Project description:The monitoring of global transcription patterns during development is a useful first step to understand mechanisms underlying growth, differentiation and patterning in a given species. However such large scale developmental studies are so far only available from a few selected model organisms such as mouse, Drosophila and the nematode C. elegans. Genomic scale information from the lophotrochozoa is now emerging. The recently characterized neuronal transcriptome of the sea hare Aplysia californica (~200’000 ESTs and ~40,000 unique non-redundant sequences representing about 55-70% of all neuronal transcripts including splice forms and non-coding RNAs) provides new insights and opportunities into problems of molluscan development and specifically neurogenesis. Regulatory genes used in development are recruited for the functions of adult nervous systems such as synaptogenesis, specific wiring in networks and structural changes underlying synaptic plasticity. While this similarity reflects a basic concept in biology, namely the recruitment of the same genes for different functions, it has never been tested on a large scale genomic level. We used representative oligo-arrays constructed from transcripts obtained from the Aplysia nervous system to explore the following two questions: 1) What neuronal genes are differentially expressed during embryonic development of the sea hare Aplysia. 2) What gene expression changes can be observed in correlation with gastrulation, metamorphosis, and larval neurogenesis. For this purpose we hybridized RNA from 3 embryonic (64 cells, gastrula, trochophore) and 4 larval stages (pre-hatching, post-hatching, pre-metamorphosis, postmetamorphosis) against a reference sample consisting of equal contributions from all stages. Our analysis revealed that all embryonic and larval stages can be distinguished based on their transcription profiles. A comparison of the Aplysia atlas with similar studies in Drosophila and mouse reveals interesting differences. We identified several new transcription factors which are differentially expressed during early embryonic development. Various other transcripts involved in metabolism and differentiation were characterized. These genes can be candidate targets for understanding neuronal growth, synaptogenesis and memory mechanisms. We conclude that the microarray technology provides us with a powerful tool for efficient survey and functional annotation of the neuronal transcriptome in Aplysia.
Project description:Genome-wide transcriptional changes in development provide important insight into mechanisms underlying growth, differentiation, and patterning. However, such large-scale developmental studies have been limited to a few representatives of Ecdysozoans and Chordates. Here, we characterize transcriptomes of embryonic, larval, and metamorphic development in the marine mollusc Aplysia californica and reveal novel molecular components associated with life history transitions. Specifically, we identify more than 20 signal peptides, putative hormones, and transcription factors in association with early development and metamorphic stages-many of which seem to be evolutionarily conserved elements of signal transduction pathways. We also characterize genes related to biomineralization-a critical process of molluscan development. In summary, our experiment provides the first large-scale survey of gene expression in mollusc development, and complements previous studies on the regulatory mechanisms underlying body plan patterning and the formation of larval and juvenile structures. This study serves as a resource for further functional annotation of transcripts and genes in Aplysia, specifically and molluscs in general. A comparison of the Aplysia developmental transcriptome with similar studies in the zebra fish Danio rerio, the fruit fly Drosophila melanogaster, the nematode Caenorhabditis elegans, and other studies on molluscs suggests an overall highly divergent pattern of gene regulatory mechanisms that are likely a consequence of the different developmental modes of these organisms.
Project description:The monitoring of global transcription patterns during development is a useful first step to understand mechanisms underlying growth, differentiation and patterning in a given species. However such large scale developmental studies are so far only available from a few selected model organisms such as mouse, Drosophila and the nematode C. elegans. Genomic scale information from the lophotrochozoa is now emerging. The recently characterized neuronal transcriptome of the sea hare Aplysia californica (~200’000 ESTs and ~40,000 unique non-redundant sequences representing about 55-70% of all neuronal transcripts including splice forms and non-coding RNAs) provides new insights and opportunities into problems of molluscan development and specifically neurogenesis. Regulatory genes used in development are recruited for the functions of adult nervous systems such as synaptogenesis, specific wiring in networks and structural changes underlying synaptic plasticity. While this similarity reflects a basic concept in biology, namely the recruitment of the same genes for different functions, it has never been tested on a large scale genomic level. We used representative oligo-arrays constructed from transcripts obtained from the Aplysia nervous system to explore the following two questions: 1) What neuronal genes are differentially expressed during embryonic development of the sea hare Aplysia. 2) What gene expression changes can be observed in correlation with gastrulation, metamorphosis, and larval neurogenesis. For this purpose we hybridized RNA from 3 embryonic (64 cells, gastrula, trochophore) and 4 larval stages (pre-hatching, post-hatching, pre-metamorphosis, postmetamorphosis) against a reference sample consisting of equal contributions from all stages. Our analysis revealed that all embryonic and larval stages can be distinguished based on their transcription profiles. A comparison of the Aplysia atlas with similar studies in Drosophila and mouse reveals interesting differences. We identified several new transcription factors which are differentially expressed during early embryonic development. Various other transcripts involved in metabolism and differentiation were characterized. These genes can be candidate targets for understanding neuronal growth, synaptogenesis and memory mechanisms. We conclude that the microarray technology provides us with a powerful tool for efficient survey and functional annotation of the neuronal transcriptome in Aplysia. We used a reference design for this study where we hybridized each of the 8 developmental stages of Aplysia (cleavage, gastrula, trochophore, first veliger, hatching veliger, pre-metamorphosis (stage 6), post-metamorphosis (stage 7), post-metamorphosis 60 hours (pm60)
Project description:Study objectiveTo characterize sleep in the marine mollusk, Aplysia californica.DesignAnimal behavior and activity were assessed using video recordings to measure activity, resting posture, resting place preference, and behavior after rest deprivation. Latencies for behavioral responses were measured for appetitive and aversive stimuli for animals in the wake and rest states.SettingCircadian research laboratory for Aplysia.Patients or participantsA. californica from the Pacific Ocean.InterventionsN/A.Measurements and resultsAplysia rest almost exclusively during the night in a semi-contracted body position with preferential resting locations in the upper corners of their tank. Resting animals demonstrate longer latencies in head orientation and biting in response to a seaweed stimulus and less frequent escape response steps following an aversive salt stimulus applied to the tail compared to awake animals at the same time point. Aplysia exhibit rebound rest the day following rest deprivation during the night, but not after similar handling stimulation during the day.ConclusionsResting behavior in Aplysia fulfills all invertebrate characteristics of sleep including: (1) a specific sleep body posture, (2) preferred resting location, (3) reversible behavioral quiescence, (4) elevated arousal thresholds for sensory stimuli during sleep, and (5) compensatory sleep rebound after sleep deprivation.