title: A crayfish molar tooth protein with putative mineralized exoskeletal chitinous matrix properties.
abstract: Some crustaceans possess exoskeletons that are reinforced with calcium carbonate. In the crayfish Cherax quadricarinatus, the molar tooth, which is part of the mandibular exoskeleton, contains an unusual crystalline enamel-like apatite layer. As this layer resembles vertebrate enamel in composition and function, it offers an interesting example of convergent evolution. Unlike other parts of the crayfish exoskeleton, which is periodically shed and regenerated during the molt cycle, molar mineral deposition takes place during the pre-molt stage. The molar mineral composition transforms continuously from fluorapatite through amorphous calcium phosphate to amorphous calcium carbonate and is mounted on chitin. The process of crayfish molar formation is entirely extracellular and presumably controlled by proteins, lipids, polysaccharides, low-molecular weight molecules and calcium salts. We have identified a novel molar protein termed Cq-M15 from C. quadricarinatus and cloned its transcript from the molar-forming epithelium. Its transcript and differential expression were confirmed by a next-generation sequencing library. The predicted acidic pI of Cq-M15 suggests its possible involvement in mineral arrangement. Cq-M15 is expressed in several exoskeletal tissues at pre-molt and its silencing is lethal. Like other arthropod cuticular proteins, Cq-M15 possesses a chitin-binding Rebers-Riddiford domain, with a recombinant version of the protein found to bind chitin. Cq-M15 was also found to interact with calcium ions in a concentration-dependent manner. This latter property might make Cq-M15 useful for bone and dental regenerative efforts. We suggest that, in the molar tooth, this protein might be involved in calcium phosphate and/or carbonate precipitation.
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel National Institute for Biotechnology in the Negev, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Jenny
authors.initials: J
authors.lastname: Tynyakov
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel National Institute for Biotechnology in the Negev, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Shmuel
authors.initials: S
authors.lastname: Bentov
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Shai
authors.initials: S
authors.lastname: Abehsera
authors.affiliation: Department of Biotechnology Engineering, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Galit
authors.initials: G
authors.lastname: Yehezkel
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Ziv
authors.initials: Z
authors.lastname: Roth
authors.affiliation: Department of Biotechnology Engineering, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Isam
authors.initials: I
authors.lastname: Khalaila
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Simy
authors.initials: S
authors.lastname: Weil
authors.affiliation: Department of Biotechnology Engineering, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Amir
authors.initials: A
authors.lastname: Berman
authors.affiliation: National Institute for Biotechnology in the Negev, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Inbar
authors.initials: I
authors.lastname: Plaschkes
authors.affiliation: Israel Oceanographic and Limnological Research, Haifa 8511911, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Tom
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel National Institute for Biotechnology in the Negev, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel.
authors.forename: Eliahu D
authors.initials: ED
authors.lastname: Aflalo
authors.affiliation: Department of Life Sciences, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel National Institute for Biotechnology in the Negev, Ben-Gurion University, PO Box 653, Beer-Sheva 84105, Israel sagia@bgu.ac.il.
authors.forename: Amir
authors.initials: A
authors.lastname: Sagi
mesh_terms: D060105:Animal Shells / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001031:Apatites / Q000737:chemistry / Q000378:metabolism; D060829:Arthropod Proteins / Q000737:chemistry* / Q000235:genetics; D003400:Astacoidea / Q000033:anatomy & histology* / Q000254:growth & development; D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism; D002130:Calcium Phosphates / Q000737:chemistry / Q000378:metabolism; D002686:Chitin / Q000737:chemistry*
chemical_list: D001031:Apatites; D060829:Arthropod Proteins; D002130:Calcium Phosphates; D002686:Chitin; C020243:calcium phosphate; D002119:Calcium Carbonate; C025105:fluorapatite
keywords: Biomineralization; Calcium; Chitin; Crustacean; Hydroxyapatite; RNAi