Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, United States of America.
PLoS One. 2013;8(3):e59306. doi: 10.1371/journal.pone.0059306. Epub 2013 Mar 13.
Ciliopathies lead to multiorgan pathologies that include renal cysts, deafness, obesity and retinal degeneration. Retinal photoreceptors have connecting cilia joining the inner and outer segment that are responsible for transport of molecules to develop and maintain the outer segment process. The present study evaluated meckelin (MKS3) expression during outer segment genesis and determined the consequences of mutant meckelin on photoreceptor development and survival in Wistar polycystic kidney disease Wpk/Wpk rat using immunohistochemistry, analysis of cell death and electron microscopy. MKS3 was ubiquitously expressed throughout the retina at postnatal day 10 (P10) and P21. However, in the mature retina, MKS3 expression was restricted to photoreceptors and the retinal ganglion cell layer. At P10, both the wild type and homozygous Wpk mutant retina had all retinal cell types. In contrast, by P21, cells expressing rod- and cone-specific markers were fewer in number and expression of opsins appeared to be abnormally localized to the cell body. Cell death analyses were consistent with the disappearance of photoreceptor-specific markers and showed that the cells were undergoing caspase-dependent cell death. By electron microscopy, P10 photoreceptors showed rudimentary outer segments with an axoneme, but did not develop outer segment discs that were clearly present in the wild type counterpart. At p21 the mutant outer segments appeared much the same as the P10 mutant outer segments with only a short axoneme, while the wild-type controls had developed outer segments with many well-organized discs. We conclude that MKS3 is not important for formation of connecting cilium and rudimentary outer segments, but is critical for the maturation of outer segment processes.
纤毛病导致多器官病变，包括肾囊肿、耳聋、肥胖和视网膜变性。视网膜光感受器有连接纤毛，将内节和外节连接起来，负责运输分子以发育和维持外节过程。本研究评估了 Meckelin（MKS3）在外节发生过程中的表达，并通过免疫组织化学、细胞死亡分析和电子显微镜检查，确定了突变 Meckelin 对 Wistar 多囊肾病 Wpk/Wpk 大鼠光感受器发育和存活的影响。MKS3 在出生后第 10 天（P10）和 P21 在整个视网膜中广泛表达。然而，在成熟的视网膜中，MKS3 的表达仅限于光感受器和视网膜神经节细胞层。在 P10，野生型和纯合 Wpk 突变型视网膜均具有所有视网膜细胞类型。相比之下，到 P21，表达杆状和锥状特异性标志物的细胞数量减少，视蛋白的表达似乎异常定位于细胞体。细胞死亡分析与光感受器特异性标志物的消失一致，并表明细胞正在经历半胱天冬酶依赖性细胞死亡。通过电子显微镜，P10 光感受器显示出具有轴突的基本外节，但未发育出明显存在于野生型对应物中的外节盘。在 p21 时，突变体的外节看起来与 P10 突变体的外节相同，只有一个短的轴突，而野生型对照已经发育出许多组织良好的外节盘。我们得出结论，MKS3 对于连接纤毛和基本外节的形成不是很重要，但对于外节过程的成熟至关重要。
