m6 A promotes planarian regeneration.

Regeneration is the regrowth of damaged tissues or organs, a vital process in response to damages from primitive organisms to higher mammals. Planarian possesses active whole-body regenerative capability owing to its vast reservoir of adult stem cells, neoblasts, providing an ideal model to delineate the underlying mechanisms for regeneration. RNA N6 -methyladenosine (m6 A) modification participates in many biological processes, including stem cell self-renewal and differentiation, in particular the regeneration of haematopoietic stem cells and axons. However, how m6 A controls regeneration at the whole-organism level remains largely unknown. Here, we demonstrate that the depletion of m6 A methyltransferase regulatory subunit wtap abolishes planarian regeneration, potentially through regulating genes related to cell-cell communication and cell cycle. Single-cell RNA-seq (scRNA-seq) analysis unveils that the wtap knockdown induces a unique type of neural progenitor-like cells (NP-like cells), characterized by specific expression of the cell-cell communication ligand grn. Intriguingly, the depletion of m6 A-modified transcripts grn, cdk9 or cdk7 partially rescues the defective regeneration of planarian caused by wtap knockdown. Overall, our study reveals an indispensable role of m6 A modification in regulating whole-organism regeneration.

An insight into planarian regeneration.

BACKGROUND: Planarian has attracted increasing attentions in the regeneration field for its usefulness as an important biological model organism attributing to its strong regeneration ability. Both the complexity of multiple regulatory networks and their coordinate functions contribute to the maintenance of normal cellular homeostasis and the process of regeneration in planarian. The polarity, size, location and number of regeneration tissues are regulated by diverse mechanisms. In this review we summarize the recent advances about the importance genetic and molecular mechanisms for regeneration control on various tissues in planarian. METHODS: A comprehensive literature search of original articles published in recent years was performed in regards to the molecular mechanism of each cell types during the planarian regeneration, including neoblast, nerve system, eye spot, excretory system and epidermal. RESULTS: Available molecular mechanisms gave us an overview of regeneration process in every tissue. The sense of injuries and initiation of regeneration is regulated by diverse genes like follistatin and ERK signaling. The Neoblasts differentiate into tissue progenitors under the regulation of genes such as egfr-3. The regeneration polarity is controlled by Wnt pathway, BMP pathway and bioelectric signals. The neoblast within the blastema differentiate into desired cell types and regenerate the missing tissues. Those tissue specific genes regulate the tissue progenitor cells to differentiate into desired cell types to complete the regeneration process. CONCLUSION: All tissue types in planarian participate in the regeneration process regulated by distinct molecular factors and cellular signaling pathways. The neoblasts play vital roles in tissue regeneration and morphology maintenance. These studies provide new insights into the molecular mechanisms for regulating planarian regeneration.

Pathological analysis and surgical modalities selection of cT1N0M0 solitary papillary thyroid carcinoma in the isthmus.

BACKGROUND: prognosis, identify clinicopathological characteristics, and determine optimal modalities for cT1N0M0 solitary papillary thyroid carcinoma in the isthmus (PTCI). METHODS: The clinical data of 124 patients with cT1N0M0 solitary PTCI from 3 medical centers were analyzed retrospectively. Of these, 32 participants had undergone total thyroidectomy plus unilateral central neck dissection, 36 had received total thyroidectomy plus bilateral central neck dissection, 24 had less-than-total thyroidectomy plus unilateral central neck dissection, and 32 had less-than-total thyroidectomy plus bilateral central neck dissection. We compared the effects of different surgical modalities and clinicopathological characteristics on the prognosis of cT1N0M0 solitary PTCI. RESULTS: There was no significant difference in postoperative recurrence-free survival between participants who received different extents of central region lymph node dissection and thyroidectomies (P>0.05). Temporary hypocalcemia occurred in participants who underwent total thyroidectomy plus bilateral central neck dissection [chi-square (χ2) =7.87, P=0.005]. Tumors with primary lesions ≥0.55 cm were prone to have central lymph node metastasis [95% confidence interval (CI): 0.51 to 0.71, P=0.047]. Multiple logistic analysis suggested that age over 55 years [odds ratio (OR) =11.90, 95% CI: 1.36 to 104.03, P=0.025], tumor size greater than 0.55 cm (OR =4.16, 95% CI: 1.28 to 13.52, P=0.018), and absence of nodular goiter (OR =2.57, 95% CI: 1.05 to 6.32, P=0.04) were risk factors for central lymph node metastasis of patients with cT1N0M0 solitary PTCI. CONCLUSIONS: Less-than-total thyroidectomy is recommended for patients with cT1N0M0 solitary PTCI. Central lymph node dissection is recommended for patients who are prone to have central occult lymph node metastases with tumor size ≥55 cm, older than 55 years, and without nodular goiter.