Department of Biology, University of Washington, Seattle, WA 98195, USA; Department of Molecular and Cell Biology, University of California, Merced, Merced, CA 95343, USA.
Department of Orthopaedics and Sports Medicine, University of Washington School of Medicine, Seattle, WA 98109, USA.
Curr Biol. 2020 Oct 19;30(20):R1254-R1255. doi: 10.1016/j.cub.2020.08.014.
We previously reported that the polysaccharide chitin, a key component of arthropod exoskeletons and fungal cell walls, is endogenously produced by fishes and amphibians in spite of the widely held view that it was not synthesized by vertebrates [1]. Genes encoding chitin synthase enzymes were found in the genomes of a number of fishes and amphibians and shown to be correspondingly expressed at the sites where chitin was localized [1,2]. In this report, we present evidence suggesting that chitin is prevalent within the specialized electrosensory organs of cartilaginous fishes (Chondrichthyes). These organs, the Ampullae of Lorenzini (AoL), are widely distributed and comprise a series of gel-filled canals emanating from pores in the skin (Figure 1A). The canals extend into bulbous structures called alveoli that contain sensory cells capable of detecting subtle changes in electric fields (Figure 1B) [3,4]. The findings described here extend the number of vertebrate taxa where endogenous chitin production has been detected and raise questions regarding chitin's potential function in chondrichthyan fishes and other aquatic vertebrates.
我们之前曾报道，甲壳素是节肢动物外骨骼和真菌细胞壁的主要成分，尽管普遍认为脊椎动物不能合成甲壳素，但鱼类和两栖类动物会内源性地产生甲壳素[1]。在一些鱼类和两栖类动物的基因组中发现了编码几丁质合酶的基因，并在甲壳素定位的部位相应地表达[1,2]。在本报告中，我们提出了证据表明甲壳素普遍存在于软骨鱼类（软骨鱼纲）的特殊电感受器器官中。这些器官，即罗氏壶腹（Ampullae of Lorenzini，AoL），广泛分布，由一系列从皮肤孔中伸出的充满凝胶的通道组成（图 1A）。这些通道延伸到称为肺泡的球状结构中，其中包含能够检测到电场细微变化的感觉细胞（图 1B）[3,4]。这里描述的发现扩展了检测到内源性甲壳素产生的脊椎动物分类群的数量，并提出了关于甲壳素在软骨鱼类和其他水生脊椎动物中的潜在功能的问题。
