Djnedd4L Is Required for Head Regeneration by Regulating Stem Cell Maintenance in Planarians

SUMOylation and ubiquitylation are homologous processes catalyzed by homologous enzymes, and they are involved in nearly all aspects of eukaryotic biology. Planarians, which have the remarkable ability to regenerate their central nervous system (CNS), provide an excellent opportunity to investigate the molecular processes of CNS regeneration in vivo. In this study, we analyzed gene expression profiles during head regeneration with an RNA-seq-based screening approach and found that Djnedd4L and Djubc9 were required for head regeneration in planarians. RNA interference targeting of Djubc9 caused the phospho-H3 mitotic cells to decrease in quantity, or even become absent as a part of the Djubc9 RNAi phenotype, which also showed the collapse of the stem cell lineage along with the reduced expression of epidermal differentiation markers. Furthermore, we found that Djnedd4L RNAi induced increased cell division and promoted the premature differentiation during regeneration. Taken together, our findings show that Djubc9 and Djnedd4L are required for stem cell maintenance in the planarian Dugesia japonica, which helps to elucidate the role of SUMOylation and ubiquitylation in regulating the regeneration process

<i>Djck1α</i> Is Required for Proper Regeneration and Maintenance of the Medial Tissues in Planarians

CK1α (Casein kinase 1α) is a member of the casein kinase 1(CK1) family that is involved in diverse cellular processes, but its functions remain unclear in stem cell development. Freshwater planarians are capable of whole-body regeneration, making it a classic model for the study of regeneration, tissue homeostasis, and polarity in vivo. To investigate the roles of CK1α in regeneration and homeostasis progress, we characterize a homolog of CK1α from planarian Dugesia japonica. We find that Djck1α, which shows an enriched expression pattern in the nascent tissues, is widely expressed especially in the medial regions of planarians. Knockdown of CK1α by RNAi presents a thicker body due to dorsal hyperplasia, along with defects in the medial tissues including nerve proliferation, missing epidermis, intestine disturbance, and hyper-proliferation during the progression of regeneration and homeostasis. Moreover, we find that the ck1α RNAi animals exhibit expansion of the midline marker slit. The eye deficiency induced by slit RNAi can be rescued by ck1α and slit double RNAi. These results suggest that ck1α is required for the medial tissue regeneration and maintenance in planarian Dugesia japonica by regulating the expression of slit, which helps to further investigate the regulation of planarian mediolateral axis

Optimal Cost-Based Strengthening of Complex Networks

Most real-world complex systems are extremely vulnerable to targeted attacks, making their immunization an important yet challenging task. One of the most effective attack strategies is targeting articulation points specifically. In this study, we first propose a generalized definition of network robustness. Then we address the problem of strengthening network robustness with the minimum cost by exploiting the intuition behind the attack strategy based on articulation points, that is proven to be NP-hard. Accordingly, we propose a heuristic for solving this problem, subject to a cost function whose choice determines the obtained network regime. Experiments on both random and real-world networks show that our algorithm strengthens the robustness by using significantly cheaper edge additions than state-of-the-art methods. Moreover, our algorithm excels against general attack strategies by revealing the essence of strengthening network robustness, that is, increasing the size of the giant connected component optimally in the process of node removal. While considering the realistic problem, our algorithm also provides a reasonable scheme to add edges at a low cost.Peer reviewe

Meis1 Controls the Differentiation of Eye Progenitor Cells and the Formation of Posterior Poles during Planarian Regeneration

As a member of TALE family, Meis1 has been proven to regulate cell proliferation and differentiation during cell fate commitment; however, the mechanism is still not fully understood. The planarian, which has an abundance of stem cells (neoblasts) responsible for regenerating any organ after injury, is an ideal model for studying the mechanisms of tissue identity determination. Here, we characterized a planarian homolog of Meis1 from the planarian Dugesia japonica. Importantly, we found that knockdown of DjMeis1 inhibits the differentiation of neoblasts into eye progenitor cells and results in an eyeless phenotype with normal central nervous system. Furthermore, we observed that DjMeis1 is required for the activation of Wnt signaling pathway by promoting the Djwnt1 expression during posterior regeneration. The silencing of DjMeis1 suppresses the expression of Djwnt1 and results in the inability to reconstruct posterior poles. In general, our findings indicated that DjMeis1 acts as a trigger for the activation of eye and tail regeneration by regulating the differentiation of eye progenitor cells and the formation of posterior poles, respectively

Reciprocal Relationship between Internet Addiction and Network-Related Maladaptive Cognition among Chinese College Freshmen: A Longitudinal Cross-Lagged Analysis

This study explored the reciprocal relationship between Internet addiction (IA) and network-related maladaptive cognition (NMC) in Chinese college freshmen. A short-term longitudinal survey with a sample of 213 college freshmen was conducted in Shandong province, China. The results revealed that IA can significantly predict the generation and development of NMCs, and that when such maladaptive cognitions have been established, they can further adversely affect the extent of the students’ IA. A vicious cycle was observed between these two variables, with IA having predictive priority in its relationship with NMC. This study also determined that the relationship between these two variables was the same for both males and females; therefore, the final model we established can be extensively applied to Chinese college freshmen, regardless of gender. Understanding the reciprocal relationship between these two variables can assist in interventions in IA at the outset of students’ college life