptotic cells are retained at the outer surfaces of the CNS, and subperineurial glia contain an abundance of apoptotic cells. Some apoptotic cells are expelled from the CNS, which suggests that the removal of apoptotic cells can occur in the absence of macrophages. The number of subperineurial glia is unaffected by changes in the rate of neuronal apoptosis.
果蝇胚胎中枢神经系统（CNS）中的细胞死亡通过凋亡进行，在超微结构上表现为核浓缩、细胞质体积缩小以及细胞内细胞器的保留。凋亡细胞不会在中枢神经系统中积聚，而是会被吞噬性血细胞持续清除和吞噬。为了确定胚胎神经胶质细胞是否能发挥吞噬细胞的功能，我们研究了果蝇中枢神经系统的连续电子显微镜切片。神经系统中的凋亡细胞被多种神经胶质细胞吞噬，包括中线神经胶质细胞、界面（或纵向束）神经胶质细胞和神经根神经胶质细胞。然而，中枢神经系统中大多数凋亡细胞是被神经束膜下神经胶质细胞以类似于脊椎动物中枢神经系统小胶质细胞的方式吞噬的。巨噬细胞与神经束膜下神经胶质细胞紧密相邻，这表明神经胶质细胞可能将凋亡细胞的形态传递给巨噬细胞。受母体效应突变双尾 - D影响的胚胎没有巨噬细胞。在没有巨噬细胞的情况下，大多数凋亡细胞保留在中枢神经系统的外表面，并且神经束膜下神经胶质细胞含有大量凋亡细胞。一些凋亡细胞从中枢神经系统排出，这表明在没有巨噬细胞的情况下也能发生凋亡细胞的清除。神经束膜下神经胶质细胞的数量不受神经元凋亡速率变化的影响。
