Investigation on association and expression of ESR2 as a candidate gene for boar sperm quality and fertility

Sodium Fluoride In Vitro Treatment Affects the Expression of Gonadotropin and Steroid Hormone Receptors in Chicken Embryonic Gonads

Simple Summary

Effects of in vitro sodium fluoride (NaF) treatment on the mRNA expression of luteinizing hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), estrogen receptors (ESR1 and ESR2), progesterone receptor (PGR), and the immunolocalization of PGRs were examined in gonads of 14-day-old chicken embryos. In the ovary, the NaF treatment significantly increased mRNA levels of all investigated receptors. In the testes, the lowest applied dose of NaF (1.7 mM) significantly decreased the expression of FSHR, ESR1, ESR2, and PGR. Alternatively, the higher NaF dose (7.1 mM) elevated PGR mRNA level in the male gonad. Immunohistochemical analysis revealed that the NaF exposure increased PGR expression in the ovarian cortex, while it decreased its expression in the testes. Collectively, these data indicate that: (i) NaF may disturb the chicken embryonic development, and (ii) different mechanisms of this toxicant action exist within the female and male gonads.

Abstract

Sodium fluoride (NaF), in addition to preventing dental decay may negatively affect the body. The aim of this study was to examine the effect of a 6 h in vitro treatment of gonads isolated from 14-day-old chicken embryos with NaF at doses of 1.7 (D1), 3.5 (D2), 7.1 (D3), and 14.2 mM (D4). The mRNA expression of luteinizing hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), estrogen receptors (ESR1 and ESR2), progesterone receptor (PGR), and the immunolocalization of progesterone receptors were examined in the tissue. In the ovary, the expression of FSHR and LHR increased following the NaF treatment. In the case of FSHR the highest stimulatory effect was noticed in the D2 group, while the expression of LHR increased in a dose-dependent manner. A gradual increase in ESR1 and PGR mRNA levels was also observed in the ovary following the NaF treatment, but only up to the D3 dose of NaF. The highest ESR2 level was also found in the D3 group. In the testes, the lowest dose of NaF significantly decreased the expression of FSHR, ESR1, ESR2, and PGR. On the other hand, an increase in PGR expression was observed in the D3 group. The expression of LHR in the testes was not affected by the NaF treatment. Immunohistochemical analysis showed that NaF exposure increased progesterone receptor expression in the ovarian cortex, while it decreased its expression in the testes. These results reveal that NaF may disturb the chicken embryonic development and different mechanisms of this toxicant action exist within the females and males.

Genomics of Heat Tolerance in Reproductive Performance Investigated in Four Independent Maternal Lines of Pigs

Improving swine climatic resilience through genomic selection has the potential to minimize welfare issues and increase the industry profitability. The main objective of this study was to investigate the genetic and genomic determinism of tolerance to heat stress in four independent purebred populations of swine. Three female reproductive traits were investigated: total number of piglets born (TNB), number of piglets born alive (NBA) and average birth weight (ABW). More than 80,000 phenotypic and 12,000 genotyped individuals were included in this study. Genomic random-regression models were fitted regressing the phenotypes of interest on a set of 95 environmental covariates extracted from public weather station records. The models yielded estimates of (genomic) reactions norms for individual pigs, as indicator of heat tolerance. Heat tolerance is a heritable trait, although the heritabilities are larger under comfortable than heat-stress conditions (larger than 0.05 vs. 0.02 for TNB; 0.10 vs. 0.05 for NBA; larger than 0.20 vs. 0.10 for ABW). TNB showed the lowest genetic correlation (-38%) between divergent climatic conditions, being the trait with the strongest impact of genotype by environment interaction, while NBA and ABW showed values slightly negative or equal to zero reporting a milder impact of the genotype by environment interaction. After estimating genetic parameters, a genome-wide association study was performed based on the single-step GBLUP method. Heat tolerance was observed to be a highly polygenic trait. Multiple and non-overlapping genomic regions were identified for each trait based on the genomic breeding values for reproductive performance under comfortable or heat stress conditions. Relevant regions were found on chromosomes (SSC) 1, 3, 5, 6, 9, 11, and 12, although there were important regions across all autosomal chromosomes. The genomic region located on SSC9 appears to be of particular interest since it was identified for two traits (TNB and NBA) and in two independent populations. Heat tolerance based on reproductive performance indicators is a heritable trait and genetic progress for heat tolerance can be achieved through genetic or genomic selection. Various genomic regions and candidate genes with important biological functions were identified, which will be of great value for future functional genomic studies.

Association between single-nucleotide polymorphisms within candidate genes and fertility in Landrace and Duroc pigs

Finding effective predictors of traits related to boar fertility is essential for increasing the efficiency of artificial insemination systems in pig breeding. The objective of this study was to find associations between single-nucleotide polymorphisms (SNPs) within candidate genes and fertility in the breeds Landrace and Duroc. Animals with breeding values for total number of piglets born, were re-sequenced for exonic regions of 14 candidate genes related to male and female fertility using samples from 16 Landrace boars and 16 Duroc boars (four with high and four with low breeding value of total number of piglets born for each breed for male fertility, and the same for female fertility) to detect genetic variants. Genotyping for the detected SNPs was done in 619 Landrace boars and 513 Duroc boars. Two SNPs in BMPR1 and one SNP in COX-2 were found significantly associated with the total number of piglets born in Landrace. In Duroc, two SNPs in PLC_z, one SNP in VWF and one SNP in ZP3 were found significantly associated with total number of piglets born. These SNPs explained between 0.27% and 1.18% of the genetic variance. These effects are too low for being used directly for selection purposes but can be of interest in SNP-panels used for genomic selection.

Weighted single-step GWAS identified candidate genes associated with semen traits in a Duroc boar population

BACKGROUND

In the pig production industry, artificial insemination (AI) plays an important role in enlarging the beneficial impact of elite boars. Understanding the genetic architecture and detecting genetic markers associated with semen traits can help in improving genetic selection for such traits and accelerate genetic progress. In this study, we utilized a weighted single-step genome-wide association study (wssGWAS) procedure to detect genetic regions and further candidate genes associated with semen traits in a Duroc boar population. Overall, the full pedigree consists of 5284 pigs (12 generations), of which 2693 boars have semen data (143,113 ejaculations) and 1733 pigs were genotyped with 50 K single nucleotide polymorphism (SNP) array.

RESULTS

Results show that the most significant genetic regions (0.4 Mb windows) explained approximately 2%~ 6% of the total genetic variances for the studied traits. Totally, the identified significant windows (windows explaining more than 1% of total genetic variances) explained 28.29, 35.31, 41.98, and 20.60% of genetic variances (not phenotypic variance) for number of sperm cells, sperm motility, sperm progressive motility, and total morphological abnormalities, respectively. Several genes that have been previously reported to be associated with mammal spermiogenesis, testes functioning, and male fertility were detected and treated as candidate genes for the traits of interest: Number of sperm cells, TDRD5, QSOX1, BLK, TIMP3, THRA, CSF3, and ZPBP1; Sperm motility, PPP2R2B, NEK2, NDRG, ADAM7, SKP2, and RNASET2; Sperm progressive motility, SH2B1, BLK, LAMB1, VPS4A, SPAG9, LCN2, and DNM1; Total morphological abnormalities, GHR, SELENOP, SLC16A5, SLC9A3R1, and DNAI2.

CONCLUSIONS

In conclusion, candidate genes associated with Duroc boars' semen traits, including the number of sperm cells, sperm motility, sperm progressive motility, and total morphological abnormalities, were identified using wssGWAS. KEGG and GO enrichment analysis indicate that the identified candidate genes were enriched in biological processes and functional terms may be involved into spermiogenesis, testes functioning, and male fertility.

H2AFZ, RNF4 and NR4A1 loci are associated with boar semen quality by population association studies

Spermatogenesis is a complex process regulated by many genes. In this study, H2AFZ, RNF4 and NR4A1 genes were selected as candidate genes for boar semen quality traits based on their functions during spermatogenesis, and the associations of three loci (H2AFZ c.192 + 210-192 + 213delCGAT, RNF4 c.374 + 358 T > C and NR4A1 c.956 + 796 A > G) with sperm quality traits were analyzed in Duroc (n = 185), Large White (n = 87) and Landrace (n = 49) pig populations. The results showed H2AFZ c.192 + 210-192 + 213delCGAT AA boars produced 1.52% lower abnormal sperm rate (ASR) than AB boars in Landrace pigs (p < 0.05); RNF4 c.374 + 358 TC boars produced 0.31 × 10⁸/ml higher sperm concentration (SCON) than CC boars (p < 0.05) in Large White pigs; NR4A1 c.956 + 796 A > G was associated with ASR in Duroc and Large White pigs and was associated with sperm motility (MOT) in Large White and Landrace pigs. This study indicated the H2AFZ, RNF4 and NR4A1 loci were the potential molecular markers for improving the semen quality traits in boars.

Weighted single-step GWAS and gene network analysis reveal new candidate genes for semen traits in pigs

Background

In recent years, there has been increased interest in the study of the molecular processes that affect semen traits. In this study, our aim was to identify quantitative trait loci (QTL) regions associated with four semen traits (motility, progressive motility, number of sperm cells per ejaculate and total morphological defects) in two commercial pig lines (L1: Large White type and L2: Landrace type). Since the number of animals with both phenotypes and genotypes was relatively small in our dataset, we conducted a weighted single-step genome-wide association study, which also allows unequal variances for single nucleotide polymorphisms. In addition, our aim was also to identify candidate genes within QTL regions that explained the highest proportions of genetic variance. Subsequently, we performed gene network analyses to investigate the biological processes shared by genes that were identified for the same semen traits across lines.

Results

We identified QTL regions that explained up to 10.8% of the genetic variance of the semen traits on 12 chromosomes in L1 and 11 chromosomes in L2. Sixteen QTL regions in L1 and six QTL regions in L2 were associated with two or more traits within the population. Candidate genes SCN8A, PTGS2, PLA2G4A, DNAI2, IQCG and LOC102167830 were identified in L1 and NME5, AZIN2, SPATA7, METTL3 and HPGDS in L2. No regions overlapped between these two lines. However, the gene network analysis for progressive motility revealed two genes in L1 (PLA2G4A and PTGS2) and one gene in L2 (HPGDS) that were involved in two biological processes i.e. eicosanoid biosynthesis and arachidonic acid metabolism. PTGS2 and HPGDS were also involved in the cyclooxygenase pathway.

Conclusions

We identified several QTL regions associated with semen traits in two pig lines, which confirms the assumption of a complex genetic determinism for these traits. A large part of the genetic variance of the semen traits under study was explained by different genes in the two evaluated lines. Nevertheless, the gene network analysis revealed candidate genes that are involved in shared biological pathways that occur in mammalian testes, in both lines.

Electronic supplementary material

The online version of this article (10.1186/s12711-018-0412-z) contains supplementary material, which is available to authorized users.

Genetic parameters for semen quality and quantity traits in five pig lines

We aimed to estimate genetic parameters for semen quality and quantity traits as well as for within-boar variation of these traits to evaluate their inclusion in breeding goals. Genetic parameters were estimated within line using a multiple-trait (4 × 4) repeatability animal model fitted for 5 pig lines, considering 4 semen traits: sperm motility (MOT), sperm progressive motility (PROMOT), log-transformed number of sperm cells per ejaculate (lnN), and total morphological abnormalities (ABN). The within-boar variation of these traits was analyzed based on a multiple-trait (2 × 2) approach for SD and average (AVG) and a single-trait analysis for CV. The average heritabilities across the 5 lines estimated by multiple-trait analysis were 0.18 ± 0.07 (MOT), 0.22 ± 0.08 (PROMOT), 0.16 ± 0.04 (lnN), and 0.20 ± 0.04 (ABN). The average genetic correlations were favorable between MOT and PROMOT (0.86 ± 0.10), between MOT and ABN (-0.66 ± 0.25), and between PROMOT and ABN (-0.65 ± 0.25). As determined by within-boar variation analysis, AVG exhibited the greatest heritabilities followed by SD and CV, respectively, for the traits MOT and ABN. For PROMOT, average SD heritability was lower than CV heritability, whereas for lnN, they were the same. The average genetic correlations between AVG and SD were favorable for MOT (-0.60 ± 0.13), PROMOT (-0.79 ± 0.14), and ABN (0.78 ± 0.17). The moderate heritabilities indicate the possibility of effective selection of boars based on semen traits. Average and SD are proposed as appropriate traits for selection regarding uniformity.

SNP g.1007A>G within the porcine DNAL4 gene affects sperm motility traits and percentage of midpiece abnormalities

The flagellar beating of a spermatozoa's axoneme is caused by the varying activation and inactivation of dynein molecules. Dynein, axonemal, light chain 4 (DNAL4) is a functional candidate gene for sperm motility as it encodes a small subunit of the dyneins. We resequenced the porcine DNAL4 using three artificial insemination (AI) boars each with high (>68%) or low (<60%) motility, and detected 23 SNP. These were then genotyped for 82 AI boars. Using spermatological records, significantly negative genetic correlations between ejaculate volume (VOL) and the further spermatological parameters concentration (CONC) (r = -.43), motility of undiluted semen (MOTUD) (r = -.09), motility after 24 h (MOT1) (r = -.17) and after 48 hr (MOT2) (r = -.23) were estimated. Significantly positive correlations existed between CONC and MOT1 (r = .07) as well as MOT2 (r = .10), between MOTUD and MOT1 (r = .33), between MOTUD and MOT2 (r = .36), and finally between MOT1 and MOT2 (r = .70). Significantly negatively correlated were all motility traits with the parameters abnormal acrosome (AA) (MOTUD r = -.06; MOT1 r = -.08, and MOT2 r = -.1) and presence of cytoplasmic droplet (CD) (MOTUD r = -.07; MOT1 r = -.08; MOT2 r = -.07). Association analyses (single marker regression model; SMR) propose that SNP g.1007A>G, located in the second intron, reduces motility significantly (MOTUD -4.59%; MOT1 -10.33%; MOT2 -19.37%). According to the dominant-recessive model (DRM), genotype AA is always superior compared to genotypes AG and GG (i.e. MOTUD 67.67%, 64.16% and 53.91%; MOT1 54.17%, 43.75% and 28.44%; MOT2 44.12%, 24.91% and 4.97%). The average effect of gene substitution (g.1007A>G) on abnormal midpiece (AM) was 0.71%, the genotypic values-as expressed by LSmeans-were 0.1 (AA) and 0.81 (AG).

Analyses of Long Non-Coding RNA and mRNA profiling using RNA sequencing in chicken testis with extreme sperm motility

Sperm motility is the most important indicator in evaluating roosters' fecundity. However, the genetic mechanisms underlying chicken sperm motility is not yet clear. Long non-coding RNA (lncRNA) play epigenetic roles in reproduction. In this study, RNA sequencing was employed to profile the testis transcriptome (lncRNA and mRNA) of six Beijing-you cocks divergent in sperm motility. In total, 2,597 lncRNAs were identified in the chicken testis, including 1,267 lincRNAs, 975 anti-sense lncRNAs, and 355 intronic lncRNAs. They shared similar features with previous studies. Of these lncRNAs, 124 were differentially expressed. Among 17,690 mRNAs detected in this study, 544 were differentially expressed, including a bunch of genes with known functions on sperm motility. GO annotation analysis revealed these genes were involved in ATP binding, cilium assembly, and oxidation-reduction processes. Integrating analysis of lncRNA and mRNA profiles predicted 10 lncRNA-gene pairs, including 8 co-regulated and 2 inversely-regulated pairs. To the best of our knowledge, this is the first genome-wide investigation of the lncRNAs in the chicken testis associated with sperm motility. Our results provided a catalog of chicken testis lncRNAs and genes worthy of further studies to understand their roles in cocks' reproductive performance regulation.

Whole genome detection of signature of positive selection in African cattle reveals selection for thermotolerance

As African indigenous cattle evolved in a hot tropical climate, they have developed an inherent thermotolerance; survival mechanisms include a light-colored and shiny coat, increased sweating, and cellular and molecular mechanisms to cope with high environmental temperature. Here, we report the positive selection signature of genes in African cattle breeds which contribute for their heat tolerance mechanisms. We compared the genomes of five indigenous African cattle breeds with the genomes of four commercial cattle breeds using cross-population composite likelihood ratio (XP-CLR) and cross-population extended haplotype homozygosity (XP-EHH) statistical methods. We identified 296 (XP-EHH) and 327 (XP-CLR) positively selected genes. Gene ontology analysis resulted in 41 biological process terms and six Kyoto Encyclopedia of Genes and Genomes pathways. Several genes and pathways were found to be involved in oxidative stress response, osmotic stress response, heat shock response, hair and skin properties, sweat gland development and sweating, feed intake and metabolism, and reproduction functions. The genes and pathways identified directly or indirectly contribute to the superior heat tolerance mechanisms in African cattle populations. The result will improve our understanding of the biological mechanisms of heat tolerance in African cattle breeds and opens an avenue for further study.

Of Oestrogens and Sperm: A Review of the Roles of Oestrogens and Oestrogen Receptors in Male Reproduction

The crucial role that oestrogens play in male reproduction has been generally accepted; however, the exact mechanism of their action is not entirely clear and there is still much more to be clarified. The oestrogen response is mediated through oestrogen receptors, as well as classical oestrogen receptors’ variants, and their specific co-expression plays a critical role. The importance of oestrogen signalling in male fertility is indicated by the adverse effects of selected oestrogen-like compounds, and their interaction with oestrogen receptors was proven to cause pathologies. The aims of this review are to summarise the current knowledge on oestrogen signalling during spermatogenesis and sperm maturation and discuss the available information on oestrogen receptors and their splice variants. An overview is given of species-specific differences including in humans, along with a detailed summary of the methodology outcome, including all the genetically manipulated models available to date. This review provides coherent information on the recently discovered mechanisms of oestrogens’ and oestrogen receptors’ effects and action in both testicular somatic and germ cells, as well as in mature sperm, available for mammals, including humans.

Transcript levels of genes implicated in steroidogenesis in the testes and fat tissue in relation to androstenone accumulation in fat of pubertal pigs

The present study was performed to measure messenger RNA levels of steroidogenic enzymes in testes and fat tissue and determine whether they are related to fat androstenone level. Real-time polymerase chain reaction experiments were performed on 26 testes and 12 adipose tissue samples from pubertal boars using 21 genes. The absence of significant correlations between fat androstenone and the transcriptional activity of the SRD5A2 and SRD5A3 genes but the high correlation coefficient with that of the SRD5A1 gene (r = 0.62, P < 0.05) suggests that the enzyme coded by SRD5A1 is mainly responsible for the last step of androstenone synthesis. The testicular transcriptional activities of CYP17, CYP11A1, CYP19A, AKR1C-pig6, SRD5A1, LHCGR, and AR were significantly correlated. Only transcriptional levels of CYP17, CYP11A1, CYP19A, SRD5A1, and AKR1C-pig6 were correlated with the fat concentration of androstenone (0.57 < r < 0.70, P < 0.05) confirming that the amount of androstenone stored in fat is related to the production in testes of androstenone and more generally to all sex steroids. Altogether, our data are in favor of a preponderant role of AKR1C-pig6 instead of HSD17B3 for testicular synthesis of steroids. Concerning fat tissue, our data do not support a significant de novo biosynthesis of steroids in porcine adipose tissues. The presence of transcripts coding for steroid enzymes, especially those of AKR1C-pig6, suggests that steroids can be transformed. None of transcript abundance was related to androstenone accumulation (P > 0.1). Therefore, steroids synthesized elsewhere can be transformed in fat tissue but synthesis of androstenone is unlikely.

Epigenetic effects of prenatal estradiol-17β exposure on the reproductive system of pigs

There is growing evidence that early life exposure to endocrine disrupting chemicals might increase the risk for certain adult onset diseases, in particular reproductive health problems and hormone dependent cancers. Studies in rodents suggest that perinatal exposure to even low doses of estrogenic substances can cause adverse effects, including epigenetic reprogramming of the prostate and increased formation of precancerous lesions. We analyzed the effects of an in utero exposure to the strongest natural estrogen, estradiol-17β, in a pig model. Two different low and one high dose of estradiol-17β (0.05, 10 and 1000 μg/kg body weight/day) were orally applied to gilts during pregnancy and potential effects on the reproductive system of the offspring were analyzed. No significant effects on sperm vitality parameters and testes size were observed in adult boars. However, prenatal exposure to the high dose decreased absolute, but not relative weight of the testes in prepubertal piglets. RNA sequencing revealed significantly regulated genes of the prepubertal prostate, while testes and uteri were not affected. Notably, we found an increased prostate expression of CCDC80 and a decreased ADH1C expression in the low dose treatment groups. BGN and SPARC, two genes associated with prostate tumor progression, were as well more abundant in exposed animals. Strikingly, the gene body DNA methylation level of BGN was accordingly increased in the high dose group. Thus, while only prenatal exposure to a high dose of estrogen altered testes development and local DNA methylation of the prostate, even low dose exposure had significant effects on gene expression in the prostate of prepubertal piglet offspring. The relevance of these distinct, but subtle transcriptional changes following low dose treatment lacking a clear phenotype calls for further long-term investigations. An epigenetic reprogramming of the pig prostate due to prenatal estrogen cannot be neglected.

Preliminary study of FMO1, FMO5, CYP21, ESR1, PLIN2 and SULT2A1 as candidate gene for compounds related to boar taint

An association study between polymorphisms of six genes and boar taint related compounds androstenone, skatole and indole was performed in a boar population (n=370). Significant association (P<0.05) was detected for SNP of FMO5 (g.494A>G) with all boar taint compounds, SNP of CYP21 (g.3911T>C) with skatole and indole, and SNP of ESR1 (g.672C>T) with androstenone and indole. mRNA expression of CYP21 and ESR1 was higher in CAB (castrated boar) compared to non-castrated boars; whereas, the expression of FMO5 and ESR1 was higher in LBT (low boar taint) compared to HBT (high boar taint) in liver tissue. FMO5, CYP21 and ESR1 proteins were less detectable in HBT compared with LBT and CAB in liver tissues. These findings suggest that FMO5, CYP21 and ESR1 gene variants might have effects on the boar taint compounds.

A genome-wide association study reveals a novel candidate gene for sperm motility in pigs

Sperm motility is one of the most widely used parameters in order to evaluate boar semen quality. However, this trait can only be measured after puberty. Thus, the use of genomic information appears as an appealing alternative to evaluate and improve selection for boar fertility traits earlier in life. With this study we aimed to identify SNPs with significant association with sperm motility in two different commercial pig populations and to identify possible candidate genes within the identified QTL regions. We performed a single-SNP genome-wide association study using genotyped animals from a Landrace-based (L1) and a Large White-based (L2) pig populations. For L1, a total of 602 animals genotyped for 42,551 SNPs were used in the association analysis. For L2, a total of 525 animals genotyped for 40,890 SNPs were available. After the association analysis, a false discovery rate q-value ≤0.05 was used as the threshold for significant association. No SNPs were significantly associated with sperm motility in L1, while six SNPs on Sus scrofa chromosome 1 (position 117.26-119.56Mb) were significant in L2. The mitochondrial methionyl-tRNA formyltransferase (MTFMT) gene, which affects translation efficiency of proteins in sperm cells, was identified as a putative candidate gene. The significant markers identified in this study may be useful to enhance the genetic improvement of sperm motility by selection of boars at an earlier age under a marker assisted selection strategy.