A transporter that allows phosphate ions to control the polymorph of exoskeletal calcium carbonate biomineralization

Shai A. Shaked, Shai Abehsera, Andreas Ziegler, Shmuel Bentov, Rivka Manor, Simy Weil, Ehud Ohana, Jerry Eichler, Eliahu D. Aflalo, Amir Sagi

Research output: Contribution to journalArticlepeer-review

Abstract

The SLC20A2 transporter supplies phosphate ions (Pi) for diverse biological functions in vertebrates, yet has not been studied in crustaceans. Unlike vertebrates, whose skeletons are mineralized mainly by calcium phosphate, only minute amounts of Pi are found in the CaCO3-mineralized exoskeletons of invertebrates. In this study, a crustacean SLC20A2 transporter was discovered and Pi transport to exoskeletal elements was studied with respect to the role of Pi in invertebrate exoskeleton biomineralization, revealing an evolutionarily conserved mechanism for Pi transport in both vertebrates and invertebrates. Freshwater crayfish, including the study animal Cherax quadricarinatus, require repeated molt cycles for their growth. During the molt cycle, crayfish form transient exoskeletal mineral storage organs named gastroliths, which mostly contain amorphous calcium carbonate (ACC), an unstable polymorph long-thought to be stabilized by Pi. RNA interference experiments via CqSLC20A2 dsRNA injections reduced Pi content in C. quadricarinatus gastroliths, resulting in increased calcium carbonate (CaCO3) crystallinity and grain size. The discovery of a SLC20A2 transporter in crustaceans and the demonstration that knocking down its mRNA reduced Pi content in exoskeletal elements offers the first direct proof of a long-hypothesized mechanism by which Pi affects CaCO3 biomineralization in the crustacean exoskeleton. This research thus demonstrated the distinct role of Pi as an amorphous mineral polymorph stabilizer in vivo, suggesting further avenues for amorphous biomaterial studies.

Original languageEnglish
Pages (from-to)221-232
Number of pages12
JournalActa Biomaterialia
Volume178
DOIs
StatePublished - 1 Apr 2024

Keywords

  • Amorphous calcium carbonate (ACC)
  • Biomineralization
  • Crustacean exoskeleton
  • Phosphate
  • SLC20 transporter

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Biotechnology
  • Biomedical Engineering
  • Biomaterials

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