Tissue expression and antibacterial activity of host defense peptides in chicken.

BACKGROUND: Host defence peptides are a diverse group of small, cationic peptides and are important elements of the first line of defense against pathogens in animals. Expression and functional analysis of host defense peptides has been evaluated in chicken but there are no direct, comprehensive comparisons with all gene family and individual genes. RESULTS: We examined the expression patterns of all known cathelicidins, ß-defensins and NK-lysin in multiple selected tissues from chickens. CATH1 through 3 were predominantly expressed in the bone marrow, whereas CATHB1 was predominant in bursa of Fabricius. The tissue specific pattern of ß-defensins generally fell into two groups. ß-defensin1-7 expression was predominantly in bone marrow, whereas ß-defensin8-10 and ß-defensin13 were highly expressed in liver. NK-lysin expression was highest in spleen. We synthesized peptide products of these gene families and analysed their antibacterial efficacy. Most of the host defense peptides showed antibacterial activity against E.coli with dose-dependent efficacy. ß-defensin4 and CATH3 displayed the strongest antibacterial activity among all tested chicken HDPs. Microscopic analyses revealed the killing of bacterium by disrupting membranes with peptide treatment. CONCLUSIONS: These results demonstrate dose-dependent antimicrobial effects of chicken HDPs mediated by membrane damage and demonstrate the differential tissue expression pattern of bioactive HDPs in chicken and the relative antimicrobial potency of the peptides they encode.

Spatial and temporal action of chicken primordial germ cells during initial migration.

In most animals, primordial germ cells (PGCs) originate from an extragonadal region and migrate across the embryo to the gonads, where they differentiate and function. During their migration, PGCs move passively by morphogenetic movement of the embryo or move actively through signaling molecules. To uncover the underlying mechanism of first-phase PGC migration toward the germinal crescent in chickens, we investigated the spatial and temporal action of PGCs during primitive streak formation. Exogenously transplanted PGCs migrated toward the anterior region of the embryo and the embryonic gonads when they were transplanted into the subgerminal cavity, but not into the posterior marginal zone, in Eyal-Giladi and Kochav stage X embryos. These results indicate that for passive migration toward the anterior region the initial location of PGCs should be the central region. Notably, although PGCs and DF-1 cells migrated passively toward the anterior region, only PGCs migrated to the germinal crescent, where endogenous PGCs mainly reside, by active movement. In a live-imaging experiment with green fluorescence protein-expressing transgenic embryos, exogenous PGCs demonstrated markedly faster migration when they reached the anterior one-third of the embryo, while somatic cells showed epiblast movement with constant speed. Also, migrating PGCs exhibited successive contraction and expansion indicating their active migration. Our results suggest that chicken PGCs use sequential passive and active forces to migrate toward the germinal crescent.

The dynamic development of germ cells during chicken embryogenesis.

Appropriate regulation of cell proliferation during embryogenesis is crucial for the maintenance of germness. An in-depth understanding of germ cell developmental processes may yield valuable information on germ cell biology and applied sciences. However, direct evidences about germ cell proliferation and cell cycling during avian embryonic development has not been well-studied. Thus, we explored chicken germ cell dynamics during embryonic development via flow cytometry employing a germ cell-specific anti-cVASA antibody (the chicken VASA homolog is termed CVH) and propidium iodide staining. The numbers of male germ cells increased significantly during early embryonic development, but proliferation was decreased significantly with accumulation at the G0/G1 phase after embryonic d 14 (E.14), indicating initiation of mitotic arrest in the testis. On the other hand, the number of female germ cells increased significantly throughout embryogenesis, and proliferating cells were continuously evident in the ovary to the time of hatching, although gradual accumulation of cells at the G2/M phase was also evident. 5-ethynyl-2΄-deoxyuridine (EdU) incorporation analysis revealed that populations of mitotically active germ cells existed in both sexes during late embryogenesis, indicating either the maintenance of stem cell populations, or asynchronous meiosis. Collectively, these results indicate that chicken germ cells exhibited conserved developmental processes that were clearly sexually dimorphic.