Evidence of Chitin in the Ampullae of Lorenzini of Chondrichthyan Fishes

Phillips, Molly; Tang, Wei; Hassan, Khan; Daza, Daniel Ocampo; Kaya, Murat; Sargn, Idris; Amemiya, Chris T.

doi:10.1101/687301

Cited by 4 publications

(17 citation statements)

References 11 publications

(14 reference statements)

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“…Low magnification fluorescence microscopy was used to study the structure of formalin-fixed tissues from little skate (Leucoraja erinacea) and spotted ratfish (H. colliei) that were stained with fluorescent probes consisting of the chitin binding domain (CBD) (12,14) (Supplemental Figure 2A, B). CBD detects chitin within AoL gel material in a highly specific manner (12), and served as a marker of the fine outlines of the gel. While gel inside fixed whole-mount AoL exhibited wavy fabric-like patterns (Supplemental Figure 2A), the gel of sectioned AoL appeared to be organized into small packets that looked to be extruded from individual cells (Supplemental Figure 2B).…”

Section: Resultsmentioning

confidence: 99%

“…CC-BY-NC-ND 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2021.01.04.425255 doi: bioRxiv preprint 8 polysaccharides from AoL gel ( Figure 2H), indicating that chitin likely composes at least some portion of the globules (12).…”

Section: Resultsmentioning

confidence: 99%

“…AoL from an adult L. erinacea specimen were dissected from the hyoid cluster and labeled with CBD and DAPI following protocols described in (12). Whole-mount tissues were imaged using a Leica M205FA fluorescent stereoscope equipped with a DFC360FX monochrome CCD camera and a DFC425C color CCD camera.…”

Section: Cbd Staining and Fluorescence Microscopymentioning

confidence: 99%

“…Wax sections of formalin-fixed H. colliei tissues were prepared using standard processing, embedding and microtomy protocols and stained following protocols described in (12), and epifluorescent images were taken using either a Leica DMR upright epifluorescent microscope equipped with a SPOT RT Slider cooled 1.4 megapixel color/monochrome CCD camera and an Insight 4 megapixel color CCD camera (Diagnostic Instruments).…”

Section: Cbd Staining and Fluorescence Microscopymentioning

confidence: 99%

“…Cellular contamination during AoL gel extraction, however, makes the interpretation of proteomic datasets challenging. We recently reported evidence suggesting that chitin is another polysaccharide component of the gel, but it remains unknown if the chitin molecules are modified in some way or complexed with other components in order to promote solubility in the aqueous gel (12).…”

Section: Introductionmentioning

confidence: 99%

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Structural Characteristics and Proton Conductivity of the Gel Within the Electrosensory Organs of Cartilaginous Fishes

Phillips

Wheeler

Robinson

et al. 2021

Preprint

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The Ampullae of Lorenzini (AoL) of cartilaginous fishes are sensory organs used to detect environmental electric fields. The proximal ends of the organs are externally visible as pores in the skin that lead into gel-filled tubular canals which terminate in rounded chambers filled with highly specialized electrosensory cells. The viscoelastic gel that fills the organs is composed of proteins and polysaccharides that are not yet completely characterized but are thought to play a critical role in the electrosensing mechanism. Although recent studies have identified various components of AoL gel, it has remained unclear how the component molecules are structurally arranged and how their structure influences the overall function of the AoL. Here we present the first microscopic descriptions and x-ray scattering data from AoL gel extracted from spotted ratfish (Hydrolagus colliei). Our results suggest that AoL gel is colloidal in nature and composed of spherical globules that are approximately 10-100 nm in size. We investigated the structural influence of the protein components of the gel specifically by analyzing gel that had been digested in situ via enzymatic proteolysis. By comparing gel before and after digestion using microscopy, x-ray scattering analyses, and proton conductivity measurements, we directly observed the structural and functional influence of proteins in AoL gel. The findings described here represent the first detailed structural analysis of AoL gel and lay the groundwork for more detailed studies into the specific interactions of molecules inside AoL gel at the nanoscale, with particular reference to their mechanistic role in electrosensing.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Cbd Staining and Fluorescence Microscopymentioning

confidence: 99%

Section: Cbd Staining and Fluorescence Microscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural Characteristics and Proton Conductivity of the Gel Within the Electrosensory Organs of Cartilaginous Fishes

Phillips

Wheeler

Robinson

et al. 2021

Preprint

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Colloidal structure and proton conductivity of the gel within the electrosensory organs of cartilaginous fishes

et al. 2021

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Summary Cartilaginous fishes possess gel-filled tubular sensory organs called Ampullae of Lorenzini (AoL) that are used to detect electric fields. Although recent studies have identified various components of AoL gel, it has remained unclear how the molecules are structurally arranged and how their structure influences the function of the organs. Here we describe the structure of AoL gel by microscopy and small-angle X-ray scattering and infer that the material is colloidal in nature. To assess the relative function of the gel's protein constituents, we compared the microscopic structure, X-ray scattering, and proton conductivity properties of the gel before and after enzymatic digestion with a protease. We discovered that while proteins were largely responsible for conferring the viscous nature of the gel, their removal did not diminish proton conductivity. The findings lay the groundwork for more detailed studies into the specific interactions of molecules inside AoL gel at the nanoscale.

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Gene family expansion and functional diversification of chitinase and chitin synthase genes in Atlantic salmon (Salmo salar)

Holen

Kent

Vaaje‐Kolstad

et al. 2022

Preprint

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Background: Chitin is one of the most abundant polysaccharides in nature, forming important structures in insects, crustaceans, and fungal cell walls. Vertebrates on the other hand are generally considered "non-chitinous" organisms, despite having highly conserved chitin metabolism associated genes. Recent work has revealed that the largest group of vertebrates, the teleosts, have the potential to both synthesize and degrade endogenous chitin. Yet little is still known about the genes and proteins responsible for these dynamic processes. Here we used comparative genomics, transcriptomics, and chromatin accessibility data to characterize the repertoire, evolution, and regulation of genes involved in chitin-metabolism in teleosts, with a particular focus on Atlantic salmon. Results: Reconstruction of gene family phylogenies provide evidence for an expansion of teleost and salmonid chitinase and chitin synthase genes after multiple whole-genome duplications. Analyses of multi-tissue gene expression data demonstrated a strong bias of gastrointestinal tract expression for chitin metabolism genes, but with different spatial and temporal tissue specificities. Finally, we integrated transcriptomes from a developmental time series of the gastrointestinal tract with chromatin accessibility data to identify putative transcription factors responsible for regulating chitin-metabolism gene expression (CDX1 and CDX2) as well as tissue-specific divergence in the regulation of gene duplicates (FOXJ2). These transcription factors are also potential regulators of multiple glycosyltransferases being co-expressed with the chitin remodeling genes. Conclusion: The findings presented here add support to the hypothesis that chitin metabolism genes in teleosts play a role in developing and maintaining a chitin-based barrier in the teleost gut and provide a basis for further investigations into the molecular basis of this barrier.

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Evidence of Chitin in the Ampullae of Lorenzini of Chondrichthyan Fishes

Cited by 4 publications

References 11 publications

Structural Characteristics and Proton Conductivity of the Gel Within the Electrosensory Organs of Cartilaginous Fishes

Structural Characteristics and Proton Conductivity of the Gel Within the Electrosensory Organs of Cartilaginous Fishes

Colloidal structure and proton conductivity of the gel within the electrosensory organs of cartilaginous fishes

Gene family expansion and functional diversification of chitinase and chitin synthase genes in Atlantic salmon (Salmo salar)

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