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.
Highlights
Highest expression in the blastocyst[8]
Eleven small heat shock protein genes from chicken are entered in the GenBank database, including the HSP30 subfamily, which is restricted to oviparous animals[19]
To identify the expression of small heat shock protein (sHSP) in chicken stage X blastoderm, 11 sHSP genes from the GenBank database were examined by RT-PCR and qRTPCR using cDNA from Chicken embryonic fibroblasts (CEFs) and stage X blastoderms
Summary
Highest expression in the blastocyst[8]. mouse embryonic stem cells show a unique stress-resistant gene expression signature, including Hspb[1], that becomes downregulated during embryoid body formation[9]. SHSP genes are expressed in the dauer stage of Caenorhabditis elegans and in the cyst of Artemia franciscana, which are so-called diapause states described in many reports as stress-tolerant and developmental arrest[10,11]. Embryonic diapause has not been reported, developmental arrest, so-called cold torpor, of the embryos of the earlier eggs in a single clutch is common at the beginning of incubation, until all eggs in the clutch have been laid[24]. Bloom et al reported that chicken Eyal-Giladi and Kochav (EGK) stage X blastoderms after oviposition[25] could survive 3–4 weeks in a dormant state under conditions of cold storage and that this involved expressing HSP70 and anti-apoptotic B-cell CLL/lymphoma (BCL) family genes[26]. The expression and functions of small HSPs in the stress-tolerant avian blastoderm have yet to be investigated. We demonstrated that avian HSP25 was important in the protection of future embryonic cells in the blastoderm
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