Embryonic development in the reduced folate carrier knockout mouse is modulated by maternal folate supplementation.
BACKGROUND
The reduced folate carrier (RFC1) is a ubiquitously expressed integral membrane protein that mediates delivery of 5-methyltetrahydrofolate into mammalian cells. In this study, embryonic/fetal development is characterized in an RFC1 knockout mouse model in which pregnant dams receive different levels of folate supplementation.


METHODS
RFC1(+/-) males were mated to RFC1(+/-) females, and pregnant dams were treated with vehicle (control) or folic acid (25 or 50 mg/kg) by daily subcutaneous injection (0.1 mL/10 g bwt), beginning on E0.5 and continuing throughout gestation until the time of sacrifice.


RESULTS
Without maternal folate supplementation, RFC1 nullizygous embryos die shortly postimplantation. Supplementation of pregnant dams with 25 mg/kg/day folic acid prolongs survival of mutant embryos until E9.5-E10.5, but they are developmentally delayed relative to wild-type littermates, display a marked absence of erythropoiesis, severe neural tube and limb bud defects, and failure of chorioallantoic fusion. Fgfr2 protein levels are significantly reduced or absent in the extraembryonic membranes of RFC1 nullizygous embryos. Maternal folate supplementation with 50 mg/kg/day results in survival of 22% of RFC1 mutants to E18.5, but they develop with multiple malformations of the eyelids, lungs, heart, and skin.


CONCLUSIONS
High doses of daily maternal folate supplementation during embryonic/fetal development are necessary for early postimplantation embryonic viability of RFC1 nullizygous embryos, and play a critical role in chorioallantoic fusion, erythropoiesis, and proper development of the neural tube, limbs, lungs, heart, and skin.
Gelineau-van Waes
Janee
J
Department of Genetics, Cell Biology & Anatomy, University of Nebraska Medical Center, Omaha, Nebraska 68198-5455, USA. jvanwaes@unmc.edu
Heller
Steven
S
Bauer
Linda K
LK
Wilberding
Justin
J
Maddox
Joyce R
JR
Aleman
Francisco
F
Rosenquist
Thomas H
TH
Finnell
Richard H
RH
D000015:Abnormalities, Multiple / Q000453:epidemiology / Q000209:etiology; D000818:Animals; D049033:Chorioallantoic Membrane / Q000187:drug effects / Q000502:physiology; D019587:Dietary Supplements; D004622:Embryo, Mammalian / Q000187:drug effects* / Q000502:physiology; D047108:Embryonic Development / Q000187:drug effects*; D004920:Erythropoiesis / Q000187:drug effects / Q000502:physiology; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D005494:Folic Acid Deficiency; D026901:Membrane Transport Proteins / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D011247:Pregnancy; D058978:Reduced Folate Carrier Protein
D026901:Membrane Transport Proteins; D058978:Reduced Folate Carrier Protein; C548700:Slc19a1 protein, mouse; D005492:Folic Acid