以遺傳及分子生物學技術搜尋和線蟲生殖腺引導細胞遷移和細胞屍 體吞噬相關之基因

Abstract

Rac GTPases 的功能和細胞骨骼的重組有關，而 CED－10 是線蟲的 Rac GTPases 之一。目前已知在線蟲的生殖腺引導細胞（ distal tip cell , DTC ) 中， CED－10 受到 CED－2 / CED－5 / CED－12 複合體的活化，使細胞骨骼重組，伸展細胞表面，促使細胞得以遷移，而 DTC 遷移的路徑可由生殖腺的形狀來推斷。因此當 ced-2 、ced-5 、ced-10 或ced-12 突變時，生殖腺的形狀會產生改變。然而在這條訊息路徑中，上游的受器及受體尚未被發現。 筆者利用 genetic screen 技術試圖找出和 DTC 遷移有關的新基因。找出一個ced-5的新突變株：ced-5 ( tp4 ) ，該突變株主要的表型為 DTC 遷移的第三階段發生錯誤，往反方向進行或是以不規則的方式行進造成生殖腺的塊狀凝集。此外筆者利用 Yeast－two－hybrid 技術，以ced-10為餌，試圖在線蟲的 DNA library 中找出和ced-10有直接關係的基因，但由 DNA library 的問題，並未找到相關的基因。 在哺乳動物的系統中，integrin 被認為是影響細胞附著、遷移、訊息傳導及基因表現的主要受器。在線蟲中ina－1、pat－2 是 iniegrina α次單位，Pat－3 是β次單位。筆者利用基本的遺傳技術及 RNA interference ( RNAi ) 技術驗證 ina－1 確實會影響 DTC 的遷移，但並非處於ced-10訊息路徑的上游。而 ina－1 會影響胚胎發育早期的細胞屍體吞噬，作用於ced-1、 ced-6、ced-7 這條訊息路徑中。

Rac GTPases are involved in cytoskeletal rearrangement. CED- 10 is one of members of Rac GTPase family in Caenorhabditis elegans. In C. elegans DTCs (Distal Tip Cells), CED-2/CED-5/CED-12 ternary complex translocate to plasma membrane and activate CED- 10, leading to the cyto skeletal reorganization that occurs in the polarized extension of cell surface. By this arrangement, DTC can migrate through cell autonomous and surrounding signals. Gonad arms of C. elegans is generated by the symmetrical migration of DTCs, so gonad shapes indicate DTCs migration paths. When ced-2, ced-5, ced-l0 or ced-12 mutate, gonads shapes alter. In ced-l0 signaling pathway of DTC migration, upstream molecules haven’t been figure out. I have undertaken genetic screen to search new genes involved in DTC migration mechanism. I have found a ced-5 new allele, ced-5(tp4), which mainly has opposite direction of third phase migration or clump gonads resulted in irregular migration. And I use Yeast-Two-Hybrid to seek for molecules directly interacted with CED-10 in C. elegans library. But I didn’t find any gene from Yeast-Two-Hybrid. Integrins are a large family of cell surface receptors that mediate cell adhension and influence migration, signal transduction, and gene expression in mammalian system. ina-1 and pat-2 are homologues of integrin α subunit and pat-3 is the only homologue of integrin β subunit. Our genetics data and RNA interference (RNAi ) results indicate that ina-1 influences DTC migration through other pathway, but not ced-10 signaling pathway. And ina-1 involved in ced-1, ced-6, ced-7 cell corpses engulfment pathway.