Molecular Cloning and Expression Analysis of a GnRH-Like Dodecapeptide in the Swordtip Squid,Loligo edulis

Abstract

In vertebrates, gonadotropin-releasing hormone (GnRH), which is synthesized in the brain, is a key peptide involved in gonadal maturation regulated by the brain-pituitary-gonadal axis. GnRH isoforms and their primary structures have recently been determined in two species of non-chordates, the octopus (Octopus vulgaris) and sea hare (Aplysia californica), which are mollusks. Octopus and sea hare GnRHs are dodecapeptides that contain the structural core of chordate GnRH; however, chordate GnRHs, including tunicate GnRH, are decapeptides. in this study, we examined a GnRH-like peptide in the swordtip squid, Loligo edulis, to provide information on the structural evolution of GnRH in non-chordates. We isolated the full-length cDNA of a GnRH-like molecule from the central nervous system (CNS) of the squid. The open reading frame of this cDNA encodes a protein of 90 amino acids, which consists of a putative signal peptide, a GnRH dodecapeptide, a processing site, and a GnRH-associated peptide. This architecture is generally conserved in chordates. Compared to octopus GnRH, Squid GnRH is identical in the deduced amino acid sequence of the peptide, and 80.5% similar in base sequence. in a phylogenetic analysis, prepro-GnRHs of octopus, sea hare, and squid were segregated from all chordate prepro-GnRHs, in a group designated GnRHS. The squid prepro-GnRH mRNA was expressed mainly in the CNS. This study is the first report of GnRH cDNA cloning in squid and the third in non-chordates.

Oct-GnRH, the first protostomian gonadotropin-releasing hormone-like peptide and a critical mini-review of the presence of vertebrate sex steroids in molluscs

“…A partial cDNA characterized by an exactly similar sequence to the oct-GnRH precursor has been cloned from the cuttlefish S. officinalis, and its expression has been detected in the brain and ovary (Di Cristo et al, 2009a). The open reading frame of the cDNA cloned from the central nervous system (CNS) of swordtip squid Uroteuthis edulis, is 80.5% similar to that of oct-GnRH in nucleotide sequence (Onitsuka et al, 2009) (Fig. 1a).…”

A Gonadotropin-Releasing Hormone-Like Molecule Modulates the Activity of Diverse Central Neurons in a Gastropod Mollusk, Aplysia Californica

“…), a sea urchin ( Strongylocentrotus purpuratus ), and a leech ( Helobdella robusta ) by searching within the expressed sequence tag database (Tsai and Zhang, 2008; Roch et al, 2011). GnRH from two species of cephalopod mollusk, common cuttlefish ( Sepia officinalis ; Di Cristo et al, 2009) and sword tip squid ( Loligo edulis ; Onitsuka et al, 2009) share the same peptide sequence as the common octopus ( Octopus vulgaris ; Iwakoshi et al, 2002). The isolated or deduced sequences of these GnRH peptides have either 11 or 12 amino acids with the insertion of 2 amino acids downstream of the N-terminal pyroglutamyl residue (Iwakoshi et al, 2002; Zhang et al, 2008; Di Cristo et al, 2009; Onitsuka et al, 2009; Tsai et al, 2010; Roch et al, 2011).…”

“…GnRH from two species of cephalopod mollusk, common cuttlefish ( Sepia officinalis ; Di Cristo et al, 2009) and sword tip squid ( Loligo edulis ; Onitsuka et al, 2009) share the same peptide sequence as the common octopus ( Octopus vulgaris ; Iwakoshi et al, 2002). The isolated or deduced sequences of these GnRH peptides have either 11 or 12 amino acids with the insertion of 2 amino acids downstream of the N-terminal pyroglutamyl residue (Iwakoshi et al, 2002; Zhang et al, 2008; Di Cristo et al, 2009; Onitsuka et al, 2009; Tsai et al, 2010; Roch et al, 2011). The primary structure of these six novel forms of GnRHs differs markedly from that of chordate GnRHs, challenging the conventional belief that the decapeptide structure of chordate GnRHs is universally conserved.…”

Development of a time-resolved fluoroimmunoassay for octopus gonadotropin-releasing hormone

“…This finding accelerated the study of protostome GnRH, the existence of which had previously been suggested by immunohistochemistry using a heterologous antibody raised against vertebrate GnRH. The full-length cDNA of oct-GnRH was subsequently isolated from the swordtip squid Loligo edulis [8] and the European common cuttlefish Sepia officinalis [9]. The fulllength cDNA of a GnRH-like peptide has also been isolated from the central nervous system (CNS) of a gastropod mollusk, the sea hare Aplysia californica [10].…”