Peters J H, Hynes R O
Division of Pulmonary Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
Cell Adhes Commun. 1996 Aug;4(2):103-25. doi: 10.3109/15419069609010766.
Fibronectins (FNs) are extracellular matrix glycoproteins that are essential for embryonic development. In order to gain clues to possible developmental roles played by the particular isoforms of FN, we used indirect immunofluorescence microscopy to examine and compare the distributions of the alternatively spliced EIIIB, EIIIA, and V segments, as well as the total pool of FNs, in serial sections from mouse embryos. Antibodies to each of these segments produced staining patterns that colocalized during gastrulation (E7.5) and during early morphogenesis of somites and notochord (E9.5). During the period of continuing organogenesis in the latter half of gestation (E10.5 to E16.5), the antibodies generally continued to produce similar staining patterns localized to epithelial basement membranes, stromal connective tissues, blood vessel walls, and muscles. However, as development proceeded, there was a gradual decline in the intensity of staining for the spliced segments relative to the total pool of FN, with a particularly noticeable decline in staining for EIIIB and EIIIA segments in certain glandular organs, including the liver. A specific reduction in expression of these latter two segments was also evident in the uterus and placenta at early timepoints in gestation. However, the most dramatic difference in the expression of the spliced segments occurred in developing hyaline cartilage, which showed a selective reduction in staining for the EIIIA segment that was evident in the axial skeletal precursors by E12.5 and complete throughout the embryo by E15.5. Our findings suggest that the alternatively spliced EIIIB, EIIIA, and V segments are included in the FN that is required for the morphogenesis of "FN dependent" structures, including somites, notochord, and the vasculature. Conversely, these segments would appear to play divergent, and sometimes exclusive, biological roles in specific tissues such as liver, cartilage, and placenta.
纤连蛋白（FNs）是细胞外基质糖蛋白，对胚胎发育至关重要。为了探寻FN特定异构体可能发挥的发育作用线索，我们使用间接免疫荧光显微镜检查并比较了小鼠胚胎连续切片中可变剪接的EIIIB、EIIIA和V片段以及FN总量的分布情况。针对这些片段各自的抗体产生的染色模式在原肠胚形成期（E7.5）以及体节和脊索早期形态发生期（E9.5）共定位。在妊娠后半期持续器官发生阶段（E10.5至E16.5），这些抗体通常继续产生类似的染色模式，定位于上皮基底膜、基质结缔组织、血管壁和肌肉。然而，随着发育进行，相对于FN总量，剪接片段的染色强度逐渐下降，在某些腺器官（包括肝脏）中EIIIB和EIIIA片段的染色下降尤为明显。在妊娠早期的子宫和胎盘中，这后两个片段的表达也有特异性降低。然而，剪接片段表达最显著的差异出现在发育中的透明软骨中，EIIIA片段的染色选择性降低，在E12.5时在轴向骨骼前体中明显可见，到E15.5时在整个胚胎中完全可见。我们的研究结果表明，可变剪接的EIIIB、EIIIA和V片段包含在“FN依赖性”结构（包括体节、脊索和脉管系统）形态发生所需的FN中。相反，这些片段在特定组织（如肝脏、软骨和胎盘）中似乎发挥着不同的，有时是排他性的生物学作用。
