Candidate Genes For Reproductive Traits Research Articles

ZALEŻNOŚCI POMIĘDZY POLIMORFIZMAMI GENÓW RBP4, FSHB I EGF A CECHAMI ROZRODCZYMI U ŚWIŃ

Genes encoding retinol binding protein 4 (RBP4), follicle stimulating hormone subunit beta (FSHB) and epidermal growth factor (EGF) have been proposed as candidate genes for reproduction traits in pigs. The study presented in this work aimed to find associations between variants of these genes and reproduction traits in pigs reared in Poland. Investigation included Polish Large White x Polish Landrace (n = 288) crossbreed and Yorkshire (n = 195) breed sows. Insertion-deletion polymorphism (indel) in EGF gene was determined by means of PCR (polymerase chain reaction) method, however single nucleotide polymorphism (SNP) in RBP4 and FSHB genes by means of PCR-RFLP (restriction fragment length polymorphism) method. Obtained results showed that total number born (TNB) and number born alive (NBA) in 1st, 2nd and 5th parities were associated with RBP4 gene variants, TNB and NBA in first two parities with FSHB variants, however both traits in all parities with EGF variants (p ≤ 0.05 or p ≤ 0.01). In case of RBP4 gene, heterozygous genotype (AB) was favorable for analyzed traits, however in relation to FSHB and EGF genes homozygous genotypes, AA and BB respectively. Obtained results indicate that polymorphism in three analyzed genes is associated with important reproductive traits of pigs kept in Poland.

Genome-wide comparative analysis reveals selection signatures for reproduction traits in prolific Suffolk sheep.

The identification of genome-wide selection signatures can reveal the potential genetic mechanisms involved in the generation of new breeds through natural or artificial selection. In this study, we screened the genome-wide selection signatures of prolific Suffolk sheep, a new strain of multiparous mutton sheep, to identify candidate genes for reproduction traits and unravel the germplasm characteristics and population genetic evolution of this new strain of Suffolk sheep. Whole-genome resequencing was performed at an effective sequencing depth of 20× for genomic diversity and population structure analysis. Additionally, selection signatures were investigated in prolific Suffolk sheep, Suffolk sheep, and Hu sheep using fixation index (F ST) and heterozygosity H) analysis. A total of 5,236.338Gb of high-quality genomic data and 28,767,952 SNPs were obtained for prolific Suffolk sheep. Moreover, 99 selection signals spanning candidate genes were identified. Twenty-three genes were significantly associated with KEGG pathway and Gene Ontology terms related to reproduction, growth, immunity, and metabolism. Through selective signal analysis, genes such as ARHGEF4, CATIP, and CCDC115 were found to be significantly correlated with reproductive traits in prolific Suffolk sheep and were highly associated with the mTOR signaling pathway, the melanogenic pathway, and the Hippo signaling pathways, among others. These results contribute to the understanding of the evolution of artificial selection in prolific Suffolk sheep and provide candidate reproduction-related genes that may be beneficial for the establishment of new sheep breeds.

Genome-wide association study reveals the candidate genes for reproduction traits in Yunong black pigs.

Enhancing pig reproductive efficiency has the potential to have a significant positive economic impact on the pig business. We collected four reproduction records of 734 Yunong black pigs in this study, including the total number of piglets born (TNB), the number born alive (NBA), the average birth interval of piglets (ABI) and the average birth weight (ABW). A total of 453 Yunong black pigs were genotyped with Porcine 50K SNP BeadChip. Twenty-five SNPs and 35 genomic areas were found to have a substantial impact on the reproductive performance of Yunong black pigs by single-locus GWAS and single-step GWAS (ssGWAS). For the ssGWAS, we found that the two genomic regions (12.67-13.85 and 14.26-15.01Mb) on Sus scrofa chromosome X were associated with TNB, NBA and ABI. It is worth noting that CNC10110530 and CNC100141254 significantly affected the TNB by both GWAS methods. Finally, we further determined the gene functions by enrichment analysis and a literature search, and identified 28 of them as candidate genes affecting the reproductive performance of Yunong black pigs, including RET, EIF1AX, NELL2, CTPS2, S100G, RBBP7 and PDHA1. This study further promotes understanding of the genetic mechanism of porcine reproductive performance, and also provides more molecular markers for pig breeding.

A unique 15-bp InDel in the first intron of BMPR1B regulates its expression in Taihu pigs

BackgroundBMPR1B (Bone morphogenetic protein receptor type-1B) is a receptor in the bone morphogenetic protein (BMP) family and has been identified as a candidate gene for reproductive traits in pigs. Our previous study in Taihu pigs found a specific estrogen response element (ERE) in the first intron of the BMPR1B gene that is associated with the number born alive trait. However, little is known about the mechanism by which the ERE regulates the expression of BMPR1B in the endometrium.ResultsHere, a 15-bp InDel (insertion/deletion) (AGCCAGAAAGGAGGA) was identified as a unique variation in Taihu pigs, and was shown to be responsible for the binding of the type I receptor of estrogen (ESR1) to the ERE using dual-luciferase assays. Four BMPR1B transcripts (T1, T2, T3, and T4) were identified by 5′ RACE in endometrial tissue. Expression of T3 and T4 in the endometrium of Meishan pigs was significantly higher than in Duroc pigs during pregnancy. Luciferase assays showed that three distinct BMPR1B promoters may drive expression of T1, T3, and T4. Interestingly, ERE-mediated enhancement of T4 promoter activity significantly increased expression of Transcript T4 in the endometrium of Taihu pigs (P < 0.05). In contrast, the ERE inhibited activity of the T3 promoter and decreased expression of the T3 transcript in the Duroc background (P < 0.05). In summary, we identified a 15-bp InDel in the Taihu ERE that can be used as a molecular marker for the number born alive trait, characterized the 5′ untranslated regions (UTRs) of BMPR1B transcripts in the endometrium, and determined how the transcripts are processed by alternative splicing events.ConclusionsOur results provide a foundation for understanding the transcriptional regulation of BMPR1B and its contributions to the unique breeding prolificacy characteristics of Taihu pigs.

Identification of copy number variations and candidate genes for reproduction traits in Finnish pig populations

Animal breeding programs can be improved by genetic markers associated with production and reproduction traits.Reproduction traits are important for economic success of pig production and therefore development of genetictools for selection is of high interest to pig breeding. In this study our objective was to identify genomic regions associatedwith fertility traits in two Finnish pig breeds using large scale SNP genotyping and genome wide associationanalysis and characterization of copy number variations (CNV). Since CNVs are structural variations of the genomethey potentially have a large effect on gene expression and protein function. We analyzed 1265 genotyped boarsfor nine different reproduction traits and identified 46 CNV regions encompassing 13 genes. 11 of the CNV regionswere shared between the breeds, 20 were unique to the Finnish Yorkshire and 15 to the Finnish Landrace. The genomewide association (GWAS) analysis identified zero to five reproduction associated genomic regions per trait.Furthermore, we identified 23 genomic regions with 20 candidate genes associated with fertility traits using GWASanalysis. The identified CNV regions were compared against GWAS regions to detect candidate regions with an effecton reproduction traits. This study reports candidate genes and genomic regions within two Finnish pig breedsfor reproduction traits, which can be utilized in breeding programs.

Single-step genome-wide association study and candidate genes networks affecting reproductive traits in Iranian Holstein cattle

The process of reproductive in domestic livestock is one of the most importantchallenges of animal husbandry. Fertility is an important trait that contributes to herd profitability, and it can be improved by genomic information. One of the best ways to examine the association between single nucleotide polymorphisms (SNPs) and phenotypic performance is genome-wide association study (GWAS). This study aimed to perform single-step GWAS (ssGWAS) on reproductive traits in Holstein heifers and cows (born from 1992 to 2018) which were obtained from Animal Breeding Center of Iran. Reproductive traits included: age at first service (AFS), age at first calving (AFC), interval between first and last insemination (IFL), calving interval (CI), days from calving to first service (DFS), gestation length (GL), days open (DO), pregnancy rate (PR) and number of services per conception (NS). The animals were genotyped using SNP panels of different densities (Illumina and GeenSeek Genomic companies) and imputed to a 50K SNP density. The number of genotyped animals after quality control was 1654 and the total number of animals in the pedigree file was 3452730. Gene set enrichment analysis (GSEA) as well as pathway analysis were performed to maximize ssGWAS potential. In total 32 significant SNPs (P < 0.05) were observed of which 11 and 21 SNPs were located within candidate genes of reproductive traits in heifers and cows, respectively. Novel potential candidate genes for reproductive traits included PSEN1, ENSBTAG00000050002, USH2A, DMXL1, AVEN, CCDC93, PARP16, MRPL11, PSMA5, PABPN1, CENPF, and MRPL40. Moreover, the most significant gene ontology term was proteolysis which is involved in cellular protein catabolic process (for gestation length). As a result, the SNPs and candidate genes identified in this study could be used in genomic testing to improve fertility performance of Iranian Holstein dairy cattle and provide new information about the genetic architecture of traits.

Identification of candidate genes for reproductive traits in cattle using a functional interaction network approach

Reproduction is a key element in cattle production systems. Systems biology approaches, including those involving gene networks, have been applied to genetic dissection complex phenotypes in cattle. A set of 385 genes associated with reproductive traits in cattle were included in a protein-protein network analysis to identify and prioritize candidate genes related to phenotypic differences in cattle reproduction. Genes belonging to the ubiquitin family - Ubiquitin C ( Ubc , Gene ID: 444874) and Ubiquitin B ( Ubb , Gene ID: 281370) -had the highest probability of being associated with these traits in cattle. Both proteins were identified as important hubs in a protein-protein interaction network, each having 3,775 interactions of 3,856 possible. Resequencing of the Ubb gene coding region to evaluate the presence of SNPs in a discovery population identified the G/T (rs110366695) transversion. This causes emergence of a stop codon and a protein truncated by 287 aa. The allelic frequency distributions found in two beef cattle breeds highlight the promise of further research into the effects of protein truncation and the potential of these proteins as molecular markers for semen quality.

BMP7 is a candidate gene for reproductive traits in Yorkshire sows

Bone morphogenetic protein 7 (BMP7) is of the BMP subfamily, and has effects on female fertility by regulating steroidogenesis, granulosa cell states, and follicular development. In the present study, there was assessment of the combined genotypes formed by the three variants within the 3′-UTR of BMP7 gene as associations with sow reproductive functions. The 3′-UTR of the BMP7 gene of pigs was identified using the 3′ RACE assay, and its full-length sequence was found to be 1538 bp in length. Multiple RNA regulatory elements were detected in this region, luciferase activity assays were performed and results indicated miR-22−3p affects BMP7 by directly binding to the miRNA response element in the 3′-UTR (c.2358–2382). In addition, two novel complete linkage variants, c.2256 G > C and a 7-bp indel (c.2259–2265), were identified within the 3′-UTR of the BMP7 gene of pigs. Importantly, combined genotypes with these two novel variants and c.1569A > G, a variant previously identified in the BMP7 3′-UTR of pigs, were associated with sow reproductive traits, including the total number of piglets born, number of dead piglets at birth, and litter weight in the Yorkshire pig population studies. Results from the present study confirm that BMP7 is a candidate gene for the reproductive traits in Yorkshire sows.

Prolactin gene polymorphisms and associations with reproductive traits in Indonesian local ducks.

Background and Aim:Reproductive traits play an important role in population increases and the egg production (EP) abilities of Indonesian local ducks (ILD). The prolactin (PRL) gene is a single chain polypeptide hormone belonging to a family of growth hormone genes that are mainly synthesized in the anterior pituitary gland in all vertebrates. It has a significant effect on reproductive traits and EP. Single nucleotide polymorphisms (SNPs) present in PRL are a useful molecular marker for EP. This study aimed to identify the PRL polymorphisms based on these SNPs and to uncover the associations with reproductive traits in ILD.Materials and Methods:A total of 280 ILDs consisting of Tegal and Magelang (F0) ducks and their reciprocal crosses, namely, Gallang (F1) and Maggal (F1), were maintained and specific variables were recorded, that is, age at first egg, body weight at first egg, first egg weight, and EP, for 90 days. Allele and genotype frequencies were used to determine the Hardy-Weinberg (H-W) equilibrium. The association between the SNP genotypes of PRL and reproductive traits was analyzed using one-way analysis of variance, following the GLM procedure of SAS. The genotypic effects on the reproductive traits were determined using regression analysis.Results:This study successfully amplified a polymerase chain reaction product of 190 bp, which was used to identify the SNP. Results indicated that PRL in ILDs is polymorphic. A SNP was found at position 164 nt (c.164G >A), consisting of three different genotypes, namely, GG, GA, and AA. The genotypes of Tegal and Magelang (F0), and Gallang (F1) populations were not in H-W equilibrium. The Maggal population (F1) was in H-W equilibrium. Significant associations were detected between the genotypes and EP in all ILDs (p<0.01), following a regression line of y=2.337x+64.605, with a determination coefficient of 0.0188 (r=0.14).Conclusion:PRL can be recommended as a candidate gene for reproductive traits in ILD, especially EP.

Whole-genome sequencing identifies potential candidate genes for reproductive traits in pigs

Reproductive performance is a complex quantitative trait, that is determined by multiple genes, regulatory pathways and environmental factors. A list of major genes with large effect have been detected, although multiple QTLs are identified. To identify candidate genes for pig prolificacy, whole genome variants from five high- and five low-prolificacy Yorkshire sows were collected using whole-genome resequencing. A total of 13,955,609 SNPs and 2,666,366 indels were detected across the genome. Common differential SNPs and indels were identified between the two groups of sows. Genes encoding components of the TGF-beta signaling pathway were enriched with the variations, including BMP5, BMP6, BMP7, ACVR1, INHBA, ZFYVE9, TGFBR2, DCN, ID4, BAMBI, and ACVR2A. Several differential variants within these genes related to reproductive traits were identified to be associated with litter size. A comparison of selective regions and published QTL data suggests that NEDD9, SLC39A11, SNCA, and UNC5D are candidate genes for reproduction traits.

Revealing new candidate genes for reproductive traits in pigs: combining Bayesian GWAS and functional pathways.

BackgroundReproductive traits such as number of stillborn piglets (SB) and number of teats (NT) have been evaluated in many genome-wide association studies (GWAS). Most of these GWAS were performed under the assumption that these traits were normally distributed. However, both SB and NT are discrete (e.g. count) variables. Therefore, it is necessary to test for better fit of other appropriate statistical models based on discrete distributions. In addition, although many GWAS have been performed, the biological meaning of the identified candidate genes, as well as their functional relationships still need to be better understood. Here, we performed and tested a Bayesian treatment of a GWAS model assuming a Poisson distribution for SB and NT in a commercial pig line. To explore the biological role of the genes that underlie SB and NT and identify the most likely candidate genes, we used the most significant single nucleotide polymorphisms (SNPs), to collect related genes and generated gene-transcription factor (TF) networks.ResultsComparisons of the Poisson and Gaussian distributions showed that the Poisson model was appropriate for SB, while the Gaussian was appropriate for NT. The fitted GWAS models indicated 18 and 65 significant SNPs with one and nine quantitative trait locus (QTL) regions within which 18 and 57 related genes were identified for SB and NT, respectively. Based on the related TF, we selected the most representative TF for each trait and constructed a gene-TF network of gene-gene interactions and identified new candidate genes.ConclusionsOur comparative analyses showed that the Poisson model presented the best fit for SB. Thus, to increase the accuracy of GWAS, counting models should be considered for this kind of trait. We identified multiple candidate genes (e.g. PTP4A2, NPHP1, and CYP24A1 for SB and YLPM1, SYNDIG1L, TGFB3, and VRTN for NT) and TF (e.g. NF-κB and KLF4 for SB and SOX9 and ELF5 for NT), which were consistent with known newborn survival traits (e.g. congenital heart disease in fetuses and kidney diseases and diabetes in the mother) and mammary gland biology (e.g. mammary gland development and body length).Electronic supplementary materialThe online version of this article (doi:10.1186/s12711-016-0189-x) contains supplementary material, which is available to authorized users.

Association of non-synonymous SNPs of &amp;lt;i&amp;gt;OPN&amp;lt;/i&amp;gt; gene with litter size traits in pigs

Abstract. Osteopontin (OPN) gene is a secreted phosphoprotein which appears to play a key function in the conceptus implantation, placentation and maintenance of pregnancy in pigs. The objectives of this study were to verify the non-synonymous single nucleotide polymorphisms (SNPs) and their association with litter size traits in commercial Thai Large White pigs. A total of 320 Thai Large White sows were genotyped using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Three SNPs at c.425G&gt; A, c.573T&gt; C and c.881C&gt; T revealed amino acid exchange rates of p.110Ala&gt; Thr, p.159Val&gt; Ala and p.262Pro&gt; Ser, respectively, and were then segregated. These three SNPs were significantly associated with total number born (TNB) and number born alive (NBA) traits. No polymorphisms of the two SNP markers (c.278A&gt; G and c.452T&gt; G) were observed in this study. Moreover, the SNPs at c.425G&gt; A and c.573T&gt; C were found to be in strong linkage disequilibrium. The association of OPN with litter size emphasizes the importance of porcine OPN as a candidate gene for reproductive traits in pig breeding.

Identification of Reproduction-Related Gene Polymorphisms Using Whole Transcriptome Sequencing in the Large White Pig Population.

Recent developments in high-throughput sequencing techniques have enabled large-scale analysis of genetic variations and gene expression in different tissues and species, but gene expression patterns and genetic variations in livestock are not well-characterized. In this study, we have used high-throughput transcriptomic sequencing of the Finnish Large White to identify gene expression patterns and coding polymorphisms within the breed in the testis and oviduct. The main objective of this study was to identify polymorphisms within genes that are highly and specifically expressed in male and/or female reproductive organs. The differential expression (DE) analysis underlined 1234 genes highly expressed in the testis and 1501 in the oviduct. Furthermore, we used a novel in-house R-package hoardeR for the identification of novel genes and their orthologs, which underlined 55 additional DE genes based on orthologs in the human, cow, and sheep. Identification of polymorphisms in the dataset resulted in a total of 29,973 variants, of which 10,704 were known coding variants. Fifty-seven nonsynonymous SNPs were present among genes with high expression in the testis and 67 were present in the oviduct, underlining possible influential genes for reproduction traits. Seven genes (PGR, FRAS1, TCF4, ADAT1, SPAG6, PIWIL2, and DNAH8) with polymorphisms were highlighted as reproduction-related based on their biological function. The expression and SNPs of these genes were confirmed using RT-PCR and Sanger sequencing. The identified nonsynonymous mutations within genes highly expressed in the testis or oviduct provide a list of candidate genes for reproduction traits within the pig population and enable identification of biomarkers for sow and boar fertility.

Association of EphA4 polymorphism with swine reproductive traits and mRNA expression of EphA4 during embryo implantation

The swine erythropoietin-producing hepatocellular A4 (EphA4) gene, which was detected in the endometrium during embryo implantation in pigs, was one of the potential candidate genes for reproductive traits. In the study, two single nucleotide polymorphism (SNP) loci (EphA4_1 and EphA4_2) in exon 3 of EphA4 gene were analyzed to determine whether EphA4 influenced total number born (TNB) and number born alive (NBA). Association of two diallelic polymorphisms with reproductive traits was assessed in Landrace, Yorkshire and Duroc populations with 2,014 litter records of 765 sows. The results showed that G allele at EphA4_1 locus or C allele at EphA4_2 locus seemed to have advantageous effects on litter size. And the combined analyzed results demonstrated that genotype AGTC, AGCC and GGCC are better than genotype AATT, AATC and AGTT for TNB and NBA in either single parity or all parities. The results in this study demonstrated that EphA4 gene was significantly associated with litter size in pigs. In addition, a high mRNA expression of EphA4 was found in small intestine, large intestine, stomach and endometrium, and the expression decreased during implantation in pigs. Further studies were needed to confirm these preliminary researches.

Polymorphism in NPY and IGF-I genes associate with reproductive traits in Wenchang chicken.

Alleles of physiological candidate genes for reproductive traits, insulin-like growth factor-I (IGF-I) and neuropeptide Y (NPY) were assessed to determine the association with total egg production (NE), average days of continual egg-laying (ADCE) and number of double-yolked eggs (DYE) in Wenchang chicken (Chinese indigenous breed). PCR-RFLP method was used for genotypes identification. The frequency of restriction enzyme A/a alleles in the population was 0.46 (A) and 0.54 (a) for NPY. The frequency of restriction enzyme B/b alleles in the population was 0.53 (B) and 0.47 (b) for IGF-I, respectively. Four significant associations were found (P < 0.05): between NPY and NE (300 d) and between IGF-I polymorphism and NE (300 d), NE (400 d) and ADCE. Two significant effects were observed: for NPY and NE (300 d) and for IGF-I and NE (300 d). The current research supports the effects of NPY and IGF-I genes on reproductive traits of chickens. Key words: Chicken, NPY, IGF-I, reproduction, SNP.

PDK1 and HR46 Gene Homologs Tie Social Behavior to Ovary Signals

The genetic basis of division of labor in social insects is a central question in evolutionary and behavioral biology. The honey bee is a model for studying evolutionary behavioral genetics because of its well characterized age-correlated division of labor. After an initial period of within-nest tasks, 2–3 week-old worker bees begin foraging outside the nest. Individuals often specialize by biasing their foraging efforts toward collecting pollen or nectar. Efforts to explain the origins of foraging specialization suggest that division of labor between nectar and pollen foraging specialists is influenced by genes with effects on reproductive physiology. Quantitative trait loci (QTL) mapping of foraging behavior also reveals candidate genes for reproductive traits. Here, we address the linkage of reproductive anatomy to behavior, using backcross QTL analysis, behavioral and anatomical phenotyping, candidate gene expression studies, and backcross confirmation of gene-to-anatomical trait associations. Our data show for the first time that the activity of two positional candidate genes for behavior, PDK1 and HR46, have direct genetic relationships to ovary size, a central reproductive trait that correlates with the nectar and pollen foraging bias of workers. These findings implicate two genes that were not known previously to influence complex social behavior. Also, they outline how selection may have acted on gene networks that affect reproductive resource allocation and behavior to facilitate the evolution of social foraging in honey bees.

Polymorphisms within promoter of Japanese flounder (Paralichthys olivaceus) ovary cytochrome P450-c19 (CYP19a) gene associated with reproductive traits

Cytochrome P450 aromatase, which is encoded by the CYP19a gene, converts androgens to estradiol. Considerable evidence suggests that estrogens play an important role in fish reproductive process. Therefore CYP19a is an excellent candidate gene for reproductive traits. Variants in the promoter of the CYP19a gene might also be involved in the control of aromatase expression and affect regulatory mechanism linking cholesterol metabolism to the synthesis of sex steroids. In this study, nine single-nucleotide polymorphisms (SNPs) were detected with polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP), namely A-680G, G-672A, AGTAGT-649 inserting or deleting, T-623C, C-410A, T7-454A, T-402C, TTTCCAGACTGA-345 inserting or deleting, and G-297C. Nine SNPs within the promoter of the CYP19a gene were tested for association with four reproductive traits [serum testosterone (T), serum 17beta-estradiol (E(2)), hepatosomatic index (HSI), and gonadosomatic index (GSI)] in a population of 50 female Japanese flounder individuals. A locus, P3 (TTTCCAGACTGA-345 inserting or deleting, G-297C), was significantly associated with 17beta-estradiol (E(2)) level (P < 0.05) in female Japanese flounder. In addition, there was significant association between one diplotype based on nine SNPs and reproductive trait. The genetic effect for E(2) level of diplotype D3 was significantly higher than those of other diplotypes (P < 0.05). Results indicate that these genetic effects of those variants on E(2) level may help to explain CYP19a gene status in the reproductive endocrinology of Japanese flounder.

Identification of polymorphism and association analysis with reproductive traits in the porcine RNF4 gene

The ring finger protein 4 gene ( RNF4), which might play a role in fetal germ cell development as well as in oocyte and granulosa cell maturation, was one of the potential candidate genes for reproductive traits. In the present work, we isolated the complete coding sequence of porcine RNF4 gene, identified a single nucleotide polymorphism (SNP: T/C) in intron5, and developed a PCR- SacII-RFLP genotyping assay. Association of this SNP with reproductive traits was assessed in three populations with diverse genetic backgrounds. One was Chinese Qingping sows. Another was consisted of crossbred sows derived from Landrace, Large White, Chinese Tongcheng and/or Chinese Meishan (Line DIV). The third is Large White × Meishan (LW × M) F 2 slaughtered population. Statistical analysis demonstrated that, in the first parity, the difference between RNF4 genotypes and reproductive traits of both Qingping and Line DIV sows was not significant. In the second and subsequent litters, CC animals in Qingping population had more piglets born (+1.74 piglets) and piglets born alive (+2.02 piglets) than sows with the TT genotype ( P < 0.05). Line DIV sows inheriting the CC genotype had additional 0.69 piglets born compared to the TC animals ( P < 0.05) in second and subsequent litters. No significant difference was observed between genotypes and reproductive tracts components in F 2 animals. In addition, we found RNF4 gene has a significant additive effect on both piglet born and piglet born alive in Qingping animals ( P < 0.05). Results here suggested that the RNF4 SNP was significantly associated with litter size in two populations and could be useful in selection for increasing litter size in pigs. Further studies were needed to confirm these preliminary researches.

Associations between the prolactin receptor gene polymorphism and reproductive traits of boars

The prolactin receptor gene (PRLR), located on chromosome 16 in pigs, is a candidate gene for reproductive traits. The experiment was aimed to detect the DNA mutations in this gene and to find probable relations between the genotype and some reproductive traits in boars. The polymorphism in the PRLR gene was identified by PCR-RFLP method using specific primers and the restriction enzyme AluI. In total 229 boars of various breeds were genotyped. The frequency of allele A was estimated at 0.62 and allele B at 0.38. Genotype AA was found at a frequency of 0.45, AB at 0.35 and BB at 0.20. We found associations between PRLR genotype and ejaculate volume, sperm concentration, percentage of live sperm, and number of live sperm in the ejaculate (P < 0.01).

A study of association between genetic markers in candidate genes and reproductive traits in one generation of a commercial broiler breeder hen population.

Markers of alleles for three physiological candidate genes for reproductive traits, growth hormone (GHR), gonadotropin-releasing hormone receptor (GNRHR) and neuropeptide Y (NPY) were assessed for the association with the total egg production, number of double-yolked eggs and age at first egg in a single generation of a broiler breeder (Gallus gallus) pedigree dam line. Single-nucleotide polymorphisms and deletions were detected in the GHR, GNRHR and NPY genes. Genotypes were identified using a PCR-RFLP assay. The frequency of restriction enzyme+/-alleles in the population was for GHR 0.68 (NspI-) and 0.32 (NspI+), for NPY 0.78 (DraI+) and 0.22 (DraI-) and for GNRHR 0.54 (Bpu1102I+) and 0.46 (Bpu1102I-). Trait data from a total of 772 hens in 67 sire families from one generation of the pedigree dam line were recorded. However, the analysis used only the offspring of heterozygous sires to reduce the influence of selection and genetic background (n=33 sire families for GHR; n=14 sire families for NPY; n=36 sire families for GNRHR). A dominance effect of NPY on age at first egg and an additive effect of GNRHR on the number of double-yolked eggs were found (P<0.05).