Screening for reproductive biomarkers in Bactrian camel via iTRAQ analysis of proteomes

Exploring the Mechanism of H2S Synthesis in Male Bactrian Camel Poll Glands Based on Data Independent Acquisition Proteomics and Non-Targeted Metabolomics

During estrus, the poll glands of male Bactrian Camels (Camelus Bactrianus) become slightly raised, exuding a large amount of pale yellow watery secretion with a characteristic odor that may contain hydrogen sulfide (H2S). However, whether H2S can be synthesized in the poll glands of male Bactrian Camels and its role in inducing camel estrus remains unclear. This study aimed to identify differentially expressed proteins (DEPs) and signaling pathways in the poll gland tissues of male Bactrian Camels using data independent acquisition (DIA) proteomics. Additionally, gas chromatography-mass spectrometry (GC-MS) was performed to identify differentially expressed metabolites (DEMs) in the neck hair containing secretions during estrus in male Bactrian Camels, to explore the specific expression patterns and mechanisms in the poll glands of camels during estrus. The results showed that cystathionine-γ-lyase (CTH) and cystathionine-β-synthase (CBS), which are closely related to H2S synthesis in camel poll glands during estrus, were mainly enriched in glycine, serine, and threonine metabolism, amino acid biosynthesis, and metabolic pathways. In addition, both enzymes were widely distributed and highly expressed in the acinar cells of poll gland tissues in camels during estrus. Meanwhile, the neck hair secretion contains high levels of amino acids, especially glycine, serine, threonine, and cystathionine, which are precursors for H2S biosynthesis. These results demonstrate that the poll glands of male Bactrian Camels can synthesize and secrete H2S during estrus. This study provides a basis for exploring the function and mechanism of H2S in the estrus of Bactrian Camels.

Cholecystokinin-mediated effect of insulin pathway on the steroidogenic activity of follicular granulosa cells in Camelus bactrianus: In vitro study

The current study aimed to explore the molecular mechanism by which the cholecystokinin (CCK)-mediated CCKAR and CCKBR, as well as the molecular mechanisms of CCK-mediated insulin signalling pathway, regulate oestrogen in the granulosa cells. Also, the expression of CCK in ovaries, uterus, hypothalamus and pituitary gland was investigated in Camelus bactrianus. Ovaries, uterus, hypothalamus and pituitary gland were collected from six, three before ovulation (control) and three after ovulation, slaughtered Camelus bactrianus. Ovulation was induced by IM injection of seminal plasma before slaughtering in the ovulated group. The results showed that there were differences in the transcription and protein levels of CCK in various tissues before and after ovulation (p < .05, p < .01). After transfection with p-IRES2-EGFP-CCK, the mRNA and protein levels of CCK, CCKAR, CCKBR and ER in follicular granulosa cells were significantly upregulated (p < .05, p < .01), and the content of E2 was significantly upregulated (p < .01); On the contrary, after transfection with si-CCK, the mRNA and protein levels of CCK, CCKAR, CCKBR and ER in follicular granulosa cells were significantly downregulated (p < .05, p < .01), and the content of E2 was significantly downregulated (p < .01). Regulating CCK can affect the mRNA levels of INS, INSR, IGF and IGF-R. In summary, regulating the expression level of CCK can activate insulin-related signalling pathways by CCKR, thereby regulating the steroidogenic activity of granulosa cells.

Genome-wide scan for runs of homozygosity in South American Camelids

BACKGROUND

Alpaca (Vicugna pacos), llama (Lama glama), vicugna (Vicugna vicugna) and guanaco (Lama guanicoe), are the camelid species distributed over the Andean high-altitude grasslands, the Altiplano, and the Patagonian arid steppes. Despite the wide interest on these animals, most of the loci under selection are still unknown. Using whole-genome sequencing (WGS) data we investigated the occurrence and the distribution of Runs Of Homozygosity (ROHs) across the South American Camelids (SACs) genome to identify the genetic relationship between the four species and the potential signatures of selection.

RESULTS

A total of 37 WGS samples covering the four species was included in the final analysis. The multi-dimensional scaling approach showed a clear separation between the four species; however, admixture analysis suggested a strong genetic introgression from vicugna and llama to alpaca. Conversely, very low genetic admixture of the guanaco with the other SACs was found. The four species did not show significant differences in the number, length of ROHs (100-500 kb) and genomic inbreeding values. Longer ROHs (> 500 kb) were found almost exclusively in alpaca. Seven overlapping ROHs were shared by alpacas, encompassing nine loci (FGF5, LOC107034918, PRDM8, ANTXR2, LOC102534792, BSN, LOC116284892, DAG1 and RIC8B) while nine overlapping ROHs were found in llama with twenty-five loci annotated (ERC2, FZD9, BAZ1B, BCL7B, LOC116284208, TBL2, MLXIPL, PHF20, TRNAD-AUC, LOC116284365, RBM39, ARFGEF2, DCAF5, EXD2, HSPB11, LRRC42, LDLRAD1, TMEM59, LOC107033213, TCEANC2, LOC102545169, LOC116278408, SMIM15, NDUFAF2 and RCOR1). Four overlapping ROHs, with three annotated loci (DLG1, KAT6B and PDE4D) and three overlapping ROHs, with seven annotated genes (ATP6V1E1, BCL2L13, LOC116276952, BID, KAT6B, LOC116282667 and LOC107034552), were detected for vicugna and guanaco, respectively.

CONCLUSIONS

The signatures of selection revealed genomic areas potentially selected for production traits as well as for natural adaptation to harsh environment. Alpaca and llama hint a selection driven by environment as well as by farming purpose while vicugna and guanaco showed selection signals for adaptation to harsh environment. Interesting, signatures of selection on KAT6B gene were identified for both vicugna and guanaco, suggesting a positive effect on wild populations fitness. Such information may be of interest to further ecological and animal production studies.

Gas/Liquid Chromatography-Mass Spectrometry Analysis of Key Functional Substances Regulating Poll Gland Secretion in Male Camels during Seasonal Estrus

Increased poll gland secretion is a major characteristic and indicator of estrus in male Bactrian camels; however, research on these poll glands and their secretion is extremely rare. In this study, we determine the chemical composition of poll gland secretions and identify the key functional substances that regulate seasonal estrus in male camels. A GC/LC-MS dual platform was used to analyze ventral hair (control) and neck mane samples containing poll gland secretions from male Bactrian camels during estrus. Multidimensional and single-dimensional analyses were used to screen differentially expressed metabolites (DEMs) between groups. Functional prediction of enriched metabolites was performed using a Human Metabolome Database comparison and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, which were then compared with a behavioral analysis of male Bactrian camels in estrus. A total of 1172 DEMs and 34 differential metabolic pathways were identified. One metabolite group was found to relate to steroid synthesis and metabolism, and another metabolite group was associated with neural metabolism. Therefore, we speculate that steroids and neurochemicals jointly regulate estrous behavior in male Bactrian camels, thus providing theoretical insights into the development and function of poll glands in Bactrian camels.

Proteomic analysis of iTRAQ in melatonin-treated sheep epididymal epithelial cells

During maturation, spermatozoa acquire motility and fertilizing capacity as they transit through the epididymis. Melatonin is a lipophilic hormone with multiple functions in regulating the fertility. Previous studies have shown that melatonin affected the capacitation or maturation of sperm in the epididymis. The aim of this study was to investigate the effects of melatonin on epididymal caput epithelial cells in sheep. In the study, we used iTRAQ labelling coupled with LC-MS/MS for quantitative identification of differentially expressed proteins in melatonin-treated sheep epididymal caput epithelial cells. We identified 69 differentially expressed protein; 41 were upregulated and 28 were downregulated in samples from sheep in melatonin treated. We validated the differential expression of a subset of these proteins using qPCR and Western blot. Gene ontology annotation identified that the differentially expressed proteins function in cellular processes and metabolic processes. Notably, five of the differentially expressed proteins as SOD1, COL1A1, PRM1, NQO2, and FN1 are involved in sperm migration and sperm maturation. KEGG enrichment analysis demonstrated significant enrichment in several cardiac-related pathways, such as "PI3K-Akt signaling pathway", "AGE-RAGE signaling pathway in diabetic complications", "ECM-receptor interaction", and "Ribosome". Our results suggest that candidate biomarker (SOD1, COL1A1, PRM1, NQO2, and FN1) discovery can aid in understanding sperm development and maturation in sheep. These results provide insights into the potential mechanisms of melatonin regulation of sperm maturation in epididymal caput epithelial cells.

RBP4 regulates androgen receptor expression and steroid synthesis in Sertoli cells from Bactrian camels

Retinol-binding protein (RBP4) plays an important role in the transport and metabolism of retinol. In addition, RBP4 contributes to testicular homeostasis, including maintenance of spermatogenesis and synthesis of androgens that mediate their physiological functions through the androgen receptor. RBP4 in Sertoli cells regulates testosterone and dihydrotestosterone synthesis and secretion, although the mechanisms have yet to be revealed. In this study, we examined the expression and function of RBP4 in Sertoli cells isolated from Bactrian camels. qRT-PCR analysis of various Bactrian camel tissues revealed high expression of RBP4 in the testis and epididymis. To examine RBP4 function, Sertoli cells isolated from testes were transfected with an RBP4 overexpression plasmid or RBP4-targeting siRNA. RBP4 overexpression resulted in significant inhibition of transcription and translation of the steroidogenic enzymes 3βHSD and SRD5A1 concomitant with a significant decrease in androgen receptor expression and dihydrotestosterone secretion. Conversely, RBP4 knockdown significantly increased the expression of 3βHSD, SRD5A1, and androgen receptor and enhanced the secretion of dihydrotestosterone and testosterone. These data reveal a novel role for RBP4 in regulating steroid synthesis in Sertoli cells from Bactrian camels.

Screening and Identification of Differential Ovarian Proteins before and after Induced Ovulation via Seminal Plasma in Bactrian Camels

Simple Summary

Camelidae are induced ovulators whose ovulation is tightly regulated by multiple factors. Understanding the biological mechanisms underlying follicular development, hormone secretion, and ovulation requires investigating the potential molecular pathways involved in these mechanisms. However, little is known about these molecular pathways in Bactrian camels. To screen and identify candidate biomarkers after seminal plasma (SP)-induced ovulation in the ovaries, we performed comprehensive proteomic and molecular biological analyses of the ovaries from camels that were intramuscularly injected with either seminal plasma or phosphate-buffered saline. Identification of these candidate biomarkers will enable a better understanding of reproduction in Bactrian camels. Our findings suggest candidate proteins for further studies on the molecular mechanisms of induced ovulation.

Abstract

Camelidae are induced ovulators whose ovulation is tightly regulated by multiple factors. Understanding the biological mechanisms underlying follicular development, hormone secretion, and ovulation requires investigating the potential molecular pathways involved. However, little is known about these pathways in Bactrian camels. To screen and identify candidate biomarkers after inducing ovulation, this study performed comprehensive proteomic and molecular biological analyses of the ovaries from two camel groups (n = 6). We identified 5075 expressed ovarian proteins, of which 404 were differentially expressed (264 upregulated, 140 downregulated) (p < 0.05 or p < 0.01), in samples from plasma-induced versus control camels. Gene ontology annotation identified the potential functions of the differentially expressed proteins (DEPs). These results validated the differential expression for a subset of these proteins using Western blot (p < 0.05) and immunofluorescence staining. Three DEPs (FST, NR5A1, and PRL) were involved in neurochemical signal transduction, as well as endocrine and reproductive hormone regulatory processes. The Kyoto Encyclopedia of Genes and Genomes analysis indicated the involvement of several pathways, including the calcium, cAMP, gonadotropin-releasing hormone, MAPK, and neuroactive ligand–receptor signaling pathways, suggesting that induced ovulation depends on the hypothalamic–pituitary–ovarian axis. Identifying these candidate biomarkers enables a better understanding of Bactrian camel reproduction. Ovarian proteomic profiling and the measurement of selected proteins using more targeted methods is a promising approach for studying induced-ovulation mechanisms.

Exploring the genomic resources of seven domestic Bactrian camel populations in China through restriction site-associated DNA sequencing

The domestic Bactrian camel is a valuable livestock resource in arid desert areas. Therefore, it is essential to understand the roles of important genes responsible for its characteristics. We used restriction site-associated DNA sequencing (RAD-seq) to detect single nucleotide polymorphism (SNP) markers in seven domestic Bactrian camel populations. In total, 482,786 SNPs were genotyped. The pool of all remaining others were selected as the reference population, and the Nanjiang, Sunite, Alashan, Dongjiang, Beijiang, Qinghai, and Hexi camels were the target populations for selection signature analysis. We obtained 603, 494, 622, 624, 444, 588, and 762 selected genes, respectively, from members of the seven target populations. Gene Ontology classifications and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed, and the functions of these genes were further studied using Genecards to identify genes potentially related to the unique characteristics of the camel population, such as heat resistance and stress resistance. Across all populations, cellular process, single-organism process, and metabolic process were the most abundant biological process subcategories, whereas cell, cell part, and organelle were the most abundant cellular component subcategories. Binding and catalytic activity represented the main molecular functions. The selected genes in Alashan camels were mainly enriched in ubiquitin mediated proteolysis pathways, the selected genes in Beijiang camels were mainly enriched in MAPK signaling pathways, the selected genes in Dongjiang camels were mainly enriched in RNA transport pathways, the selected genes in Hexi camels were mainly enriched in endocytosis pathways, the selected genes in Nanjiang camels were mainly enriched in insulin signaling pathways, while the selected genes in Qinghai camels were mainly enriched in focal adhesion pathways; these selected genes in Sunite camels were mainly enriched in ribosome pathways. We also found that Nanjiang (HSPA4L and INTU), and Alashan camels (INO80E) harbored genes related to the environment and characteristics. These findings provide useful insights into the genes related to the unique characteristics of domestic Bactrian camels in China, and a basis for genomic resource development in this species.

Domestic animal proteomics in the 21st century: A global retrospective and viewpoint analysis

Animal production and health are of significant economic importance, particularly regarding the world food supply. Animal and veterinary sciences have evolved immensely in the past six decades, particularly in genetics, nutrition, housing, management and health. To address major challenges such as those posed by climate change or metabolic disorders, it is of utmost importance to use state-of-the-art research tools. Proteomics and the other post-genomic tools (transcriptomics or metabolomics) are among them. Proteomics has experienced a considerable development over the last decades. This brought developments to different scientific fields. The use and adoption of proteomics tools in animal and veterinary sciences has some limitations (database availability or access to proteomics platforms and funding). As a result, proteomics' use by animal science researchers varies across the globe. In this viewpoint article, we focus on the developments of domestic animal proteomics over the last decade in different regions of the globe and how the researchers have coped with such challenges. In the second part of the article, we provide examples of funding, educational and laboratory establishment initiatives designed to foster the development of (animal-based) proteomics. International scientific collaboration is a definitive and key feature in the development and advancement of domestic animal proteomics. SIGNIFICANCE: Animal production and health are very important for food supply worldwide particularly as a source of proteinaceous foods. Animal and veterinary sciences have evolved immensely in the last decades. In order to address the major contemporary challenges facing animal and veterinary sciences, it is of utmost importance to use state-of-the-art research tools such as Proteomics and other Omics. Herein, we focus on the major developments in domestic animal proteomics worldwide during the last decade and how different regions of the world have used the technology in this specific research field. We address also major international efforts aiming to increase the research output in this area and highlight the importance of international cooperation to address specific problems inherent to domestic animal proteomics.