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The phosphate transporter PiT1 (Slc20a1) revealed as a new essential gene for mouse liver development.

Beck L, Leroy C, Beck-Cormier S, Forand A, Salaün C, Paris N, Bernier A, Ureña-Torres P, Prié D, Ollero M, Coulombel L, Friedlander G - PLoS ONE (2010)

Bottom Line: In contrast, mutant fetal livers display decreased proliferation and massive apoptosis.Animals carrying two copies of hypomorphic PiT1 alleles (resulting in 15% PiT1 expression comparing to wild-type animals) survive at birth but are growth-retarded and anemic.This work is the first to illustrate a specific in vivo role for PiT1 by uncovering it as being a critical gene for normal developmental liver growth.

View Article: PubMed Central - PubMed

Affiliation: INSERM, U845, Centre de Recherche Croissance et Signalisation, Paris, France. laurent.beck@inserm.fr

ABSTRACT

Background: PiT1 (or SLC20a1) encodes a widely expressed plasma membrane protein functioning as a high-affinity Na(+)-phosphate (Pi) cotransporter. As such, PiT1 is often considered as a ubiquitous supplier of Pi for cellular needs regardless of the lack of experimental data. Although the importance of PiT1 in mineralizing processes have been demonstrated in vitro in osteoblasts, chondrocytes and vascular smooth muscle cells, in vivo evidence is missing.

Methodology/principal findings: To determine the in vivo function of PiT1, we generated an allelic series of PiT1 mutations in mice by combination of wild-type, hypomorphic and PiT1 alleles expressing from 100% to 0% of PiT1. In this report we show that complete deletion of PiT1 results in embryonic lethality at E12.5. PiT1-deficient embryos display severely hypoplastic fetal livers and subsequent reduced hematopoiesis resulting in embryonic death from anemia. We show that the anemia is not due to placental, yolk sac or vascular defects and that hematopoietic progenitors have no cell-autonomous defects in proliferation and differentiation. In contrast, mutant fetal livers display decreased proliferation and massive apoptosis. Animals carrying two copies of hypomorphic PiT1 alleles (resulting in 15% PiT1 expression comparing to wild-type animals) survive at birth but are growth-retarded and anemic. The combination of both hypomorphic and alleles in heterozygous compounds results in late embryonic lethality (E14.5-E16.5) with phenotypic features intermediate between and hypomorphic mice. In the three mouse lines generated we could not evidence defects in early skeleton formation.

Conclusion/significance: This work is the first to illustrate a specific in vivo role for PiT1 by uncovering it as being a critical gene for normal developmental liver growth.

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Related in: MedlinePlus

Impaired PiT1 expression in mice does not affect early skeleton development.(A–B) Alcian blue staining of PiT1+/+ and PiT1Δ5/Δ5 E12.5 whole embryos. (C–H) Alcian blue staining of PiT1+/+ and PiT1neo/Δ5 E15.5 whole embryos. Higher magnification views (E–H) demonstrate no difference in skeletal development of the heterozygous compounds. (I–L) Alcian blue and alizarin red S double staining of one-day old PiT1+/+ and PiT1neo/neo newborn pups. Note the lack of alizarin red staining in humerus, verterbraes, cranial vault and upper facial skeleton (black arrows). (M–N) Alcian blue and alizarin red S double staining of 15-day old PiT1+/+ and PiT1neo/neo mice. No staining difference could be evidenced anymore.
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pone-0009148-g009: Impaired PiT1 expression in mice does not affect early skeleton development.(A–B) Alcian blue staining of PiT1+/+ and PiT1Δ5/Δ5 E12.5 whole embryos. (C–H) Alcian blue staining of PiT1+/+ and PiT1neo/Δ5 E15.5 whole embryos. Higher magnification views (E–H) demonstrate no difference in skeletal development of the heterozygous compounds. (I–L) Alcian blue and alizarin red S double staining of one-day old PiT1+/+ and PiT1neo/neo newborn pups. Note the lack of alizarin red staining in humerus, verterbraes, cranial vault and upper facial skeleton (black arrows). (M–N) Alcian blue and alizarin red S double staining of 15-day old PiT1+/+ and PiT1neo/neo mice. No staining difference could be evidenced anymore.

Mentions: Since PiT1 has been extensively studied in bone and cartilage, we investigated whether these tissues were affected in PiT1 mutant mice. Alcian blue staining of the initial cartilage matrix revealed no difference between E12.5 PiT1Δ5/Δ5 and PiT1+/+ embryos (Fig. 9A and B), or later in development between E15.5 PiT1neo/Δ5 and PiT1+/+ embryos (Fig. 9C to H). Alcian blue/alizarin red S double staining of newborn PiT1neo/neo and wild-type skeletons showed an impaired mineralization of both long bones in which endochondral (arising from cartilaginous mold) ossification takes place, and in the cranial vault and portions of the upper facial skeleton that develop by intramembranous ossification without replacing a cartilaginous mold (Fig. 9I to L). However, these differences were not seen on all of the hypomorphic newborn pups (data not shown), suggesting that the impaired mineralization may have been already corrected. Consistent with this hypothesis, staining of 2-weeks-old skeletons demonstrated no detectable difference between PiT1neo/neo and PiT1+/+ mice (Fig. 9M and N). Our data do not exclude an in vivo role for PiT1 in bone and cartilage biology, but indicate that a normal expression of PiT1 is not essential for early skeleton formation during mouse development.


The phosphate transporter PiT1 (Slc20a1) revealed as a new essential gene for mouse liver development.

Beck L, Leroy C, Beck-Cormier S, Forand A, Salaün C, Paris N, Bernier A, Ureña-Torres P, Prié D, Ollero M, Coulombel L, Friedlander G - PLoS ONE (2010)

Impaired PiT1 expression in mice does not affect early skeleton development.(A–B) Alcian blue staining of PiT1+/+ and PiT1Δ5/Δ5 E12.5 whole embryos. (C–H) Alcian blue staining of PiT1+/+ and PiT1neo/Δ5 E15.5 whole embryos. Higher magnification views (E–H) demonstrate no difference in skeletal development of the heterozygous compounds. (I–L) Alcian blue and alizarin red S double staining of one-day old PiT1+/+ and PiT1neo/neo newborn pups. Note the lack of alizarin red staining in humerus, verterbraes, cranial vault and upper facial skeleton (black arrows). (M–N) Alcian blue and alizarin red S double staining of 15-day old PiT1+/+ and PiT1neo/neo mice. No staining difference could be evidenced anymore.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2818845&req=5

pone-0009148-g009: Impaired PiT1 expression in mice does not affect early skeleton development.(A–B) Alcian blue staining of PiT1+/+ and PiT1Δ5/Δ5 E12.5 whole embryos. (C–H) Alcian blue staining of PiT1+/+ and PiT1neo/Δ5 E15.5 whole embryos. Higher magnification views (E–H) demonstrate no difference in skeletal development of the heterozygous compounds. (I–L) Alcian blue and alizarin red S double staining of one-day old PiT1+/+ and PiT1neo/neo newborn pups. Note the lack of alizarin red staining in humerus, verterbraes, cranial vault and upper facial skeleton (black arrows). (M–N) Alcian blue and alizarin red S double staining of 15-day old PiT1+/+ and PiT1neo/neo mice. No staining difference could be evidenced anymore.
Mentions: Since PiT1 has been extensively studied in bone and cartilage, we investigated whether these tissues were affected in PiT1 mutant mice. Alcian blue staining of the initial cartilage matrix revealed no difference between E12.5 PiT1Δ5/Δ5 and PiT1+/+ embryos (Fig. 9A and B), or later in development between E15.5 PiT1neo/Δ5 and PiT1+/+ embryos (Fig. 9C to H). Alcian blue/alizarin red S double staining of newborn PiT1neo/neo and wild-type skeletons showed an impaired mineralization of both long bones in which endochondral (arising from cartilaginous mold) ossification takes place, and in the cranial vault and portions of the upper facial skeleton that develop by intramembranous ossification without replacing a cartilaginous mold (Fig. 9I to L). However, these differences were not seen on all of the hypomorphic newborn pups (data not shown), suggesting that the impaired mineralization may have been already corrected. Consistent with this hypothesis, staining of 2-weeks-old skeletons demonstrated no detectable difference between PiT1neo/neo and PiT1+/+ mice (Fig. 9M and N). Our data do not exclude an in vivo role for PiT1 in bone and cartilage biology, but indicate that a normal expression of PiT1 is not essential for early skeleton formation during mouse development.

Bottom Line: In contrast, mutant fetal livers display decreased proliferation and massive apoptosis.Animals carrying two copies of hypomorphic PiT1 alleles (resulting in 15% PiT1 expression comparing to wild-type animals) survive at birth but are growth-retarded and anemic.This work is the first to illustrate a specific in vivo role for PiT1 by uncovering it as being a critical gene for normal developmental liver growth.

View Article: PubMed Central - PubMed

Affiliation: INSERM, U845, Centre de Recherche Croissance et Signalisation, Paris, France. laurent.beck@inserm.fr

ABSTRACT

Background: PiT1 (or SLC20a1) encodes a widely expressed plasma membrane protein functioning as a high-affinity Na(+)-phosphate (Pi) cotransporter. As such, PiT1 is often considered as a ubiquitous supplier of Pi for cellular needs regardless of the lack of experimental data. Although the importance of PiT1 in mineralizing processes have been demonstrated in vitro in osteoblasts, chondrocytes and vascular smooth muscle cells, in vivo evidence is missing.

Methodology/principal findings: To determine the in vivo function of PiT1, we generated an allelic series of PiT1 mutations in mice by combination of wild-type, hypomorphic and PiT1 alleles expressing from 100% to 0% of PiT1. In this report we show that complete deletion of PiT1 results in embryonic lethality at E12.5. PiT1-deficient embryos display severely hypoplastic fetal livers and subsequent reduced hematopoiesis resulting in embryonic death from anemia. We show that the anemia is not due to placental, yolk sac or vascular defects and that hematopoietic progenitors have no cell-autonomous defects in proliferation and differentiation. In contrast, mutant fetal livers display decreased proliferation and massive apoptosis. Animals carrying two copies of hypomorphic PiT1 alleles (resulting in 15% PiT1 expression comparing to wild-type animals) survive at birth but are growth-retarded and anemic. The combination of both hypomorphic and alleles in heterozygous compounds results in late embryonic lethality (E14.5-E16.5) with phenotypic features intermediate between and hypomorphic mice. In the three mouse lines generated we could not evidence defects in early skeleton formation.

Conclusion/significance: This work is the first to illustrate a specific in vivo role for PiT1 by uncovering it as being a critical gene for normal developmental liver growth.

Show MeSH
Related in: MedlinePlus