Amphioxus Gli knockout disrupts the development of left-right asymmetry but has limited impact on neural patterning

The Gli transcription factors are the primary mediators of Hedgehog (Hh) signaling. Vertebrate genomes contain multiple Gli paralogues with different functions downstream of Hh signal receipt, in part explaining the complexity of cellular responses to Hh that allow concentration-dependent target gene activation. Amphioxus is a chordate that split from the vertebrate lineage early in the evolution of chordates, before the genome duplications that occurred in early vertebrate evolution. It has a single Gli gene whose transcripts can be alternately spliced to yield two protein isoforms called GliS and GliL. We generated two knockout mutations in amphioxus Gli, one that affects the whole gene and a second that only affects GliL. Both knockouts showed major morphological and molecular defects in the development of left-right asymmetry, a phenotype that is similar but not identical to that previously found in Hh mutants. Hh signaling also patterns the amphioxus neural tube. Here, however, knockout of GliL showed no identifiable phenotype, while knockout of the full gene showed only small changes to the expression of one gene family, Olig. Other genes that were prominently affected by Hh knockout were not altered in expression in either knockout. Reasons for the differences between Hh and Gli knockouts in the pharynx and neural tube are discussed in the context of the likely different functions of amphioxus Gli isoforms.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00195-w.

WNT5A, β‑catenin and SUFU expression patterns, and the significance of microRNA deregulation in placentas with intrauterine growth restriction

Placental insufficiency is a common cause of intrauterine growth restriction (IUGR). It affects ~10% of pregnancies and increases fetal and neonatal morbidity and mortality. Although Wnt and Hh pathways are crucial for embryonic development and placentation, their role in the pathology of IUGR is still not sufficiently explored. The present study analyzed the expression of positive regulators of the Wnt pathway, WNT5A and β‑catenin, and the expression of the Hh pathway negative regulator suppressor of fused (SUFU). Immunohistochemical and reverse transcription‑quantitative PCR (RT‑qPCR) assays were performed on 34 IUGR and 18 placental tissue samples from physiologic singleton‑term pregnancies. Epigenetic mechanisms of SUFU gene regulation were also investigated by methylation‑specific PCR analysis of its promoter and RT‑qPCR analysis of miR‑214‑3p and miR‑378a‑5p expression. WNT5A protein expression was higher in endothelial cells of placental villi from IUGR compared with control tissues. That was also the case for β‑catenin protein expression in trophoblasts and endothelial cells and SUFU protein expression in trophoblasts from IUGR placentas. The SUFU gene promoter remained unmethylated in all tissue samples, while miR‑214‑3p and miR‑378a‑5p were downregulated in IUGR. The present results suggested altered Wnt and Hh signaling in IUGR. DNA methylation did not appear to be a mechanism of SUFU regulation in the pathogenesis of IUGR, but its expression could be regulated by miRNA targeting.

High-fat diet intake ameliorates the expression of hedgehog signaling pathway in adult rat liver

BACKGROUND

Disproportionate fatty diet intake provokes hepatic lipid accumulation that causes non-alcoholic fatty liver disease, triggering the embryonically conserved Hedgehog (Hh) pathway in the adult liver. The present study incorporates exploring the impact of chronically administered unsaturated (D-1) and saturated (D-2) fat-enriched diets on hematological parameters, liver functioning, and lipid profile in the rat model. Besides, hepatohistology and real time gene expression analysis of Hh signaling pathway genes i.e., Shh, Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were carried out.

METHODS AND RESULTS

Fifteen Rattus norvegicus (♂) of 200 ± 25 g weight were grouped into control, D-1, and D-2. Animals were fed on their respective diets for 16 weeks. Fatty diet intake resulted in neutropenia, lymphocytosis, monocytosis, polycythemia, and macrocytosis in both experimental groups. Altered liver injury biomarkers, hypertriglyceridemia, and significantly increased very-low-density lipoprotein VLDL were also noted in both high-fat diet (HFD) groups as compared to control. Hepatohistological examination showed disrupted microarchitecture, infiltration of inflammatory cells, cellular necrosis, widened sinusoidal spaces, and microvesicular steatotic hepatocytes in D-1 and D-2. Collagen deposition in both HFD groups marks the extent of fibrosis. Significant upregulation of hedgehog pathway genes was found in fatty diet groups. In comparison with the control group, Shh Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were upregulated in D-1. In D-2 Shh, Hhip, and Smo expressions were upregulated, Ihh exhibited downregulation as compared to control.

CONCLUSION

Excess fat deposits in liver due to chronic consumption of high-fat diet results in anomalous architecture and functioning. High-fat diet induced significant variations in Hh pathway genes expression; especially Shh, Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were upregulated. Infiltration of inflammatory cells ( ), widened sinusoidal spaces (▲), cellular necrosis, and micro vesicular steatotic hepatocytes (*) were shown in the liver. Significant collagen deposition in both HFD groups i.e. D-1 and D-2 confirmed liver fibrosis. Excessive intake of dietary fats impaired normal liver functioning and liver inflammation triggered Hh signaling in adult rats.

Stromal cells of giant cell tumor of bone show primary cilia in giant cell tumor of bone

Giant cell tumor of bone (GCTB) is a locally aggressive primary bone neoplasm composed by tumoral stromal cells (SCs) and a reactive component that consists of monocytic/histiocytic cells that give rise by fusion to osteoclast-like multinucleated cells. Recently, specific Histone 3.3 mutations have been demonstrated in SCs of GCTB. Many of the pathways related to bone proliferation and regulation depend on the primary cilium, a microtubule-based organelle that protrudes outside the cell and acts as a sensorial antenna. In the present work, we aimed to study the presence and role of primary cilia in GCTB. Ultrastructural, immunohistochemical, and immunofluorescence studies were performed in order to demonstrate, for the first time, that the primary cilium is located in spindle-shaped SCs of GCTB. Moreover, we showed Hedgehog (Hh) signaling pathway activation in these cells. Hence, primary cilia may play a relevant role in GCTB tumorogenesis through Hh signaling activation in SCs. RESEARCH HIGHLIGHTS: Transmission electron microscopy allows describing and differentiating cellular subpopulations in giant cell tumor of bone (GCTB). The primary cilium is present in some tumoral stromal cells of GCTB. Hedgehog signalling is activated in these cells.

Identification and spatiotemporal expression of gpr161 genes in zebrafish

G protein coupled Receptor 161 (GPR161) is a ciliary orphan GPCR. It is reported to play critical roles in regulating vertebrate Hedgehog (Hh) signaling pathway, that is conserved in metazoan and functions in earlier embryogenesis and homeostasis of adult metabolism. However, to date, all GPR161 functional studies were performed only in mouse. Knock out gpr161 in NIH3T3 cell lines, the common material for Hh mechanism research, failed to give any obvious Hh pathway defects, raising the question that whether GPR161 functions in Hh pathway is conserved in vertebrate system. Here, we described the characterization and spatiotemporal expression of two zebrafish gpr161 homologs, gpr161a and gpr161b. gpr161a was renamed of the gpr161 previously identified, while gpr161b was novel identified. The whole-mount in situ hybridization and quantitative PCR results showed that gpr161a is initially expressed in maternal manner while gpr161b is not. Although these two gpr161 showed ubiquitously expressed at early embryonic stages, each of them had tissue specific accumulation. gpr161a is abundant in the central nervous system (CNS) and adaxial cells, where are rich of Hh responding cells. Together gpr161a was highly expressed in muscle and intestine in adult fishes. These results strongly suggest the regulating roles of Gpr161 a in zebrafish Hh signal transduction. gpr161b was also accumulated in the CNS but mainly at the midline in the neural tube, similar pattern as wnt5b expression in such area, suggesting its potential function correlated with WNT signaling pathway. Interestingly, we also found the specific accumulation of gpr161 in posterior blood island (PBI) at 24 hours post fertilization (hpf), indicating the gpr161 may play roles in early hematopoiesis in zebrafish. Our work provides a starting point to unveil the divergent functions of gpr161 in vertebrate and will shed light on the studies of mechanism of Hh and WNT pathways, as well as early hematopoiesis.

Leptin Promotes White Adipocyte Browning by Inhibiting the Hh Signaling Pathway

Leptin is an important secretory protein that regulates the body’s intake and energy consumption, and the functions of the Hh signaling pathway related to white adipocyte browning are controversial. It has been reported that leptin plays a critical role in adipogenesis by regulating the Hh signaling pathway, but whether there is a functional relationship between leptin, the Hh signaling pathway, and adipocyte browning is not clear. In this research, mouse white pre-adipocytes were isolated to explore the influence of the Hh signal pathway and leptin during the process described above. This showed that leptin decreased high fat diet-induced obese mice body weight and inhibited the Hh signaling pathway, which suggested that leptin and the Hh signaling pathway have an important role in obesity. After activation of the Hh signaling pathway, significantly decreased browning fat-relative gene expression levels were recorded, whereas inhibition of the Hh signaling pathway significantly up-regulated the expression of these genes. Similarly, leptin also up-regulated the expression of these genes, and increased mitochondrial DNA content, but decreased the expression of Gli, the key transcription factors of the Hh signaling pathway. In short, the results show that leptin promotes white adipocyte browning through inhibiting the Hh signaling pathway. Overall, these results demonstrate that leptin serves as a potential intervention to decrease obesity by inhibiting the Hh signaling pathway.

Expression of hydrogen sulfide synthases and Hh signaling pathway components correlate with the clinicopathological characteristics of papillary thyroid cancer patients

OBJECTIVE

To examine whether the expression levels of endogenous H₂S synthases and hedgehog (Hh) signaling pathway components correlate with the clinicopathological characteristics of papillary thyroid cancer (PTC) patients.

METHODS

A retrospective analysis was conducted of clinicopathological data obtained from 176 patients diagnosed with PTC, and immunohistochemical methods were used to detect the expression levels of endogenous H₂S synthases cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (MPST), as well as three molecules in the Hh signaling pathway: sonic hedgehog (SHH), patched (PTCH), and smoothened (SMO). Specimens of PTC tissue (n=176) and normal para-cancerous thyroid tissue (n=134) were obtained from 176 patients who underwent a total thyroidectomy or thyroid glandular follicle and isthmus resection and analyzed by immunohistochemical methods for their levels of CSE, CBS, MPST, SHH, PTCH, and SMO expression.

RESULTS

We found that CSE was overexpressed in PTC tissues, while CBS and MPST were only slightly expressed in PTC tissues at levels similar to those in adjacent normal tissues. The levels of CSE expression were positively correlated with tumor size, extrathyroidal extension (ETE), and lymph node metastasis (LNM), but were not correlated with patient gender, age, or TNM stage. SHH, PTCH, and SMO Hh signaling pathway components were widely expressed in PTC tissues, and their expression correlated with larger tumor size, ETE, and LNM, but not with patient gender, age, or TNM stage, suggesting that activation of the Hh signaling pathway is involved in thyroid tumor progression.

CONCLUSIONS

These data suggest that a high level of CSE expression accompanied by Hh signaling pathway activation is involved in the pathogenesis and progression of PTC.

Cloning and characterization of adipogenin and its overexpression enhances fat accumulation of bovine myosatellite cells

Adipogenin (ADIG) is an adipocyte-specific membrane protein highly expressed in adipose tissues and is increased during the adipocyte differentiation. However, the roles and mechanisms of ADIG on fat accumulation and adipocyte differentiation in ex vivo still largely unknown. In this study, we isolated bovine myosatellite cells based on adhesion characteristics to investigate whether ADIG overexpression could promote trans-differentiation and increase fat accumulation in myosatellite cells. Immunofluorescence labeling was then used for the phenotypic characteristics of myosatellite. Our results showed that, after induction of differentiation, adenovirus mediated ADIG overexpression could upregulate expression level of PPARγ, and Oil Red O staining showed larger lipid drops compared to control groups. In consistent, key components of Hh signaling pathway were down regulated when infected with ADIG adenovirus, even though treated with inhibitor of Hh signaling pathway together could not induce further decrease. In addition, bioinformatics analysis of ADIG was also performed for its structure and function.

Disruption of Smad4 in odontoblasts and dental epithelial cells influences the phenotype of multiple keratocystic odontogenic tumors

Keratocystic odontogenic tumors (KCOTs) are cystic epithelial neoplasms with a high recurrence rate. The molecular mechanisms underlying the initiation and progression of KCOTs are still largely unknown. Previous research showed that specific ablation of Smad4 in odontoblasts and dental epithelia resulted in spontaneous KCOTs in mice, and that constitutively activated Hedgehog (Hh) signaling was detected in the cyst epithelia of both Smad4(Co/Co) OC-Cre and Smad4(Co/Co) K5-Cre mice. Here, we ablated Smad4 in mouse odontoblasts and dental epithelia and compared the sizes and numbers of KCOTs. Both the number and size of KCOTs in Smad4(Co/Co) OC-Cre mice were larger than those in Smad4(Co/Co) K5-Cre mice, suggesting that paracrine signals from root odontoblasts play a more important role than those from Hertwig's epithelial root sheath (HERS) cells.