Stephen Ryerse Jan, Ann Nagel Barbara
Department of Pathology, St. Louis University School of Medicine, 1402 South Grand Blvd., 63104, St. Louis, Missouri, USA.
Wilehm Roux Arch Dev Biol. 1984 Jul;193(4):187-196. doi: 10.1007/BF01260338.
Developmental changes in the distribution of gap junctions in early, mid and late third larval stage wing discs and in pupariation+6 h and pupariation+24 h stage wing discs fromDrosophila melanogaster were analyzed by quantitative electron microscopy. Gap junctions occur in all 12 intradisc regions examined in each of the five developmental stages. Their distribution is non-random and changes during development which suggests that they are developmentally regulated. The gap junctions are not static structures, rather they grow and regress during development. The changes tend to be gradual ones without sudden increases or decreases. Gap junctions continuously form and grow in size throughout the third larval stage and during the first 6 h following pupariation. Their surface density, number, percent of the lateral plasma membrane area, and absolute area as well as the lateral plasma membrane surface density all increase during this time. Between pupariation+ 6 h and pupariation+24 h all but one of these parameters decrease indicative of gap junctional breakdown. Gap junctions are most numerous and change least during development in the apical cell regions where intercellular contacts are close and stable. They change most in the basal cell regions where intercellular contacts tend to be looser and change during development. The most dramatic change is in the absolute area which increases by a factor of 23 between the early third larval stage and pupariation+24 h. At pupariation the rate of gap junction growth undergoes a transient increase before the phase of disassembly begins. Developmental changes in gap junction surface density are closely coupled with changes in the lateral plasma membrane surface density which suggests that these may be coregulated. Evidence from mutants suggests that when the number and density of gap junctions fail to increase in proportion to lateral plasma membrane growth, wing disc development will be abnormal. Our results support the idea that some minimum gap junction density is required for normal development and that this must increase as development proceeds. The results are consistent with the notion that gap junctions are involved in pattern formation and growth control and are discussed with respect to the acquisition of competence for metamorphosis, disc growth, disc morphogenesis and changes in the hormonal environment.
通过定量电子显微镜分析了黑腹果蝇三龄幼虫早期、中期和晚期以及化蛹后6小时和化蛹后24小时翅盘中间隙连接分布的发育变化。在五个发育阶段的每一个阶段所检查的所有12个盘内区域中均存在间隙连接。它们的分布是非随机的，并且在发育过程中发生变化，这表明它们受到发育调控。间隙连接不是静态结构，而是在发育过程中生长和消退。这些变化往往是渐进的，没有突然的增加或减少。在整个三龄幼虫阶段以及化蛹后的前6小时，间隙连接持续形成并增大尺寸。在此期间，它们的表面密度、数量、占外侧质膜面积的百分比、绝对面积以及外侧质膜表面密度均增加。在化蛹后6小时至化蛹后24小时之间，除一个参数外，所有这些参数均下降，表明间隙连接解体。间隙连接在顶端细胞区域数量最多且在发育过程中变化最小，在该区域细胞间接触紧密且稳定。它们在基部细胞区域变化最大，在该区域细胞间接触往往较松散且在发育过程中发生变化。最显著的变化是绝对面积，在三龄幼虫早期至化蛹后24小时之间增加了23倍。在化蛹时，间隙连接生长速率在解体阶段开始之前经历短暂增加。间隙连接表面密度的发育变化与外侧质膜表面密度的变化紧密相关，这表明它们可能受到共同调节。来自突变体的证据表明，当间隙连接的数量和密度未能与外侧质膜生长成比例增加时，翅盘发育将异常。我们的结果支持这样的观点，即正常发育需要一定的最小间隙连接密度，并且随着发育的进行这一密度必须增加。结果与间隙连接参与模式形成和生长控制的观点一致，并就变态能力的获得、翅盘生长、翅盘形态发生以及激素环境变化进行了讨论。
