Lymphatic development

The lymphatic system is essential for fluid homeostasis, immune responses, and fat absorption, and is involved in many pathological processes, including tumor metastasis and lymphedema. Despite its importance, progress in understanding the origins and early development of this system has been hampered by lack of defining molecular markers and difficulties in observing lymphatic cells in vivo and performing genetic and experimental manipulation of the lymphatic system. Recent identification of new molecular markers, new genes with important functional roles in lymphatic development, and new experimental models for studying lymphangiogenesis has begun to yield important insights into the emergence and assembly of this important tissue. This review focuses on the mechanisms regulating development of the lymphatic vasculature during embryogenesis. Birth Defects Research (Part C) 87:222–231, 2009. © 2009 Wiley‐Liss, Inc.     

Gene regulatory networks in embryonic stem cells and brain development

Embryonic stem cells (ESCs) are endowed with the ability to generate multiple cell lineages and carry great therapeutic potentials in regenerative medicine. Future application of ESCs in human health and diseases will embark on the delineation of molecular mechanisms that define the biology of ESCs. Here, we discuss how the finite ESC components mediate the intriguing task of brain development and exhibit biomedical potentials to cure diverse neurological disorders. Birth Defects Research (Part C) 87:182–191, 2009. © 2009 Wiley‐Liss, Inc.     

Saving hearts through basic research

Despite the recent advances in molecular medicine and health care, cardiovascular diseases are still the leading cause of morbidity and mortality throughout the world. In 2006, nearly every other death in Germany resulted from disease of the circulatory system, and congenital heart diseases are thought to account for a high number of stillbirths and spontaneous abortions. Remarkable progress in basic research over the past decades has improved our understanding of the molecular mechanisms that govern a cardiac fate and has helped to establish cell‐based therapeutic approaches to improve the course of cardiovascular diseases. Birth Defects Research (Part C) 87:273–283, 2009. © 2009 Wiley‐Liss, Inc.     

Role of environmental factors in axial skeletal dysmorphogenesis

Approximately 1 in 1000 live births is afflicted with an axial skeletal defect. Although many of the known human teratogens can produce axial skeletal defects, the etiology of over half of the observed defects is unknown. The high morbidity associated with these defects demands that we continue to elucidate the mechanisms of axial skeletal teratogens. Advances in cell and molecular biology with respect to normal development and somitogenesis and the pathogenesis and mechanisms of teratogenesis are occurring at a tremendous rate. This allows teratologists and developmental toxicologists the opportunity to revisit old problems with new tools to elucidate common mechanisms between various environmental insults and discover novel targets that aid in the understanding of normal and pathogenic development of the spine. Birth Defects Research (Part C) 90:118–132, 2010. © 2010 Wiley‐Liss, Inc.     

The effects of nicotine on human fetal development

Maternal smoking during pregnancy continues to represent a major public health concern. Nicotine is extremely harmful to the developing fetus through many different mechanisms, and the harms increase with later gestational age at exposure. Pregnancies complicated by maternal nicotine use are more likely to have significant adverse outcomes. Nicotine‐exposed children tend to have several health problems throughout their lives, including impaired function of the endocrine, reproductive, respiratory, cardiovascular, and neurologic systems. Poor academic performance and significant behavioral disruptions are also common, including ADHD, aggressive behaviors, and future substance abuse. To diminish the adverse effects from cigarette smoking, some women are turning to electronic cigarettes, a new trend that is increasing in popularity worldwide. They are largely perceived as being safer to use in pregnancy than traditional cigarettes, although there is not adequate evidence to support this claim. At this time, electronic cigarette use during pregnancy cannot be recommended. Birth Defects Research (Part C) 108:181–192, 2016. © 2016 Wiley Periodicals, Inc.     

ABCDXXX: The obscenity of postmarketing surveillance for teratogenic effects

Our current system of postmarketing surveillance, which is based on voluntary reporting of suspected teratogenic effects, is a failure. Postmarketing surveillance should, at a minimum, provide reassurance that every approved drug treatment does not produce a teratogenic effect as great as thalidomide embryopathy or fetal alcohol syndrome. This means that postmarketing surveillance should be able to detect a twofold or greater increase in the frequency of major congenital anomalies, a fivefold or greater increase in the frequency of intellectual disability, or a characteristic pattern of minor anomalies and functional abnormalities that occurs with a frequency of at least 10% among the children of women who were treated with the drug during pregnancy. Effective surveillance for teratogenic effects could be accomplished through a complementary set of mechanisms that includes pregnancy exposure registries or cohorts as well as direct examination of a small subset of infants whose mothers received the treatment during various periods of pregnancy. If this routine surveillance reveals a "signal" (i.e., an indication suggesting a possible teratogenic effect), further study would be needed to establish whether the observed effect is real and causal. Once a signal of possible teratogenicity in humans has been recognized, validating or refuting it would become an urgent matter. Birth Defects Research (Part A) 94:670-676, 2012. ? 2012 Wiley Periodicals, Inc.     

Prenatal exposure: The effects of prenatal cocaine and methamphetamine exposure on the developing child

Prenatal substance use remains a significant issue in the United States. Initial reports regarding prenatal cocaine and methamphetamine exposure suggested profound adverse effects on child development. However, subsequent prospective, longitudinal investigations have found more subtle effects. What follows is a brief review of the health, growth, behavioral, and intellectual outcomes for children exposed to prenatal cocaine and prenatal methamphetamine. Factors that may mitigate or intensify subtle adverse effects manifested in exposed children will also be discussed. Birth Defects Research (Part C) 108:142–146, 2016. © 2016 Wiley Periodicals, Inc.     

Funding for teratology information services: Up, down, and all around

Funding for Teratology Information Services has been an ongoing struggle over the 25 years of its existence. Traditional and novel funding mechanisms have been explored with varying success. The importance of providing teratology risk assessment and counseling to all women of reproductive age is now an established health care objective. Sufficient and stable funding for these services is essential. Birth Defects Research (Part A) 94:660-663, 2012. ? 2012 Wiley Periodicals, Inc.     

Cell fate determination during tooth development and regeneration

Teeth arise from sequential and reciprocal interactions between the oral epithelium and the underlying cranial neural crest‐derived mesenchyme. Their formation involves a precisely orchestrated series of molecular and morphogenetic events, and gives us the opportunity to discover and understand the nature of the signals that direct cell fates and patterning. For that reason, it is important to elucidate how signaling factors work together in a defined number of cells to generate the diverse and precise patterned structures of the mature functional teeth. Over the last decade, substantial research efforts have been directed toward elucidating the molecular mechanisms that control cell fate decisions during tooth development. These efforts have contributed toward the increased knowledge on dental stem cells, and observation of themolecular similarities that exist between tooth development andregeneration. Birth Defects Research (Part C) 87:199–211, 2009. © 2009 Wiley‐Liss, Inc.     

Molecular regulation of vertebrate retina cell fate

The specification of retinal cell fate is a multistep process that begins during early development and results from the spatio‐temporal coordination of cell cycle, cell differentiation, and morphogenesis. This review focuses on recent advances in understanding the molecular mechanisms underlying the distinct steps of retinal specification. Emphasis is placed on key regulatory events that control the multipotency of retinal progenitors, the generation of cell diversity, and the establishment of the clock that determines the ordered generation of retinal cell types. These basic studies have paved the way to the latest progress on the isolation and in vitro generation of retinal stem cells, which is presented in the light of possible therapeutic applications. Birth Defects Research (Part C) 87:284–295, 2009. © 2009 Wiley‐Liss, Inc.     

Congenital anomalies of the kidney and urinary tract: An embryogenetic review

Congenital anomalies of the kidney and urinary tract (CAKUT) represent a broad range of disorders that result from abnormalities of the urinary collecting system, abnormal embryonic migration of the kidneys, or abnormal renal parenchyma development. These disorders are commonly found in humans, accounting for 20–30% of all genetic malformations diagnosed during the prenatal period. It has been estimated that CAKUT are responsible for 30–50% of all children with chronic renal disease worldwide and that some anomalies can predispose to adult‐onset diseases, such as hypertension. Currently, there is much speculation regarding the pathogenesis of CAKUT. Common genetic background with variable penetrance plays a role in the development of the wide spectrum of CAKUT phenotypes. This review aims to summarize the possible mechanisms by which genes responsible for kidney and urinary tract morphogenesis might be implicated in the pathogenesis of CAKUT. Birth Defects Research (Part C) 102:374–381, 2014. © 2014 Wiley Periodicals, Inc.     

How do digits emerge? – mathematical models of limb development

The mechanism that controls digit formation has long intrigued developmental and theoretical biologists, and many different models and mechanisms have been proposed. Here we review models of limb development with a specific focus on digit and long bone formation. Decades of experiments have revealed the basic signaling circuits that control limb development, and recent advances in imaging and molecular technologies provide us with unprecedented spatial detail and a broader view of the regulatory networks. Computational approaches are important to integrate the available information into a consistent framework that will allow us to achieve a deeper level of understanding, and that will help with the future planning and interpretation of complex experiments, paving the way to in silico genetics. Previous models of development had to be focused on very few, simple regulatory interactions. Algorithmic developments and increasing computing power now enable the generation and validation of increasingly realistic models that can be used to test old theories and uncover new mechanisms. Birth Defects Research (Part C) 102:1–12, 2014. © 2014 Wiley Periodicals, Inc.     

Zebrafish: A tool for chemical screens

The zebrafish has proven to be an invaluable vertebrate animal model for developmental biology. Recent technological advances have added an arsenal of tools to expand its use into the realm of drug discovery. This includes methodology to generate transgenic reporter lines that allow for the direct visualization of fluorescent markers in live embryos. With the addition of automated imaging and analysis of embryos treated with small molecules, these innovations have expanded its utility into high throughput chemical screens. This review will highlight some of these advances that have propelled zebrafish as a tool for drug discovery. Birth Defects Research (Part C) 90:185–192, 2010. © 2010 Wiley‐Liss, Inc.     

Epidermal patterning and induction of different hair types during mouse embryonic development

An intriguing question in developmental biology is how epidermal pattern formation processes are established and what are the molecular mechanisms involved in these events. The establishment of the pattern is concomitant with the formation of ectodermal appendages, which involves complex interactions between the epithelium and the underlying mesenchyme. Among ectodermal appendages, hair follicles are the “mini organs” that produce hair shafts. Several developmental and structural features are common to all hair follicles and to the hair shaft they produce. However, many different hair types are produced in a single organism. Also, different characteristics can be observed depending on the part of the body where the hair follicle is formed. Here, we review the mechanisms involved in the patterning of different hair types during mouse embryonic development as well as the influence of the body axes on hair patterning. Birth Defects Research (Part C) 87:263–272, 2009. © 2009 Wiley‐Liss, Inc.     

Computational models for mechanics of morphogenesis

In the developing embryo, tissues differentiate, deform, and move in an orchestrated manner to generate various biological shapes driven by the complex interplay between genetic, epigenetic, and environmental factors. Mechanics plays a key role in regulating and controlling morphogenesis, and quantitative models help us understand how various mechanical forces combine to shape the embryo. Models allow for the quantitative, unbiased testing of physical mechanisms, and when used appropriately, can motivate new experimentaldirections. This knowledge benefits biomedical researchers who aim to prevent and treat congenital malformations, as well as engineers working to create replacement tissues in the laboratory. In this review, we first give an overview of fundamental mechanical theories for morphogenesis, and then focus on models for specific processes, including pattern formation, gastrulation, neurulation, organogenesis, and wound healing. The role of mechanical feedback in development is also discussed. Finally, some perspectives aregiven on the emerging challenges in morphomechanics and mechanobiology. Birth Defects Research (Part C) 96:132–152, 2012. © 2012 Wiley Periodicals, Inc.     

Scarless fetal skin wound healing update

Scar formation, a physiologic process in adult wound healing, can have devastating effects for patients; a multitude of pathologic outcomes, affecting all organ systems, stems from an amplification of this process. In contrast to adult wound repair, the early‐gestation fetal skin wound heals without scar formation, a phenomenon that appears to be intrinsic to fetal skin. An intensive research effort has focused on unraveling the mechanisms that underlie scarless fetal wound healing in an attempt to improve the quality of healing in both children and adults. Unique properties of fetal cells, extracellular matrix, cytokine profile, and gene expression contribute to this scarless repair. Despite the great increase in knowledge gained over the past decades, the precise mechanisms regulating scarless fetal healing remain unknown. Herein, we describe the current proposed mechanisms underlying fetal scarless wound healing in an effort to recapitulate the fetal phenotype in the postnatal environment. Birth Defects Research (Part C) 96:237–247, 2012. © 2012 Wiley Periodicals, Inc.     

Frequency of holoprosencephaly in the International Clearinghouse Birth Defects Surveillance Systems: searching for population variations

BACKGROUND: Holoprosencephaly (HPE) is a developmental field defect of the brain that results in incomplete separation of the cerebral hemispheres that includes less severe phenotypes, such as arhinencephaly and single median maxillary central incisor. Information on the epidemiology of HPE is limited, both because few population‐based studies have been reported, and because small studies must observe a greater number of years in order to accumulate sufficient numbers of births for a reliable estimate. METHODS: We collected data from 2000 through 2004 from 24 of the 46 Birth Defects Registry Members of the International Clearinghouse for Birth Defects Surveillance and Research. This study is based on more than 7 million births in various areas from North and South America, Europe, and Australia. RESULTS: A total of 963 HPE cases were registered, yielding an overall prevalence of 1.31 per 10,000 births. Because the estimate was heterogeneous, possible causes of variations among populations were analyzed: random variation, under‐reporting and over‐reporting bias, variation in proportion of termination of pregnancies among all registered cases and real differences among populations. CONCLUSIONS: The data do not suggest large differences in total prevalence of HPE among the studied populations that would be useful to generate etiological hypotheses. Birth Defects Research (Part A), 2008. © 2008 Wiley‐Liss, Inc.     

Molecular mechanisms of membrane interaction at implantation

Successful pregnancy is dependent upon the implantation of a competent embryo into a receptive endometrium. Despite major advancement in our understanding of reproductive medicine over the last few decades, implantation failure still occurs in both normal pregnancies and those created artificially by assisted reproductive technology (ART). Consequently, there is significant interest in elucidating the etiology of implantation failure. The complex multistep process of implantation begins when the developing embryo first makes contact with the plasma membrane of epithelial cells within the uterine environment. However, although this biological interaction marks the beginning of a fundamental developmental process, our knowledge of the intricate physiological and molecular processes involved remains sparse. In this synopsis, we aim to provide an overview of our current understanding of the morphological changes which occur to the plasma membrane of the uterine endothelium, and the molecular mechanisms that control communication between the early embryo and the endometrium during implantation. A multitude of molecular factors have been implicated in this complex process, including endometrial integrins, extracellular matrix molecules, adhesion molecules, growth factors, and ion channels. We also explore the development of in vitro models for embryo implantation to help researchers investigate mechanisms which may underlie implantation failure. Understanding the precise molecular pathways associated with implantation failure could help us to generate new prognostic/diagnostic biomarkers, and may identify novel therapeutic targets. Birth Defects Research (Part C) 108:19–32, 2016. © 2016 Wiley Periodicals, Inc.