Lingling Qiu

Discovery of novel long non-coding RNAs induced by subgroup J avian leukosis virus infection in chicken

Abstract Avian leukosis virus subgroup J (ALV‐J) is an avian oncogenic retrovirus that has led to severe economic losses in the poultry industry in China in recent decades. Here, using high throughput transcriptome sequencing of HD11 and CEF cells infected with ALV‐J, a set of 4804 novel long non‐coding transcripts and numerous differentially expressed long non‐coding RNAs (lncRNAs) were identified. We also found that they share relatively shorter transcripts and fewer exon numbers compared to mRNA. Correlation analysis suggested that many lncRNAs may activate gene expression in an enhancer‐like manner other than through transcriptional regulation. Expression level analyses in vivo showed that three lncRNAs (NONGGAT001975.2, NONGGAT005832.2 and NONGGAT009792.2) may be associated with immune response regulation and could function as novel biomarkers for ALV‐J infection. Our findings provides new insight into the pathological process of ALV‐J infection and should serve as a high‐quality resource for further research on epigenetic influences on disease‐resistance breeding as well as immune system and genomic studies. HighlightsCatalog of lncRNAs during ALV‐J infection in both somatic and immune cells were provided.Functional differences in noncoding RNA regulation between them characterized for the first time.Chicken lncRNAs are shorter, have fewer exons and shorter exons than protein‐coding genes.Many lncRNAs may activate gene expression in an enhancer‐like manner other than transcriptional regulation.We found and validated three lncRNAs that could function as novel biomarkers for ALV‐J infection.

Discovery of piRNAs Pathway Associated with Early-Stage Spermatogenesis in Chicken

Piwi-interacting RNAs (piRNAs) play a key role in spermatogenesis. Here, we describe the piRNAs profiling of primordial germ cells (PGCs), spermatogonial stem cells (SSCs), and the spermatogonium (Sp) during early-stage spermatogenesis in chicken. We obtained 31,361,989 reads from PGCs, 31,757,666 reads from SSCs, and 46,448,327 reads from Sp cells. The length distribution of piRNAs in the three samples showed peaks at 33 nt. The resulting genes were subsequently annotated against the Gene Ontology (GO) database. Five genes (RPL7A, HSPA8, Pum1, CPXM2, and PRKCA) were found to be involved in cellular processes. Interactive pathway analysis (IPA) further revealed three important pathways in early-stage spermatogenesis including the FGF, Wnt, and EGF receptor signaling pathways. The gene Pum1 was found to promote germline stem cell proliferation, but it also plays a role in spermatogenesis. In conclusion, we revealed characteristics of piRNAs during early spermatogonial development in chicken and provided the basis for future research.

Discovery of microRNAs during early spermatogenesis in chicken

Spermatogenesis is a complex process that involves many elements. However, until now, little is known at the molecular level about spermatogenesis in poultry. Here we investigated microRNAs and their target genes that may be involved in germ cell development and spermatogonial in chicken. We used next-generation sequencing to analyze miRNA expression profiles in three types of germline cells: primordial germ cells (PGCs), spermatogonial stem cells (SSCs), and spermatogonia (Sp) during early stage of spermatogenesis. After validated the candidate miRNAs and corresponding genes’ expression in three types of cells, we found 15 miRNAs that were enriched 21 target genes that may be involved in spermatogenesis. Among the enriched miRNAs, miR-202-5p/3p were up-regulated in the Sp library and down-regulated in the PGCs library. Through RT-qPCR and Dual-Luciferase reporter assay, we confirmed that miR-202-5p bind to LIMK2 and involved in germ cell development. Collectively, we firstly discover the novel miRNAs, like miR-202-5p, and its related genes and pathways, expressed during the early spermatogonial stage in chicken, which will provide new clues for deciphering the molecular mechanism of the miRNAs regulating germline stem cell differentiation and spermatogenesis in chicken.

DNA methylation-mediated transcription factors regulate Piwil1 expression during chicken spermatogenesis.

The P-element induced wimpy testis (Piwi) protein family is responsible for initiating spermatogenesis and maintaining the integrity of germ cells and stem cells, but little is known regarding its transcriptional regulation in poultry. Here, we characterized the methylation status of the Piwil1 promoter in five different spermatogenic cell lines using direct bisulfite pyrosequencing and determined that methylation correlates negatively with germ cell type-specific expression patterns of piwil1. We demonstrated that methylation of the −148 CpG site, which is the predicted binding site for the transcription factors TCF3 and NRF1, was differentially methylated in different spermatogenic cells. This site was completely methylated in PGCs (primordial germ cells), but was unmethylated in round spermatids. A similar result was obtained in the region from +121 to +139 CpG sites of the Piwil1 promoter CpG island, which was predicted to contain SOX2 binding sites. In addition, demethylation assays further demonstrated that DNA methylation indeed regulates Piwil1 expression during chicken spermatogenesis. Combined with transcription factor binding site prediction, we speculate that methylation influences the recruitment of corresponding transcription factors. Collectively, we show the negative correlation between promoter methylation and piwil1 expression and that the spatiotemporal expression of chicken Piwil1 from the PGC stage to the round spermatid stage is influenced by methylation-mediated transcription factor regulation.

Expression patterns of NLRC5 and key genes in the STAT1 pathway following infection with Salmonella pullorum.

NLRC5, a protein belonging to the NOD-like receptor protein family (NLRs), is highly expressed in immune tissues and cells. NLRC5 plays an important role in the immune response of humans, where its regulatory mechanism has been elucidated. However, the function and regulation of NLRC5 in chickens remains unclear. In this study, temporal expression characteristics of NLRC5 and associated genes in the STAT1 pathway in chickens following infection with Salmonella pullorum were investigated using quantitative real-time polymerase chain reaction and hierarchical cluster analyses. The role of transcription factor STAT1 in NLRC5 promoter activity was studied via point mutation of the STAT1-binding cis-element and dual-luciferase assays. Our results showed a strong correlation between NLRC5 and NF-κB. In addition, STAT1 played a crucial role in NLRC5 promoter activity, and may be activated via the interferon pathway. There was also a close relationship between CD80 and NF-κB, and CD80 may up-regulate NF-κB expression and enhance its protein activity in chickens. These findings reveal the temporal characteristics of chicken NLRC5 and STAT1 genes during S. pullorum infection, and highlight the role of STAT1 in NLRC5 promoter activity. This information aids our understanding of the regulatory mechanisms of NLRC5 and associated genes, and will help elucidate their function in the immune response of chickens.

Comprehensive Transcriptome Analysis Reveals Competing Endogenous RNA Networks During Avian Leukosis Virus, Subgroup J-Induced Tumorigenesis in Chickens

Avian leukosis virus subgroup J (ALV-J) is an avian oncogenic retrovirus that induces myeloid tumors and hemangiomas in chickens and causes severe economic losses with commercial layer chickens and meat-type chickens. High-throughput sequencing followed by quantitative real-time polymerase chain reaction and bioinformatics analyses were performed to advance the understanding of regulatory networks associated with differentially expressed non-coding RNAs and mRNAs that facilitate ALV-J infection. We examined the expression of mRNAs, long non-coding RNAs (lncRNAs), and miRNAs in the spleens of 20-week-old chickens infected with ALV-J and uninfected chickens. We found that 1723 mRNAs, 7,883 lncRNAs and 13 miRNAs in the spleen were differentially expressed between the uninfected and infected groups (P < 0.05). Transcriptome analysis showed that, compared to mRNA, chicken lncRNAs shared relatively fewer exon numbers and shorter transcripts. Through competing endogenous RNA and co-expression network analyses, we identified several tumor-associated or immune-related genes and lncRNAs. Along transcripts whose expression levels significantly decreased in both ALV-J infected spleen and tumor tissues, BCL11B showed the greatest change. These results suggest that BCL11B may be mechanistically involved in tumorigenesis in chicken and neoplastic diseases, may be related to immune response, and potentially be novel biomarker for ALV-J infection. Our results provide new insight into the pathology of ALV-J infection and high-quality transcriptome resource for in-depth study of epigenetic influences on disease resistance and immune system.

Long-term in vitro culture and preliminary establishment of chicken primordial germ cell lines

Primordial germ cells (PGCs) are precursors of functional gametes and can be used as efficient transgenic tools and carriers in bioreactors. Few methods for long-term culture of PGCs are available. In this study, we tested various culture conditions for PGCs, and used the optimum culture system to culture chicken gonad PGCs for about three hundred days. Long-term-cultured PGCs were detected and characterized by karyotype analysis, immunocytochemical staining of SSEA-1, c-kit, Sox2, cDAZL, and quantitative RT-PCR for specific genes like Tert, DAZL, POUV, and NANOG. Cultured PGCs labeled with PKH26 were reinjected into Stage X recipient embryos and into the dorsal aorta of Stage 14–17 embryos to assay their ability of migration into the germinal crescent and gonads, respectively. In conclusion, the most suitable culture system for PGCs is as follows: feeder layer cells treated with 20 μg/mL mitomycin C for 2 hours, and with 50% conditioned medium added to the factor culture medium. PGCs cultured in this system retain their pluripotency and the unique ability of migration without transformation, indicating the successful preliminary establishment of chicken primordial germ cell lines and these PGCs can be considered for use as carriers in transgenic bioreactors.

Circular RNA and mRNA profiling reveal competing endogenous RNA networks during avian leukosis virus, subgroup J-induced tumorigenesis in chickens

Avian leukosis virus subgroup J (ALV-J) can induce myeloid tumors and hemangiomas in chickens and causes severe economic losses with commercial layer chickens and meat-type chickens. Here, we generated ribominus RNA sequencing data from three normal chicken spleen tissues and three ALV-J-infected chicken spleen tissues. Structure analysis of transcripts showed that, compared to mRNAs and lncRNAs, chicken circRNAs shared relatively shorter transcripts and similar GC content. Differentially expression analysis showed 152 differentially expressed circRNAs with 106 circRNAs up regulated and 46 circRNAs down regulated. Through comparing differentially expressed circRNA host genes and mRNAs and performed ceRNA network analysis, we found several tumor or immune-related genes, in which, there were four genes existed in both differentially expressed mRNAs and circRNA host genes (Dock4, Fmr1, Zfhx3, Ralb) and two genes (Mll, Aoc3) involved in ceRNA network. We further characterized one exon-intron circRNA derived from HRH4 gene in the ceRNA network, termed circHRH4, which is an abundant and stable circRNA expressed in various tissues and cells in chicken and localizes in cytoplasm. Our results provide new insight into the pathology of ALV-J infection and circRNAs may also mediate tumorigenesis in chicken.

piRNA-19128 regulates spermatogenesis by silencing of KIT in chicken

Spermatogenesis is a complex process. Some studies have shown that Piwi‐interacting RNAs (piRNAs) play an important role in spermatogenesis. To verify the evaluate between piRNAs and PIWI proteins in chicken and its possible role in spermatogenesis and reproductive stem cell proliferation and differentiation, we performed immunoprecipitation and deep sequencing analyses and determined the expression profiles of small RNAs in primordial germ cells (PGCs), spermatogonial stem cells (SSCs), spermatogonia (Sa) cells, and spermatozoa. Length analysis showed that piRNAs bound to PIWIL1 mainly contained 23‐30 nt. Base preference analysis showed “1U‐10A”; moreover, base preference of piRNAs was obvious in all of germline cells. Here we reported the TE family of gallus gallus, and targeted by piRNA. Target gene of piRNA annotation enrichment analysis identified candidate genes KIT, SRC, WNT4, and HMGB2. Kyoto Encyclopedia of Genes and Genomes analysis showed that these genes were associated with steroid hormone biosynthesis, Notch signaling pathway, and melanogenesis. These results indicate that chicken piRNAs perform important regulatory roles during spermatogenesis similar to mice piRNAs. Chicken piRNAs interacted with PIWI proteins and regulated spermatogenesis and germ cell proliferation and differentiation. Further, we observed a negative correlation between piRNA‐19128 and KIT expression. Results of dual‐luciferase reporter assay confirmed that piRNA‐19128 directly interacted with KIT, suggesting that it plays a key role in the regulation spermatogenesis by inhibiting KIT expression. Thus, the present study provides information on the length and base preference of chicken piRNAs and suggests that piRNA‐19128 regulates spermatogenesis in chicken by silencing KIT.

Reticuloendotheliosis Virus Inhibits the Immune Response Acting on Lymphocytes from Peripheral Blood of Chicken

Chicken reticuloendotheliosis virus (REV) causes the atrophy of immune organs and immuno-suppression. The pathogenic mechanisms of REV are poorly understood. The aim of this study was to use RNA sequencing to analyse the effect of REV on immunity and cell proliferation in chicken lymphocytes from peripheral blood in vitro. Overall, 2977 differentially expressed genes (DEGs) were examined from cells between infected with REV or no; 56 DEGs related to cell proliferation and 130 DEGs related to immunity were identified. MTT, Q-PCR, and FCM indicated that REV reduced the number of lymphocytes by inhibiting the transition of S/G1 phase through FOXO and p53 pathways. Similarly, REV infection would destroy the immune defense of lymphocytes through MAPK-AP1 via Toll-like receptor-, NOD-like receptor-, and salmonella infection pathways to reduce the secretion of IL8 and IL18. In addition, the reduction of lymphocytes also might be responsible for the lower levels of IL8 and IL18, and the rescue of lymphocytes would been activated still through FOXO and p53 pathways. Moreover, the immune response for REV in lymphocytes would activate by up-regulating the expression of NOD1, MYD88, and AP1 through Toll-like receptor-/NOD-like receptor/salmonella-MAPK-AP1 pathways. These results indicate that REV could affect lymphocytes from peripheral blood by inhibit the cell proliferation and the immune system. It also was revealed that NOD1, MYD88, and AP1 were the key genes to activate the immune response through Toll-like receptor-/NOD-like receptor/salmonella-MAPK-AP1 pathways. These findings establish the groundwork and provide new clues for deciphering the molecular mechanism underlying REV infection in chickens.