Ahn Hong Ryul, Kim Gil Jung
Present address: Functional Food Center, Korea Institute of Science and Technology, Gangneung Institute, Gangneung 210-340, Korea.
Dept. of Marine Molecular Biotechnology, Gangneung-Wonju National University, Gangneung 210-702, Korea.
Dev Reprod. 2012 Dec;16(4):371-8. doi: 10.12717/DR.2012.16.4.371.
Notch signaling plays fundamental roles in various animal development. It has been suggested that Hr-Notch, a Notch homologue in the ascidian Halocynthia roretzi, is involved in the formation of peripheral neurons by suppressing the neural fates and promoting the epidermal differentiation. However, roles of Notch signaling remain controversial in the formation of nervous system in ascidian embryos. To precisely investigate functions of Notch signaling, we have isolated and characterized Hr-Numb, a Numb homologue which is a negative regulator of Notch signaling, in H. roretzi. Maternal expression of Hr-Numb mRNAs was detected in egg cytoplasm and the transcripts were inherited by the animal blastomeres. Its zygotic expression became evident by the early neurula stage and the transcripts were detected in dorsal neural precursor cells. Suppression of Hr-Numb function by an antisense morpholino oligonucleotide resulted in larvae with defect in brain vesicle and palps formation. Similar results have been obtained by overexpression of the constitutively activated Hr-Notch forms. Therefore, these results suggest that Hr-Numb is involved in Notch signaling during ascidian embryogenesis.
Notch信号通路在各种动物发育过程中发挥着重要作用。有研究表明，海鞘Halocynthia roretzi中的Notch同源物Hr-Notch通过抑制神经命运和促进表皮分化参与外周神经元的形成。然而，Notch信号通路在海鞘胚胎神经系统形成中的作用仍存在争议。为了精确研究Notch信号通路的功能，我们在海鞘Halocynthia roretzi中分离并鉴定了Hr-Numb，它是Notch信号通路的负调控因子Numb的同源物。在卵细胞质中检测到Hr-Numb mRNA的母源表达，并且转录本由动物极的卵裂球继承。其合子表达在神经胚早期变得明显，并且在背侧神经前体细胞中检测到转录本。用反义吗啉代寡核苷酸抑制Hr-Numb功能导致幼虫脑泡和触须形成缺陷。通过组成型激活的Hr-Notch形式的过表达也获得了类似的结果。因此，这些结果表明Hr-Numb在海鞘胚胎发生过程中参与Notch信号通路。
