Three-dimensional magnetic resonance imaging of fetal head molding and brain shape changes during the second stage of labor.

To demonstrate and describe fetal head molding and brain shape changes during delivery, we used three-dimensional (3D) magnetic resonance imaging (MRI) and 3D finite element mesh reconstructions to compare the fetal head between prelabor and the second stage of labor. A total of 27 pregnant women were examined with 3D MRI sequences before going into labor using a 1 Tesla open field MRI. Seven of these patients subsequently had another set of 3D MRI sequences during the second stage of labor. Volumes of 2D images were transformed into finite element 3D reconstructions. Polygonal meshes for each part of the fetal body were used to study fetal head molding and brain shape changes. Varying degrees of fetal head molding were present in the infants of all seven patients studied during the second phase of labor compared with the images acquired before birth. The cranial deformation, however, was no longer observed after birth in five out of the seven newborns, whose post-natal cranial parameters were identical to those measured before delivery. The changing shape of the fetal brain following the molding process and constraints on the brain tissue were observed in all the fetuses. Of the three fetuses presenting the greatest molding of the skull bones and brain shape deformation, two were delivered by cesarean-section (one after a forceps failure and one for engagement default), while the fetus presenting with the greatest skull molding and brain shape deformation was born physiologically. This study demonstrates the value of 3D MRI study with 3D finite element mesh reconstruction during the second stage of labor to reveal how the fetal brain is impacted by the molding of the cranial bones. Fetal head molding was systematically observed when the fetal head was engaged between the superior pelvic strait and the middle brim.

Arginine methylation provides epigenetic transcription memory for retinoid-induced differentiation in myeloid cells.

Cellular differentiation is governed by changes in gene expression, but at the same time, a cell's identity needs to be maintained through multiple cell divisions during maturation. In myeloid cell lines, retinoids induce gene expression and a well-characterized two-step lineage-specific differentiation. To identify mechanisms that contribute to cellular transcriptional memory, we analyzed the epigenetic changes taking place on regulatory regions of tissue transglutaminase, a gene whose expression is tightly linked to retinoid-induced differentiation. Here we report that the induction of an intermediary or "primed" state of myeloid differentiation is associated with increased H4 arginine 3 and decreased H3 lysine 4 methylation. These modifications occur before transcription and appear to prime the chromatin for subsequent hormone-regulated transcription. Moreover, inhibition of methyltransferase activity, pre-acetylation, or activation of the enzyme PAD4 attenuated retinoid-regulated gene expression, while overexpression of PRMT1, a methyltransferase, enhanced retinoid responsiveness. Taken together, our results suggest that H4 arginine 3 methylation is a bona fide positive epigenetic marker and regulator of transcriptional responsiveness as well as a signal integration mechanism during cell differentiation and, as such, may provide epigenetic memory.

Genome-wide localization of histone 4 arginine 3 methylation in a differentiation primed myeloid leukemia cell line.

Methylation of arginine residues in proteins is involved in modulation of various protein-protein interactions. At the chromatin level H4R3 methylation provides a signal integration step during myeloid differentiation. In order to globally characterize the role of arginine methylation in signal integration and developmental processes we decided to map genomic loci marked by protein arginine methyl transferase 1 (PRMT1) via histone H4 arginine 3 methylation. For this, we used the myeloid leukemia cell line, HL60, which is known to differentiate along the monocyte/macrophage or granulocyte lineage. We used chromatin immunoprecipitation with an antibody specific for the H4 arginine 3 methyl epitope followed by cloning to isolate genomic loci marked by this modification. After sequencing and in silico analysis we found that all of the genomic hits identified were intronic or within 5 kb of 5' ends of specific genes. The locations identified were enriched in conserved transcription factor binding sites of POU2F1, MEF-2 and FOXL1 factors. A significant number of the genes in the proximity of the identified genomic loci are involved in signaling pathways and developmental processes including immune response of myeloid cells.

Quantification of elasticity changes in the myometrium during labor using Supersonic Shear Imaging: a feasibility study.

Very little is known about the myometrium's physiology in terms of its elasticity but shear wave elastography could be an efficient tool to better understand it. This could considerably help the prevention of difficult births, the consequences of which are tremendous for neonate morbidity and pathologies. The purpose of this paper is to show the feasibility of the in vivo monitoring of myometrial stiffness changes in contraction and relaxation during pregnancy. In this study, Supersonic Shear Wave Imaging, a real-time and quantitative imaging technique that has been proven efficient for the investigation of tissue elasticity, was used to quantify the uterus shear-wave speed and stiffness in 6 patients, through the abdomen, using an 8-MHz linear ultrasound probe. Changes in shear wave speed were tracked in real time during the uterine contraction and were well correlated with the uterine pressure, which is currently considered to be a gold standard. These results open a new way to better understand the myometrium contraction during labour.