Milkfish (Chanos chanos)
growth hormone cDNA cloning and mRNA expression in embryos and early larval
stages
E.G.T. de Jesus, F.G. Ayson, Y. Amemiya, S. Moriyama,
S. Hyodo, T. Hirano, H. Kawauchi-2002
Aquaculture, 208(1-2): 177-188
Abstract:
In an attempt to understand growth regulation in
milkfish, the milkfish growth hormone (GH) and its cDNA were characterized
and the expression of GH mRNA in embryos and larvae was examined by RT-PCR.
The milkfish GH was purified from an alkaline extract of the pituitary by
reverse-phase high-performance liquid chromatography and detected as an
immuno-positive protein with anti-salmon GH serum. The complete sequence of
milkfish pre-GH was determined by cDNA cloning and nucleotide sequencing. On
the basis of the N-terminal amino acid analysis of the native protein, the
pre-GH was found to consist of a signal peptide of 22 amino acids and a
mature protein of 188 amino acids. Milkfish GH shows higher amino acid
sequence identity with GHs of carps (91-94%) and salmonids (70%) than with
GHs of more advanced teleosts (<60%) in good accordance with its
taxonomic position in teleosts. It has five half Cys residues, four of which
are at positions homologous with those of other known GHs and the extra Cys
with those of carp GHs. The molecular weight of milkfish GH was estimated to
be 22 kDa, which is comparable to the theoretical value. This suggests that
milkfish GH is a simple protein, although it has two potential N-glycosylation
sites. Semiquantitative RT-PCR showed that GH mRNA expression was relatively
weak in embryos and newly hatched larvae but was already strong in 2-day old
and older larvae.
*A patent is pending (IPO-1-1999-01458) for the cDNA
sequence of milkfish GH reported in this paper.