Suppressive effects of valproic acid on caudal fin regeneration in adult zebrafish

Transcriptional Signature of Valproic Acid-Induced Neural Tube Defects in Human Spinal Cord Organoids

In vertebrates, the entire central nervous system is derived from the neural tube, which is formed through a conserved early developmental morphogenetic process called neurulation. Although the perturbations in neurulation caused by genetic or environmental factors lead to neural tube defects (NTDs), the most common congenital malformation and the precise molecular pathological cascades mediating NTDs are not well understood. Recently, we have developed human spinal cord organoids (hSCOs) that recapitulate some aspects of human neurulation and observed that valproic acid (VPA) could cause neurulation defects in an organoid model. In this study, we identified and verified the significant changes in cell-cell junctional genes/proteins in VPA-treated organoids using transcriptomic and immunostaining analysis. Furthermore, VPA-treated mouse embryos exhibited impaired gene expression and NTD phenotypes, similar to those observed in the hSCO model. Collectively, our data demonstrate that hSCOs provide a valuable biological resource for dissecting the molecular pathways underlying the currently unknown human neurulation process using destructive biological analysis tools.

The Expression and Function of lincRNA-154324 and the Adjoining Protein-Coding Gene vmp1 in the Caudal Fin Regeneration of Zebrafish

Caudal fin regeneration is regulated by a variety of mechanisms, but the role of long non-coding RNA (lncRNA) has rarely been studied. The present study aimed to describe the landscape of lncRNAs during caudal fin regeneration using whole transcriptome sequencing, and then to conduct a functional study on the target lncRNAs using real-time fluorescent quantitative PCR (RT-qPCR), in situ hybridization, and the CRISPR/Cas9 method for lncRNA gene knockout. The results of the transcriptome sequencing showed that a total of 381 lncRNAs were differentially expressed, among which ENSDART00000154324 (lincRNA-154324) was found to be highly related to caudal fin regeneration, and thus it was chosen as the target lncRNA for the subsequent functional study. The results regarding the temporal and spatial expression of lincRNA-154324 and the gene knockout results from CRISPR/Cas9 indicated that lincRNA-154324 is involved in the caudal fin regeneration of zebrafish. Importantly, we serendipitously discovered that the cis correlation coefficient between lincRNA-154324 and its neighboring gene vacuole membrane protein 1 (vmp1) is extremely high, and they are essential for the process of caudal fin regeneration. Moreover, studies have found that vmp1 plays an important role in protein secretion, organelle formation, multicellular development, and autophagy. Collectively, our result may provide a framework for the identification and analysis of lncRNAs involved in the regeneration of the zebrafish caudal fin.

egfl6 expression in the pharyngeal pouch is dispensable for craniofacial development

Epidermal growth factor-like domain multiple 6 (Egfl6) is a basement membrane protein and plays an important role in hair follicle morphogenesis, angiogenesis, notochord development in vertebrates. Although egfl6 expression in the developing head was observed in zebrafish, its role for craniofacial development and the determination of the pharyngeal region expressing egfl6, have not been reported yet. Here, we report the expression patterns and function of egfl6 in craniofacial development in zebrafish. egfl6 was expressed sequentially in the developing pharyngeal pouches that are key epithelial structures governing the development of the vertebrate head. However, loss-of-function mutations in egfl6 did not cause any craniofacial defects, including the pouches as well as the thymus and facial cartilages whose development is contingent upon appropriate pouch formation. egfl6 was unlikely redundant with egfl7 expressed in a distinct pharyngeal region from that of egfl6 in craniofacial development because reduction of egfl7 with a MO in egfl6 mutants did not affect craniofacial development. In addition, we found that egfl6 carried an endogenous start loss mutation in the wild-type Tübingen strain, implying egfl6 would be a non-functional gene. Taken all together, we suggest that egfl6 expression in the pharyngeal pouches is not required for craniofacial development in zebrafish.