Congenital absence of the thymus

Human immunity to fungal infections

Fungi increasingly threaten health globally. Mycoses range from life-threatening, often iatrogenic conditions, to enigmatic syndromes occurring without apparent immunosuppression. Despite some recent advances in antifungal drug development, complementary therapeutic strategies are essential for addressing these opportunistic pathogens. One promising avenue is leveraging host immunity to combat fungal infections; this necessitates deeper understanding of the molecular immunology of human fungal susceptibility to differentiate beneficial versus harmful immunopathological responses. Investigating human models of fungal diseases in natural settings, particularly through genetic immunodeficiencies and ethnographic-specific genetic vulnerabilities, reveals crucial immune pathways essential for fighting various yeasts and molds. This review highlights the diversity in intrinsic fungal susceptibility across individuals and populations, through genetic- and autoantibody-mediated processes, complementing previous principles learned from animal studies and iatrogenic contexts. Improved understanding of human immunity to fungal diseases will facilitate the development of host-directed immunotherapies and targeted public health interventions, paving the way for precision medicine in fungal disease management.

Rebuilding and rebooting immunity with stem cells

Advances in modern medicine have enabled a rapid increase in lifespan and, consequently, have highlighted the immune system as a key driver of age-related disease. Immune regeneration therapies present exciting strategies to address age-related diseases by rebooting the host's primary lymphoid tissues or rebuilding the immune system directly via biomaterials or artificial tissue. Here, we identify important, unanswered questions regarding the safety and feasibility of these therapies. Further, we identify key design parameters that should be primary considerations guiding technology design, including timing of application, interaction with the host immune system, and functional characterization of the target patient population.

Primary and secondary defects of the thymus

The thymus is the primary site of T-cell development, enabling generation, and selection of a diverse repertoire of T cells that recognize non-self, whilst remaining tolerant to self- antigens. Severe congenital disorders of thymic development (athymia) can be fatal if left untreated due to infections, and thymic tissue implantation is the only cure. While newborn screening for severe combined immune deficiency has allowed improved detection at birth of congenital athymia, thymic disorders acquired later in life are still underrecognized and assessing the quality of thymic function in such conditions remains a challenge. The thymus is sensitive to injury elicited from a variety of endogenous and exogenous factors, and its self-renewal capacity decreases with age. Secondary and age-related forms of thymic dysfunction may lead to an increased risk of infections, malignancy, and autoimmunity. Promising results have been obtained in preclinical models and clinical trials upon administration of soluble factors promoting thymic regeneration, but to date no therapy is approved for clinical use. In this review we provide a background on thymus development, function, and age-related involution. We discuss disease mechanisms, diagnostic, and therapeutic approaches for primary and secondary thymic defects.

The Subtlety of 22q11.2 Deletion Syndrome in a Preterm Neonate

To date, 22q11.2 deletion syndrome (DS) is regarded as the most commonly diagnosed DS in humans. The location of the deletion on chromosome 22 affects the phenotypic presentation, which ranges from subtle to severe. Common manifestations include congenital heart defects, calcium deficiency, clefts and other midline defects, immunodeficiencies, and neurocognitive delay. This wide range of clinical manifestations can complicate diagnostic reasoning as many align with other disease processes commonly observed in preterm neonates. This article presents the case of a preterm neonate born at 25-weeks' gestation with 22q11.2 DS. The clinical presentation of this neonate included a right aortic arch, ventricular septal defect, hypocalcemia, borderline severe combined immunodeficiency, and abnormal thyroid function. The infant's hospital course is followed to highlight the challenges clinicians face when suspicious of a genetic disorder in a preterm neonate.

Autoimmunity in Primary Immunodeficiencies (PID)

Primary immunodeficiency (PID) may impact any component of the immune system. The number of PID and immune dysregulation disorders is growing steadily with advancing genetic detection methods. These expansive recognition methods have changed the way we characterize PID. While PID were once characterized by their susceptibility to infection, the increase in genetic analysis has elucidated the intertwined relationship between PID and non-infectious manifestations including autoimmunity. The defects permitting opportunistic infections to take hold may also lead the way to the development of autoimmune disease. In some cases, it is the non-infectious complications that may be the presenting sign of PID autoimmune diseases, such as autoimmune cytopenia, enteropathy, endocrinopathies, and arthritis among others, have been reported in PID. While autoimmunity may occur with any PID, this review will look at certain immunodeficiencies most often associated with autoimmunity, as well as their diagnosis and management strategies.

Comparison of Postoperative, In-Hospital Outcomes After Complete Repair of Tetralogy of Fallot Between 22q11.2 Deletion Syndrome and Trisomy 21

22q11.2 deletion syndrome (22q11) and trisomy 21 (T21) are frequently associated with tetralogy of Fallot (TOF). We hypothesized that there are differences in postoperative length of stay (LOS) and occurrence of postoperative interventions after complete repair of TOF when comparing children with 22q11 to those with T21. Using the Pediatric Health Information System, we performed a retrospective cohort study of patients who underwent complete repair of TOF from 2004 to 2019. Three groups were identified: 22q11, T21, and controls (those without a coded genetic syndrome). Outcomes were postoperative LOS and composite occurrence (yes/no) of at least one postoperative intervention. Bivariate and multivariate comparisons were made among groups; odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using the control group as the comparator. There were 6924 subjects (n = 493 22q11, n = 455 T21, n = 5976 controls). In bivariate analysis, 22q11 was associated with a longer LOS compared to T21 (OR 2.37 [2.16, 2.60] vs. 1.25 [1.12, 1.39], p < 0.001), and 22q11 more often underwent postoperative intervention (OR 3.42 [CI 2.56, 4.57] vs. 1.38 [CI 0.91, 2.11]; p < 0.001). In multivariate analysis, 22q11 was also associated with longer LOS (adjusted OR 1.35 [1.26, 1.44] vs. 1.12 [1.04, 1.20]; p < 0.001), but there was no difference in the adjusted odds of postoperative intervention. Children with 22q11 are more likely to experience adverse outcomes after repair of TOF compared to those with T21; the differences are most pronounced for LOS.

Isolated absent right pulmonary artery in an infant with 22q11 deletion

DiGeorge syndrome is a rare spectrum of disorder affecting structures derived from third and fourth pharyngeal pouches characterised by aplasia or hypoplasia of thymus and parathyroid glands, and conotruncal anomalies. Presentation includes infants with hypocalcemic seizures, CHD, or recurrent infection. This case report illustrates a unique combination of proximal interruption of right pulmonary artery and aberrant right subclavian artery in a 3-month-old infant who was subsequently diagnosed as DiGeorge syndrome. This constellation of vascular anomalies in an infant with DiGeorge syndrome has not been previously reported in the literature.

Relationship between parent-reported gastrointestinal symptoms, sleep problems, autism spectrum disorder symptoms, and behavior problems in children and adolescents with 22q11.2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q) is a chromosome disorder, where a segment of chromosome 22, located at q11.2, is missing. This study aims to investigate the relationship between a number of parent-reported comorbid conditions including gastrointestinal symptoms, sleep problems, autism spectrum disorder (ASD) symptoms and behavior problems in children and adolescents with 22q deletion syndrome.

METHOD

The Gastrointestinal Symptom Inventory, Children's Sleep Habits Questionnaire, Behavior Problem Inventory-Short Form and the Social Communication Questionnaire were completed by parents of 149 children and adolescents aged 3-18 years with a diagnosis of 22q.

RESULTS

A series of correlations and hierarchical multiple regressions were conducted to examine the relationships between GI symptoms, sleep problems and behavior problems in children and adolescents with 22q deletion syndrome. A significant moderate relationship was found between GI symptoms and sleep problems. Gender and ASD symptoms predicted GI symptoms. Significant small relationships were found between GI symptoms and self-injurious behavior. Significant small to moderate relationships were found between sleep problems and self-injurious behavior, aggressive/destructive behavior, and sterotyped behavior. Sleep problems predicted challenging behavior.

CONCLUSIONS

This research demonstrated the importance of studying the relationship between comorbidities, including gastrointestinal symptoms, sleep problems, and behavior problems and how they shape the phenotype of 22q deletion syndrome.

Gastrostomy and Tracheostomy After Complete Repair of Tetralogy of Fallot in Children With 22q11.2 Deletion Syndrome

OBJECTIVES

Caring for a child with gastrostomy and/or tracheostomy can cause measurable parental stress. It is generally known that children with 22q11.2 deletion syndrome are at greater risk of requiring gastrostomy or tracheostomy after heart surgery, although the magnitude of that risk after complete repair of tetralogy of Fallot has not been described. We sought to determine the degree to which 22q11.2 deletion is associated with postoperative gastrostomy and/or tracheostomy after repair of tetralogy of Fallot.

DESIGN

Retrospective cohort study.

SETTING

Pediatric Health Information System.

PATIENTS

Children undergoing complete repair of tetralogy of Fallot (ventricular septal defect closure and relief of right ventricular outflow tract obstruction) from 2003 to 2016. Patients were excluded if they had pulmonary atresia, other congenital heart defects, and/or genetic diagnoses other than 22q11.2 deletion.

MEASUREMENTS AND MAIN RESULTS

Two groups were formed on the basis of 22q11.2 deletion status. Outcomes were postoperative tracheostomy and postoperative gastrostomy. Bivariate analysis and Kaplan-Meier analysis at 150 days postoperatively were performed. There were 4,800 patients, of which 317 (7%) had a code for 22q11.2 deletion. There were no significant differences between groups for age at surgery or sex. Patients with 22q11.2 deletion had significantly higher rates of gastrostomy (18% vs 5%; p < 0.001) and higher rates of tracheostomy (7% vs 1%; p < 0.001); there was no difference for mortality. Kaplan-Meier analyses also showed higher rates of gastrostomy (p = 0.024) and tracheostomy (p = 0.037).

CONCLUSIONS

The present study establishes rates of postoperative gastrostomy and tracheostomy in children with 22q11.2 deletion after complete repair of tetralogy of Fallot. These data are useful to clinicians for providing families with preoperative counseling.

Thymus Inception: Molecular Network in the Early Stages of Thymus Organogenesis

The thymus generates central immune tolerance by producing self-restricted and self-tolerant T-cells as a result of interactions between the developing thymocytes and the stromal microenvironment, mainly formed by the thymic epithelial cells. The thymic epithelium derives from the endoderm of the pharyngeal pouches, embryonic structures that rely on environmental cues from the surrounding mesenchyme for its development. Here, we review the most recent advances in our understanding of the molecular mechanisms involved in early thymic organogenesis at stages preceding the expression of the transcription factor Foxn1, the early marker of thymic epithelial cells identity. Foxn1-independent developmental stages, such as the specification of the pharyngeal endoderm, patterning of the pouches, and thymus fate commitment are discussed, with a special focus on epithelial–mesenchymal interactions.

The Role of Alpha-Synuclein and Other Parkinson's Genes in Neurodevelopmental and Neurodegenerative Disorders

Neurodevelopmental and late-onset neurodegenerative disorders present as separate entities that are clinically and neuropathologically quite distinct. However, recent evidence has highlighted surprising commonalities and converging features at the clinical, genomic, and molecular level between these two disease spectra. This is particularly striking in the context of autism spectrum disorder (ASD) and Parkinson's disease (PD). Genetic causes and risk factors play a central role in disease pathophysiology and enable the identification of overlapping mechanisms and pathways. Here, we focus on clinico-genetic studies of causal variants and overlapping clinical and cellular features of ASD and PD. Several genes and genomic regions were selected for our review, including SNCA (alpha-synuclein), PARK2 (parkin RBR E3 ubiquitin protein ligase), chromosome 22q11 deletion/DiGeorge region, and FMR1 (fragile X mental retardation 1) repeat expansion, which influence the development of both ASD and PD, with converging features related to synaptic function and neurogenesis. Both PD and ASD display alterations and impairments at the synaptic level, representing early and key disease phenotypes, which support the hypothesis of converging mechanisms between the two types of diseases. Therefore, understanding the underlying molecular mechanisms might inform on common targets and therapeutic approaches. We propose to re-conceptualize how we understand these disorders and provide a new angle into disease targets and mechanisms linking neurodevelopmental disorders and neurodegeneration.

22q11.2 deletion syndrome and congenital heart disease

The 22q11.2 deletion syndrome has an estimated prevalence of 1 in 4-6,000 livebirths. The phenotype varies widely; the most common features include: facial dysmorphia, hypocalcemia, palate and speech disorders, feeding and gastrointestinal disorders, immunodeficiency, recurrent infections, neurodevelopmental and psychiatric disorders, and congenital heart disease. Approximately 60-80% of patients have a cardiac malformation most commonly including a subset of conotruncal defects (tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B), conoventricular and/or atrial septal defects, and aortic arch anomalies. Cardiac patients with a 22q11.2 deletion do not generally experience higher mortality upon surgical intervention but suffer more peri-operative complications than their non-syndromic counterparts. New guidelines suggest screening for a 22q11.2 deletion in the patient with tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B, conoventricular septal defects as well as those with an isolated aortic arch anomaly. Early identification of a 22q11.2 deletion in the neonate or infant when other syndromic features may not be apparent allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features. Screening the at-risk child or adult allows for important age-specific clinical, neurodevelopmental, psychiatric, and reproductive issues to be addressed.

22q11 Deletion Syndrome with Vascular Anomalies

DiGeorge syndrome, also termed 22q11.2 deletion syndrome, represents a spectrum of disorders that include thymic aplasia/hypoplasia, parathyroid aplasia/hypoplasia, conotruncal vascular anomalies, and velocardiofacial (Shprintzen) syndrome. This case report describes a novel constellation of cardiovascular anomalies in a 31-year-old patient with 22q11.2 deletion confirmed by fluorescence in situ hybridization at the age of 24. CT angiogram of the thorax revealed a right aortic arch with mirror image branching and unilateral absence of the left pulmonary artery with collateral flow through left intercostal arteries and hypertrophied left bronchial artery. This particular cluster of vascular findings has not been previously described in the imaging literature in a patient with known 22q11.2 deletion.

Visual memory profile in 22q11.2 microdeletion syndrome: are there differences in performance and neurobiological substrates between tasks linked to ventral and dorsal visual brain structures? A cross-sectional and longitudinal study

Background

Children affected by the 22q11.2 deletion syndrome (22q11.2DS) have a specific neuropsychological profile with strengths and weaknesses in several cognitive domains. Specifically, previous evidence has shown that patients with 22q11.2DS have more difficulties memorizing faces and visual-object characteristics of stimuli. In contrast, they have better performance in visuo-spatial memory tasks. The first focus of this study was to replicate these results in a larger sample of patients affected with 22q11.2DS and using a range of memory tasks. Moreover, we analyzed if the deficits were related to brain morphology in the structures typically underlying these abilities (ventral and dorsal visual streams). Finally, since the longitudinal development of visual memory is not clearly characterized in 22q11.2DS, we investigated its evolution from childhood to adolescence.

Methods

Seventy-one patients with 22q11.2DS and 49 control individuals aged between 9 and 16 years completed the Benton Visual Retention Test (BVRT) and specific subtests assessing visual memory from the Children’s Memory Scale (CMS). The BVRT was used to compute spatial and object memory errors. For the CMS, specific subtests were classified into ventral, dorsal, and mixed subtests. Longitudinal data were obtained from a subset of 26 patients and 22 control individuals.

Results

Cross-sectional results showed that patients with 22q11.2DS were impaired in all visual memory measures, with stronger deficits in visual-object memory and memory of faces, compared to visuo-spatial memory. No correlations between morphological brain impairments and visual memory were found in patients with 22q11.2DS. Longitudinal findings revealed that participants with 22q11.2DS made more object memory errors than spatial memory errors at baseline. This difference was no longer significant at follow-up.

Conclusions

Individuals with 22q11.2DS have impairments in visual memory abilities, with more pronounced difficulties in memorizing faces and visual-object characteristics. From childhood to adolescence, the visual cognitive profile of patients with 22q11.2DS seems globally stable even though some processes show an evolution with time. We hope that our results will help clinicians and caregivers to better understand the memory difficulties of young individuals with 22q11.2DS. This has a particular importance at school to facilitate recommendations concerning intervention strategies for these young patients.

Disrupted fornix integrity in children with chromosome 22q11.2 deletion syndrome

The fornix is the primary subcortical output fiber system of the hippocampal formation. In children with 22q11.2 deletion syndrome (22q11.2DS), hippocampal volume reduction has been commonly reported, but few studies as yet have evaluated the integrity of the fornix. Therefore, we investigated the fornix of 45 school-aged children with 22q11.2DS and 38 matched typically developing (TD) children. Probabilistic diffusion tensor imaging (DTI) tractography was used to reconstruct the body of the fornix in each child׳s brain native space. Compared with children, significantly lower fractional anisotropy (FA) and higher radial diffusivity (RD) was observed bilaterally in the body of the fornix in children with 22q11.2DS. Irregularities were especially prominent in the posterior aspect of the fornix where it emerges from the hippocampus. Smaller volumes of the hippocampal formations were also found in the 22q11.2DS group. The reduced hippocampal volumes were correlated with lower fornix FA and higher fornix RD in the right hemisphere. Our findings provide neuroanatomical evidence of disrupted hippocampal connectivity in children with 22q11.2DS, which may help to further understand the biological basis of spatial impairments, affective regulation, and other factors related to the ultra-high risk for schizophrenia in this population.

Modeling a model: Mouse genetics, 22q11.2 Deletion Syndrome, and disorders of cortical circuit development

Understanding the developmental etiology of autistic spectrum disorders, attention deficit/hyperactivity disorder and schizophrenia remains a major challenge for establishing new diagnostic and therapeutic approaches to these common, difficult-to-treat diseases that compromise neural circuits in the cerebral cortex. One aspect of this challenge is the breadth and overlap of ASD, ADHD, and SCZ deficits; another is the complexity of mutations associated with each, and a third is the difficulty of analyzing disrupted development in at-risk or affected human fetuses. The identification of distinct genetic syndromes that include behavioral deficits similar to those in ASD, ADHC and SCZ provides a critical starting point for meeting this challenge. We summarize clinical and behavioral impairments in children and adults with one such genetic syndrome, the 22q11.2 Deletion Syndrome, routinely called 22q11DS, caused by micro-deletions of between 1.5 and 3.0 MB on human chromosome 22. Among many syndromic features, including cardiovascular and craniofacial anomalies, 22q11DS patients have a high incidence of brain structural, functional, and behavioral deficits that reflect cerebral cortical dysfunction and fall within the spectrum that defines ASD, ADHD, and SCZ. We show that developmental pathogenesis underlying this apparent genetic "model" syndrome in patients can be defined and analyzed mechanistically using genomically accurate mouse models of the deletion that causes 22q11DS. We conclude that "modeling a model", in this case 22q11DS as a model for idiopathic ASD, ADHD and SCZ, as well as other behavioral disorders like anxiety frequently seen in 22q11DS patients, in genetically engineered mice provides a foundation for understanding the causes and improving diagnosis and therapy for these disorders of cortical circuit development.

Thymic and bone marrow output in individuals with 22q11.2 deletion syndrome

BACKGROUND

The 22q11.2 deletion syndrome (22q11.2DS) is a congenital multisystem anomaly characterized by typical facial features, palatal anomalies, congenital heart defects, hypocalcemia, immunodeficiency, and cognitive and neuropsychiatric symptoms. The aim of our study was to investigate T- and B-lymphocyte characteristics associated with 22q11.2DS.

METHODS

Seventy-five individuals with 22q11.2DS were tested for T and B lymphocytes by examination of T-cell receptor rearrangement excision circles (TRECs) and B-cell κ-deleting recombination excision circles (KRECs), respectively.

RESULTS

The 22q11.2DS individuals displayed low levels of TRECs, while exhibiting normal levels of KRECs. There was a significant positive correlation between TREC and KREC in the 22q11.2DS group, but not in controls. Both TREC and KREC levels showed a significant decrease with age and only TREC was low in 22q11.2DS individuals with recurrent infections. No difference in TREC levels was found between 22q11.2DS individuals who underwent heart surgery (with or without thymectomy) and those who did not.

CONCLUSION

T-cell immunodeficiency in 22q11.2DS includes low TREC levels, which may contribute to recurrent infections in individuals with this syndrome. A correlation between T- and B-cell abnormalities in 22q11.2DS was identified. The B-cell abnormalities could account for part of the immunological deficiency seen in 22q11.2DS.

MicroRNAs: Small but amazing, and their association with endothelin

MicroRNAs (miRNAs) are small non-coding RNA molecules involved in the expressional regulation of genes by inhibiting gene translation. MicroRNAs are recruited and incorporated into the miRISC, ribonucleoprotein complex, targeting specific mRNAs through mechanisms specific for a miRNA sequence. Here we review the biogenesis, regulation, and monitoring of miRNAs, as well as the current evidence for potential roles of miRNAs in human diseases associated with activation of the endothelin system. These diseases include cancer, kidney disease, cardiovascular diseases, inflammatory diseases, infectious diseases, and blood diseases, that may all be aggravated by aberrant miRNA expression. In this review we will also discuss regulatory mechanisms determining production of miRNA as well as measuring or targeting miRNAs as potential novel approaches for diagnosis and treatment. Targeting miRNAs possibly will allow one to detect diseases or to interfere with the progression of diseases associated with activation of the endothelin system.

Psychiatric disorders and intellectual functioning throughout development in velocardiofacial (22q11.2 deletion) syndrome

OBJECTIVE

Velocardiofacial syndrome (VCFS) is associated with cognitive deficits and high rates of schizophrenia and other neuropsychiatric disorders. We report the data from two large cohorts of individuals with VCFS from Israel and Western Europe to characterize the neuropsychiatric phenotype from childhood to adulthood in a large sample.

METHOD

Individuals with VCFS (n = 172) aged 5 to 54 years were evaluated with structured clinical interviews for psychiatric disorders and age-appropriate versions of the Wechsler intelligence tests.

RESULTS

The frequency of psychiatric disorders was high and remarkably similar between samples. Psychotic disorders and depression were uncommon during childhood but increased in rates during adulthood (depressive disorders: 40.7% in young adults [aged 18-24 years]; psychotic disorders: 32.1% in adults [age >24 years]). Cognitive scores were inversely associated with age in subjects with VCFS, including patients without psychosis. Specifically, Verbal IQ (VIQ) scores negatively correlated with age, and the subjects with VCFS and psychotic disorders had significantly lower VIQ scores than nonpsychotic VCFS subjects.

CONCLUSIONS

Neuropsychiatric deficits in individuals with VCFS seem to follow a developmental pattern. The VIQ scores are negatively associated with age and rates of mood, and psychotic disorders increase dramatically during young adulthood. The data presented here support careful monitoring of psychiatric symptoms during adolescence and young adulthood in VCFS. Prospective longitudinal studies are needed to examine the nature of age-related cognitive changes and their association with psychiatric morbidity in VCFS.

Pediatric radiology in the Philadelphia region: a history of pedigrees and legacies

The specialty of pediatric radiology in the Philadelphia region has grown and evolved over the past eight decades originating from early "visiting" radiologists to Drs. Hope and Kirkpatrick, the "giants" of the 1950s and 1960s, to over 40 actively practicing pediatric radiologists. Clinical excellence, commitment to teaching, and advancement of knowledge through research remain the goals and ideals, much as they were many years ago. Philadelphia has been a fertile home and environment for this development, mostly because of outstanding leaders and role models who have trained and influenced generations of pediatric radiologists. The purpose of this article is to tell the story of this growth and development and to explore the intellectual origins, professional "genealogy," and legacies left by those who created this tradition.

Psychiatric phenotypes associated with neurogenetic disorders

Advances in understanding the human genome and clinical application have led to identification of genetically based disorders that have distinctive behavioral phenotypes and risk for serious psychiatric disorders. Some patients have unrecognized genetic disorders presenting as psychiatric symptoms. Practitioners must be knowledgeable about the association between symptoms and underlying genetic bases. Treatment of neurogenetic disorders includes providing information about causes and prognoses. Patients are served best if they remain long term with a multidisciplinary team of providers who recognize the realities of a lifetime course, the high risk for symptom recurrence, and the need for providing information and support to families and coordinating medical and psychiatric care.

Atypical cortical connectivity and visuospatial cognitive impairments are related in children with chromosome 22q11.2 deletion syndrome

Background

Chromosome 22q11.2 deletion syndrome is one of the most common genetic causes of cognitive impairment and developmental disability yet little is known about the neural bases of those challenges. Here we expand upon our previous neurocognitive studies by specifically investigating the hypothesis that changes in neural connectivity relate to cognitive impairment in children with the disorder.

Methods

Whole brain analyses of multiple measures computed from diffusion tensor image data acquired from the brains of children with the disorder and typically developing controls. We also correlated diffusion tensor data with performance on a visuospatial cognitive task that taps spatial attention.

Results

Analyses revealed four common clusters, in the parietal and frontal lobes, that showed complementary patterns of connectivity in children with the deletion and typical controls. We interpreted these results as indicating differences in connective complexity to adjoining cortical regions that are critical to the cognitive functions in which affected children show impairments. Strong, and similarly opposing patterns of correlations between diffusion values in those clusters and spatial attention performance measures considerably strengthened that interpretation.

Conclusion

Our results suggest that atypical development of connective patterns in the brains of children with chromosome 22q11.2 deletion syndrome indicate a neuropathology that is related to the visuospatial cognitive impairments that are commonly found in affected individuals.

Abnormal cortical activation during response inhibition in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is a well-known genetic risk factor for schizophrenia. The catechol-O-methyltransferase (COMT) gene falls within the 22q11.2 minimal critical region of the deletion. Brain activity, as measured by functional magnetic resonance imaging (fMRI) during a Go/NoGo, response inhibition task was assessed in adolescents with 22q11.2DS (n = 13), typically developing (TD) controls (n = 14), and controls with developmental disability (DD, n = 9). Subjects with 22q11.2DS were also genotyped for the COMT Met/Val polymorphism. Groups did not differ on task performance. However, compared to both control groups, the 22q11.2DS group showed greater brain activation within left parietal regions. Comparison of brain activation between 22q11.2DS Met and Val subgroups revealed significantly increased activation (Met>Val) in the cingulate but not the dorsolateral prefrontal cortex. These preliminary findings suggest that adolescents with 22q11.2DS compensate for executive dysfunction via recruitment of parietal regions. Further, the COMT Met subgroup of 22q11.2DS may recruit additional cingulate activation for tasks requiring attention and inhibition. 22q11.2DS is a unique model for learning about the deleterious effects of decreased dosage of the COMT gene on brain function.

Velocardiofacial syndrome

Velocardiofacial syndrome (VCFS) is the most common known microdeletion in humans. It is also the most common known genetic risk factor for schizophrenia. The aim of this article is to describe the clinical characteristics of the syndrome, with emphasis on the myriad psychiatric disorders and abnormal behaviors from a developmental perspective. In addition, the possible pathways that lead to the psychotic symptoms and cognitive deficits are discussed. Guidelines are suggested to alert clinicians to the possibility of the presence of VCFS, and the cumulative clinical experience and limited research on psychiatric treatments for VCFS are presented. There is an urgent need to conduct treatment trials in this high-risk population.

Lymphocyte numbers and subsets in the human blood. Do they mirror the situation in all organs?

Lymphocyte numbers in the blood are used to evaluate the immune status on a daily basis in medicine. Several studies have documented the normal ranges of lymphocytes and lymphocyte subsets in the peripheral blood. A variety of techniques and criteria have revealed clear differences between the lymphocyte subsets in childhood and adolescence. Race and gender are also variables for blood lymphocytes, and even environmental factors seem to influence the numbers of some lymphocyte populations. However, do all these variations in lymphocyte subsets in the peripheral blood mirror changes in the lymphocyte populations of the whole body, or is it just a result of different migratory habits of cells? The factors influencing the distribution of lymphocytes in the peripheral blood with regard to the different abilities of T and B cells to migrate to distinct lymphoid or non-lymphoid tissue are summarized. In addition it will be described how the removal of organs (e.g. thymus, spleen, liver) influences the distribution of lymphocytes in the blood. All these parameters should be considered not only in the clinical situation when the immune status of a patient is extrapolated from the lymphocyte numbers in the blood, but also when interpreting treatment effects in patients.

DiGeorge syndrome: new insights

Most patients with the clinical features of DiGeorge, velocardiofacial, and conotruncal anomaly face syndromes share a common genetic cause, namely, a deletion of chromosome 22q11, and define the most common deletion syndrome known at this time. The clinical features of the 22q11 deletion syndrome are highly variable between individuals; some have subtle findings, whereas others are severely affected. The most common clinical features include specific types of congenital heart disease, hypocalcemia, immunodeficiency, facial dysmorphia, palate anomalies, velopharyngeal dysfunction, renal anomalies, and speech and feeding disorders as well as neurocognitive, behavioral, and psychiatric disorders. A significant number of patients with tetralogy of Fallot, truncus arteriosus, an interrupted aortic arch, isolated aortic arch anomalies, and perimembranous ventricular septal defects have a 22q11 deletion. Routine testing for a 22q11 deletion in this subset of patients should be considered to provide anticipatory medical intervention and appropriate family counseling.

Complete DiGeorge anomaly in the absence of neonatal hypocalcemia and velofacial and cardiac defects

We report an atypical case of complete DiGeorge (DG) anomaly that presented initially exclusively as severe combined immunodeficiency (SCID). The child had severe infections at diagnosis, in keeping with the SCID phenotype; however, normal lymphocyte counts and immunoglobulin levels were noted at admission, which delayed diagnosis. Importantly, the child presented without neonatal hypocalcemia or velofacial or cardiac abnormalities at the time of diagnosis, which masked underlying DG. This case outlines the difficulties in making the diagnosis of SCID in a timely manner and illustrates the variation in presentation of the 22q11.2 deletion syndrome. There should be a high index of suspicion for primary immunodeficiency among children with severe infections and, because management may vary, DG anomaly should be considered in the differential diagnosis of T- B+ natural killer+ SCID.

High specificity PCR screening for 22q11.2 microdeletion in three different ethnic groups

Congenital heart defects are the most common of all human birth defects. Numerous studies have shown that a deletion within chromosome 22q11 is associated with DiGeorge syndrome and certain forms of sporadic congenital cardiovascular disease. We have determined the value of a PCR assay using markers D22S941, D22S944 and D22S264 designed for the screening of 22q11.2 deletion through consecutive homozygosity in an ethnically admixed urban population. The study population comprised 149 unrelated men and women from three different ethnic groups (white, mulatto and black). Test specificity for the overall population was estimated at 98.3%. We found no significant difference when comparing heterozygosity indices and ethnicity (P value = 0.43 (D22S944), 0.22 (D22S264), and 0.58 (D22S941)). There was no significant difference regarding assay specificity between the three different ethnic groups studied. This assay could constitute a cost-effective way to screen a large number of patients at increased risk, since PCR techniques are easily available, are fast, can be automatized, and are significantly less expensive than fluorescence in situ hybridization.

Association between divergence and interspersed repeats in mammalian noncoding genomic DNA

The amount of noncoding genomic DNA sequence that aligns between human and mouse varies substantially in different regions of their genomes, and the amount of repetitive DNA also varies. In this report, we show that divergence in noncoding nonrepetitive DNA is strongly correlated with the amount of repetitive DNA in a region. We investigated aligned DNA in four large genomic regions with finished human sequence and almost or completely finished mouse sequence. These regions, totaling 5.89 Mb of DNA, are on different chromosomes and vary in their base composition. An analysis based on sliding windows of 10 kb shows that the fraction of aligned noncoding nonrepetitive DNA and the fraction of repetitive DNA are negatively correlated, both at the level of an entire region and locally within it. This conclusion is strongly supported by a randomization study, in which repetitive elements are removed and randomly relocated along the sequences. Thus, regions of noncoding genomic DNA that accumulated fewer point mutations since the primate-rodent divergence also suffered fewer retrotransposition events. These results indicate that some regions of the genome are more "flexible" over the time scale of mammalian evolution, being able to accommodate many point mutations and insertions, whereas other regions are more "rigid" and accumulate fewer changes. Stronger conservation is generally interpreted as indicating more extensive or more important function. The evidence presented here of correlated variation in the rates of different evolutionary processes across noncoding DNA must be considered in assessing such conservation for evidence of selection.

Induction of lymphocyte differentiation by epidermal cultures

Human and murine lymphoid cell populations were induced to express terminal deoxynucleotidyl transferase, a marker of early lymphoid differentiation, by exposure to allogeneic or syngeneic epidermal cells. Control growth medium, fibroblasts, or a mammary epithelial cell line did not induce this marker. These findings suggest that epidermal cells can induce lymphoid cell differentiation in vitro.