H. Santacruz et al., MOLECULAR CHARACTERIZATION OF A HEAT-SHOCK COGNATE CDNA OF ZEBRAFISH,HSC70, AND DEVELOPMENTAL EXPRESSION OF THE CORRESPONDING TRANSCRIPTS, Developmental genetics, 21(3), 1997, pp. 223-233
To elucidate the potential role of the hsp70 gene family in developmen
tal processes in vertebrates, we chose io study the expression of one
of these genes in zebrafish. A zebrafish gastrula cDNA library was scr
eened with a Pleurodeles waltl hsp70 cDNA probe. A 2.3-kb cDNA was thu
s isolated and sequenced. The predicted amino acid sequence contained
an open reading frame encoding for a 649-amino acid polypeptide. Seque
nce 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 reveal
ed that transcripts were expressed al normal temperature, but the leve
l of transcript expression increased after heal shock. Moreover, exper
iments of the neosynthesis of total proteins in heal shock conditions
and corresponding immunoblotting assays showed thai 24-h-stage embryos
are able to respond to heal shock. The quantity of 70 kDa proteins, r
ecognized by a specific antibody of the HSP/C70 protein family, is exp
ressed in control condition and increased significantly after heal sho
ck. Furthermore, Northern blot analysis of transcript expression showe
d that the corresponding mRNAs were detected throughout embryonic deve
lopment in the absence of any heal shock. Our clone, named hsc70, thus
corresponded io a cognate member of the hsp70 gene family, expressed
under normal conditions during development, but also heal inducible. T
he spatio-temporal pattern of transcripts during development was deter
mined by in situ hybridization on wholemount embryos at different stag
es. 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) an
d in a fraction of the somites. These results suggest that the hsc70 g
ene may be involved in developmental differentiation events. (C) 1997
Wiley-Liss, Inc.