Chemically induced congenital thymic dysgenesis in the rat: a model of the DiGeorge syndrome

Structure-Based Optimization of a Novel Class of Aldehyde Dehydrogenase 1A (ALDH1A) Subfamily-Selective Inhibitors as Potential Adjuncts to Ovarian Cancer Chemotherapy

Aldehyde dehydrogenase (ALDH) activity is commonly used as a marker to identify cancer stem-like cells. The three ALDH1A isoforms have all been individually implicated in cancer stem-like cells and in chemoresistance; however, which isoform is preferentially expressed varies between cell lines. We sought to explore the structural determinants of ALDH1A isoform selectivity in a series of small-molecule inhibitors in support of research into the role of ALDH1A in cancer stem cells. An SAR campaign guided by a cocrystal structure of the HTS hit CM39 (7) with ALDH1A1 afforded first-in-class inhibitors of the ALDH1A subfamily with excellent selectivity over the homologous ALDH2 isoform. We also discovered the first reported modestly selective single isoform 1A2 and 1A3 inhibitors. Two compounds, 13g and 13h, depleted the CD133⁺ putative cancer stem cell pool, synergized with cisplatin, and achieved efficacious concentrations in vivo following IP administration. Compound 13h additionally synergized with cisplatin in a patient-derived ovarian cancer spheroid model.

The role of chordin/Bmp signals in mammalian pharyngeal development and DiGeorge syndrome

The chordin/Bmp system provides one of the best examples of extracellular signaling regulation in animal development. We present the phenotype produced by the targeted inactivation of the chordin gene in mouse. Chordin homozygous mutant mice show, at low penetrance, early lethality and a ventralized gastrulation phenotype. The mutant embryos that survive die perinatally, displaying an extensive array of malformations that encompass most features of DiGeorge and Velo-Cardio-Facial syndromes in humans. Chordin secreted by the mesendoderm is required for the correct expression of Tbx1 and other transcription factors involved in the development of the pharyngeal region. The chordin mutation provides a mouse model for head and neck congenital malformations that frequently occur in humans and suggests that chordin/Bmp signaling may participate in their pathogenesis.

Advances in the molecular genetics of congenital structural heart disease

Molecular genetic analyses have generated significant advances in our understanding of congenital heart disease. Techniques of genetic mapping with polymorphic microsatellites and fluorescence in situ hybridization (FISH) have provided informative tools for localization and identification of disease genes. Some cardiovascular diseases have proven to result from single gene defects. Others relate to more complex etiologies involving several genes and their interactions. Elucidation of the molecular genetic etiologies of congenital heart disease prompts consideration of DNA testing for cardiac disorders. Future integration of these diagnostic modalities with improved treatments may ultimately decrease morbidity and mortality from congenital heart diseases.

Development of the thymus

Proper development of the thymus is critical for an individual to acquire full immune capability. A full complement of the components that participate in thymic development, interacting with each other at the correct time, is required for maturation. In order to establish the microenvironment necessary for T-cell differentiation, the epithelial primordium of the thymus must expand from pharyngeal endoderm with the aid of contributions from the ectoderm. Experimental studies have established the importance of mesenchymal derivatives from the neural crest in functional development of the epithelial primordium. Interfering with this process inhibits thymic development in a manner similar to that observed in congenital conditions such as the DiGeorge syndrome and the fetal alcohol syndrome. These observations provide clues to understanding the origin of defects in thymus-dependent immunity, and point the way to studies that will expand our understanding of the controls that are involved in genetic and environmental factors impacting on this process.

Congenital heart disease in CHARGE association

This study reviews the spectrum of congenital heart disease and associated anomalies in 59 patients with the CHARGE association. We have analyzed our clinical experience in managing the cardiovascular anomalies and have reviewed outcome and risk factors for mortality. This study also highlights problems of cardiac management in children born with multiple system involvement. Twenty patients have died; actuarial survival was 78% at 1 year and 60% at 10 years. In only four of the nonsurvivors could their demise be ascribed to their underlying congenital heart disease. We found the outlook for survival was poor if more than one of the following three features were present; cyanotic cardiac lesions, bilateral posterior choanal atresia, or tracheoesophageal fistula. However, mortality was largely due not to the structural heart or choanal abnormalities, but instead reflected the underlying pharyngeal and laryngeal incoordination which resulted in aspiration of secretions. Furthermore, outcome is likely to be improved if collaboration between specialist surgical teams allows necessary procedures to be performed using the minimum of anesthetics. Examination of both the short- and long-term management of these children has stressed the importance of a multidisciplinary approach to their care. The pattern of cardiac defects was not random; lesions within the Fallot spectrum accounted for 33% of their congenital heart disease. Atrioventricular septal defects were also overrepresented. Not all cardiovascular defects could be explained by hypothesizing a neural crest etiology.

Inhibition of epibranchial placode-derived ganglia in the developing rat by bisdiamine

Although bisdiamine has been shown to affect the development of mammals, its effect on the nervous system has gone largely unrecognized. In the present study, rats were given bisdiamine by gavage on days 9 and 10 of pregnancy. They were sacrificed at intervals and the fetuses were prepared for study of serial sections stained with hematoxylin and eosin, or by immunohistochemical reaction with HNK-1 monoclonal antibody. HNK-1 reacted strongly with the nervous system, allowing precise analysis of the components and their relationships. Controls receiving no bisdiamine were prepared and studied in parallel with the experimental fetuses. Administration of bisdiamine inhibited development of the petrosal and nodose ganglia, altered associations of the glossopharyngeal, vagus, and hypoglossal nerves, and inhibited contributions of vagal nerve fibers to the developing enteric system. The proximal ganglia of the glossopharyngeal and vagus nerves developed normally. It is concluded that bisdiamine affects, directly or indirectly, the differentiation of nervous components derived from the epibranchial placodes. It seems likely that these placode-derived components serve as pioneer neurons in establishing the pathway for the posteriorly extending trunks of the glossopharyngeal and vagus nerves. The early changes in congenital conditions such as the DiGeorge syndrome may not be limited to alterations in neural crest derivatives. It may be worthwhile to investigate more closely whether there are alterations in the nervous system associated with these syndromes.

Microdeletions within 22q11 associated with sporadic and familial DiGeorge syndrome

DiGeorge syndrome (DGS) is a developmental field defect of the third and fourth pharyngeal pouches. It is associated with deletion of 22q11 in 11% of cases. Molecular genetic analysis with probes from 22q11-pter reveals that a subset of markers is hemizygous in DGS patients with normal karyotypes. There is no apparent difference in the phenotype or the severity of the disorder between patients with the smallest detectable submicroscopic deletion and those with the largest cytogenetically visible abnormality. A microdeletion was found in a mildly affected child and in the severely affected child of a mildly affected father. Dysmorphology, especially cardiac outflow tract anomalies, resulting from 22q11 deletion may be more common than currently realized since chromosomes are unlikely to be checked if the complete spectrum of DGS is not present. Antenatal diagnosis, through detection of hemizygosity at 22q11, will be a possibility for mildly affected parents unwilling to risk the birth of a severely affected child.

Localization of 27 DNA markers to the region of human chromosome 22q11-pter deleted in patients with the DiGeorge syndrome and duplicated in the der22 syndrome

DiGeorge syndrome is a human developmental field defect with the pathological features of an abnormality of embryogenesis at 4 to 6 weeks of gestation. Cytogenetic analyses of patients have revealed a number of instances of monosomy 22q11-pter in this condition. We have analyzed 52 DNA markers that map to 22q11-pter and have found 27 that are deleted in DiGeorge syndrome patients with known monosomy for part of this region and that are duplicated in patients with the der22 syndrome. The set of clones mapping to the DiGeorge region was further assigned to a proximal or a distal location within the deletion.

The DiGeorge anomaly as a developmental field defect

The DiGeorge "syndrome" is a characteristic malformation pattern involving craniofacial, cardiac, thymic, and parathyroid structures. Evidence is accumulating that the DiGeorge "syndrome" is actually not a syndrome, but a polytopic developmental field defect. We present evidence of causal heterogeneity of the DiGeorge anomaly. This heterogeneity will be discussed in the light of recent findings that indicate that the dysmorphogenetically reactive unit responsible for the phenotype of the DiGeorge anomaly is a population of cephalic neural crest cells.

Fetal alcohol syndrome and DiGeorge anomaly: critical ethanol exposure periods for craniofacial malformations as illustrated in an animal model

Acute maternal ethanl (alcohol) administration induces different craniofacial anomalies in the offspring of experimental animals, depending on the gestational day of teratogen exposure. Previous studies in our laboratories have illustrated the sequence of developmental changes leading to the "typical" fetal alcohol syndrome (FAS) craniofacial phenotype which results from teratogen exposure during gastrulation. These facial features are accompanied by deficiencies in median forebrain derivatives. Ethanol teratogenesis at this time apparently results in a loss of midline territory of the embryonic disc with little effects on neural crest-dependent laterally derived structures including the visceral arches. Acute ethanol exposure in mice 1 1/2 days later, at a time when neural crest cells are populating the frontonasal prominence and the visceral arches, results in a craniofacial phenotype that is similar to that noted in the DiGeorge anomaly or sequence. Sequential scanning electron microscopic analysis in our laboratory of embryos exposed on day 8 1/2 have illustrated deficiencies in the developing facial prominences and the visceral arches. The developing forebrain and midbrain appear hypoplastic. We have also observed heart, great vessel, and thymus abnormalities in these fetuses. Histologic analyses indicate that a common pathogenetic basis for the above-mentioned (day 8 1/2-induced) fetal alcohol effects appears to be an interference with the integrity of the cranial (including occipital) neural crest. Other discrete cell populations may also be involved since we have observed abnormalities in other regions, including placodal and closing membrane tissues. This animal model provides evidence linking maternal ethanol abuse during the 3rd or 4th weeks of human gestation to the development in the conceptus of FAS or DiGeorge anomally craniofacial characteristics, respectively. As the DiGeorge anomaly has been noted in the offspring of alcoholic women, this animal model indicates that ethanol and/or its metabolites is, in these cases, the causative agent.

Errors of morphogenesis and inborn errors of immunity 20 years after the discovery of DiGeorge anomaly

The heuristic concept of "inborn errors of metabolism" was introduced more then 70 years ago and by analogy has prompted the more recent introduction of the term "inborn errors of immunity". It is now well recognized that many inborn errors of immunity can be considered inborn errors of metabolism. Typically, many forms of severe combined immunodeficiency result from adenosine deaminase deficiency, i.e., an inborn error of purine metabolism. On the other hand, errors of immunity are often associated with "errors of morphogenesis", resulting from an intrinsically abnormal developmental process (malformation), a secondary or extrinsic interference with originally normal development (disruption), or an abnormal organization of cells into tissues (dysplasia). Twenty years after the original description, the DiGeorge anomaly should be considered an inborn error of morphogenesis and immunity due either to disruption or less frequently to malformation. In other immunodeficiencies, such as ataxia telangiectasia, the morphologic and immunologic errors result from a dyshistogenesis, i.e., dysplasia. Also, true malformation syndromes, such as Down's syndrome, are consistently associated with immunodeficiency.