A self-generated Toddler gradient guides mesodermal cell migration

The sculpting of germ layers during gastrulation relies on coordinated migration of progenitor cells, yet the cues controlling these long-range directed movements remain largely unknown. While directional migration often relies on a chemokine gradient generated from a localized source, we find that zebrafish ventrolateral mesoderm is guided by the uniformly expressed and secreted protein Toddler/ELABELA/Apela, acting as a self-generated gradient. We show that the Apelin receptor, which is specifically expressed in mesodermal cells, has a dual role during gastrulation, acting as a scavenger receptor to generate a Toddler gradient, and as a chemokine receptor to sense this guidance cue. Thus, we uncover a single receptor-based self-generated gradient as the enigmatic guidance cue that can robustly steer the directional migration of mesoderm through the complex and continuously changing environment of the gastrulating embryo.

Phospholipid Profiles for Phenotypic Characterization of Adipose-Derived Multipotent Mesenchymal Stromal Cells

Multipotent mesenchymal stromal cells (MSC) have emerged as therapeutic tools for a wide range of pathological conditions. Yet, the still existing deficits regarding MSC phenotype characterization and the resulting heterogeneity of MSC used in different preclinical and clinical studies hamper the translational success. In search for novel MSC characterization approaches to complement the traditional trilineage differentiation and immunophenotyping assays reliably across species and culture conditions, this study explored the applicability of lipid phenotyping for MSC characterization and discrimination. Human peripheral blood mononuclear cells (PBMC), human fibroblasts, and human and equine adipose-derived MSC were used to compare different mesodermal cell types and MSC from different species. For MSC, cells cultured in different conditions, including medium supplementation with either fetal bovine serum or platelet lysate as well as culture on collagen-coated dishes, were additionally investigated. After cell harvest, lipids were extracted by chloroform/methanol according to Bligh and Dyer. The lipid profiles were analysed by an untargeted approach using liquid chromatography coupled to mass spectrometry (LC-MS) with a reversed phase column and an ion trap mass spectrometer. In all samples, phospholipids and sphingomyelins were found, while other lipids were not detected with the current approach. The phospholipids included different species of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS) in all cell types, whereas phosphatidylglycerol (PG) species were only present in MSC. MSC from both species showed a higher phospholipid species diversity than PBMC and fibroblasts. Few differences were found between MSC from different culture conditions, except that human MSC cultured with platelet lysate exhibited a unique phenotype in that they exclusively featured PE O-40:4, PG 38:6 and PG 40:6. In search for specific and inclusive candidate MSC lipid markers, we identified PE O-36:3 and PG 40:7 as potentially suitable markers across culture conditions, at which PE O-36:3 might even be used across species. On that basis, phospholipid phenotyping is a highly promising approach for MSC characterization, which might condone some heterogeneity within the MSC while still achieving a clear discrimination even from fibroblasts. Particularly the presence or absence of PG might emerge as a decisive criterion for future MSC characterization.

Regulation of stem cell identity by miR-200a during spinal cord regeneration

Axolotls are an important model organism for multiple types of regeneration, including functional spinal cord regeneration. Remarkably, axolotls can repair their spinal cord after a small lesion injury and can also regenerate their entire tail following amputation. Several classical signaling pathways that are used during development are reactivated during regeneration, but how this is regulated remains a mystery. We have previously identified miR-200a as a key factor that promotes successful spinal cord regeneration. Here, using RNA-seq analysis, we discovered that the inhibition of miR-200a results in an upregulation of the classical mesodermal marker brachyury in spinal cord cells after injury. However, these cells still express the neural stem cell marker sox2. In vivo lineage tracing allowed us to determine that these cells can give rise to cells of both the neural and mesoderm lineage. Additionally, we found that miR-200a can directly regulate brachyury via a seed sequence in the 3UTR of the gene. Our data indicate that miR-200a represses mesodermal cell fate after a small lesion injury in the spinal cord when only glial cells and neurons need to be replaced.

GLIS1, a potential candidate gene affect fat deposition in sheep tail

Fat deposition in sheep tails is as a result of a complicated mechanism. Mongolian sheep (MG) and Small Tail Han sheep (STH) are two fat-tailed Chinese indigenous sheep breeds while DairyMeade and East Friesian (DS) are two thin-tailed dairy sheep breeds recently introduced to China. In this study, population genomics analysis was applied to identify candidate genes associated with sheep tails based on an in-depth whole-genome sequencing of MG, STH and DS. The selective signature analysis demonstrated that GLIS1, LOC101117953, PDGFD and T were in the significant divergent regions between DS and STH–MG. A nonsynonymous point mutation (g.27807636G>T) was found within GLIS1 in STH–MG and resulted in a Pro to Thr substitution. As a pro-adipogenic factor, GLIS1 may play critical roles in the mesodermal cell differentiation during fetal development affecting fat deposition in sheep tails. This study gives a new insight into the genetic basis of species-specific traits of sheep tails.

Temporal integration of inductive cues on the way to gastrulation

Markers for the endoderm and mesoderm germ layers are commonly expressed together in the early embryo, potentially reflecting cells’ ability to explore potential fates before fully committing. It remains unclear when commitment to a single-germ layer is reached and how it is impacted by external signals. Here, we address this important question in Drosophila, a convenient model system in which mesodermal and endodermal fates are associated with distinct cellular movements during gastrulation. Systematically applying endoderm-inducing extracellular signal-regulated kinase (ERK) signals to the ventral medial embryo—which normally only receives a mesoderm-inducing cue—reveals a critical time window during which mesodermal cell movements and gene expression are suppressed by proendoderm signaling. We identify the ERK target gene huckebein (hkb) as the main cause of the ventral furrow suppression and use computational modeling to show that Hkb repression of the mesoderm-associated gene snail is sufficient to account for a broad range of transcriptional and morphogenetic effects. Our approach, pairing precise signaling perturbations with observation of transcriptional dynamics and cell movements, provides a general framework for dissecting the complexities of combinatorial tissue patterning.

Comparative evaluation of isogenic mesodermal and ectomesodermal chondrocytes from human iPSCs for cartilage regeneration

Generating phenotypic chondrocytes from pluripotent stem cells is of great interest in the field of cartilage regeneration. In this study, we differentiated human induced pluripotent stem cells into the mesodermal and ectomesodermal lineages to prepare isogenic mesodermal cell–derived chondrocytes (MC-Chs) and neural crest cell–derived chondrocytes (NCC-Chs), respectively, for comparative evaluation. Our results showed that both MC-Chs and NCC-Chs expressed hyaline cartilage–associated markers and were capable of generating hyaline cartilage–like tissue ectopically and at joint defects. Moreover, NCC-Chs revealed closer morphological and transcriptional similarities to native articular chondrocytes than MC-Chs. NCC-Ch implants induced by our growth factor mixture demonstrated increased matrix production and stiffness compared to MC-Ch implants. Our findings address how chondrocytes derived from pluripotent stem cells through mesodermal and ectomesodermal differentiation are different in activities and functions, providing the crucial information that helps make appropriate cell choices for effective regeneration of articular cartilage.

A Robust Circular RNA-Associated Three-Gene Prognostic Signature for Patients with Gastric Cancer

Accumulating evidence has demonstrated that circular RNAs (circRNAs) play vital roles in cancer progression. However, the underlying molecular mechanisms of circRNAs remain poorly elucidated in gastric cancer (GC). The main purpose of present study is to explore the underlying regulatory mechanism by constructing a circRNA-associated competitive endogenous RNA (ceRNA) network and further establish a robust prognostic signature for patients with GC. Based on expression data of circRNA, microRNA, and mRNA derived from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases, a circRNA-associated ceRNA network, containing 15 cirRNAs, 9 microRNAs, and 35 mRNAs, was constructed using the Starbase database. Functional enrichment analysis showed that the ceRNA network might be involved in many cancer-related pathways, such as regulation of transcription from RNA polymerase II promoter, mesodermal cell differentiation, and focal adhesion. A protein-protein interaction network was constructed based on genes within the circRNA-associated ceRNA network. We found that six of ten hub genes within the PPI network were significantly associated with overall survival (OS). Thus, using the LASSO method, we constructed a three-gene prognostic signature based on TCGA-GC cohort, which could classify GC patients into low-risk and high-risk groups with significant difference in OS ( HR = 1.9 , 95 % CI = 1.14 ‐ 3.2 , and log-rank p = 0.001 ). The prognostic performance of the three-gene signature was verified in GSE15459 ( HR = 1.9 , 95 % CI = 1.27 ‐ 3.0 , and log − rank p = 2.2 E − 05 ) and GSE84437 ( HR = 1.5 , 95 % CI = 1.17 ‐ 2.0 , and log − rank p = 6.3 E − 04 ). Multivariate Cox analysis further revealed that the three-gene prognostic signature could serve as an independent risk factor for OS. Taken together, our findings contribute to a better understanding of the underlying mechanisms of circRNAs in GC progression. Furthermore, a robust prognostic signature is meaningful to facilitate individualized treatment for patients with GC.

GLIS1, a Potential Candidate Gene Affect Fat Deposition in Sheep Tail

Fat deposition in sheep tails has complicated mechanisms. In this study, the population genomics analysis has been applied to identify candidate genes associated with fat tails based on high depth whole-genome sequencing of Mongolia sheep (MG, fat-tailed), Small Tail Han sheep (STH, fat-tailed) and two dairy sheep breeds DairyMeade and East Friesian (DS, thin-tailed). The selective signature analysis demonstrated that GLIS1, LOC101117953, PDGFD and T were in the significant divergent regions between DS and STH-MG. A nonsynonymous point mutation (g. 27807636G>T) was found within GLIS1 in STH-MG and resulting in a Pro to Thr substitution. As a pro-adipogenic factor, GLIS1 may play critical roles in the mesodermal cell differentiation during sheep fetal development and affect the fat deposition in sheep tails. This study provides a new insight into the genetic basis of species-specific traits of fat tails.

Hes5.9 Coordinate FGF and Notch Signaling to Modulate Gastrulation via Regulating Cell Fate Specification and Cell Migration in Xenopus tropicalis

Gastrulation drives the establishment of three germ layers and embryonic axes during frog embryonic development. Mesodermal cell fate specification and morphogenetic movements are vital factors coordinating gastrulation, which are regulated by numerous signaling pathways, such as the Wnt (Wingless/Integrated), Notch, and FGF (Fibroblast growth factor) pathways. However, the coordination of the Notch and FGF signaling pathways during gastrulation remains unclear. We identified a novel helix–loop–helix DNA binding domain gene (Hes5.9), which was regulated by the FGF and Notch signaling pathways during gastrulation. Furthermore, gain- and loss-of-function of Hes5.9 led to defective cell migration and disturbed the expression patterns of mesodermal and endodermal marker genes, thus interfering with gastrulation. Collectively, these results suggest that Hes5.9 plays a crucial role in cell fate decisions and cell migration during gastrulation, which is modulated by the FGF and Notch signaling pathways.