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Background Planarians reliably regenerate all body parts after injury, including a fully functional head and central nervous system. But until now, the expression dynamics and functional role of miRNAs and other small RNAs during the process of head regeneration are not well understood. Furthermore, little is known about the evolutionary conservation of the relevant small RNAs pathways, rendering it difficult to assess whether insights from planarians will apply to other taxa. Results In this study, we applied high throughput sequencing to identify miRNAs, tRNA fragments and piRNAs that are dynamically expressed during head regeneration in Dugesia japonica. We further show that knockdown of selected small RNAs, including three novel Dugesia-specific miRNAs, during head regeneration induces severe defects including abnormally small-sized eyes, cyclopia and complete absence of eyes. Conclusions Our findings suggest that a complex pool of small RNAs takes part in the process of head regeneration in Dugesia japonica and provide novel insights into global small RNA expression profiles and expression changes in response to head amputation. Our study reveals the evolutionary conserved role of miR-124 and brings further promising candidate small RNAs into play that might unveil new avenues for inducing restorative programs in non-regenerative organisms via small RNA mimics based therapies.

Additional file 1: Supplemental_Data_S1. The reference sequences for mRNAs (including UTRs).

14-3-3 proteins are a family of highly conserved acidic proteins that regulate cellular processes. They act as a kind of important signaling molecules taking part in many crucial decisions throughout the development process. We have isolated and characterized two members of the 14-3-3 family, namely, Dj14-3-3 α and Dj14-3-3 ζ in the planarian Dugesia japonica. The Dj14-3-3 α and ζ genes encode polypeptides of 260 and 255 amino acids respectively. We have proved that the Dj14-3-3 α and ζ genes were especially expressed in the pharynx in adult and regenerating planarians by in situ hybridization and they were not involved in regeneration process. Besides, Dj14-3-3 α and ζ genes can compensate each other in planarians by RNA interference. The Dj14-3-3 α and ζ were significantly up-regulated expression when planarians were stimulated with the pathogen-associated molecular patterns including lipopolysaccharide (LPS), peptidoglycan (PGN), β-Glu and Poly (I:C), indicating that the Dj14-3-3 α and ζ may be involved in the immune responses.

The myosin regulatory light chain (RLC) proteins play an important role in cellular processes, especially in muscle contraction. The planarian intestine is a fascinating system for studying the organogenesis during regeneration. In this paper, A homolog gene of Rlc, DjRlc, was identified and characterized in Dugesia japonica. The DjRlc sequence analysis revealed that it contains an opening reading frame encoding a putative protein of 175 amino acids with functionally domains that are highly conserved, including an EF-Hand motif and Ca2+ binding sites. Whole mount in situ hybridization showed that DjRlc is predominantly expressed in the intestine of intact and regenerating planarians. The cross sections of planarians revealed that the DjRlc distributes in the muscle of intact planarians. Knockdown of RNA interference of DjRlc by dsRNA-DjRlc affected the intestinal morphology, causing distinct defects in branching morphogenesis. These finding suggest that DjRlc is required for intestinal regeneration.

Previous study has demonstrated that high mobility group nucleosome-binding domain 5 (HMGN5) is involved in tumorigenesis and the development of multidrug resistance in several human cancers. However, the role of HMGN5 in esophageal squamous cell carcinoma (ESCC) remains unclear. Here, we showed that HMGN5 was significantly upregulated in ESCC cells. Knockdown of HMGN5 significantly inhibited cell growth and induced cell apoptosis of ESCC cells. Moreover, knockdown of HMGN5 increased the sensitivity of ESCC cells towards cisplatin. By contrast, overexpression of HMGN5 showed the opposite effects. Further experiments demonstrated that HMGN5 regulated the expression of multidrug resistance 1, cyclin B1, and Bcl-2. Overall, our results reveal that HMGN5 promotes tumor progression of ESCC and is also an important regulator of chemoresistance. Our study suggests that inhibition of HMGN5 may be a potential strategy for improving effectiveness of ESCC treatment.

A growing body of evidence suggests that frizzled-7 (FZD7) is an important oncogene in multiple human malignancies and is involved in regulating sensitivity to chemotherapeutic drugs. However, little is known about the expression and function of FZD7 in esophageal squamous cell carcinoma (ESCC). In this study, we aimed to investigate the functional significance of FZD7 in ESCC. Here, we found that both mRNA and protein expression levels of FZD7 were highly upregulated in ESCC cell lines. The knockdown of FZD7 inhibited cell growth, induced cell apoptosis, and suppressed cell migration and invasion of ESCC cells in vitro . Furthermore, knockdown of FZD7 promoted chemosensitivity to cisplatin in ESCC cells and suppressed the expression of multidrug resistance protein 1. Moreover, the silencing of FZD7 also significantly impeded the activation of Wnt signaling in ESCC cells. Taken together, our study reveals an oncogenic role of FZD7 in the progression of ESCC and suggests that FZD7 might serve as a potential therapeutic target for treatment of ESCC.

Vinculin is a cytoskeletal protein associated with cell-cell and cell-matrix junctions, playing an important role in linkage of integrin adhesion molecules to the actin cytoskeleton. The planarian nervous system is a fascinating system for studying the organogenesis during regeneration. In this paper, a homolog gene of Vinculin, DjVinculin, was identified and characterized in Dugesia japonica. The DjVinculin sequence analysis revealed that it contains an opening reading frame encoding a putative protein of 975 amino acids with functionally domains that are highly conserved, including eight anti-parallel α-helical bundles organized into five distinct domains. Whole mount in situ hybridization showed that DjVinculin was predominantly expressed in the brain of intact and regenerating planarians. RNA interference of DjVinculin caused distinct defects in brain morphogenesis and influences the regeneration of planarian GABAergic neurons. The expression level of DjGAD protein was decreased in the DjVinculin-knockdown planarians. These findings suggest that DjVinculin is required for GABAergic neurons regeneration.

Bartonella infection is distributed worldwide with animal and public health. Recent studies have shown that host cells infection by Bartonella has a series of different infection stages, beginning with encounter and adherence to the cells. In this study, we expressed and purified recombinant Bartonella henselae (B. henselae) α-enolase. And we found that B. henselae α-enolase is highly conserved in Bartonella species. The interacting protein partners of B. henselae α-enolase were showed by String-11. The interactions between B. henselae α-enolase and human plasminogen were subsequently confirmed by ELISA, pull down, T7 phage display and molecular docking assays. And the plasminogen-binding sites of B. henselae α-enolase are predicted at 247FYKNGSYFY255. These findings will help elucidate and improve the understanding of the molecular mechanisms of Bartonella infection.

Puromycin-sensitive aminopeptidase (PSA) belongs to the M1 zinc metallopeptidase family. PSA is the most abundant aminopeptidase in the brain and plays a role in the metabolism of neuropeptides including those involved in neurodegeneration. A cDNA DjPsa was identified from the planarian Dugesia japonica cDNA library. It contains a 639-bp open reading frame corresponding to a deduced protein of 212 amino acids. Whole mount in situ hybridization revealed that DjPsa is expressed in the brain and ventral nerve cords of intact and regenerating animals and demonstrates a tissue and stage-specific expression pattern of DjPsa in developing embryos and larvae. Knocking down DjPsa gene expression with RNA interference during planarian regeneration inhibits the brain reformation completely. The results suggest that DjPsa is required for planarian brain regeneration.