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Fertility is declining in domestic animals across the world. The reduction in fertility could be attributed to male, female and managemental factors. Although artificial insemination (AI) using frozen semen emerged 50 years back, fertility rate with AI technology is less and unpredictable. In AI industry, one bull is used to produce at least three lakh insemination doses; hence, the selection of fertile bulls becomes very important. Since standard semen evaluation tests are not sufficient to predict bull fertility accurately, the researchers have sought laboratory assays / molecular tests that would accurately predict the fertilizing potential of a semen sample. In this context, biotechnological advances in "omic technologies" help to understand the events associated to spermatogenesis, sperm function, fertilization and embryonic development ending in birth of viable healthy offspring. Profiling fertility-regulating biomolecules substances in spermatozoa or seminal plasma are considered to be helpful to predict fertility. [ABSTRACT FROM AUTHOR]

The region-specific expression of seminal proteins in testis and excurrent duct system determines the quality and function of the spermatozoa. In the present study, localization and expression of some of the seminal proteins such as insulin-like growth factor receptor 1β (IGF-1Rβ), phosphatidylethanolamine-binding protein 4 (PEBP4), α-tubulin and tissue factor pathway inhibitor 2 (TFPI2) were carried out in testis, excurrent duct system and spermatozoa of buffalo. IGF-1Rβ was localized in the cells of the seminiferous tubules of the testis, except in primary spermatocytes. The PEBP4 was localized only in the elongated spermatid, whereas α-tubulin and TFPI2 proteins were localized in all cells of the seminiferous tubule including spermatocyte. In the buffalo spermatozoa, IGF-1Rβ, PEBP4, α-tubulin and TFPI2 were localized in the acrosome region, the post-acrosomal region till the tail end, post-acrosome to the entire tail region and the equatorial region, respectively. The study indicates that IGF-1R, α-tubulin and PEBP4 proteins regulate spermatogenesis, whereas TFPI2 may be involved during the zona binding process of the buffalo spermatozoa., (© 2020 Blackwell Verlag GmbH.)

With artificial insemination (AI) and other precision dependent assisted reproductive technologies (ART) being followed in large scale in human and animal reproduction, assessing semen quality and fertilizability is under continuous scrutiny. Various tests have been developed to predict semen quality, but so far no single, highly reliable test is available. In this regard, transcriptomic profiling of spermatozoa assumes significance as it carries the information about spermatogenesis, sperm function, and paternal roles in post-fertilization events. Human spermatozoal transcriptome profiling has been carried out on a large number of individuals to predict the semen quality. A study in human indicated that the outcome of some idiopathic couples seeking reproductive care could be helped using transcriptomic profiling of spermatozoa. Such studies have a direct impact on the bovine dairy industry, wherein AI is practiced. Limited studies in bovine spermatozoal transcriptome profiling have revealed that the spermatozoa contain various classes of RNA, like in human. Approximately 13,000 bovine genes yield a series of spermatozoal transcripts, of which most are fragmented in nature. Their abundance is indicative of the timing of events associated with spermatogenesis, e.g., PRM1, IGF1, BMP2; sperm function, TSSK6, CRISP, HSFY2; fertility, UBE2D3, Integrin-β, LDC-1; and embryonic development, miR34c-5p, BCL2L11, BRCA1. The most abundant translated bovine transcripts are BSP3 and SPATA18, and are involved in regulation of germ cell development and the maintenance of chromatin integrity during spermatogenesis respectively. The presence of transcripts associated with placental development, e.g., placental associated glycoproteins (PAGs) have suggested their possible influence beyond early embryonic development. Changes in transcript levels like RPL31 and PRKCE that increase, and PRM1 that decreases, during cryopreservation need to be defined in order to optimize cryopreservation and fertility yield. Spermatozoal transcriptome profiling with validation studies are warranted in large numbers of animals to elucidate their significance for selecting fertile bulls for the breeding program. Abbreviations: AI: artificial insemination; BSE: breeding soundness evaluation; cfs-mRNA: cell-free seminal mRNA; piRNA: PIWI-interacting RNA; tRNA: transfer RNA; fg: femtogram; TPM: transcripts per million reads; RPKM: reads per kilobase million; rRNA: ribosomal RNA; mt-RNA: mitochondrial RNA; lncRNA: long non-coding RNA; sncRNA: small noncoding RNA; snoRNA: small nucleolar RNA; snRNA: small nuclear RNA; miRNA: microRNA; snaR: small NF90-associated RNAs; SINES: short interspersed nuclear elements; LINES: long interspersed nuclear elements; MER: medium reiterated sequence; F1 offspring: filial 1 offspring; PAGs: placental associated glycoproteins; TCP: Transcription factor T complex protein; BSP3: bovine seminal plasma protein 3; SCNT: somatic cell nuclear transfer; qPCR: quantitative (real-time) polymerase chain reaction; SSH: suppression subtractive hybridization; SNP: single nucleotide polymorphism; 2-DE: 2 dimensional gel electrophoresis; LC-MS/MS: liquid chromatography-tandem mass spectrometry.

Spermatozoal transcripts expression levels could be used to assess fertility potential of a male. The objective of the present study was to elucidate the predictive ability of the expression levels of growth, apoptosis and homeostasis regulating transcripts on sperm functions and fertility. The expression levels of spermatozoal RNA isolated from the neat semen samples were related to the good (discarded ejaculate, <25%; n = 7) and poor (discarded ejaculate, >40%, n = 6) quality semen producer and bulls (n = 12) with known conception rate. The relative fold expression levels of BMP2 were significantly (p < 0.01) higher in good than the poor semen producers and positively associated with post-thaw sperm velocity parameters (LIN and VAP). The NGF expressions fold levels had significant (p < 0.05) positive relationship with mitochondrial membrane potential of neat semen samples. The genes involved in the apoptotic, UBE2D3 (r = -0.61, p = 0.02), CASP3 (r = -0.57, p = 0.03) and homeostatic, HSFY2 (r = -0.61, p < 0.02) regulators had significant negative correlation with the percentage of post-thaw fast progressive motile spermatozoa. The expression level of TRADD had significant negative influence on the mitochondrial membrane potential (r = -0.54, p = 0.05) of neat semen samples and conception rate (r = -0.57, p < 0.05). The expression levels of BMP2 had highly significant positive correlation with NGF (r = 0.99, p < 0.01) and CASP3 (r = 0.56, p = 0.05). The BMP2 expression level might be used to predict the quality of the semen and TRADD determine the conception rate of the bull. The study provides ample evidence that the sperm transcripts expression levels might be used to predict quality semen production and bull fertility., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Mammalian spermatozoa deliver various classes of RNAs to the oocyte during fertilization, and many of them may regulate fertility. The objective of the present study was to determine the composition and abundance of spermatozoal transcripts in fresh bull semen. The entire transcriptome of the spermatozoa from bulls (n = 3) was sequenced using two different platforms (Ion Proton and Illumina) to identify the maximum number of genes present in the spermatozoa. The bovine spermatozoa contained transcripts for 13,833 genes (transcripts per million, TPM > 10). Both intact and fragmented transcripts were found. These spermatozoal transcripts were associated with various stages of spermatogenesis, spermatozoal function, fertilization, and embryo development. The presence of intact transcripts of pregnancy-associated glycoproteins (PAGs) in the spermatozoa suggest a possible influence of sperm transcripts beyond early embryonic development. The specific regions (exon, intron, and exon-intron) of the particular spermatozoal transcripts might help regulate fertilization. This study demonstrates that the use of two different RNA-seq platforms provides a comprehensive profile of bovine spermatozoal RNA. Spermatozoal RNA profiling may be useful as a non-invasive method to delineate possible causes of male infertility and to predict fertility in a manner that is more effective than the conventional methods.

Sperm RNA can be used to understand the past spermatogenic process, future successful fertilization, and embryo development. To study the sperm RNA composition and function, isolation of good quality RNA with sufficient quantity is essential. The objective of this study was to assess the influence of sperm input concentrations and RNA isolation methods on RNA yield and quality in bull sperm. The fresh semen samples from bulls (n = 6) were snap-frozen in liquid nitrogen and stored at -80 °C. The sperm RNA was isolated using membrane-based methods combined with TRIzol (RNeasy+TRIzol and PureLink+TRIzol) and conventional methods (TRIzol, Double TRIzol, and RNAzol RT). Based on fluorometric quantification, combined methods resulted in significantly (P < 0.05) higher total RNA yields (800-900 ng/30-40 × 10(6)) as compared with other methods and yielded 20 to 30 fg of RNA/spermatozoon. The quality of RNA isolated by membrane-based methods was superior to that isolated by conventional methods. The sperm RNA was observed to be intact as well as fragmented (50-2000 bp). The study revealed that the membrane-based methods with a cocktail of lysis solution and an optimal input concentration of 30 to 40 million sperm were optimal for maximum recovery of RNA from bull spermatozoa., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The buffalo seminal plasma protein profile and its relationship with sperm quality have not been studied in detail. Thus, the aim of the present study was to profile buffalo seminal plasma proteins and to assess the relationship between differentially expressed proteins and sperm characteristics. Semen samples (n = 44) were collected from 11 Murrah buffalo bulls (four ejaculates from each animal) and seminal plasma protein profiling was performed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Matrix-assisted laser desorption ionisation time-of-flight analysis of one of the differentially expressed proteins, namely the 11-12 kDa protein, identified it as tuberoinfundibular peptide of 39 residues (TIP39). Western blot analysis confirmed the presence of TIP39, with TIP39 expression in seminal plasma varying among bulls. Based on TIP39 levels, bulls were classified into two groups, those with high and low protein. The percentages of spermatozoa positive for mitochondrial membrane potential test, chromatin distribution test, synthetic media sperm penetrability test and acrosomal integrity test were significantly (P < 0.05) high in the high protein group. The present study is the first to demonstrate the presence of TIP39 in buffalo seminal plasma and the positive effect of TIP39 on the functional parameters and fertilising ability of spermatozoa.

The composition of sperm proteins influences the fertilizing ability of sperm and hence the present study was conducted (i) to profile sperm proteins expression patterns in bulls of differing fertility index and (ii) to identify and relate the abundant sperm proteins with bull fertility. The semen samples were collected from Holstein-Friesian bulls (n = 12) varying in conception rate (CR) (high/low). The frozen semen straws (three ejaculates, from each bull) were used to study (a) sperm kinetic parameters, (b) plasmalemma integrity, (c) mitochondrial membrane potential, and (d) chromatin distribution. Three bulls were randomly selected from each group (n = 3) and the neat sperm pellets were subjected to percoll purification, followed by protein isolation using 0.1% Triton X100. The sperm kinetic parameters, plasmalemma integrity, mitochondrial membrane potential, and the chromatin distribution did not differ significantly between groups. The number of acidic (pI; 3.1-5.6, 37%) and basic (pI; 7.9-10.0, 27%) proteins and their pattern of expression varied significantly (p < 0.05) between high and low fertile bulls. The abundant sperm protein spots in 2D-gel electrophoresis (2DE) were identified as seminal plasma protein PDC-109 (i.e., protein with N-terminus aspartic acid, D and carboxy terminus cystine, having 109 amino acids) and its isoform and spermadhesin-1 (SPADH1). The western blot analysis confirmed the presence of PDC-109 isoform proteins at 15.4 kDa (pI 5.3 and 5.5). The seminal plasma protein PDC-109 was abundant in the low fertile when compared to the high fertile group (p < 0.05). This study suggests that the imbalance in acidic and basic sperm proteins may influence sperm fertility and sperm PDC-109 levels above a certain threshold affects bull fertility.