Hedgehog signaling pathway regulated the target genes for adipogenesis in silkworm Bombyx mori

Smoothened antagonist sonidegib affects the development of D. melanogaster larvae via suppression of epidermis formation

Hedgehog (Hh) signaling is essential for the regulation of embryonic growth and development, the maintenance of stem cell autostasis, and tissue formation, whether in vertebrates or invertebrates. However, exploration into the Hh pathway antagonists in Drosophila or other pests of agricultural importance has been scant. In order to gain a better understanding of the potential utility of the antagonists in insect investigations, a conventional Hh antagonist, sonidegib, was used to evaluate the effects on the development of Drosophila larvae. The results showed that early instar larvae exposed to sonidegib exhibited new epidermal abnormalities and decreased motility after molting. Transcriptome analysis revealed that Sonidegib had a profound effect on chitin-based cuticle development throughout all stages of larvae. Physiological experiments revealed that sonidegib suppressed the epidermis formation and decreased the chitin content. The results of this study shed new light on the potential use of Hh antagonists in agricultural pest management.

Chromosome-level genome assembly of Dastarcus helophoroides provides insights into CYP450 genes expression upon insecticide exposure

BACKGROUND

Dastarcus helophoroides is an important natural enemy of cerambycids, and is wildly used in biological control of pests. Nevertheless, the absence of complete genomic information limits the investigation of the underlying molecular mechanisms. Here, a chromosome-level of Dastarcus helophoroides genome is assembled using a combination strategy of Illumina, PacBio, 10x™ Genomics, and Hi-C.

RESULTS

The final assembly is 609.09 Mb with contig N50, scaffold N50 and GC content of 5.46 Mb, 42.56 Mb and 31.50%, respectively, and 95.25% of the contigs anchor into 13 chromosomes. In total 14 890 protein-coding genes and 65.37% repeat sequences are predicted in the assembly genome. The phylogenetic analysis of single-copy gene families shared among 20 insect species indicates that Dastarcus helophoroides is placed as the sister species to clade (Nitidulidae+Curculionoidea+Chrysomeloidea) + Tenebrionoidea, and diverges from the related species ~242.9 Mya. In total 36 expanded gene families are identified in Dastarcus helophoroides genome, and are functionally related to drug metabolism and metabolism of xenobiotics by cytochrome P450. Some members of CYP4 Clade and CYP6 Clade are up-regulated in Dastarcus helophoroides adults upon insecticide exposure, of which expressions of DhCYP4Q, DhCYP6A14X1 and DhCYP4C1 are significantly up-regulated. The silencing of the three genes leads to adults more sensitive to insecticide and increased knocked-down rate, which may indicate their critical roles in stress resistance and detoxication.

CONCLUSION

Our study systematically integrated the chromosome-level genome, transcriptome and gene expression of Dastarcus helophoroides, which will provide valuable resources for understanding mechanisms of pesticide metabolism, growth and development, and utilization of the natural enemy in integrated control. © 2022 Society of Chemical Industry.

The morphogen Hedgehog is essential for proper adult morphogenesis in Bombyx mori

The well-known morphogen Hedgehog (Hh) is indispensable for embryo patterning and organ development from invertebrates to vertebrates. The role of Hh signaling pathway has been extensively investigated in the model organism Drosophila melanogaster, whereas its biological functions are still poorly understood in non-drosophilid insects. In the current study, we describe comprehensive investigation of Hh biological roles in the model lepidopteran insect Bombyx mori by using both CRISPR/Cas9-mediated gene ablation and Gal4/UAS-mediated ectopic expression. Direct injection of Cas9 protein and Hh-specific sgRNAs into preblastoderm embryos induced complete lethality. In contrast, Hh mutants obtained by the binary transgenic CRISPR/Cas9 system showed no deleterious phenotypes during embryonic and larval stages. However, mutants showed abnormalities from the pupal stage and most of adult body appendages exhibited severe developmental defects. Molecular analysis focused on wing development reveal that Hh signaling, Imd signaling and Wnt signaling pathways were distorted in Hh mutant wings. Ectopic expression by using the binary Gal4/UAS system induce early larval lethality. On contrary, moderate overexpression of Hh by using a unitary transgenic system resulted in severe defects in adult leg and antenna development. Our data directly provide genetic evidence that Hh plays vital roles in imaginal discs development and proper adult morphogenesis in B. mori.

The Characterization and Differential Analysis of m6A Methylation in Hycole Rabbit Muscle and Adipose Tissue and Prediction of Regulatory Mechanism about Intramuscular Fat

N6-methyladenosine (m⁶A) widely participates in various life processes of animals, including disease, memory, growth and development, etc. However, there is no report on m⁶A regulating intramuscular fat deposition in rabbits. In this study, m⁶A modification of Hycole rabbit muscle and adipose tissues were detected by MeRIP-Seq. In this case, 3 methylases and 12 genes modified by m⁶A were found to be significantly different between muscle and adipose tissues. At the same time, we found 3 methylases can regulate the expression of 12 genes in different ways and the function of 12 genes is related to fat deposition base on existing studies. 12 genes were modified by m⁶A methylase in rabbit muscle and adipose tissues. These results suggest that 3 methylases may regulate the expression of 12 genes through different pathways. In addition, the analysis of results showed that 6 of the 12 genes regulated eight signaling pathways, which regulated intramuscular fat deposition. RT-qPCR was used to validate the sequencing results and found the expression results of RT-qPCR and sequencing results are consistent. In summary, METTL4, ZC3H13 and IGF2BP2 regulated intramuscular fat by m⁶A modified gene/signaling pathways. Our work provided a new molecular basis and a new way to produce rabbit meat with good taste.

Myoblast proliferation during flight muscle development in Manduca sexta is unaffected by reduced neural signaling

In holometabolous insects, metamorphosis involves restructuring the musculature to accommodate adult-specific anatomy and behaviors. Evidence from experiments on remodeled muscles, as well as those that develop de novo, suggests that signals from the nervous system support adult muscle development by controlling myoblast proliferation rate. However, the dorsolongitudinal flight muscles (DLMs) of Manduca sexta undergo a mixed developmental program involving larval muscle fibers, and it is not known if neurons play the same role in the formation of these muscles. To address this question, we have blocked the most promising candidate pathways for neural input and examined the DLMs for changes in proliferation. Our results show that DLM development does not depend on neural activity, Hedgehog signaling, or EGF signaling. It remains to be determined how DLM growth is controlled and why neurally mediated proliferation differs between individual muscles.

Leptin: an entry point for the treatment of peripheral tissue fibrosis and related diseases

Leptin is a small peptide mainly secreted by adipocyte, which acts on the central nervous system of the hypothalamus to regulate the body's energy balance by inhibiting food intake, it also can directly act on specific cells through leptin receptors (for example, ObRa, which exists in the blood-brain barrier or kidneys), thereby affect cell metabolism. Excessive deposition of extracellular matrix (ECM) causes damage to normal tissues or destruction of organ structure, which will eventually lead to tissue or organ fibrosis. The sustainable development of fibrosis can lead to structural damage and functional decline of organs, and even exhaustion, which seriously threatens human health and life. In recent years, studies have found that leptin directly alleviates the fibrosis process of various tissues and organs in mammals. Therefore, we speculate that leptin may become a significant treatment for fibrosis of various tissues and organs in the future. So, the main purpose of this review is to explore the specific mechanism of leptin in the process of fibrosis in multiple tissues and organs, and to provide a theoretical basis for the treatment of various tissues and organs fibrosis and related diseases caused by it, which is of great significance in the future.

Hedgehog promotes cell proliferation in the midgut of silkworm, Bombyx mori

The Hedgehog (Hh) signaling pathway is one of the major regulators of embryonic development and tissue homeostasis in multicellular organisms. However, the role of this pathway in the silkworm, especially in the silkworm midgut, remains poorly understood. Here, we report that Bombyx mori Hedgehog (BmHh) is expressed in most tissues of silkworm larvae and that its functions are well-conserved throughout evolution. We further demonstrate that the messenger RNA of four Hh signaling components, BmHh ligand, BmPtch receptor, signal transducer BmSmo and transcription factor BmCi, are all upregulated following Escherichia coli or Bacillus thuringiensis infection, indicating the activation of the Hh pathway. Simultaneously, midgut cell proliferation is strongly promoted. Conversely, the repression of Hh signal transduction with double-stranded RNA or cyclopamine inhibits the expression of BmHh and BmCi and reduces cell proliferation. Overall, these findings provide new insights into the Hh signaling pathway in the silkworm, B. mori.

Molecular Mechanisms of Adipogenesis: The Anti-adipogenic Role of AMP-Activated Protein Kinase

Obesity is now a widespread disorder, and its prevalence has become a critical concern worldwide, due to its association with common co-morbidities like cancer, cardiovascular diseases and diabetes. Adipose tissue is an endocrine organ and therefore plays a critical role in the survival of an individual, but its dysfunction or excess is directly linked to obesity. The journey from multipotent mesenchymal stem cells to the formation of mature adipocytes is a well-orchestrated program which requires the expression of several genes, their transcriptional factors, and signaling intermediates from numerous pathways. Understanding all the intricacies of adipogenesis is vital if we are to counter the current epidemic of obesity because the limited understanding of these intricacies is the main barrier to the development of potent therapeutic strategies against obesity. In particular, AMP-Activated Protein Kinase (AMPK) plays a crucial role in regulating adipogenesis – it is arguably the central cellular energy regulation protein of the body. Since AMPK promotes the development of brown adipose tissue over that of white adipose tissue, special attention has been given to its role in adipose tissue development in recent years. In this review, we describe the molecular mechanisms involved in adipogenesis, the role of signaling pathways and the substantial role of activated AMPK in the inhibition of adiposity, concluding with observations which will support the development of novel chemotherapies against obesity epidemics.

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.

The TEA domain family transcription factor TEAD4 represses murine adipogenesis by recruiting the cofactors VGLL4 and CtBP2 into a transcriptional complex

The Hippo signaling pathway is known to play an important role in multiple physiological processes, including adipogenesis. However, whether the downstream components of the Hippo pathway are involved in adipogenesis remains unknown. Here we demonstrate that the TEA domain family (TEAD) transcription factors are essential for adipogenesis in murine 3T3-L1 preadipocytes. Knockdown of TEAD1-4 stimulated adipogenesis and increased the expression of adipocyte markers in these cells. Interestingly, we found that the TEAD4 knockdown-mediated adipogenesis proceeded in a Yes-associated protein (YAP)/TAZ (Wwtr1)-independent manner and that adipogenesis suppression in WT cells involved formation of a ternary complex comprising TEAD4 and the transcriptional cofactors C-terminal binding protein 2 (CtBP2) and vestigial-like family member 4 (VGLL4). VGLL4 acted as an adaptor protein that enhanced the interaction between TEAD4 and CtBP2, and this TEAD4-VGLL4-CtBP2 ternary complex dynamically existed at the early stage of adipogenesis. Finally, we verified that TEAD4 directly targets the promoters of major adipogenesis transcription factors such as peroxisome proliferator-activated receptor γ (PPARγ) and adiponectin, C1Q, and collagen domain-containing (Adipoq) during adipogenesis. These findings reveal critical insights into the role of the TEAD4-VGLL4-CtBP2 transcriptional repressor complex in suppression of adipogenesis in murine preadipocytes.

Localization and functional analysis of the insect-specific RabX4 in the brain of Bombyx mori

Rab proteins are small monomeric GTPases/GTP-binding proteins, which form the largest branch of the Ras superfamily. The different Rab GTPases are localized to the cytosolic face of specific intracellular membranes, where they function as regulators of distinct steps in membrane trafficking. RabX4 is an insect-specific Rab protein that has no close homolog in vertebrates. There is little information about insect-specific Rab proteins. RabX4 was expressed in Escherichia coli and subsequently purified. Antibodies against Bombyx mori RabX4 were produced in rabbits for western immunoblotting and immunohistochemistry. Western blotting of neural tissues revealed a single band, at approximately 26 kD. RabX4-like immunohistochemical reactivity was restricted to neurons of the pars intercerebralis and dorsolateral protocerebrum in the brain. Further immunohistochemical analysis revealed that RabX4 colocalized with Rab6 and bombyxin in the corpus allatum, a neuronal organ that secretes neuropeptides synthesized in the brain into the hemolymph. RabX4 expression in the frontal ganglion, part of the insect stomatogastric nervous system that is found in most insect orders, was restricted to two neurons on the outer region and did not colocalize with allatotropin or Rab6. Furthermore, RNA interference of RabX4 decreased bombyxin expression levels in the brain. These findings suggest that RabX4 is involved in the neurosecretion of a secretory organ in Bombyx mori.