Characterization of the sperm-associated body and its role in the fertilization of the chicken Gallus domesticus

Transcriptome analysis and identification of genes associated with individual fertilization rate differences in hen infundibulum

1. Fertilisation rate is closely related to the reproductive performance and economic status of chicken laying breeders. In this study, two flocks (n = 1,029 in population I and n = 358 in population II) in the later laying period were used for investigating the individual differences among population fertilisation rates (FRs).2. The funnel and distal parts of the infundibulum were collected from nine individuals (five with low FR and four with high FR from population II) and RNA-sequencing (RNA-seq) method was used to investigate the transcriptome differences in fertilisation. Differences in fertilisation regulation were investigated by comparing the different parts (funnel and distal) of the infundibulum between the low FR and high FR groups.3. There were notable individual FR differences in both categories. Some individuals had a relative high FR (≥90%) for a long time (>5 days after AI), contrarily, some individuals lost the ability to fertilise eggs in a very short time.4. Differentially expressed genes (DEGs), such as DUSP7, PPP1R3B, FYB, OVA, OVALX and OVALY may be associated with sperm functional regulation, fertilisation and early-stage fertilised ovum development processes. DEGs such as AVBD1, AVBD2, AVBD6, NFATC2 and BANK1 indicated a severe immune response to sperm survival and fertilisation in the oviduct.5. The results suggested that individual differences should be considered in the breeding and reproduction process. The DEGs identified in this study may promote our understanding of different fertilisation regulation in laying breeders.

The crystal polymorphism of calcium carbonate is determined by the matrix structure in quail eggs

Two calcified structures, the eggshell and sperm-associated body (SB), are present in the eggs of the Japanese quail, Coturnix japonica. X-ray diffractometry showed that calcium carbonates take the form of calcite in the eggshell and aragonite in the SB. The aim of the present study was to identify the factors that determine the morphology of calcium carbonate crystals. The matrix of EDTA-treated eggshell was a meshwork of vesicles, 200 to 500 nm in diameter, connected by fine fibers or fibrous sheets. The matrix of SB cortex was a radiation of rod-shaped projections approximately 130 nm in width. In vitro crystal formation was achieved by adding dissociated matrix substances to test solutions. When eggshell matrix material was added, formation of calcite crystals, which had many vesicular holes on their surface, was observed. When SB matrix material dissociated by sonication was added, rhombohedral calcite crystals formed at protein concentrations of 100 microg/mL or lower, and elongated and bundled crystals formed at concentrations of 150 microg/mL or higher. When SB matrix material dissociated by pipetting was added, aragonite crystals formed. These observations indicate that the matrix structure is the principal factor in determining the crystal polymorphism of calcium carbonate.

A reappraisal of the factors involved in in vitro initiation of the acrosome reaction in chicken spermatozoa

Chicken spermatozoa may remain in the female oviduct for a prolonged period before induction of the acrosome reaction on contact with the inner perivitelline layer (IPVL). By contrast, the acrosome reaction may be induced very rapidlyin vitroin the presence of IPVL and Ca2+. In the present study, we examined the extent to which the chicken acrosome reaction can be induced in media of various compositions in the presence or absence of IPVL and/or Ca2+and other factors known to be efficient in mammals. We also compared the efficacy of perivitelline layer (PL) taken at various states of oocyte maturation in initiating the reaction. The acrosome reaction was induced in less than 5 min in the presence of Ca2+and IPVL. Incubation of spermatozoa in different saline media (Beltsville poultry semen extender (BPSE); Dulbecco's modified eagle medium; NaCl-TES buffer) without IPVL showed a significant induction of acrosome reaction in BPSE supplemented with 5 mM Ca2+and in the three media after supplementation with Ca2+and Ca2+ionophore A23187. By contrast, the acrosome reaction was never induced without Ca2+. BSA, NaHCO3, and progesterone did not stimulate the acrosome reaction. Ca2+plus PL taken at various physiological states (follicle IPVL, ovulated IPVL, oviposited IPVL, and/or outer perivitelline layer) strongly stimulated the acrosome reaction, the latest states being the most efficient. Although PL induced the acrosome reaction in the presence of extracellular Ca2+, it was not possible to induce hyperactivation in chicken spermatozoa. Taken together, these results emphasize the central role of Ca2+in thein vitroinitiation of the acrosome reaction in chickens and show specific features of this induction in birds.