Molecular characterization of cell types in the squid Loligo vulgaris
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Curated by eLife
eLife assessment
This manuscript describes cell types in the head of the squid, Loligo vulgaris, through expression patterns of key genes identified in single cell transcriptomics. This topic is generally of great comparative interest. It will contribute to a better understanding of the cephalopod nervous and sensory systems, providing a basis for future comparative and evolutionary research.
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Abstract
Cephalopods are set apart from other mollusks by their advanced behavioral abilities and the complexity of their nervous systems. Because of the great evolutionary distance that separates vertebrates from cephalopods, it is evident that higher cognitive features have evolved separately in these clades despite the similarities that they share. Alongside their complex behavioral abilities, cephalopods have evolved specialized cells and tissues, such as the chromatophores for camouflage or suckers to grasp prey. Despite significant progress in genome and transcriptome sequencing, the molecular identities of cell types in cephalopods remain largely unknown. We here combine single-cell transcriptomics with in situ gene expression analysis to uncover cell type diversity in the European squid Loligo vulgaris . We describe cell types that are conserved with other phyla such as neurons, muscles, or connective tissues but also cephalopod-specific cells, such as chromatophores or sucker cells. Moreover, we investigate major components of the squid nervous system including progenitor and developing cells, differentiated cells of the brain and optic lobes, as well as sensory systems of the head. Our study provides a molecular assessment for conserved and novel cell types in cephalopods and a framework for mapping the nervous system of L. vulgaris .
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eLife assessment
This manuscript describes cell types in the head of the squid, Loligo vulgaris, through expression patterns of key genes identified in single cell transcriptomics. This topic is generally of great comparative interest. It will contribute to a better understanding of the cephalopod nervous and sensory systems, providing a basis for future comparative and evolutionary research.
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Reviewer #1 (Public Review):
In this manuscript, the authors have assembled a reference transcriptome of the whole head of Loligo vulgaris and used it to perform single cell transcriptomics. With about 20,000 cells, they identify 32 clusters corresponding to a few identifiable cell types - neurons, stem cells, sensory cells, and epidermis. They use select marker genes from these clusters and perform HCR in situs on Loligo heads to describe these cell types. Their in situs describe a region similar to the lateral lip seen in other cephalopods where neural progenitors are found and from where neurons migrate into the brain.
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Reviewer #2 (Public Review):
In 'Molecular characterization of cell types in the squid Loligo vulgaris', the authors study profile cell types of the squid brain, using single cell RNAseq and FISH for anatomical localization. They reveal many different cell types, some of which have correspondences in other organisms and some of which reflect cephalopod-specific innovations. The current study is one of 4 recent preprints (Styfhals et al. 2022, Songco-Casey et al. 2022, Gavriouchkina et al. 2022) profiling cephalopod tissues using scRNAseq and FISH-based anatomical localization. Together these studies begin to reveal the cellular complexity of these fascinating animals.
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Reviewer #3 (Public Review):
In this manuscript, the authors leverage new single-cell sequencing data to unravel cell type diversity in the head of Loligo vulgaris hatchlings. This analysis recovers 33 clusters and the authors describe the cell type populations with HCR in situ hybridization. This work provides an important next step in describing neural and sensory cells in an understudied class of invertebrates that goes beyond traditional morphological characterization.
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