Citrate Transporter Expression and Localization: The Slc13a5^Flag Mouse Model

Area of Science:

• Biochemistry
• Genetics
• Developmental Biology

Background:

• The sodium-citrate cotransporter (NaCT), encoded by the SLC13A5 gene, is vital for citrate transport in amelogenesis.
• Mutations in SLC13A5 are linked to early infantile epileptic encephalopathy 25 and amelogenesis imperfecta.
• Citrate is highly concentrated and mineral-bound in developing enamel.

Purpose of the Study:

• To develop a reporter mouse model for precise localization of NaCT during tooth development.
• To investigate the mechanism of citrate entry into developing enamel.

Main Methods:

• Generation of Slc13a5^Flag reporter mice expressing a C-terminally Flag-tagged NaCT.
• Validation of the reporter mouse model using Sanger sequencing and phenotypic analysis.
• Extensive characterization of tooth development via microscopy, in situ hybridization, and immunohistochemistry.

Main Results:

• Slc13a5^Flag reporter mice exhibited normal development and tooth formation.
• NaCT-Flag was localized to the outer membranes of secretory and maturation-stage ameloblasts, with strong signals on the Tomes process.
• The papillary layer and odontoblast outer membranes also showed NaCT-Flag staining, while ANK expression was absent in ameloblasts.

Conclusions:

• The developed Slc13a5^Flag reporter mice provide a reliable tool for studying NaCT localization and function.
• NaCT's presence on ameloblast membranes suggests citrate enters enamel either paracellularly or via bidirectional NaCT transport.
• These findings advance our understanding of citrate homeostasis in amelogenesis and related disorders.