Androgens and androgen receptor signaling contribute to ovarian development in the chicken embryo

Characterizing structural variants based on graph-genotyping provides insights into pig domestication and local adaption

Structural variants (SVs), such as deletions (DELs) and insertions (INSs), contribute substantially to pig genetic diversity and phenotypic variation. Using a library of SVs discovered from long-read primary assemblies and short-read sequenced genomes, we map pig genomic SVs with a graph-based method for re-genotyping SVs in 402 genomes. Our results demonstrate that those SVs harboring specific trait-associated genes may greatly shape pig domestication and local adaptation. Further characterization of SVs reveals that some population-stratified SVs may alter the transcription of genes by affecting regulatory elements. We identify that the genotypes of two DELs (296-bp DEL, chr7: 52,172,101-52,172,397; 278-bp DEL, chr18: 23,840,143-23,840,421) located in muscle-specific enhancers are associated with the expression of target genes related to meat quality (FSD2) and muscle fiber hypertrophy (LMOD2 and WASL) in pigs. Our results highlight the role of SVs in domestic porcine evolution, and the identified candidate functional genes and SVs are valuable resources for future genomic research and breeding programs in pigs.

No effects of the antiandrogens cyproterone acetate (CPA), flutamide and p,p'-DDE on early sexual differentiation but CPA-induced retardation of embryonic development in the domestic fowl (Gallus gallus domesticus)

Because a wide range of environmental contaminants are known to cause endocrine disorders in humans and animals, in vivo tests are needed to identify such endocrine disrupting chemicals (EDCs) and to assess their biological effects. Despite the lack of a standardized guideline, the avian embryo has been shown to be a promising model system which responds sensitively to EDCs. After previous studies on the effects of estrogenic, antiestrogenic and androgenic substances, the present work focuses on the effects of in ovo exposure to p,p'-DDE, flutamide and cyproterone acetate (CPA) as antiandrogenic model compounds regarding gonadal sex differentiation and embryonic development of the domestic fowl (Gallus gallus domesticus). The substances were injected into the yolk of fertilized eggs on embryonic day one. On embryonic day 19 sex genotype and phenotype were determined, followed by gross morphological and histological examination of the gonads. Treatment with flutamide (0.5, 5, 50 µg/g egg), p,p'-DDE (0.5, 5, 50 µg/g egg) or CPA (0.2, 2, 20 µg/g egg) did not affect male or female gonad development, assessed by gonad surface area and cortex thickness in both sexes and by the percentage of seminiferous tubules in males as endpoints. This leads to the conclusion that antiandrogens do not affect sexual differentiation during embryonic development of G. gallus domesticus, reflecting that gonads are not target organs for androgens in birds. In ovo exposure to 2 and 20 µg CPA/g egg, however, resulted in significantly smaller embryos as displayed by shortened lengths of skull, ulna and tarsometatarsus. Although gonadal endpoints were not affected by antiandrogens, the embryo of G. gallus domesticus is shown to be a suitable test system for the identification of substance-related mortality and developmental delays.

Comparative Analysis Among Different Species Reveals That the Androgen Receptor Regulates Chicken Follicle Selection Through Species-Specific Genes Related to Follicle Development

The differences in reproductive processes at the molecular level between viviparous and oviparous animals are evident, and the site in the ovary that synthesizes sex hormones (androgens and oestrogens) and the trends for enriching sex hormones during follicle development in chickens are different from those in mammals, suggesting that the effect of sex hormones on follicle development in chickens is probably different from that in viviparous animals. To explore the specific role of androgen receptors (ARs) on chicken follicular development, we matched the correspondence of follicular development stages among chickens, humans, cows and identified chicken-specific genes related to follicle development (GAL-SPGs) by comparing follicle development-related genes and their biological functions among species (chickens, humans, and cows). A comparison of the core transcription factor regulatory network of granulosa cells (or ovaries) based on super-enhancers among species (chicken, human, and mouse) revealed that AR is a core transcriptional regulator specific to chickens. In vivo experiments showed that inhibition of AR significantly reduced the number of syf (selected stage follicles) in chickens and decreased the expression of GAL-SPGs in F5 follicles, while in vitro experiments showed that inhibition of AR expression in chicken granulosa cells (GCs) significantly down-regulated the expression levels of GAL-SPGs, indicating that AR could regulate follicle selection through chicken-specific genes related to follicle development. A comparison among species (77 vertebrates) of the conserved genomic regions, where chicken super-enhancers are located, revealed that the chicken AR super-enhancer region is conserved in birds, suggesting that the role of AR in follicle selection maybe widespread in birds. In summary, we found that AR can regulate follicle selection through chicken-specific genes related to follicle development, which also emphasizes the important role of AR in follicle selection in chickens and provides a new perspective for understanding the unique process of follicle development in chickens. Our study will contribute to the application of androgens to the control of egg production in chickens and suggests that researchers can delve into the mechanisms of follicle development in birds based on androgen/androgen receptors.

Expression profiling of sexually dimorphic genes in the Japanese quail, Coturnix japonica

Research on avian sex determination has focused on the chicken. In this study, we established the utility of another widely used animal model, the Japanese quail (Coturnix japonica), for clarifying the molecular mechanisms underlying gonadal sex differentiation. In particular, we performed comprehensive gene expression profiling of embryonic gonads at three stages (HH27, HH31 and HH38) by mRNA-seq. We classified the expression patterns of 4,815 genes into nine clusters according to the extent of change between stages. Cluster 2 (characterized by an initial increase and steady levels thereafter), including 495 and 310 genes expressed in males and females, respectively, contained five key genes involved in gonadal sex differentiation. A GO analysis showed that genes in this cluster are related to developmental processes including reproductive structure development and developmental processes involved in reproduction were significant, suggesting that expression profiling is an effective approach to identify novel candidate genes. Based on RNA-seq data and in situ hybridization, the expression patterns and localization of most key genes for gonadal sex differentiation corresponded well to those of the chicken. Our results support the effectiveness of the Japanese quail as a model for studies gonadal sex differentiation in birds.

The concentration of androgen receptor and protein kinase A in male chicken following the administration of a combination of the epididymis and testicular extracts

Background and Aim

Testis (T) and epididymis (E) are waste from the abattoir that is rarely used. In fact, both organs contain important chemicals needed for spermatogenesis (e.g., hormones, proteins, and other molecules). Therefore, administration of a combination of testis and epididymis (CTE) extracts may activate androgen receptors (AR) and protein kinase A (PKA) molecules that play a prominent role in spermatogenesis. We, therefore, aimed at investigating the influence of the CTE extracts on the concentration of AR and PKA in male chicken.

Materials and Methods

This study used a completely randomized design with four treatment groups (K0, K1, K2, and K3) and five replications per group. K0 is a control group that received 1 mL normal saline, whereas K1, K2, and K3 are the test groups that received 1, 2, and 3 mL of CET extracts, respectively. Twenty male chickens (strain: broiler Mb 89), 3 weeks of age, weighing 500-700 g were used. We administered the injections in a 13-day period and on the 14^th day; we collected and processed blood samples as serum to measure the AR and PKA concentrations using commercial chicken AR and PKA enzyme-linked immunosorbent assay kits, respectively. We performed analyses by analysis of variance using SPSS 20.0.

Results

The AR concentrations in K1, K2, and K3 groups increased by 4.26%, 10.97%, and 28.04%, respectively, compared to the K0 (control group). However, this increase was not significantly different between the groups (p>0.05). Moreover, the PKA concentrations increased by 2.97%, 2.60%, and 4.08% in K1, K2, and K3 groups, respectively, compared to the control group. However, this increase was not significantly different between the groups as well (p>0.05).

Conclusion

The CTE extracts tended to increase the AR and PKA concentrations even though it is not significant. Therefore, it needs further study when using the CTE extracts for spermatogenesis in male chicken.

The Sertoli cell marker FOXD1 regulates testis development and function in the chicken

FOXD1, one of the transcription factors of the FOX family, has been shown to be important for mammalian reproduction but little is known about its function in avian species. In the present study, we identified the expression pattern and location of FOXD1 in chicken tissues and testis by performing quantitative polymerase chain reaction, immunohistochemistry and immunofluorescence, and further investigated the regulatory relationship of FOXD1 with genes involved in testis development by RNA interference. Our results showed that FOXD1 is confirmed to be significantly male-biased expressed in the brain, kidney and testis of adults as well as in embryonic gonads, and it is localised in the testicular Sertoli cell in chicken, consistent with its localisation in mammals. After knock-down of FOXD1 in chicken Sertoli cells, the expression of anti-Müllerian hormone (AMH), sex-determining region Y-box 9 (SOX9) and PKA regulatory subunits type I α (RIα) was significantly downregulated, expression of androgen receptor (AR) was notably increased whereas double-sex and MAB-3-related transcription factor 1 (DMRT1) showed no obvious change in expression. These results suggest that FOXD1 is an essential marker for Sertoli cells upstream of SOX9 expression and a potential regulator of embryonic testis differentiation and development and of normal testis function in the chicken.

Knockdown of DEAD-box helicase 4 (DDX4) decreases the number of germ cells in male and female chicken embryonic gonads

DEAD-box helicase 4 (DDX4; also known as vasa) is essential for the proper formation and maintenance of germ cells. Although DDX4 is conserved in a variety of vertebrates and invertebrates, its roles differ between species. This study investigated the function of DDX4 in chicken embryos by knocking down its expression using retroviral vectors that encoded DDX4-targeting microRNAs. DDX4 was effectively depleted invitro and invivo via this approach. Male and female gonads of DDX4-knockdown embryos contained a decreased number of primordial germ cells, indicating that DDX4 is essential to maintain a normal level of these cells in chicken embryos of both sexes. Expression of doublesex and mab-3 related transcription factor 1 (DMRT1) and sex determining region Y-box 9 (SOX9), which are involved in testis determination and differentiation, was normal in male gonads of DDX4-knockdown embryos. In contrast, expression of cytochrome P450 family 19 subfamily A member 1 (CYP19A1), which encodes aromatase and is essential for ovary development, was significantly decreased in female gonads of DDX4-knockdown embryos. Expression of forkhead box L2 (FOXL2), which plays an important role in ovary differentiation, was also slightly reduced in DDX4-knockdown embryos, but not significantly. Based on several pieces of evidence FOXL2 was hypothesised to regulate aromatase expression. The results of this study indicate that aromatase expression is also regulated by several additional pathways.

Influence of hypothyroidism on testicular mitochondrial oxidative stress by activating the p38 mitogen-activated protein kinase and c-Jun NH2-terminal kinase signaling pathways in rats

Thyroid hormone deficiency can impair testicular function. However, knowledge of the effects of mitogen-activated protein kinase (MAPK) pathways on testicular mitochondrial oxidative damage induced by hypothyroidism is still rudimentary. This study aims to explore the possible mechanisms of testicular mitochondrial oxidative damage in hypothyroidism rats. Wistar male rats were randomly divided into control (C), low- (L), and high-hypothyroidism (H) groups (1 ml/100 g body weights (BWs)/day 0, 0.001% and 0.1% propylthiouracil, respectively) by intragastric gavage for 60 days. Blood samples were collected to measure the levels of serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH). Testicular mitochondrial homogenates were used to measure the activities of superoxide dismutase (SOD), catalase (CAT), and Ca2+-ATPase as well as protein and mRNA expression of androgen receptor (AR), p38 MAPK, and c-Jun NH2-terminal kinase (JNK). Results showed that the BWs, testes weights, and levels of T3 and T4 were all significantly decreased and the testes coefficient and level of TSH were significantly increased in the H group. There were significant decreases in SOD activity in the H group as well as decreases in CAT and Ca2+-ATPase activities in the L and H groups. Additionally, protein expression of AR decreased significantly and protein expression of phosphorylated p38MAPK and JNK increased significantly in the H group. Therefore, the study suggests that hypothyroidism could affect male reproductive function by disturbing expression of AR, changing the activity of Ca2+-ATPase, inducing oxidative stress and then leading to activation of p38MAPK and JNK signaling in the testicular mitochondria.

Detection of genomic structural variations in Guizhou indigenous pigs and the comparison with other breeds

Genomic structural variation (SV) is noticed for the contribution to genetic diversity and phenotypic changes. Guizhou indigenous pig (GZP) has been raised for hundreds of years with many special characteristics. The present paper aimed to uncover the influence of SV on gene polymorphism and the genetic mechanisms of phenotypic traits for GZP. Eighteen GZPs were chosen for resequencing by Illumina sequencing platform. The confident SVs of GZP were called out by both programs of pindel and softSV simultaneously and compared with the SVs deduced from the genomic data of European pig (EUP) and the native pig outside of Guizhou, China (NPOG). A total of 39,166 SVs were detected and covered 27.37 Mb of pig genome. All of 76 SVs were confirmed in GZP pig population by PCR method. The SVs numbers in NPOG and GZP were about 1.8 to 1.9 times higher than that in EUP. And a SV hotspot was found out from the 20 Mb of chromosome X of GZP, which harbored 29 genes and focused on histone modification. More than half of SVs was positioned in the intergenic regions and about one third of SVs in the introns of genes. And we found that SVs tended to locate in genes produced multi-transcripts, in which a positive correlation was found out between the numbers of SV and the gene transcripts. It illustrated that the primary mode of SVs might function on the regulation of gene expression or the transcripts splicing process. A total of 1,628 protein-coding genes were disturbed by 1,956 SVs specific in GZP, in which 93 GZP-specific SV-related genes would lose their functions due to the SV interference and gathered in reproduction ability. Interestingly, the 1,628 protein-coding genes were mainly enriched in estrogen receptor binding, steroid hormone receptor binding, retinoic acid receptor binding, oxytocin signaling pathway, mTOR signaling pathway, axon guidance and cholinergic synapse pathways. It suggested that SV might be a reason for the strong adaptability and low fecundity of GZP, and 51 candidate genes would be useful for the configuration phenotype in Xiang pig breed.