The avian-specific small heat shock protein HSP25 is a constitutive protector against environmental stresses during blastoderm dormancy

Abstract

Small heat shock proteins (sHSPs) range in size from 12 to 42 kDa and contain an α-crystalline domain. They have been proposed to play roles in the first line of defence against various stresses in an ATP-independent manner. In birds, a newly oviposited blastoderm can survive several weeks in a dormant state in low-temperature storage suggesting that blastoderm cells are basically tolerant of environmental stress. However, sHSPs in the stress-tolerant blastoderm have yet to be investigated. Thus, we characterised the expression and function of sHSPs in the chicken blastoderm. We found that chicken HSP25 was expressed especially in the blastoderm and was highly upregulated during low-temperature storage. Multiple alignments, phylogenetic trees, and expression in the blastoderms of Japanese quail and zebra finch showed homologues of HSP25 were conserved in other avian species. After knockdown of chicken HSP25, the expression of pluripotency marker genes decreased significantly. Furthermore, loss of function studies demonstrated that chicken HSP25 is associated with anti-apoptotic, anti-oxidant, and pro-autophagic effects in chicken blastoderm cells. Collectively, these results suggest avian HSP25 could play an important role in association with the first line of cellular defences against environmental stress and the protection of future embryonic cells in the avian blastoderm.

Avian blastoderm dormancy arrests cells in G 2 and suppresses apoptosis

“…In the previous study, the antioxidants were used to protect blastoderm cells from peroxidative degradation during cold storage indicating that oxidative stress during dormancy could cause DNA double-strand breaks, which could be critical to cell cycle arrest in blastoderm cells (56). However, our results suggest that the G 2 arrest that occurs in chicken blastoderm during storage is independent of DNA damage, as reflected by the lack of g-H2AX phosphorylation (57), probably by cellular antioxidant effect of chicken HSP25 (58). After incubation at 37°C, blastoderm cells may escape G 2 arrest and progress through the cell cycle.…”

Chicken NANOG self‐associatesviaa novel folding‐upon‐binding mechanism

“…Chicken PGCs (cPGCs) were cultured in accordance with our standard procedure (21). Undifferentiated stage X blastoderm cells were prepared as previously described (22, 23). Blastoderm cells collected from the White Leghorn chicken embryos at Eyal‐Giladi and Kochav stage X and dissociated mechanically into single cells.…”

Chaperones and Beyond as Key Players in Pluripotency Maintenance

“…HSPB1 (HSP27 family) also presents an important role in zebrafish development modulating the growth of myofibrils of skeletal muscle (Middleton and Shelden, 2013). In avian blastoderms, the expression of the sHSP HSP25 is required during the embryo development for the expression of pluripotency genes and for resistance against apoptosis (Hwang et al, 2016).…”