Tissue-specific placental mosaicism for autosomal trisomies in spontaneous human abortuses: mechanisms of formation and phenotypic effects]

The frequencies of autosomal trisomies in extraembryonic human tissues were estimated in the cases of different abnormalities of prenatal development, from the confined placental mosaicism (CPM) with either relatively normal embryogenesis or restricted intrauterine growth to spontaneous abortion. A tissue-specific compartmentalization was found to be characteristic of cell lines with trisomies for individual autosomes. Analysis of various phenotypical effects of chromosomal aberrations associated with mosaicism is necessarily required to understand the mechanisms and factors responsible for tissue chromosomal mosaicism. Based on analysis of the cell karyotype during prenatal diagnosing of chromosome aberrations in tissues of both extraembryonic and embryonic origin, in 1996, Wolstenholme proposed a model of CPM for individual chromosomes. According to the model, the distribution of cell lines with autosomal trisomies between extraembryonic tissues depends on the ratio between meiotic and mitotic mutations early in embryonic development. However, the model cannot be used to study tissue chromosomal mosaicism in spontaneous abortions, because little information is available on cell karyotype in embryonic tissues themselves after intrauterine fetal death. In this work, a model of tissue-specific chromosomal mosaicism was suggested based on the data on cell karyotype determined in extraembryonic tissues alone, which can be helpful in evaluating the contribution of tissue chromosomal differences into the etiology of early intrauterine death. Along with the experimental evidence, comparative analysis of the two models indicated that the meiotic chromosome nondisjunction plays the major role in trisomy formation and the resultant spontaneous arrest of embryonic development. Other factors responsible for tissue-specific distribution of chromosomal aberrations are also discussed. These are differences in cell proliferative activity, as well as changes in compartmentalization and migration of cells with abnormal karyotypes.     

Tissue-Specific Placental Mosaicism for Autosomal Trisomies in Human Spontaneous Abortuses: Mechanisms of Formation and Phenotypical Effects

The frequencies of autosomal trisomies in extraembryonic human tissues were estimated in the cases of different abnormalities of prenatal development, from the confined placental mosaicism (CPM) with either relatively normal embryogenesis or restricted intrauterine growth to spontaneous abortion. A tissue-specific compartmentalization was found to be characteristic of cell lines with trisomies for individual autosomes. Analysis of various phenotypical effects of chromosomal aberrations associated with mosaicism is necessarily required to understand the mechanisms and factors responsible for tissue chromosomal mosaicism. Based on analysis of the cell karyotype during prenatal diagnosing of chromosome aberrations in tissues of both extraembryonic and embryonic origin, in 1996, Wolstenholme proposed a model of CPM for individual chromosomes. According to the model, the distribution of cell lines with autosomal trisomies between extraembryonic tissues depends on the ratio between meiotic and mitotic mutations early in embryonic development. However, the model cannot be used to study tissue chromosomal mosaicism in spontaneous abortions, because little information is available on cell karyotype in embryonic tissues themselves after intrauterine fetal death. In this work, a model of tissue-specific chromosomal mosaicism was suggested based on the data on cell karyotype determined in extraembryonic tissues alone, which can be helpful in evaluating the contribution of tissue chromosomal differences into the etiology of early intrauterine death. Along with the experimental evidence, comparative analysis of the two models indicated that the meiotic chromosome nondisjunction plays the major role in trisomy formation and the resultant spontaneous arrest of embryonic development. Other factors responsible for tissue-specific distribution of chromosomal aberrations are also discussed. These are differences in cell proliferative activity, as well as changes in compartmentalization and migration of cells with abnormal karyotypes.     

Comparative analysis of mRNA isoform expression in cardiac hypertrophy and development reveals multiple post-transcriptional regulatory modules

Cardiac hypertrophy is enlargement of the heart in response to physiological or pathological stimuli, chiefly involving growth of myocytes in size rather than in number. Previous studies have shown that the expression pattern of a group of genes in hypertrophied heart induced by pressure overload resembles that at the embryonic stage of heart development, a phenomenon known as activation of the "fetal gene program". Here, using a genome-wide approach we systematically defined genes and pathways regulated in short- and long-term cardiac hypertrophy conditions using mice with transverse aortic constriction (TAC), and compared them with those regulated at different stages of embryonic and postnatal development. In addition, exon-level analysis revealed widespread mRNA isoform changes during cardiac hypertrophy resulting from alternative usage of terminal or internal exons, some of which are also developmentally regulated and may be attributable to decreased expression of Fox-1 protein in cardiac hypertrophy. Genes with functions in certain pathways, such as cell adhesion and cell morphology, are more likely to be regulated by alternative splicing. Moreover, we found 3'UTRs of mRNAs were generally shortened through alternative cleavage and polyadenylation in hypertrophy, and microRNA target genes were generally de-repressed, suggesting coordinated mechanisms to increase mRNA stability and protein production during hypertrophy. Taken together, our results comprehensively delineated gene and mRNA isoform regulation events in cardiac hypertrophy and revealed their relations to those in development, and suggested that modulation of mRNA isoform expression plays an importance role in heart remodeling under pressure overload.     

Invited review: Pre- and postnatal adipose tissue development in farm animals: from stem cells to adipocyte physiology

Both white and brown adipose tissues are recognized to be differently involved in energy metabolism and are also able to secrete a variety of factors called adipokines that are involved in a wide range of physiological and metabolic functions. Brown adipose tissue is predominant around birth, except in pigs. Irrespective of species, white adipose tissue has a large capacity to expand postnatally and is able to adapt to a variety of factors. The aim of this review is to update the cellular and molecular mechanisms associated with pre- and postnatal adipose tissue development with a special focus on pigs and ruminants. In contrast to other tissues, the embryonic origin of adipose cells remains the subject of debate. Adipose cells arise from the recruitment of specific multipotent stem cells/progenitors named adipose tissue-derived stromal cells. Recent studies have highlighted the existence of a variety of those cells being able to differentiate into white, brown or brown-like/beige adipocytes. After commitment to the adipocyte lineage, progenitors undergo large changes in the expression of many genes involved in cell cycle arrest, lipid accumulation and secretory functions. Early nutrition can affect these processes during fetal and perinatal periods and can also influence or pre-determinate later growth of adipose tissue. How these changes may be related to adipose tissue functional maturity around birth and can influence newborn survival is discussed. Altogether, a better knowledge of fetal and postnatal adipose tissue development is important for various aspects of animal production, including neonatal survival, postnatal growth efficiency and health.     

The role of cardiac resident macrophage in cardiac aging

Advancements in longevity research have provided insights into the impact of cardiac aging on the structural and functional aspects of the heart. Notable changes include the gradual remodeling of the myocardium, the occurrence of left ventricular hypertrophy, and the decline in both systolic and diastolic functions. Macrophages, a type of immune cell, play a pivotal role in innate immunity by serving as vigilant agents against pathogens, facilitating wound healing, and orchestrating the development of targeted acquired immune responses. Distinct subsets of macrophages are present within the cardiac tissue and demonstrate varied functions in response to myocardial injury. The differentiation of cardiac macrophages according to their developmental origin has proven to be a valuable strategy in identifying reparative macrophage populations, which originate from embryonic cells and reside within the tissue, as well as inflammatory macrophages, which are derived from monocytes and recruited to the heart. These subsets of macrophages possess unique characteristics and perform distinct functions. This review aims to summarize the current understanding of the roles and phenotypes of cardiac macrophages in various conditions, including the steady state, aging, and other pathological conditions. Additionally, it will highlight areas that require further investigation to expand our knowledge in this field.     

Hormonal regulation of fetal growth

Fetal growth is a complex process depending on the genetics of the fetus, the availability of nutrients and oxygen to the fetus, maternal nutrition and various growth factors and hormones of maternal, fetal and placental origin. Hormones play a central role in regulating fetal growth and development. They act as maturational and nutritional signals in utero and control tissue development and differentiation according to the prevailing environmental conditions in the fetus. The insulin-like growth factor (IGF) system, and IGF-I and IGF-II in particular, plays a critical role in fetal and placental growth throughout gestation. Disruption of the IGF1, IGF2 or IGF1R gene retards fetal growth, whereas disruption of IGF2R or overexpression of IGF2 enhances fetal growth. IGF-I stimulates fetal growth when nutrients are available, thereby ensuring that fetal growth is appropriate for the nutrient supply. The production of IGF-I is particularly sensitive to undernutrition. IGF-II plays a key role in placental growth and nutrient transfer. Several key hormone genes involved in embryonic and fetal growth are imprinted. Disruption of this imprinting causes disorders involving growth defects, such as Beckwith-Wiedemann syndrome, which is associated with fetal overgrowth, or Silver-Russell syndrome, which is associated with intrauterine growth retardation. Optimal fetal growth is essential for perinatal survival and has long-term consequences extending into adulthood. Given the high incidence of intrauterine growth retardation and the high risk of metabolic and cardiovascular complications in later life, further clinical and basic research is needed to develop accurate early diagnosis of aberrant fetal growth and novel therapeutic strategies.     

A model of the structural and functional development of the normal human fetal left ventricle based on a global growth law

The purpose of this research is to study the growth of the normal human left ventricle (LV) during the fetal period from 14 to 40 weeks of gestation. A new constitutive law for the active myocardium describing the mechanical properties of the active muscle during the whole cardiac cycle has been proposed. The LV model is a thick-walled, incompressible, hyperelastic cylinder, with families of helicoidal fibers running on cylindrical surfaces [1]. Based on the works of Lin and Taber [2] done on the embryonic chick heart, we use for the human fetal heart a growth law in which the growth rate depends on the wall stresses. The parameters of the growth law are adapted to agree with sizes and volumes inferred from two dimensional ultrasound measurements performed on 18 human fetuses.Then calculations are performed to extrapolate the cardiac performance during normal growth of the fetal LV. The results presented support the idea that a growth law in which the growth rate depends linearly on the mean wall stresses averaged through the space and during whole cardiac cycle, is adapted to the normal human fetal LV development.     

Nontrophoblastic placental tumors

The aim of the study was to investigate potential influence of placental tumors on fetal outcome. The study comprised 10 cases of placental tumors. The analysis included the sonographic assessment of the tumor, signs of fetal anemia, as well as signs of hemodynamic disturbances or heart failure, and intrauterine treatment. The fetal hemodynamic was examined on the basis of Doppler blood flow in the umbilical artery and vein, middle cerebral artery, and ductus venous. The evaluation of fetal heart included the measurement of heart size, blood flow through cardiac valves and the assessment of fetal heart function based on cardiovascular score. The fetal outcome was also assessed according to birthweight, gestational age at delivery, pH, Ap score at 5th minute, abnormal neurological development and the need of intrauterine therapy. Ten cases of placental tumors were prenatally detected from 1999 to 2011. Among them 7 cases of hypoechogenic, non-vascularized cysts were identified and these neither effected the hemodynamics nor complicated fetal outcome. The vascularized tumors (chorioangioma) were the cause of severe anemia and hemodynamic disturbances and these led to fetal cardiac heart failure. In all cases of vascularized tumors from 2-3 intrauterine transfusion were performed. Rich vascularized tumors (chorioangioma) may cause hemodynamic disturbances and fetal heart failure. This may require intrauterine treatment and may result in abnormal fetal outcome and neurological development.     

A developmental study of the abnormal expression of alpha-cardiac and alpha-skeletal actins in the striated muscle of a mutant mouse

BALB/c mice possess a 5' duplication of the alpha-cardiac actin gene which is associated with abnormal levels of alpha-cardiac and alpha-skeletal actin mRNAs in adult cardiac tissue. This mutation therefore provides a potential tool for the study of the inter-relationship between the striated muscle actins. We have examined the expression of this actin gene pair throughout the development of skeletal and cardiac muscle in BALB/c mice. During embryonic and fetal development, the expression of these two genes is indistinguishable from that in normal mice, as determined by in situ hybridization. A quantitative postnatal study demonstrates that in the hearts of normal mice the level of alpha-cardiac actin mRNA declines, whereas that of alpha-skeletal actin increases. In mutant mice, these trends are exaggerated so that whereas normal mice have 95.8% alpha-cardiac mRNA and 4.2% alpha-skeletal mRNA in the adult heart, BALB/c mice have 52.4 and 47.6% of these mRNAs, respectively. This difference is also reflected at the protein level. In developing skeletal muscle, the expression of these genes follows kinetics similar to that observed in the heart with a decrease in the relative level of alpha-cardiac mRNA as the muscle matures. Cardiac actin mRNA levels are again lower in the mutant mouse, but here the effect is less striking because skeletal actin is the predominant isoform. These results are discussed in the context of the interaction between this actin gene pair in developing and adult striated muscle.     

Dynamic changes in DNA methylation during embryonic and postnatal development of an altricial wild bird

DNA methylation could shape phenotypic responses to environmental cues and underlie developmental plasticity. Environmentally induced changes in DNA methylation during development can give rise to stable phenotypic traits and thus affect fitness. In the laboratory, it has been shown that the vertebrate methylome undergoes dynamic reprogramming during development, creating a critical window for environmentally induced epigenetic modifications. Studies of DNA methylation in the wild are lacking, yet are essential for understanding how genes and the environment interact to affect phenotypic development and ultimately fitness. Furthermore, our knowledge of the establishment of methylation patterns during development in birds is limited. We quantified genome‐wide DNA methylation at various stages of embryonic and postnatal development in an altricial passerine bird, the great tit Parus major. While, there was no change in global DNA methylation in embryonic tissue during the second half of embryonic development, a twofold increase in DNA methylation in blood occurred between 6 and 15 days posthatch. Though not directly comparable, DNA methylation levels were higher in the blood of nestlings compared with embryonic tissue at any stage of prenatal development. This provides the first evidence that DNA methylation undergoes global change during development in a wild bird, supporting the hypothesis that methylation mediates phenotypic development. Furthermore, the plasticity of DNA methylation demonstrated during late postnatal development, in the present study, suggests a wide window during which DNA methylation could be sensitive to environmental influences. This is particularly important for our understanding of the mechanisms by which early‐life conditions influence later‐life performance. While, we found no evidence for differences in genome‐wide methylation in relation to habitat of origin, environmental variation is likely to be an important driver of variation in methylation at specific loci.     

心脏发育过程中的信号调控机制研究

我国是出生缺陷高发国家,其中先天性心脏病在各类出生缺陷中居于首位,严重地影响我国的人口素质.同样,后天性心脏血管疾病（心血管疾病）也是影响国民健康和社会发展的主要疾病.近年来研究表明,所谓＂后天性＂心脏血管疾病虽然大多不在胚胎期表现出功能异常,但遗传因素在发病过程中也起关键作用,因此,＂后天性＂心血管疾病也有其发育生物学基础.在一些心血管疾病中,胚胎发育基因如ANF和β-MHC的表达说明胚胎发育的某些机制参与了发病过程.由于出生缺陷和心血管疾病的防治是我国公共卫生和社会发展中亟待解决的重大健康问题,了解心血管系统正常发生发育规律和机制及发病机理并在此基础上建立新的防治策略和防治措施是生命科学需要解决的重大基础科学问题.本文主要综述了目前模式动物,特别是小鼠心脏发育过程中的信号传导调控机制的研究现状及进展.     

Anatomical distribution of glycoprotein 93 (gp93) on nerve fibers during rat brain development.

 Recent studies have implicated glycoconjugates on the membrane of growth cones as the necessary markers and intermediaries for axonal recognition, axonal motility, and pathway development. One such glycoconjugate, glycoprotein 93 (gp93), has been characterized, but the relative distribution of gp93 has yet to be described for the embryonic brain. In this study, the anatomical distribution of gp93 has been analyzed at embryonic day 15 (E15) and E18, and on postnatal day 3 in the rat by using a polyclonal gp93 antibody. Furthermore, fetal brain tissue transplanted into the adult rat eye has been tested for gp93 immunoreactivity, since central noradrenergic neurons in brainstem transplants are known to provide a continuous source of growing axons, even in adult tissue. In general, a greater abundance of gp93 immunoreactivity is apparent in the earlier embryonic stages (E15 and E18), whereas less is seen in the postnatal brain. The regions showing unique dispersal patterns of gp93 are the neuroepithelium, cerebral cortex, septo-hippocampal pathways, brainstem, and midbrain. This study has therefore focused on these areas and found implications for gp93 distribution appearing in the early development of specific neuronal pathways. Moreover, axons stain densely for gp93 within brain tissue transplants. The presence of gp93 in areas of extensive axonal outgrowth in the normal brain and in transplants suggests that this antibody is used as an early marker for axonal growth. Furthermore, gp93 might be used to map normal development in order to improve our understanding of diseases arising from developmental abnormalities. Received: 17 June 1998 / Accepted: 23 November 1998     

Polyploidization of transplanted cardiac myocytes

Pieces of cardiac ventricular tissue of late embryonic or 1-day postnatal rats, implanted beneath the kidney capsule of adult syngeneic hosts, formed viable, beating transplants. these transplants were investigated over a 40-day postoperative course. In the transplants, cellular binucleation and nuclear polyploidization occurred according to the same schedule as in the heart in situ. The composition of the classes of myocytes was identical both in the hearts in situ and in transplants, but the number of non-diploid myocytes in the intact heart reached 90%, whereas in transplants it varied from 30 to 60%. In contrast to the heart in situ, myocytes in transplants grew feebly after the phase of polyploidization. From these data one can conclude that under conditions of transplantation the temporal sequence of cellular binucleation and nuclear polyploidization follows the normal course, but that a greater number of myocytes remain in a diploid state than is the case in the normal heart. The growth of cardiac myocytes seems to be related to their level of function.     

The right ventricle, outflow tract, and ventricular septum comprise a restricted expression domain within the secondary/anterior heart field

The vertebrate heart arises from the fusion of bilateral regions of anterior mesoderm to form a linear heart tube. Recent studies in mouse and chick have demonstrated that a second cardiac progenitor population, known as the anterior or secondary heart field, is progressively added to the heart at the time of cardiac looping. While it is clear that this second field contributes to the myocardium, its precise boundaries, other lineages derived from this population, and its contributions to the postnatal heart remain unclear. In this study, we used regulatory elements from the mouse mef2c gene to direct the expression of Cre recombinase exclusively in the anterior heart field and its derivatives in transgenic mice. By crossing these mice, termed mef2c-AHF-Cre, to Cre-dependent lacZ reporter mice, we generated a fate map of the embryonic, fetal, and postnatal heart. These studies show that the endothelial and myocardial components of the outflow tract, right ventricle, and ventricular septum are derivatives of mef2c-AHF-Cre expressing cells within the anterior heart field and its derivatives. These studies also show that the atria, epicardium, coronary vessels, and the majority of outflow tract smooth muscle are not derived from this anterior heart field population. Furthermore, a transgene marker specific for the anterior heart field is expressed in the common ventricular chamber in mef2c mutant mice, suggesting that the cardiac looping defect in these mice is not due to a failure in anterior heart field addition to the heart. Finally, the Cre transgenic mice described here will be a crucial tool for conditional gene inactivation exclusively in the anterior heart field and its derivatives.     

Impaired mitochondrial function in the preimplantation embryo perturbs fetal and placental development in the mouse

The preimplantation embryo is sensitive to its environment and, despite having some plasticity to adapt, environmental perturbations can impair embryo development, metabolic homeostasis, fetal and placental development, and offspring health. This study used an in vitro model of embryo culture with increasing mitochondrial inhibition to directly establish the effect of impaired mitochondrial function on embryonic, fetal, and placental development. Culture in the absence of the carbohydrate pyruvate significantly increased blastocyst glucose oxidation via glycolysis to maintain normal levels of ATP and tricarboxylic acid (TCA) cycle activity. This culture resulted in a significant reduction in blastocyst development, trophectoderm cell number, and respiration rate but, importantly, did not impair implantation rates or fetal and placental development. In contrast, increasing concentrations of the mitochondrial inhibitor amino-oxyacetate (AOA) impaired glycolysis, TCA cycle activity, respiration rate, and ATP production; incrementally reduced blastocyst development; and decreased blastocyst inner cell mass and trophectoderm cell numbers. Importantly, AOA did not affect implantation rates; however, 5 μM AOA significantly reduced placental growth but not fetal growth, increasing the fetal:placental weight ratio. Furthermore, 50 μM AOA significantly reduced both placental and fetal growth but not the fetal:placental weight ratio. Hence, this study demonstrates that a threshold of mitochondrial function is required for normal development, and despite developmental plasticity of the embryo, impaired mitochondrial function in the embryo affects subsequent fetal and placental growth. These results highlight the importance of mitochondrial function in regulating pre- and postimplantation development; however, the effect on offspring health remains unknown.     

Age-related characteristics of the electrical activity of the cardiac fibers in the human embryo

Transmembrane action potential and intercellular electric coupling have been studied in isolated heart during various stages of intrauterine growth of human embryos as well as in heart preparations of human adults. Formation of electrical properties of ventricular myocardium was slower than that of atrial fibres and was found to be fully completed in the first 14 weeks of intrauterine growth. Intercellular electrical coupling enhanced in the course of the embryonic development as indicated by a drop in the input resistance and an increase in electronic length.