Maternal dietary creatine supplementation does not alter the capacity for creatine synthesis in the newborn spiny mouse.

We have previously reported that maternal creatine supplementation protects the neonate from hypoxic injury. Here, we investigated whether maternal creatine supplementation altered expression of the creatine synthesis enzymes (arginine:glycine amidinotransferase [AGAT], guanidinoaceteate methyltransferase [GAMT]) and the creatine transporter (solute carrier family 6 [neurotransmitter transporter, creatine] member 8: SLC6A8) in the term offspring. Pregnant spiny mice were fed a 5% creatine monohydrate diet from midgestation (day 20) to term (39 days). Placentas and neonatal kidney, liver, heart, and brain collected at 24 hours of age underwent quantitative polymerase chain reaction and Western blot analysis. Maternal creatine had no effect on the expression of AGAT and GAMT in neonatal kidney and liver, but mRNA expression of AGAT in brain tissues was significantly decreased in both male and female neonates born to mothers who were fed the creatine diet. SLC6A8 expression was not affected by maternal dietary creatine loading in any tissues. Maternal dietary creatine supplementation from midgestation in the spiny mouse did not alter the capacity for creatine synthesis or transport.

Synthetic glucocorticoid dexamethasone inhibits branching morphogenesis in the spiny mouse placenta.

High levels of maternal glucocorticoids during pregnancy can alter the developmental trajectory of some fetal organs. These perturbations are often more profound for the male fetus and have been attributed to passage of glucocorticoids through the placenta. However, the effect of excess glucocorticoids on the placenta itself is less well understood and, particularly, whether this is affected by fetal sex. Expression of genes involved in placental patterning, apoptosis, and nutrient transfer, along with their response to maternal administration of dexamethasone (DEX), has previously been shown to be dependent on fetal sex in the spiny mouse. Here we describe the placental spatiotemporal expression of genes important for branching morphogenesis (WNT4, BMP4, GREM1, TGFB1, KDR, VEGFA). Furthermore, we report that compared to TGFB1 expression in the female labyrinth, expression of TGFB1 in the male labyrinth was higher, and earlier peaks in expression levels of VEGFA (Day 19 placenta [male] vs. Day 37 labyrinth [female]) and KDR (Day 19 placenta [male] vs. Day 20 labyrinth [female]) were observed. Administration of DEX to pregnant dams for 60 h commencing at mid-gestation caused significantly different, sex-related changes in expression of genes that were constitutively different before DEX treatment (e.g., KDR, TGFB1) and those that were not (i.e., VEGFA, WNT4). Similarly, some genes which displayed similar expression profiles across gestation for both sexes also showed similar responses to DEX (e.g., BMP4), while others did not (i.e., GREM1). These results showed that constitutive and glucocorticoid-induced changes in expression of genes involved in branching morphogenesis may be influenced by fetal/placental sex and that fundamental differences exist between a male and female placenta.

The placental response to excess maternal glucocorticoid exposure differs between the male and female conceptus in spiny mice.

The placenta is the intermediary between the mother and fetus, and its primary role is to provide for the appropriate growth of the fetus. A suboptimal in utero environment has been shown to differentially affect the health of offspring, depending on their sex. Here we show that excess maternal glucocorticoids administered in midgestation (Day 20, 0.5 gestation in the spiny mouse) for 60 h, have persisting effects on the placenta that differ by fetal sex, placental region, and time after glucocorticoid exposure. Dexamethasone (DEX) exposure altered placental structure and mRNA expression from male and female fetuses both immediately (Day 23) and 2 wk posttreatment (Day 37). The immediate consequences (Day 23) of DEX were similar between males and females, with reductions in the expression of IGF1, IGF1R, and SLC2A1 in the placenta. However, by Day 37, the transcriptional and structural response of the placenta was dependent on the sex of the fetus, with placentas of male fetuses having an increase in GCM1 expression, a decrease in SLC2A1 expression, and an increase in the amount of maternal blood sinusoids in the DEX-exposed placenta. Female placentas, on the other hand, showed increased SLC2A1 and MAP2K1 expression and a decrease in the amount of maternal blood sinusoids in response to DEX exposure. We have shown that the effect of a brief glucocorticoid exposure at midgestation has persisting effects on the placenta, and this is likely to have ongoing and dynamic effects on fetal development that differ for a male and female fetus.

Zebrafish granulocyte colony-stimulating factor receptor signaling promotes myelopoiesis and myeloid cell migration.

Granulocyte colony-stimulating factor receptor (GCSFR) signaling participates in the production of neutrophilic granulocytes during normal hematopoietic development, with a particularly important role during emergency hematopoiesis. This study describes the characterization of the zebrafish gcsf and gcsfr genes, which showed broad conservation and similar regulation to their mammalian counterparts. Morpholino-mediated knockdown of gcsfr and overexpression of gcsf revealed the presence of an anterior population of myeloid cells during primitive hematopoiesis that was dependent on GCSF/GCSFR for development and migration. This contrasted with a posterior domain that was largely independent of this pathway. Definitive myelopoiesis was also partially dependent on a functional GCSF/GCSFR pathway. Injection of bacterial lipopolysaccharide elicited significant induction of gcsf expression and emergency production of myeloid cells, which was abrogated by gcsfr knockdown. Collectively, these data demonstrate GCSF/GCSFR to be a conserved signaling system for facilitating the production of multiple myeloid cell lineages in both homeostatic and emergency conditions, as well as for early myeloid cell migration, establishing a useful experimental platform for further dissection of this pathway.