Bioactive Molecular Discovery Using Deer Antlers as a Model of Mammalian Regeneration

The significance of MDK growth factor in the antler development of sika deer (Cervus nippon): An in-depth analysis

Deer antlers exhibit rapid growth during the velvet phase. As a critical endogenous growth factor in animals, midkine (MDK) is likely closely associated with the growth of antlers. However, the spatio-temporal expression pattern of MDK during the velvet phase was unclear. This study explored the physiological role of MDK by analyzing its molecular characterization and spatio-temporal expression dynamics during the growth of sika deer antlers. The study cloned the coding sequences (CDS) of MDK, which spanned 429 bp and encoded 142 amino acids. The results of bioinformatics prediction analysis showed that MDK was an extracellular hydrophilic secreted protein, which was mainly composed of random coil. MDK protein was relatively conserved in evolution and MDK protein of sika deer had the closest relatives to ruminants and the furthest relatives to Aves. The tip tissues (dermis, mesenchyme, precartilage, cartilage) of antlers were collected from three important growth and development nodes (early period, EP. middle period, MP. late period, LP), and quantitative real-time polymerase chain reaction (qRT-PCR) was chosen to detect the spatio-temporal expression of the MDK. The results showed that MDK was expressed in all tissue sites of antler tip in EP, MP, LP. MDK had a consistent expression pattern under all growth periods and was strongly expressed in dermis and cartilage. The expression of MDK was consistently up-regulated in precartilage, whereas it was first up-regulated and then down-regulated in other tissues, and it was highly significant in MP compared to EP and LP (P < 0.01). This study suggested that MDK may regulate the growth of dermis and cartilage tissues mainly by participating in the process of angiogenesis and bone formation, thus promoting the rapid growth of antlers.

Melatonin promotes the proliferation and differentiation of antler chondrocytes via RUNX2 dependent on the interaction between NOTCH1 and SHH signaling pathways

Melatonin (MT), an endogenous hormone secreted by pineal gland, has the sedative, anti-inflammatory and antioxidant functions. However, there are few studies on whether MT affects the proliferation and differentiation of antler chondrocytes. The present study investigated the influences of MT on the proliferation and differentiation of antler chondrocytes, explored its regulation on runt-related transcription factor 2 (RUNX2), NOTCH1 and sonic hedgehog (SHH) signaling, and elucidated their interplays. The results showed that MT promoted the proliferation of antler chondrocytes and induced the differentiation of chondrocytes into hypertrophic chondrocytes as evidenced by the significant increase of collagen type X (COL X), alkaline phosphatase (ALP) and matrix metalloproteinase 13 (MMP13) expression and ALP activity, the well-established markers for hypertrophic chondrocytes, but this effectiveness was neutralized by the addition of MT receptor antagonist. Further analysis indicated that MT activated the NOTCH1 and SHH signaling whose blockage abrogated the inducement of MT on the proliferation and differentiation of antler chondrocytes. SHH was identified as a downstream target of recombination signal binding protein for immunoglobulin kappa J region (RBPJ), a transcription factor of NOTCH1 signaling. Meanwhile, MT stimulated the expression of RUNX2 through activating the SHH signaling whose downstream transcription factor glioma-associated oncogene 1 (GLI1) directly controlled the transcription of RUNX2 through binding to its promoter region. Moreover, repression of GLI1 counteracted the proliferative effect of MT on antler chondrocytes and attenuated the advancement of MT on chondrocyte differentiation, while supplementation of recombinant RUNX2 protein recued above effects. Collectively, MT induced the proliferation and differentiation of antler chondrocytes via RUNX2 dependent on the interaction between NOTCH1 and SHH signaling pathways.

Haplotype-resolved Genome of Sika Deer Reveals Allele-specific Gene Expression and Chromosome Evolution

Despite the scientific and medicinal importance of diploid sika deer (Cervus nippon), its genome resources are limited and haplotype-resolved chromosome-scale assembly is urgently needed. To explore mechanisms underlying the expression patterns of the allele-specific genes in antlers and the chromosome evolution in Cervidae, we report, for the first time, a high-quality haplotype-resolved chromosome-scale genome of sika deer by integrating multiple sequencing strategies, which was anchored to 32 homologous groups with a pair of sex chromosomes (XY). Several expanded genes (RET, PPP2R1A, PPP2R1B, YWHAB, YWHAZ, and RPS6) and positively selected genes (eIF4E, Wnt8A, Wnt9B, BMP4, and TP53) were identified, which could contribute to rapid antler growth without carcinogenesis. A comprehensive and systematic genome-wide analysis of allele expression patterns revealed that most alleles were functionally equivalent in regulating rapid antler growth and inhibiting oncogenesis. Comparative genomic analysis revealed that chromosome fission might occur during the divergence of sika deer and red deer (Cervus elaphus), and the olfactory sensation of sika deer might be more powerful than that of red deer. Obvious inversion regions containing olfactory receptor genes were also identified, which arose since the divergence. In conclusion, the high-quality allele-aware reference genome provides valuable resources for further illustration of the unique biological characteristics of antler, chromosome evolution, and multi-omics research of cervid animals.

MiRNA Profiling and Its Potential Roles in Rapid Growth of Velvet Antler in Gansu Red Deer (Cervus elaphus kansuensis)

A significant variety of cell growth factors are involved in the regulation of antler growth, and the fast proliferation and differentiation of various tissue cells occur during the yearly regeneration of deer antlers. The unique development process of velvet antlers has potential application value in many fields of biomedical research. Among them, the nature of cartilage tissue and the rapid growth and development process make deer antler a model for studying cartilage tissue development or rapid repair of damage. However, the molecular mechanisms underlying the rapid growth of antlers are still not well studied. MicroRNAs are ubiquitous in animals and have a wide range of biological functions. In this study, we used high-throughput sequencing technology to analyze the miRNA expression patterns of antler growth centers at three distinct growth phases, 30, 60, and 90 days following the abscission of the antler base, in order to determine the regulatory function of miRNA on the rapid growth of antlers. Then, we identified the miRNAs that were differentially expressed at various growth stages and annotated the functions of their target genes. The results showed that 4319, 4640, and 4520 miRNAs were found in antler growth centers during the three growth periods. To further identify the essential miRNAs that could regulate fast antler development, five differentially expressed miRNAs (DEMs) were screened, and the functions of their target genes were annotated. The results of KEGG pathway annotation revealed that the target genes of the five DEMs were significantly annotated to the "Wnt signaling pathway", "PI3K-Akt signaling pathway", "MAPK signaling pathway", and "TGF-β signaling pathway", which were associated with the rapid growth of velvet antlers. Therefore, the five chosen miRNAs, particularly ppy-miR-1, mmu-miR-200b-3p, and novel miR-94, may play crucial roles in rapid antler growth in summer.

A Brief Analysis of Proteomic Profile Changes during Zebrafish Regeneration

Unlike mammals, zebrafish are capable to regenerate many of their organs, however, the response of tissue damage varies across tissues. Understanding the molecular mechanism behind the robust regenerative capacity in a model organism may help to identify and develop novel treatment strategies for mammals (including humans). Hence, we systematically analyzed the current literature on the proteome profile collected from different regenerated zebrafish tissues. Our analyses underlining that several proteins and protein families responsible as a component of cytoskeleton and structure, protein synthesis and degradation, cell cycle control, and energy metabolism were frequently identified. Moreover, target proteins responsible for the initiation of the regeneration process, such as inflammation and immune response were less frequently detected. This highlights the limitation of previous proteomic analysis and suggested a more sensitive modern proteomics analysis is needed to unfold the mechanism. This brief report provides a list of target proteins with predicted functions that could be useful for further biological studies.