FMRFamide gene and peptide expression during central nervous system development of the cephalopod mollusk, Idiosepius notoides

Abstract

Mollusks are a showcase of brain evolution represented by several classes with a varying degree of nervous system centralization. Cellular and molecular processes involved in the evolution of the highly complex cephalopod brain from a simple, monoplacophoran-like ancestor are still obscure and homologies on the cellular level are poorly established. FMRFamide (Phe-Ile-Arg-Phe-NH(2))-related peptides (FaRPs) constitute an evolutionarily conserved and diverse group of neuropeptides in the central nervous system (CNS) of many metazoans. Herein, we provide a detailed description of the developing FMRFamide-like immunoreactive (Fa-lir) CNS of the pygmy squid Idiosepius notoides using gene expression analyses and immunocytochemistry. The open reading frame of the I. notoides FMRFamide gene InFMRF predicts one copy each of FIRFamide, FLRFamide (Phe-Leu-Arg-Phe-NH(2)), ALSGDAFLRFamide (Ala-Leu-Ser-Gly-Asp-Ala-Phe-Leu-Arg-Phe-NH(2)), and 11 copies of FMRFamide. Applying matrix-assisted laser desorption/ionization time-of-flight (ToF) mass spectrometry-based peptide profiling, we characterized all predicted FaRPs except ALSGDAFLRFamide. Two cell clusters express InFMRF and show FMRFamide-like-immunoreactivity within the palliovisceral ganglia, that is, the future posterior subesophageal mass, during the lobe differentiation phase. They project neurites via ventral axonal tracts, which form the scaffold of the future subesophageal mass. In the supraesophageal mass, InFMRF is first expressed during mid-embryogenesis in the superior and inferior buccal lobes. A neurite of the peduncle commissure represents the first Fa-lir element. Later, the sub- and supraesophageal mass interconnect via Fa-lir neurites and more brain lobes express InFMRF and FMRFamide-like peptides. InFMRF expression was observed in fewer brain lobes than Fa-lir elements. The early expression of InFMRF and FMRFamide-lir peptides in the visceral system and not the remaining CNS of the cephalopod I. notoides resembles the condition found in the majority of investigated gastropods.

Molecular analysis of two FMRFamide‐encoding transcripts expressed during the development of the tropical abalone haliotis asinina

“…FMRFamide-like immunoreactivity has been reported during very early neural development in all molluscan larvae examined to date including gastropods (Croll and Voronezhskaya, 1996;Dickinson et al, 1999Dickinson et al, , 2000Dickinson and Croll, 2003), polyplacophorans (Friedrich et al, 2002;Voronezhskaya et al, 2002), scaphopods (Wanninger and Haszprunar, 2003), bivalves (Voronezhskaya et al, 2008), and cephalopods (Wollesen et al, 2008(Wollesen et al, , 2010. In fact, similar observations have also been made in representative larvae of the wider Lophotrochozoa (Hay-Schmidt, 1990a,b, 1995.…”

Expression of serotonin (5-HT) during CNS development of the cephalopod mollusk, Idiosepius notoides

“…This is in particular evident when compared to the expression pattern of another neurotransmitter, the neuropeptide FMRFamide (Wollesen et al 2010). FMRFamide-like peptides and their encoding gene are first expressed during stage 19 in the CNS of I. notoides, i.e., when the anlagen of the various ganglia have just formed (Wollesen et al 2010). Involved in cognitive processes such as learning, the modulation of sleep, circadian rhythms, and sensory processing (Johnson et al 2009), 5-HT might not be necessary in the CNS of I. notoides during early development.…”

“…Considering the well-differentiated neuropils of various brain lobes, 5-HT is expressed surprisingly late. This is in particular evident when compared to the expression pattern of another neurotransmitter, the neuropeptide FMRFamide (Wollesen et al 2010). FMRFamide-like peptides and their encoding gene are first expressed during stage 19 in the CNS of I. notoides, i.e., when the anlagen of the various ganglia have just formed (Wollesen et al 2010).…”

“…The nomenclature of each lobe in the CNS of I. notoides ( Fig. 1; Table 1) was adopted from previous studies (Young 1979;Shigeno and Yamamoto 2002;Yamamoto et al 2003;Wollesen et al 2010). Fig.…”

Mollusca

“…These neural subsets do not form a strictly linear anterior-posterior formation gradient as in many annelids, thus refl ecting the non-segmental ancestry of Mollusca (Friedrich et al 2002 ;Voronezhskaya et al 2002 ;Wanninger and Haszprunar 2003 ). In conchiferans, the anlagen of the pedal, visceral, pleural, and other major ganglia are usually recognized by immunocytochemical staining for serotonin and FMRFamide Carew 1990 , 1997a , b ;Marois and Croll 1992 ;Elekes 1993 , 2003 ;Croll and Voronezhskaya 1996 ;Diefenbach et al 1998 ;Croll 2000 ;Hinman et al 2003 ;Wanninger and Haszprunar 2003 ;Croll and Dickinson 2004 ;Voronezhskaya et al 2008 ;Wollesen et al 2009Wollesen et al , 2010Wollesen et al , 2012Kristof and Klussmann-Kolb 2010 ).…”