Suppression of limb regeneration by RNA interference of WNT4 in the swimming crab Portunus trituberculatus

An overview of recent progress in the molecular mechanisms and key biological macromolecules involved in limb regeneration of decapods

Understanding the molecular mechanisms of limb regeneration in decapods can significantly enhance aquaculture production by improving survival and growth, as well as facilitating the development of lab-grown crustacean meat as a sustainable protein source. This review explores the molecular mechanisms of decapod limb regeneration, focusing on the key signaling pathways, genes, and proteins involved in this process. The initial stages of regeneration involve immune response and hemolymph coagulation, which are regulated via signaling pathways such as Toll, MAPK, IMD, and JAK/STAT. Subsequent stages, including blastema formation and limb growth, are regulated by signaling pathways such as Wnt, Hippo, Hedgehog, Ecdysteroid, TGF-β, Notch, Insulin-like, Fibroblast Growth Factor, Epidermal Growth Factor, and BMP. This review also discusses the interplay among environmental factors, nutrition, and hormonal signaling in regeneration and how these elements influence regenerative capability. Furthermore, this review highlights existing research gaps in decapod regeneration and suggests future research directions. This review aims to bridge existing gaps in decapod regeneration research and guide future studies toward potential breakthroughs in aquaculture practices.

Identification of key genes and molecular pathways associated with claw regeneration in mud crab (Scylla paramamosain)

The mud crab (Scylla paramamosain) possesses extensive regenerative abilities, enabling it to replace missing body parts, including claws, legs, and even eyes. Studying the genetic and molecular mechanisms underlying regenerative ability in diverse animal phyla has the potential to provide new insights into regenerative medicine in humans. In the present study, we performed mRNA sequencing to reveal the genetic mechanisms underlying the claw regeneration in mud crab. Several differentially expressed genes (DEGs) were expressed in biological pathways associated with cuticle synthase, collagen synthase, tissue regeneration, blastema formation, wound healing, cell cycle, cell division, and cell migration. The top GO enrichment terms were microtubule-based process, collagen trimer, cell cycle process, and extracellular matrix structural constituent. The most enriched KEGG pathways were ECM-receptor interaction and focal adhesion. The genes encoding key functional proteins, such as collagen alpha, cuticle protein, early cuticle protein, arthrodial cuticle protein, dentin sialophosphoprotein (DSPP), epidermal growth factor receptor (EGFR), kinesin family member C1 (KIFC1), and DNA replication licensing factor mcm2-like (MCM2) were the most significant and important DEGs suspected to participate in claw regeneration. The findings of this research offer a comprehensive and insightful understanding of the genetic and molecular mechanisms underlying claw regeneration in S. paramamosain. By elucidating the specific genes and molecular pathways implicated in this process, our study contributes significantly to the broader field of regenerative biology and offers potential avenues for further exploration in crustacean limb regeneration.

Hippo Signaling Regulates Blastema Formation During Limb Regeneration in Chinese Mitten Crab (Eriocheir sinensis)

Limb autotomy and regeneration are specific adaptations of crustaceans in response to external stress and attacks, which make them a suitable model to investigate the mechanism of organ regeneration in invertebrates. In this study, the Hippo gene of Eriocheir sinensis (EsHPO) was identified, and the effects of Hippo signaling on limb regeneration were evaluated. The expression of EsHPO and other key components of Hippo signaling was down-regulated during the basal growth phase in response to limb autotomy stress and then up-regulated during the proecdysial growth phase. The descending expression patterns of Hippo signal components were correlated with transcriptional activation of YKI and downstream target genes during the blastema formation stage, which suggested that Hippo signaling plays a key role during limb regeneration in E. sinensis. To further test the hypothesis, the transcription factor YKI was blocked via verteporfin injection after autotomy, which disrupted limb regeneration by repressing wound healing and preventing blastema emergence. Furthermore, our experiments revealed that the proliferation of blastema cells was blocked by verteporfin. In addition, the expression of genes related to ECM remodeling, cell cycle progression, and apoptosis resistance was down-regulated following the injection of verteporfin. Our findings therefore indicate that Hippo signaling is essential for successful wound healing and limb regeneration in E. sinensis by inducing ECM remodeling, as well as promoting the proliferation and repressing the apoptosis of blastema cells.

Molecular Characterisation of Wnt4 and Wnt16 in the Water Flea (Daphnia pulex) and Their Expression Regulation by Polystyrene Nanoplastics

The Wnt gene family is of ancient origin and is involved in various biological processes. In this study, Wnt4 and Wnt16 were cloned from Daphnia pulex, named DpWnt4 and DpWnt16, respectively. In DpWnt4 cDNA, full-length 1684 bp, the open reading frame was 1122 bp and it encodes a 373 amino acid polypeptide. In DpWnt16 cDNA, full-length 1941 bp, the open reading frame was 1293 bp and it encodes a 430 amino acid polypeptide. The sequence analysis result showed that both DpWnt4 and DpWnt16 sequences contain a Wnt1 domain. Multiple sequence alignment and phylogenetic analysis revealed that DpWnt4 and DpWnt16 were most closely related to arthropods. The expression of DpWnt4 decreased at 0.5 mg/L group and was induced at 2 mg/L, while DpWnt16 was only induced at 2 mg/L nanoplastics group. These results help us understand more about the character of Wnt4 and Wnt16 in crustaceans and how Wnt genes respond to pollutants, especially nanoplastics.