Fetus

About: Fetus is a research topic. Over the lifetime, 21567 publications have been published within this topic receiving 646380 citations. The topic is also known as: foetus & fœtus.

MicroRNA-15a and -16-1 act via MYB to elevate fetal hemoglobin expression in human trisomy 13

Abstract: Many human aneuploidy syndromes have unique phenotypic consequences, but in most instances it is unclear whether these phenotypes are attributable to alterations in the dosage of specific genes. In human trisomy 13, there is delayed switching and persistence of fetal hemoglobin (HbF) and elevation of embryonic hemoglobin in newborns. Using partial trisomy cases, we mapped this trait to chromosomal band 13q14; by examining the genes in this region, two microRNAs, miR-15a and -16-1, appear as top candidates for the elevated HbF levels. Indeed, increased expression of these microRNAs in primary human erythroid progenitor cells results in elevated fetal and embryonic hemoglobin gene expression. Moreover, we show that a direct target of these microRNAs, MYB, plays an important role in silencing the fetal and embryonic hemoglobin genes. Thus we demonstrate how the developmental regulation of a clinically important human trait can be better understood through the genetic and functional study of aneuploidy syndromes and suggest that miR-15a, -16-1, and MYB may be important therapeutic targets to increase HbF levels in patients with sickle cell disease and β-thalassemia.

Prenatal leptin production: evidence that fetal adipose tissue produces leptin.

Abstract: In the adult, circulating leptin is highly correlated to adipose tissue mass. Whether such a relationship exists prenatally is unknown, because the actual source of fetal leptin has not been determined. In the present study, we have assessed the placental contribution to fetal and maternal circulating leptin concentrations and determined whether fetal adipose tissue produces leptin. The rate of leptin production in dually perfused human placenta was 0.036 ng/min.g. Ninety-five percent of the leptin released was delivered into the maternal circulation, vs. only 5% on the fetal side. Leptin messenger RNA and protein were detected in adipose tissue biopsies of 20-38 week human fetuses. However, leptin concentration was twice lower in fetal (0.22 +/- 0.11 ng/mg protein, n = 6) than in adult (0.49 +/- 0.12 ng/mg protein, n = 8) adipose tissue. Umbilical leptin levels closely reflected ponderal index at birth over a wide range of birth weights (1.6--4.1 kg). In sharp contrast, maternal and placental leptin concentrations were increased in pregnancies associated with fetal growth retardation. We conclude that umbilical leptin levels are independent of placental leptin production and can be taken as a marker of fat mass in human fetuses. By contrast, placental leptin production makes a substantial contribution to maternal circulating leptin levels during pregnancy.

Effect of placental function on fatty acid requirements during pregnancy.

Abstract: The fetus has an absolute requirement for the n-3/n-6 fatty acids and docosahexaenoic acid (22:6 n-3; DHA) in particular is essential for the development of the brain and retina. Most of the fat deposition in the fetus occurs in the last 10 weeks of pregnancy. The likely rate of DHA utilisation during late pregnancy cannot be met from dietary sources alone in a significant proportion of mothers. De novo synthesis makes up some of the shortfall but the available evidence suggests that the maternal adipose tissue makes a significant contribution to placental transport to the fetus. The placenta plays a crucial role in mobilising the maternal adipose tissue and actively concentrating and channelling the important n-3/n-6 fatty acids to the fetus via multiple mechanisms including selective uptake by the syncytiotrophoblast, intracellular metabolic channelling, and selective export to the fetal circulation. These mechanisms protect the fetus against low long-chain polyunsaturated fatty acid (LCPUFA) intakes in the last trimester of pregnancy and have the effect of reducing the maternal dietary requirement for preformed DHA at this time. As a result of these adaptations, small changes in the composition of the habitual maternal diet before pregnancy are likely to be more effective in improving LCPUFA delivery to the fetus than large dietary changes in late pregnancy. There is little evidence that DHA intake/status in the second half of pregnancy affects visual and cognitive function in the offspring, but more studies are needed, particularly in children born to vegetarian and vegan and mothers who may have very low intakes of DHA.