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Reduced-folate carrier (RFC) is expressed in placenta and yolk sac, as well as in cells of the developing forebrain, hindbrain, neural tube, craniofacial region, eye, limb buds and heart.

Maddox DM, Manlapat A, Roon P, Prasad P, Ganapathy V, Smith SB - BMC Dev. Biol. (2003)

Bottom Line: Though reduced-folate carrier (RFC) is one of the major proteins mediating folate transport, knowledge of the developmental expression of RFC is lacking.Clinical studies show a statistical decrease in the number of neural tube defects, craniofacial abnormalities, cardiovascular defects and limb abnormalities detected in offspring of female patients given supplementary folate during pregnancy.These findings suggest that rapidly dividing cells in the developing neural tube, craniofacial region, limb buds and heart may be particularly susceptible to folate deficiency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, USA. oxmandm@yahoo.com

ABSTRACT

Background: Folate is essential for cellular proliferation and tissue regeneration. As mammalian cells cannot synthesize folates de novo, tightly regulated cellular uptake processes have evolved to sustain sufficient levels of intracellular tetrahydrofolate cofactors to support biosynthesis of purines, pyrimidines, and some amino acids (serine, methionine). Though reduced-folate carrier (RFC) is one of the major proteins mediating folate transport, knowledge of the developmental expression of RFC is lacking. We utilized in situ hybridization and immunolocalization to determine the developmental distribution of RFC message and protein, respectively.

Results: In the mouse, RFC transcripts and protein are expressed in the E10.0 placenta and yolk sac. In the E9.0 to E11.5 mouse embryo RFC is widely detectable, with intense signal localized to cell populations in the neural tube, craniofacial region, limb buds and heart. During early development, RFC is expressed throughout the eye, but by E12.5, RFC protein becomes localized to the retinal pigment epithelium (RPE).

Conclusions: Clinical studies show a statistical decrease in the number of neural tube defects, craniofacial abnormalities, cardiovascular defects and limb abnormalities detected in offspring of female patients given supplementary folate during pregnancy. The mechanism, however, by which folate supplementation ameliorates the occurrence of developmental defects is unclear. The present work demonstrates that RFC is present in placenta and yolk sac and provides the first evidence that it is expressed in the neural tube, craniofacial region, limb buds and heart during organogenesis. These findings suggest that rapidly dividing cells in the developing neural tube, craniofacial region, limb buds and heart may be particularly susceptible to folate deficiency.

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Analysis of RFC mRNA transcripts in E9.5-E11.5 mouse embryos. RFC mRNA was widely expressed; however, structures undergoing developmental changes requiring rapid cell division expressed the mRNAs most strongly. Panels A-C demonstrate expression of RFC mRNA in embryos varying in age from E9.5 to E11.5. Light purple staining indicates the widespread nature of the RFC message. Regions of more intense staining include the forebrain, eye, hindbrain, mandible, heart, limb buds, somites, tail and yolk sac. Panel D depicts a control in situ hybridization performed with RFC sense riboprobes. Lack of background staining verifies that the signal in the experimental specimens is specific. Forebrain, FB; eye, E; hindbrain, HB; mandible, M; heart, H; limb buds, LB; somites, S; tail, T. Scale bar represents 50 μm.
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Figure 2: Analysis of RFC mRNA transcripts in E9.5-E11.5 mouse embryos. RFC mRNA was widely expressed; however, structures undergoing developmental changes requiring rapid cell division expressed the mRNAs most strongly. Panels A-C demonstrate expression of RFC mRNA in embryos varying in age from E9.5 to E11.5. Light purple staining indicates the widespread nature of the RFC message. Regions of more intense staining include the forebrain, eye, hindbrain, mandible, heart, limb buds, somites, tail and yolk sac. Panel D depicts a control in situ hybridization performed with RFC sense riboprobes. Lack of background staining verifies that the signal in the experimental specimens is specific. Forebrain, FB; eye, E; hindbrain, HB; mandible, M; heart, H; limb buds, LB; somites, S; tail, T. Scale bar represents 50 μm.

Mentions: Further analysis of RFC mRNA expression was carried out utilizing mouse embryos ranging from E9.0 to E11.5 (Figure 2). Three or more embryos were examined for each time point. RFC message was detectable in all tissues throughout the embryos, with the most intense levels of expression being confined to the forebrain, hindbrain, craniofacial region, eye (optic vesicles), mandible, heart, somites, and tail (Figure 2A). In E10.5 (Figure 2B) and E11.5 (Figure 2C) embryos, expression in the forebrain, hindbrain, craniofacial region, eye (optic vesicles), mandible, heart, somites, and tail were maintained, while additional expression became detectable in the developing limb buds. Faint signal was also visible in the yolk sac (data not shown). Negative control experiments with sense riboprobes for RFC resulted in minimal background staining (Figure 2D).


Reduced-folate carrier (RFC) is expressed in placenta and yolk sac, as well as in cells of the developing forebrain, hindbrain, neural tube, craniofacial region, eye, limb buds and heart.

Maddox DM, Manlapat A, Roon P, Prasad P, Ganapathy V, Smith SB - BMC Dev. Biol. (2003)

Analysis of RFC mRNA transcripts in E9.5-E11.5 mouse embryos. RFC mRNA was widely expressed; however, structures undergoing developmental changes requiring rapid cell division expressed the mRNAs most strongly. Panels A-C demonstrate expression of RFC mRNA in embryos varying in age from E9.5 to E11.5. Light purple staining indicates the widespread nature of the RFC message. Regions of more intense staining include the forebrain, eye, hindbrain, mandible, heart, limb buds, somites, tail and yolk sac. Panel D depicts a control in situ hybridization performed with RFC sense riboprobes. Lack of background staining verifies that the signal in the experimental specimens is specific. Forebrain, FB; eye, E; hindbrain, HB; mandible, M; heart, H; limb buds, LB; somites, S; tail, T. Scale bar represents 50 μm.
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Related In: Results  -  Collection

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Figure 2: Analysis of RFC mRNA transcripts in E9.5-E11.5 mouse embryos. RFC mRNA was widely expressed; however, structures undergoing developmental changes requiring rapid cell division expressed the mRNAs most strongly. Panels A-C demonstrate expression of RFC mRNA in embryos varying in age from E9.5 to E11.5. Light purple staining indicates the widespread nature of the RFC message. Regions of more intense staining include the forebrain, eye, hindbrain, mandible, heart, limb buds, somites, tail and yolk sac. Panel D depicts a control in situ hybridization performed with RFC sense riboprobes. Lack of background staining verifies that the signal in the experimental specimens is specific. Forebrain, FB; eye, E; hindbrain, HB; mandible, M; heart, H; limb buds, LB; somites, S; tail, T. Scale bar represents 50 μm.
Mentions: Further analysis of RFC mRNA expression was carried out utilizing mouse embryos ranging from E9.0 to E11.5 (Figure 2). Three or more embryos were examined for each time point. RFC message was detectable in all tissues throughout the embryos, with the most intense levels of expression being confined to the forebrain, hindbrain, craniofacial region, eye (optic vesicles), mandible, heart, somites, and tail (Figure 2A). In E10.5 (Figure 2B) and E11.5 (Figure 2C) embryos, expression in the forebrain, hindbrain, craniofacial region, eye (optic vesicles), mandible, heart, somites, and tail were maintained, while additional expression became detectable in the developing limb buds. Faint signal was also visible in the yolk sac (data not shown). Negative control experiments with sense riboprobes for RFC resulted in minimal background staining (Figure 2D).

Bottom Line: Though reduced-folate carrier (RFC) is one of the major proteins mediating folate transport, knowledge of the developmental expression of RFC is lacking.Clinical studies show a statistical decrease in the number of neural tube defects, craniofacial abnormalities, cardiovascular defects and limb abnormalities detected in offspring of female patients given supplementary folate during pregnancy.These findings suggest that rapidly dividing cells in the developing neural tube, craniofacial region, limb buds and heart may be particularly susceptible to folate deficiency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, USA. oxmandm@yahoo.com

ABSTRACT

Background: Folate is essential for cellular proliferation and tissue regeneration. As mammalian cells cannot synthesize folates de novo, tightly regulated cellular uptake processes have evolved to sustain sufficient levels of intracellular tetrahydrofolate cofactors to support biosynthesis of purines, pyrimidines, and some amino acids (serine, methionine). Though reduced-folate carrier (RFC) is one of the major proteins mediating folate transport, knowledge of the developmental expression of RFC is lacking. We utilized in situ hybridization and immunolocalization to determine the developmental distribution of RFC message and protein, respectively.

Results: In the mouse, RFC transcripts and protein are expressed in the E10.0 placenta and yolk sac. In the E9.0 to E11.5 mouse embryo RFC is widely detectable, with intense signal localized to cell populations in the neural tube, craniofacial region, limb buds and heart. During early development, RFC is expressed throughout the eye, but by E12.5, RFC protein becomes localized to the retinal pigment epithelium (RPE).

Conclusions: Clinical studies show a statistical decrease in the number of neural tube defects, craniofacial abnormalities, cardiovascular defects and limb abnormalities detected in offspring of female patients given supplementary folate during pregnancy. The mechanism, however, by which folate supplementation ameliorates the occurrence of developmental defects is unclear. The present work demonstrates that RFC is present in placenta and yolk sac and provides the first evidence that it is expressed in the neural tube, craniofacial region, limb buds and heart during organogenesis. These findings suggest that rapidly dividing cells in the developing neural tube, craniofacial region, limb buds and heart may be particularly susceptible to folate deficiency.

Show MeSH
Related in: MedlinePlus