Identification of the Second Form of Acrosin in Turkey Spermatozoa

Liquid semen storage-induced alteration in the protein composition of turkey (Meleagris gallopavo) spermatozoa

Liquid storage of turkey semen without the loss of fertilizing ability is of practical interest to the poultry industry. However, fertility rates from liquid-stored turkey semen decline within a few hours. A clear cause of the decline in spermatozoa quality remains unidentified. Therefore, the purpose of the present study was to monitor the dynamics of proteomic changes in spermatozoa during 48 h of liquid storage by 2-dimensional difference in-gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry. A total of 57 protein spots were differentially expressed between fresh and stored spermatozoa; 42 spots were more and 15 were less abundant after 48 h of semen storage. Raw proteomic data are available via ProteomeXchange with identifier PXD043050. The selected differentially expressed proteins (DEPs) were validated by western blotting and localized in specific spermatozoa structures by immunofluorescence, such as the head (acrosin and tubulin α), midpiece (acrosin, aconitate hydratase 2, and glycerol-3-phosphate dehydrogenase) and tail (tubulin α). Most of the DEPs that changed in response to liquid storage were related to flagellum-dependent cell motility, energy derivation through oxidation of organic compounds and induction of fertilization, suggesting the complexity of the processes leading to the decrease in stored semen quality. The damaging effect of liquid storage on spermatozoa flagellum manifested as more microtubule proteins, such as tubulins and tektins, most likely formed by posttranslational modifications, tubulin α relocation from the tail to the sperm head, which appeared after 48 h of semen storage, and decreases in fibrous shelf proteins at the same time. Motility could be affected by dysregulation of Ca2+-binding proteins and disturbances in energy metabolism in spermatozoa flagellum. Regarding sperm mitochondria, DEPs involved in energy derivation through the oxidation of organic compounds indicated disturbances in fatty acid beta oxidation and the tricarboxylic acid cycle as possible reasons for energy deficiency during liquid storage. Disturbances in acrosin and 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase zeta may be involved in rapid declines in the fertility potential of stored turkey spermatozoa. These results showed the complexity of the processes leading to a decrease in stored semen quality and broadened knowledge of the detrimental effects of liquid storage on turkey spermatozoa physiology.

Specific expression of alternatively spliced genes in the turkey (Meleagris gallopavo) reproductive tract revealed their function in spermatogenesis and post-testicular sperm maturation

The tissue-specific profile of alternatively spliced genes (ASGs) and their involvement in reproduction processes characteristic of turkey testis, epididymis, and ductus deferens were investigated for the first time in birds. Deep sequencing of male turkey reproductive tissue RNA samples (n = 6) was performed using Illumina RNA-Seq with 2 independent methods, rMATs and SUPPA2, for differential alternative splicing (DAS) event prediction. The expression of selected ASGs was validated using quantitative real-time reverse transcriptase-polymerase chain reaction. The testis was found to be the site of the highest number of posttranscriptional splicing events within the reproductive tract, and skipping exons were the most frequently occurring class of alternative splicing (AS) among the reproductive tract. Statistical analysis revealed 86, 229, and 6 DAS events in the testis/epididymis, testis/ductus deferens, and epididymis/ductus deferens comparison, respectively. Alternative splicing was found to be a mechanism of gene expression regulation within the turkey reproduction tract. In testis, modification was observed for spermatogenesis specific genes; the changes in 5' UTR could act as regulator of MEIG1 expression (a player during spermatocytes meiosis), and modification of 3' UTR led to diversification of CREM mRNA (modulator of gene expression related to the structuring of mature spermatozoa). Sperm tail formation can be regulated by changes in the 5' UTR of testicular SLC9A3R1 and gene silencing by producing dysfunctional variants of ODF2 in the testis and ATP1B3 in the epididymis. Predicted differentially ASGs in the turkey reproductive tract seem to be involved in the regulation of spermatogenesis, including acrosome formation and sperm tail formation and binding of sperm to the zona pellucida. Several ASGs were classified as cilia by actin and microtubule cytoskeleton organization. Such genes may play a role in the organization of sperm flagellum and post-testicular motility development. To our knowledge, this is the first functional investigation of alternatively spliced genes associated with tissue-specific processes in the turkey reproductive tract.

The seminal acrosin-inhibitor ClTI1/SPINK2 is a fertility-associated marker in the chicken

The seminal plasma is a very complex fluid, which surrounds sperm in semen. It contains numerous proteins including proteases and protease inhibitors that regulate proteolytic processes associated with protein activation and degradation. We previously identified a seminal protein, chicken liver trypsin inhibitor 1 (ClTI-1) over expressed in semen of roosters with high fertility, suggesting a role in male fertility. In the present study, we showed that ClTI-1 gene is actually SPINK2. Using normal healthy adult roosters, we showed that SPINK2 amount in seminal plasma was positively correlated with male fertility in chicken lines with highly contrasted genetic backgrounds (broiler and layer lines). Using affinity chromatography combined to mass spectrometry analysis and kinetic assays, we demonstrated for the first time that two chicken acrosin isoforms (acrosin and acrosin-like proteins) are the physiological serine protease targets of SPINK2 inhibitor. SPINK2 transcript was overexpressed all along the male tract, and the protein was present in the lumen as expected for secreted proteins. Altogether, these data emphasize the role of seminal SPINK2 Kazal-type inhibitor as an important actor of fertility in birds through its inhibitory action on acrosin isoforms proteins.

Fertilization 1: Sperm-Egg Interaction

In birds in the reproductive season, an egg is ovulated without cumulus cells from the largest follicle with the highest hierarchy in the ovary. The outermost part of the ovulated eggs is the perivitelline layer, a glycoprotein matrix consisting of a few ZP-glycoproteins. The fertilization starts from sperm penetration of the perivitelline layer predominantly in the germinal disc region, followed by uptake of the sperm into the egg, and goes through by the fusion of sperm male pronucleus with the female pronucleus in the egg. A series of these fertilization steps occurs in the infundibulum of the oviduct within a short period after ovulation. Some pioneering microstructural studies using electron microscopy and supporting biochemical data from later studies indicate that, in avian fertilization, sperm interacts with the perivitelline layer covering the germinal disc, locally degrade and dissolve the matrix of the perivitelline layer, and penetrate it through the hole made proteolytically at the sperm-binding site on the perivitelline layer. Several molecules and structures presumably involved in the sperm-perivitelline interaction have been characterized, especially sperm proteases and their targets in the egg perivitelline layer. On the other hand, no molecules involved in the sperm-egg membrane fusion for the male pronucleus uptake into the egg have yet been identified or characterized and, moreover, no orthologue but one have been annotated so far in the chicken genome for the mouse genes involved in the sperm-egg membrane fusion.

Effect of sex ratios, spiking and extra artificial insemination on the breeding efficiency of broiler breeders

Since early fertility decline is a permanent problem of broiler breeders, the aim of this study was to test the effects of various sex ratios, spiking strategies and additional artificial inseminations (AI) on their breeding efficiency. Six breeder flocks were analysed during the whole reproduction cycle. In Flock A the sex ratio was maintained at 10% during the whole cycle (control), while in Flock B the number of males was increased to a final ratio of 16%. In Flocks C (technological control), D, E and F the ratio of males was gradually decreased from 10% to 6.5% until the end of the cycle. Moreover, at the age of 44 weeks in Flocks D and E 50 and 100% of cockerels were replaced by young ones, respectively, while in Flock F additional artificial inseminations were applied in the second half of the reproduction cycle. The increase of sperm transport was successful only in Groups B (increase in male numbers) and D (50% replacement of old cockerels with young ones); however, it was not sufficient for increasing the fertility rates in either group. Nor did additional artificial inseminations (Flock F) have an effect on fertility. As a conclusion, it can be established that increasing the sperm count in the hens' oviducts in any way could not improve fertility in the last third of the production cycle. The results also suggest that the expensive and labour-intensive spiking technique used in broiler breeder management is useless. The prime factor responsible for the shortened persistence of fertility may be the reduced ability of the female oviduct to accept and store sperm.