Alternative promoters and renal cell-specific regulation of the mouse type IIa sodium-dependent phosphate cotransporter gene.
The type IIa sodium-dependent phosphate cotransporter (NPT2a) expressed in renal proximal tubules represents an important determinant in maintaining inorganic phosphate (Pi) homeostasis. In the present study, we identified two variant transcripts of the mouse NPT2a gene, Npt2a-v1 and Npt2a-v2, characterized by the presence of alternative first exons (either exon 1A or exon 1B). The chromosomal structure analysis revealed that the Npt2a gene comprises of two promoters (promoters 1 and 2) and 14 exons, and spans approximately 17 kb. Quantitative PCR analysis showed that renal mRNA levels of both the variants markedly decreased in X-linked vitamin D-resistant hypophosphatemic rickets (Hyp) mice compared to normal littermates. Interestingly, transcriptional activity of a reporter gene, containing Npt2a promoters 1 and 2, was renal cell-specifically increased by 1alpha, 25(OH)2D3 and its analogs. The deletion analysis revealed that the CAAT box in the Npt2a promoter 2 is important for the 1alpha, 25(OH)2D3-dependent renal cell-specific activation of the reporter gene. These data suggested that two alternative promoters control the renal expression of Npt2a gene and both Npt2a variant transcripts are down regulated in Hyp mice.
Yamamoto
Hironori
H
Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, Kuramoto-Cho 3-18-15, Tokushima City 770-8503, Japan. yamamoto@nutr.med.tokushima-u.ac.jp
Tani
Yoshiko
Y
Kobayashi
Kumi
K
Taketani
Yutaka
Y
Sato
Tadatoshi
T
Arai
Hidekazu
H
Morita
Kyoko
K
Miyamoto
Ken-ichi
K
Pike
John Wesley
JW
Kato
Shigeaki
S
Takeda
Eiji
E
D024506:5' Flanking Region / Q000235:genetics; D020121:5' Untranslated Regions / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D018938:Caco-2 Cells; D002117:Calcitriol / Q000494:pharmacology; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D033481:Chromosomes, Mammalian / Q000378:metabolism; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007668:Kidney / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008969:Molecular Sequence Data; D009893:Opossums; D009928:Organ Specificity; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa / Q000235:genetics*
D020121:5' Untranslated Regions; D012333:RNA, Messenger; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D002117:Calcitriol