TY - JOUR
T1 - The role of Na
T2 - K:2Cl cotransporter 1 (NKCC1/SLC12A2) in dental epithelium during enamel formation in mice
AU - Jalali, Rozita
AU - Lodder, Johannes C.
AU - Zandieh-Doulabi, Behrouz
AU - Micha, Dimitra
AU - Melvin, James E.
AU - Catalan, Marcelo A.
AU - Mansvelder, Huibert D.
AU - DenBesten, Pamela
AU - Bronckers, Antonius
N1 - With supplementary files
PY - 2017/11/21
Y1 - 2017/11/21
N2 - Na+:K+:2Cl- cotransporters (NKCCs) belong to the SLC12A family of cation-coupled Cl- transporters. We investigated whether enamel-producing mouse ameloblasts express NKCCs. Transcripts for Nkcc1 were identified in the mouse dental epithelium by RT-qPCR and NKCC1 protein was immunolocalized in outer enamel epithelium and in the papillary layer but not the ameloblast layer. In incisors of Nkcc1-null mice late maturation ameloblasts were disorganized, shorter and the mineral density of the enamel was reduced by 10% compared to wild-type controls. Protein levels of gap junction protein connexin 43, Na+-dependent bicarbonate cotransporter e1 (NBCe1), and the Cl--dependent bicarbonate exchangers SLC26A3 and SLC26A6 were upregulated in Nkcc1-null enamel organs while the level of NCKX4/SLC24A4, the major K+, Na+ dependent Ca2+ transporter in maturation ameloblasts, was slightly downregulated. Whole-cell voltage clamp studies on rat ameloblast-like HAT-7 cells indicated that bumetanide increased ion-channel activity conducting outward currents. Bumetanide also reduced cell volume of HAT-7 cells. We concluded that non-ameloblast dental epithelium expresses NKCC1 to regulate cell volume in enamel organ and provide ameloblasts with Na+, K+ and Cl- ions required for the transport of mineral- and bicarbonate-ions into enamel. Absence of functional Nkcc1 likely is compensated by other types of ion channels and ion transporters. The increased amount of Cx43 in enamel organ cells in Nkcc1-null mice suggests that these cells display a higher number of gap junctions to increase intercellular communication.
AB - Na+:K+:2Cl- cotransporters (NKCCs) belong to the SLC12A family of cation-coupled Cl- transporters. We investigated whether enamel-producing mouse ameloblasts express NKCCs. Transcripts for Nkcc1 were identified in the mouse dental epithelium by RT-qPCR and NKCC1 protein was immunolocalized in outer enamel epithelium and in the papillary layer but not the ameloblast layer. In incisors of Nkcc1-null mice late maturation ameloblasts were disorganized, shorter and the mineral density of the enamel was reduced by 10% compared to wild-type controls. Protein levels of gap junction protein connexin 43, Na+-dependent bicarbonate cotransporter e1 (NBCe1), and the Cl--dependent bicarbonate exchangers SLC26A3 and SLC26A6 were upregulated in Nkcc1-null enamel organs while the level of NCKX4/SLC24A4, the major K+, Na+ dependent Ca2+ transporter in maturation ameloblasts, was slightly downregulated. Whole-cell voltage clamp studies on rat ameloblast-like HAT-7 cells indicated that bumetanide increased ion-channel activity conducting outward currents. Bumetanide also reduced cell volume of HAT-7 cells. We concluded that non-ameloblast dental epithelium expresses NKCC1 to regulate cell volume in enamel organ and provide ameloblasts with Na+, K+ and Cl- ions required for the transport of mineral- and bicarbonate-ions into enamel. Absence of functional Nkcc1 likely is compensated by other types of ion channels and ion transporters. The increased amount of Cx43 in enamel organ cells in Nkcc1-null mice suggests that these cells display a higher number of gap junctions to increase intercellular communication.
KW - Gap junctions
KW - Ion transport
KW - Journal Article
KW - Mineralization
KW - PH regulation
KW - SLC26A
UR - http://www.scopus.com/inward/record.url?scp=85034667594&partnerID=8YFLogxK
UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034667594&doi=10.3389%2ffphys.2017.00924&partnerID=40&md5=e16f8d88023379842c1c9f46b3391b3c
UR - http://www.scopus.com/inward/citedby.url?scp=85034667594&partnerID=8YFLogxK
U2 - https://doi.org/10.3389/fphys.2017.00924
DO - https://doi.org/10.3389/fphys.2017.00924
M3 - Article
C2 - 29209227
SN - 1664-042X
VL - 8
SP - 1
EP - 13
JO - Frontiers in physiology
JF - Frontiers in physiology
IS - NOV
M1 - 924
ER -