Molecular characterization of a heat shock cognate cDNA of zebrafish, hsc70, and developmental expression of the corresponding transcripts

Abstract

To elucidate the potential role of the hsp70 gene family in developmental processes in vertebrates, we chose to study the expression of one of these genes in zebrafish. A zebrafish gastrula cDNA library was screened with a Pleurodeles waltl hsp70 cDNA probe. A 2.3-kb cDNA was thus isolated and sequenced. The predicted amino acid sequence contained an open reading frame encoding for a 649-amino acid polypeptide. Sequence analysis showed strong homology with hsp70-related gene sequences in other species; in particular, the strongest homology was found with the cognate members of this family. Tests of heat inducibility revealed that transcripts were expressed at normal temperature, but the level of transcript expression increased after heat shock. Moreover, experiments of the neosynthesis of total proteins in heat shock conditions and corresponding immunoblotting assays showed that 24-h-stage embryos are able to respond to heat shock. The quantity of 70 kDa proteins, recognized by a specific antibody of the HSP/C70 protein family, is expressed in control condition and increased significantly after heat shock. Furthermore, Northern blot analysis of transcript expression showed that the corresponding mRNAs were detected throughout embryonic development in the absence of any heat shock. Our clone, named hsc70, thus corresponded to a cognate member of the hsp70 gene family, expressed under normal conditions during development, but also heat inducible. The spatio-temporal pattern of transcripts during development was determined by in situ hybridization on wholemount embryos at different stages. As a maternal RNA, hsc70 mRNA was uniformly present in the embryo, up to the end of gastrulation. Later, a tissue-specific enrichment of hsc70 transcripts was detected in the central nervous system (CNS) and in a fraction of the somites. These results suggest that the hsc70 gene may be involved in developmental differentiation events.

Molecular cloning and expression of two HSP70 genes in the prawn, Macrobrachium rosenbergii

“…Mar-HSC70 mRNA was particularly enriched in the ovary of prawns. Similar enriched patterns of HSC70 transcripts have been reported in zebrafish and Drosophila during embryogenesis (Perkins et al 1990;Santacruz et al 1997). Therefore, the tissue-specific enrichment of Mar-HSC70 transcripts in prawns may signify a critical role for this stress protein during reproductive events.…”

Stress Protein HSP70 in Fish

“…Zebrafish hsc70 is expressed as a maternal protein, and mRNA in the fertilized eggs and its zygotic gene expression occur after gastrulation, especially in the brain and yolk sac (Graser et al 1996;Santacruz et al 1997). When segmentation starts, hsc70 is expressed in the dorsal trunk neural tube, the lateral plate mesoderm, and the tail bud.…”

Are hsps suitable for indicating stressed states in fish?

“…These studies and others revealed that the use of hsp as an indicator of stressed states in fish is a very complex issue. The hsp response can vary according to tissue (Rabergh et al, 2000;Smith et al, 1999), distinct hsp families (Smith et al, 1999) and stressor (Airaksinen et al, 2003), and the sensitivity of hsp expression can also vary with the species (Basu et al, 2001;Nakano and Iwama, 2002), developmental stage (Santacruz et al, 1997;Lele et al, 1997;Martin et al, 2001) and season (Fader et al, 1994).…”