Elevated expression of Piwi and piRNAs in ovaries of triploid crucian carp

Ovarian transcriptome analysis of diploid and triploid rainbow trout revealed new pathways related to gonadal development and fertility

Triploidisation represents several advantages (e.g. sterility) and therefore is routinely applied in aquaculture of several commercially important fish species, including rainbow trout. The comparative transcriptomic analysis of ovaries of triploid (3N) and diploid (2N) female rainbow trout revealed a total of 9 075 differentially expressed genes (DEGs; 4 105 genes upregulated in 2N and 4 970 genes upregulated in 3N ovaries, respectively). Identified clusters for DEGs upregulated in 3N and 2N ovaries were different, including carbohydrate and lipid metabolic process and transport, protein modification, signalling (related to folliculogenesis) and response to stimulus for DEGs upregulated in 2N, and developmental process, signalling (related to apoptosis, cellular senescence and adherence junctions) and regulation of RNA metabolic process for DEGs upregulated in 3N. The enrichment of processes involved in carbohydrate and lipid metabolism in 2N ovaries indicated high metabolism of ovarian tissue and the energy reservoir generation indispensable during the earliest stages of development. Our results highlight the importance of oocyte hydration along with oestrogen, insulin, leptin, fibroblast growth factor, and Notch signalling and pathways related to the regulation of cyclic adenosine monophosphate (cAMP) levels in proper oocyte meiotic maturation prior to ovulation in 2N ovaries. Conversely, triploidisation may lead to an increase in ovarian cellular senescence and apoptosis, which in turn can result in abnormal gonadal morphology and fibrosis. The downregulation of genes responsible for the precise regulation of meiosis and proper chromosome segregation during meiosis probably affects meiotic maturation via irregular meiotic division of chromosomes. The induction of triploidy of the rainbow trout genome resulted in enhanced expression of male-specific genes, genes responsible for re-establishing the transcriptional balance after genome reorganisation and genes involved in regulatory mechanisms, including gene silencing and DNA methylation. To the best of our knowledge, this is the first genome-wide investigation providing in-depth comprehensive and comparative gene expression patterns in the ovary from 2N and 3N rainbow trout females helping in elucidating the molecular mechanisms leading to impaired gonadal development and sterility of female triploids.

Mucus piRNAs profiles of Vibrio harveyi-infected Cynoglossus semilaevis: A hint for fish disease monitoring

The half-smooth tongue sole, Cynoglossus semilaevis, is an important cultured flatfish species. Vibrio harveyi is a common pathogen to this fish, which may result in great economic loss to C. semilaevis culture industry. piRNAs, a non-coding RNAs with 26-32 nt, have been regarded as promising biomarkers for cancer diagnosis and fish diseases. Here, we extracted the RNA from mucus of C. semilaevis and constructed the differential expression profiles of piRNAs between the sick fish (MS) and healthy fish (MC). We identified 45,696 differentially expressed piRNAs including 22,735 up-regulated piRNAs and 22,961 down-regulated piRNAs in MS group compared with MC group. The GO enrichment and KEGG pathway enrichment analyses of the differential piRNAs were carried out. The result showed immunity-related target genes mainly involved in immune system process, response to stimulus, cell killing, immune system, infectious diseases and cell growth and death. The 10 most differentially expressed piRNAs were chosen to perform the qRT-PCR, while only seven piRNAs were consistent with the sequence result. Compared with MC group, the expression levels of piR-mmu-72173>piR-rno-62831>piR-xtr-704880, piR-dme-15546979, piR-mmu-49941660, piR-mmu-29283297 and piR-mmu-1758399 were significantly lower, and piR-gga-10574 and piR-gga-134812 were significantly higher in MS group. These piRNAs may be potential biomarkers during the V. harveyi infection of C. semilaevis. This study could provide a new method to identify the infection status of C. semilaevis and understand better about the innate and adaptive immune system in C. semilaevis during bacterial infection.

Functional role of piRNAs in animal models and its prospects in aquaculture

The recent advances in the field of aquaculture over the last decade has helped the cultured‐fish industry production sector to identify problems and choose the best approaches to achieve high‐volume production. Understanding the emerging roles of non‐coding RNA (ncRNA) in the regulation of fish physiology and health will assist in gaining knowledge on the possible applications of ncRNAs for the advancement of aquaculture. There is information available on the practical considerations of epigenetic mechanisms like DNA methylation, histone modification and ncRNAs, such as microRNA in aquaculture, for both fish and shellfish. Among the non‐coding RNAs, PIWI‐interacting RNA (piRNA) is 24–31 bp long transcripts, which is primarily involved in silencing the germline transposons. Besides, the burgeoning reports and studies establish piRNAs' role in various aspects of biology. Till date, there are no reviews that summarize the recent findings available on piRNAs in animal models, especially on piRNAs biogenesis and biological action. To gain a better understanding and get an overview on the process of piRNA genesis among the different animals, this work reviews the literature available on the processes of piRNA biogenesis in animal models with special reference to aquatic animal model zebrafish. This review also presents a short discussion and prospects of piRNA’s application in relevance to the aquaculture industry.

Extracellular vesicles piwi-interacting RNAs from skin mucus for identification of infected Cynoglossus semilaevis with Vibrio harveyi

Extracellular vesicles play a regulatory role in intracellular and intercellular transmission through a variety of biological information molecules, including mRNA, small RNAs and proteins. piRNAs are one kind of regulatory small RNAs in the vesicles at the post transcriptional level. Hereby, we isolated the extracellular vesicles from skin mucus and screened the piRNA profiles of these vesicles, aiming at developing biomarkers related to bacterial infections in Cynoglossus semilaevis. The different profilings of piRNAs in mucous extracellular vesicles of C. semilaevis were compared through small RNA sequencing, between fish infected with Vibrio harveyi and healthy ones. The number of clean reads on the alignment of exosome sick (ES) group was 105, 345 and that of exosome control (EC) group was 455, 144. GO and KEGG pathway enrichment analysis showed that most of the target genes were involved in cellular process, response to stimulus, biological regulation, immune system process and signal transduction, signal molecular and interaction, transport and catabolism. The 45 final candidate piRNAs related to immunity or infectious diseases included 20 piRNAs with high expression in the ES group and 25 piRNAs with a low expression in the ES group. After verification by qRT-PCR, there was significant difference of five piRNAs expression level between infected fish and healthy fish, in line with the sequencing. The expression level of piR-mmu-16401212, piR-mmu-26829319 and piR-gga-244092 in infected fish were significantly lower than that of control group, while piR-gga-71717 and piR-gga-99034 were higher, which implying that these piRNAs in mucous extracellular vesicles can be used to identify diseased fish from normal ones. This work supplied a novel class of biomarker for infection diagnosis in fish, and it will be benefit for screening disease resistant breeding of C. semilaevis.

Comparative analyses of hypothalamus transcriptomes reveal fertility-, growth-, and immune-related genes and signal pathways in different ploidy cyprinid fish

Triploid crucian carp (TCC) is obtained by hybridization of female diploid red crucian carp (Carassius auratus red var., RCC) and male allotetraploid hybrids. In this study, high-throughput sequencing was used to conduct the transcriptome analysis of the female hypothalamus of diploid RCC, diploid common carp (Cyprinus carpio L., CC) and TCC. The key functional expression genes of the hypothalamus were obtained through functional gene annotation and differential gene expression screening. A total of 71.56 G data and 47,572 genes were obtained through sequencing and genome mapping, respectively. The Fuzzy Analysis Clustering assigned the differentially expressed genes (DEGs) into eight groups, two of which, overdominance expression (6005, 12.62%) and underdominance expression (3849, 8.09%) in TCC were further studied. KEGG enrichment analysis showed that the DEGs in overdominance were mainly enriched in four pathways. The expression of several fertility-related genes was lower levels in TCC, whereas the expression of several growth-related genes and immune-related genes was higher levels in TCC. Besides, 15 DEGs were verified by quantitative real-time PCR (qPCR). The present study can provide a reference for breeding sterility, fast-growth, and disease-resistant varieties by distant hybridization.

A Comprehensive Molecular and Clinical Analysis of the piRNA Pathway Genes in Ovarian Cancer

Simple Summary

Although ovarian cancer (OC) is one of the most lethal gynecological cancers, its development and progression remain poorly understood. The piRNA pathway is important for transposon defense and genome stability. piRNA maturation and function involve a number of genes known as the piRNA pathway genes. These genes have recently been implicated in cancer development and progression but information about their role in OC is limited. Our work aimed to provide a better understanding of the roles of piRNA pathway genes in OC. Through analyzing changes in the abundance of 10 piRNA pathway genes, we discovered gene expression differences in benign vs. cancer, chemosensitive vs. chemoresistant and post hormone treatment in OC samples and cells. Furthermore, we observed the differential effects of these genes on patient survival and OC cell invasion. Overall, this work supports a role of the piRNA pathway genes in OC progression and encourages further study of their clinical relevance.

Abstract

Ovarian cancer (OC) is one of the most lethal gynecological malignancies, yet molecular mechanisms underlying its origin and progression remain poorly understood. With increasing reports of piRNA pathway deregulation in various cancers, we aimed to better understand its role in OC through a comprehensive analysis of key genes: PIWIL1-4, DDX4, HENMT1, MAEL, PLD6, TDRD1,9 and mutants of PIWIL1 (P1∆17) and PIWIL2 (PL2L60). High-throughput qRT-PCR (n = 45) and CSIOVDB (n = 3431) showed differential gene expression when comparing benign ovarian tumors, low grade OC and high grade serous OC (HGSOC). Significant correlation of disparate piRNA pathway gene expression levels with better progression free, post-progression free and overall survival suggests a complex role of this pathway in OC. We discovered PIWIL3 expression in chemosensitive but not chemoresistant primary HGSOC cells, providing a potential target against chemoresistant disease. As a first, we revealed that follicle stimulating hormone increased PIWIL2 expression in OV-90 cells. PIWIL1, P1∆17, PIWIL2, PL2L60 and MAEL overexpression in vitro and in vivo decreased motility and invasion of OVCAR-3 and OV-90 cells. Interestingly, P1∆17 and PL2L60, induced increased motility and invasion compared to PIWIL1 and PIWIL2. Our results in HGSOC highlight the intricate role piRNA pathway genes play in the development of malignant neoplasms.

Identification and functional characterization of piwi1 gene in sea cucumber, Apostichopus japonicas

The sea cucumber (Apostichopus japonicus) is an economically important mariculture species in Asia. However, the genetic breeding of sea cucumbers is difficult because the sexes cannot be identified by appearance. Therefore, studies on sex-related genes are helpful in revealing the mechanisms of sex determination and differentiation in sea cucumbers. P-element induced wimpy testis (piwi) is a germ cell marker involved in gametogenesis in vertebrates; however, the expression pattern and function during gametogenesis remain unclear in sea cucumbers. In this study, we identified a piwi homolog gene in A. japonicus (Ajpiwi1) and investigated its expression pattern, and function. Ajpiwi1 is a maternal factor and is ubiquitously expressed in adult tissues, including the ovary and testis. Ajpiwi1 expression is strong in early oocytes, spermatocytes, and spermatogonia; weak in mature oocytes; and undetected in spermatids and intra-gonadal somatic cells. The knockdown of Ajpiwi1 by RNA interference (RNAi) led to the downregulation of other conserved sex-related genes such as dmrt1, foxl2, and germ cell-less. Therefore, Ajpiwi1 might play a critical role during gametogenesis in A. japonicus. This study creates new possibilities for studying sex-related gene functions in the sea cucumber and builds a gene function research platform based on RNAi for the first time.

Differential expression of activin βA and βB genes in female allotriploid and diploid red crucian carp Carassius auratus red var

activin β_A and β_B from diploid and allotriploid crucian carp were cloned.The differential expression of activin β_A and β_B genes in female allotriploid and diploid red crucian carp Carassius auratus red var. were studied and found to be expressed in all the tested tissues; particularly, the expression of activin β_A and β_B was elevated in the ovaries of allotriploids and differential expression in pituitaries during the non-breeding season and the breeding season period. The immunohistochemistry indicated that the abnormal triploid ovaries were dominated by small oogonium-like cells with dense signals and that the elevated expression of activin β_A and β_B in the ovaries of allotriploids may be related to allotriploid sterility.

Rapid evolution of piRNA pathway and its transposon targets in Japanese flounder (Paralichthys olivaceus)

Piwi-interacting RNA (piRNA) pathway is essential for germline specification, gametogenesis, and genome integrity as defense against transposable elements (TEs). This pathway has been suggested to have undergone rapid adaptive evolution in spite of its conserved role in TE silencing. However, with diverse sexual development patterns, piRNA pathway evolution and its adaptation to transposon activity in teleost lineages remain less known. This study illustrated the evolutionary significance of piRNA pathway via a systematic comparative analysis on diverse teleosts, including flatfish lineages. Molecular evolution of piRNA pathway and microRNA/small interfering RNA pathway genes indicated a faster evolution of piRNA pathway in teleosts than in mammals. Positive selection was detected at the PAZ (Piwi-Argonaute-Zwille) domain involved in Piwi-piRNA interaction, thereby suggesting that the amino acid substitutions were adaptive to their functions in teleost piRNA pathway. Notably, Piwil1 evolved faster in Japanese flounder than in other teleosts, and the piRNA pathway genes expressed higher in testes than in ovaries. In addition, gonadal transcriptomic analysis revealed male under-represented TE families mainly from DNA transposons, which were the potential targets of the complex formed by male-biased Piwi genes and male over-represented piRNAs in Japanese flounder testes. The potential piRNA-TE regulatory relationships suggested that the rapidly evolved piRNA pathway in Japanese flounder was likely involved in the regulation of transposon activity in germlines and could play important roles in Japanese flounder gonadal development and spermatogenesis.

Roles of piwil1 gene in gonad development and gametogenesis in Japanese flounder, Paralichthys olivaceus

PIWI family member piwil1, which associates with Piwi-interacting RNA (piRNA), is responsible in regulation of germ cell differentiation and maintenance of reproductive stem cells. In this study, we analyzed the piwil1 gene in Paralichthys olivaceus. Bioinformatics analysis and structure prediction showed that piwil1 had the conserved domains: PAZ domain and PIWI domain. Expression analysis during embryonic development implied that piwil1 gene was maternally inherited. The tissue distribution showed a sexually dimorphic gene expression pattern, with higher expression level in testis than ovary. In situ hybridization results demonstrated that piwil1 was predominantly distributed in oogonia, oocytes, sertoli cells and spermatocytes. A CpG island was predicted in the 5'-flanking region of piwil1 gene, and its methylation levels showed significant disparity between males and females, indicating that the sexually dimorphic expression of piwil1 gene might be regulated by methylation. Furthermore, we explored the distinct roles of human chorionic gonadotropin and 17α-methyltestosterone in regulating the expression of piwil1, and found that piwil1 was interacting with the HPG axis hormones. These results indicated that piwil1 might play a crucial role in gonadal development and gametogenesis in Paralichthys olivaceus.

Characterization of H3 methylation in regulating oocyte development in cyprinid fish

Histone post-modifications are important epigenetic markers involved in multiple cellular processes via regulation of gene transcription or remodeling of chromatin structure. Oocyte development is a critical process under rigorous control to prevent the generation of aberrant gametes. However, the regulatory mechanism of oocyte early development is not well-understood due to the tiny size and poor distinguishability of the gonad in juvenile stages. Here, two cyprinid hybrid fishes, a sterile allotriploid fish and a gynogenetic hybrid fish with delayed oocyte development, provided research models to investigate the mechanisms involved. We used cytogenetic and molecular methods to confirm the pachytene arrest of oocytes in allotriploid fish and gynogenetic hybrid fish. On the basis of these developmental differences, we screened 21 different histone H3 modifications by ELISA and found that four modifications (H3K4me3, H3K9me3, H3K79me, and H3K79me3) differed significantly in the two cyprinid hybrid fishes. Changes in histone methylation at the three residues (H3K4, K9, K79) were caused by specific methyltransferases and demethylases. Our results provide new insights into the epigenetic regulation of oocyte early development in fish, a process critical for understanding of reproductive biology and with practical applications in the aquacultural breeding industry.

Asymmetric expression patterns reveal a strong maternal effect and dosage compensation in polyploid hybrid fish

Background

Hybridization and polyploidization are regarded as the major driving forces in plant speciation, diversification, and ecological adaptation. Our knowledge regarding the mechanisms of duplicated-gene regulation following genomic merging or doubling is primarily derived from plants and is sparse for vertebrates.

Results

We successfully obtained an F1 generation (including allodiploid hybrids and triploid hybrids) from female Megalobrama amblycephala Yih (BSB, 2n = 48) × male Xenocypri davidi Bleeker (YB, 2n = 48). The duplicated-gene expression patterns of the two types of hybrids were explored using RNA-Seq data. In total, 5.44 × 10⁸ (69.32 GB) clean reads and 499,631 assembled unigenes were obtained from the testis transcriptomes. The sequence similarity analysis of 4265 orthologs revealed that the merged genomes were dominantly expressed in different ploidy hybrids. The differentially expressed genes in the two types of hybrids were asymmetric compared with those in both parents. Furthermore, the genome-wide expression level dominance (ELD) was biased toward the maternal BSB genome in both the allodiploid and triploid hybrids. In addition, the dosage-compensation mechanisms that reduced the triploid expression levels to the diploid state were determined in the triploid hybrids.

Conclusions

Our results indicate that divergent genomes undergo strong interactions and domination in allopolyploid offspring. Genomic merger has a greater effect on the gene-expression patterns than genomic doubling. The various expression mechanisms (including maternal effect and dosage compensation) in different ploidy hybrids suggest that the initial genomic merger and doubling play important roles in polyploidy adaptation and evolution.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4883-7) contains supplementary material, which is available to authorized users.

Piwil1 gene is regulated by hypothalamic-pituitary-gonadal axis in turbot (Scophthalmus maximus): A different effect in ovaries and testes

As constituent factors of Piwi-interacting RNA (piRNA) pathways, Piwi proteins are essential for germline maintenance and gonadal development. Previous studies show that Piwi-piRNA pathways could be regulated by hypothalamic-pituitary-gonadal (HPG) axis, however, related studies have not been reported in marine species. Here we reported the identification of turbot (Scophthalmus maximus) piwil1 gene, which was abundantly expressed in testis and ovary in a tissue-specific manner. Phylogenetic and genomic structure analyses revealed that piwil1 was conserved in its sequence and function during vertebrate evolution. We also investigated the effects of HPG axis hormones, including human chorionic gonadotropin (hCG), estradiol-17β (E2) and 17α-methyltestosterone (MT), on gonadal piwil1 expression via in vivo and in vitro approaches. In ovary, hCG and E2 suppressed piwil1 expression both in vivo and in vitro, and MT increased piwil1 expression in vivo. In testis, hCG had upregulating effects on piwil1 expression in vivo and in vitro, and MT also increased piwil1 expression in vitro. In addition, E2 suppressed expression of piwil1 in vivo. These results indicated that the decreased or increased expression of piwil1 regulated by hormones might play a crucial role during gonadal differentiation and development in S. maximus.

Identification of suh gene and evidence for involvement of notch signaling pathway on gonadal differentiation of Yellow River carp (Cyprinus carpio)

The suh gene is crucial in Notch pathway and regulates mammalian gonad development. In this study, the sequences of suh1 and suh2 genes in Yellow River carp (Cyprinus carpio) were verified. The partial 5'-flanking regions of suh1 and suh2 were analyzed and several potential transcription factor-binding sites were identified. Phylogenetic, gene structure, and chromosome synteny analyses revealed that carp suh1 and suh2 were orthologs and homologous to vertebrate suh. Investigation of the expression profiles of suh1 and suh2 with qPCR showed that these genes were abundant in the brain and gonad of carp, with suh1 exhibiting sexual dimorphism expression pattern in gonad. To study the relationship between gonad differentiation and Notch signaling, primordial gonads were exposed to DAPT, an inhibitor of Notch signaling, in vitro and in vivo. The results revealed a significant downregulation of suh1 and other Notch genes in vitro. In addition, expression of male-biased genes, such as amh, dmrt1, etc., was downregulated, whereas that of female-biased genes, such as foxl2, gdf9, etc., was upregulated. When the primordial gonads were subjected to long-term DAPT exposure, an increased proportion of ovary and delay in testis development were observed. These results suggest that suh gene may have a conservative function between teleosts and mammals. Furthermore, Notch signaling was found to be involved in gonad differentiation in Yellow River carp, and DAPT was noted to inhibit and enhance the expression of male- and female-biased genes, respectively, and induce the increase in number of females.

Identification and expression of piwil2 in turbot Scophthalmus maximus, with implications of the involvement in embryonic and gonadal development

Piwil2, a member of the Argonaute family, is involved in the biogenesis of PIWI-interacting RNAs (piRNAs) and plays an important role in regulating gametogenesis. In the present study, we identified turbot Scophthalmus maximus piwil2 gene, named Smpiwil2, which contained a PAZ domain and a PIWI domain. Sequence comparison, genomic structure and phylogenetic analyses showed that Smpiwil2 is homologous to that of teleosts and tetrapods. The Smpiwil2 transcript showed higher expression in the ovary than in the testis, demonstrating a sexually dimorphic gene expression pattern. In situ hybridization (ISH) showed that Smpiwil2 was expressed in the oogonia and all the stages of oocytes in the ovary as well as in spermatogonia and spermatocytes in the testis. Embryonic expression profile revealed that Smpiwil2 was maternally inherited, and its level was higher from the zygote to the blastula stage and subsequently decreased until hatching. Moreover, a CpG island was predicted to locate in the 5'-flanking region of Smpiwil2 gene, and its methylation levels detected by sodium bisulfite sequencing showed significant disparity between females and males, implying that the sexually dimorphic expression of Smpiwil2 might be regulated by methylation. These results indicated that Smpiwil2 had potentially vital functions in embryonic and gonadal development in this species. In addition, the temporal and sex differences in Smpiwil2 expression indicated that this gene may play different roles in gonadal development of different sexes.

Determination of dosage compensation and comparison of gene expression in a triploid hybrid fish

Background

Polyploidy and hybridization are both recognized as major forces in evolution. Most of our current knowledge about differences in gene regulation in polyploid hybrids comes from plant studies. The gene expression of diverged genomes and regulatory interactions are still unclear in lower vertebrates.

Results

We generated 229 million cleaned reads (42.23 Gbp) from triploid of maternal grass carp (Ctenopharyngodon idellus, Cyprininae, 2n = 48) × paternal blunt snout bream (Megalobrama amblycephala, Cultrinae, 2n = 48) and their diploid parents using next-generation sequencing. In total, 157,878 contigs were assembled and 15,444 genes were annotated. We examined gene expression level changes among the parents and their triploid offspring. The mechanisms of dosage compensation that reduced triploid expression levels to the diploid state were determined in triploid fish. In this situation, novel gene expression and gene silencing were observed. Then, we established a model to determine the extent and direction of expression level dominance (ELD) and homoeolog expression bias (HEB) based on the relative expression level among the parents and their triploid offspring.

Conclusions

Our results showed that the genome-wide ELD was biased toward maternal genome in triploid. Extensive alterations in homoeolog expression suggested a combination of regulatory and epigenetic interactions through the transcriptome network. Additionally, the expression patterns of growth genes provided insights into the relationship between the characteristics of growth and underlying mechanisms in triploids. Regulation patterns of triploid state suggest that various expression levels from the initial genomic merger have important roles in adaptation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3424-5) contains supplementary material, which is available to authorized users.

Homoeologue expression insights into the basis of growth heterosis at the intersection of ploidy and hybridity in Cyprinidae

Hybridization and polyploidization are considered important driving forces that form new epigenetic regulations. To study the changing patterns of expression accompanying hybridization and polyploidization, we used RNA-seq and qRT-PCR to investigate global expression and homoeologue expression in diploid and tetraploid hybrids of Carassius auratus red var. (♀) (R) and Cyprinus carpio (♂) (C). By comparing the relative expression levels between the hybrids and their parents, we defined the expression level dominance (ELD) and homoeologue expression bias (HEB) in liver tissue. The results showed that polyploidization contributed to the conversion of homoeologue ELD. In addition, hybridization had more effect on the change in HEB than polyploidization, while polyploidization had more effect on the change of global gene expression than hybridization. Meanwhile, similar expression patterns were found in growth-related genes. The results suggested that hybridization and polyploidization result in differential degrees of maternal HEB in three tissues (liver, muscle and ovary) tested. The results of this study will increase our understanding of the underlying regulation mechanism of rapid growth in diploid hybrids and allotetraploids. The differential degrees of global expression and homoeologue expression contribute to growth heterosis in newly formed hybrids, ensuring the on-going success of allotetraploid speciation.

High expression of piwi-like RNA-mediated gene silencing 1 is associated with poor prognosis via regulating transforming growth factor-β receptors and cyclin-dependent kinases in breast cancer

Previous studies have demonstrated that abnormal expression levels of PIWI may serve a crucial role in tumorigenesis. However, the pathological role and its association with prognosis remains to be fully elucidated. In the present study, the expression levels of piwi‑like RNA‑mediated gene silencing 1 (HIWI) and piwi‑like RNA‑mediated gene silencing 2 (HILI) in breast cancer tissues were reported to be high. The high expression levels of HIWI are correlated with poor prognosis in detected patients. In addition, by overexpression and interference, it was demonstrated that HIWI promotes the activity of breast cancer cells while depression of HIWI may induce apoptosis of breast cancer cells. It was additionally identified that suppression of HIWI may arrest the cells at the G2/M stage. The expression levels of transforming growth factor‑β receptor (TβR)I, TβRII, cyclin‑dependent kinase (CDK)4, CDK6 and CDK8 were observed to be regulated by HIWI, which indicated a novel mechanism of HIWI in the regulation of breast cancer progression. The present study provides novel insight into the HIWI expression in breast cancer, providing a potential biomarker for assessment of prognosis and therapy of breast cancer.

PIWIL2 promotes progression of non-small cell lung cancer by inducing CDK2 and Cyclin A expression

Background

PIWI proteins have important roles in tumorigenesis due to their interaction with piRNAs. Recent studies suggest that PIWI proteins affect prognosis of various cancers.

Methods

In the present study, PIWI genes expression was assayed in non-small cell lung cancer (NSCLC). To determine the effects of PIWIL2 on NSCLC cells, overexpression and interference assays were performed using the A549 and H460 cell lines. The tumor formation model was performed to demonstrate the effects of PIWIL2 on tumor formation in vivo.

Results

PIWIL2 was increased both at the RNA and protein level in malignant cancer tissues compared with adjacent normal tissue. Moreover, increased PIWIL2 gene expression was negatively correlated with prognosis in NSCLC patients. Overexpression and interference of PIWIL2 promoted and depressed cell proliferation, respectively. Meanwhile, PIWIL2 interference arrested cells at the G2/M stage. In addition, we found that CDK2 and Cyclin A expression were correlated with PIWIL2 expression. Moreover, transfection of PIWIL2 promoted tumor growth in nude mice.

Conclusion

Our findings shed light on the function of PIWIL2 in NSCLC and suggest potential prognostic and therapeutic value.