The impact of hypocalcemia on full scale IQ in patients with 22q11.2 deletion syndrome.

Hypocalcemia has been reported in ~50% of patients 22q11.2DS and calcium regulation is known to play a role in neuronal development and synaptic plasticity. Because calcium ions play a role in neuronal function and development, we hypothesized that hypocalcemia would be associated with adverse effects on full scale IQ index (FSIQ) in patients with 22q11.2DS. A retrospective chart review cataloguing the presence or absence of hypocalcemia in 1073 subjects with a laboratory confirmed chromosome 22q11.2 deletion evaluated at the Children's Hospital of Philadelphia was conducted. 852/1073 patients had an endocrinology evaluation with laboratory confirmed calcium levels. 466/852 (54.7%) had a diagnosis of hypocalcemia. 265/1073 subjects ranging from 0 to 51 years of age had both calcium levels measured and a neuropsychological evaluation yielding a FSIQ. The mean FSIQ for 146/265 patients with hypocalcemia was 77.09 (SD = 13.56) and the mean FSIQ for 119/265 patients with normocalcemia was 77.27 (SD = 14.25). The distribution of patients with intellectual disability (ID) (FSIQ<69), borderline IQ (FSIQ 70-79), and average IQ (FSIQ>80) between the hypocalcemic and normocalcemic groups was not statistically significant (χ2 = 0.2676, p = 0.8748). Neonatal hypocalcemic seizures were not found to be associated with ID. We found no difference in FSIQ between the hypocalcemic and non-hypocalcemic patients with 22q11.2DS. As our findings differ from a previous report in adult subjects, we speculate that this may reflect a potential benefit from early treatment of hypocalcemia and may support early 22q11.2 deletion detection in order to offer prompt diagnosis and subsequent treatment of hypocalcemia.

What is new with 22q? An update from the 22q and You Center at the Children's Hospital of Philadelphia.

22q11.2 deletion syndrome (22q11.2DS) is a disorder caused by recurrent, chromosome-specific, low copy repeat (LCR)-mediated copy-number losses of chromosome 22q11. The Children's Hospital of Philadelphia has been involved in the clinical care of individuals with what is now known as 22q11.2DS since our initial report of the association with DiGeorge syndrome in 1982. We reviewed the medical records on our continuously growing longitudinal cohort of 1,421 patients with molecularly confirmed 22q11.2DS from 1992 to 2018. Most individuals are Caucasian and older than 8 years. The mean age at diagnosis was 3.9 years. The majority of patients (85%) had typical LCR22A-LCR22D deletions, and only 7% of these typical deletions were inherited from a parent harboring the deletion constitutionally. However, 6% of individuals harbored other nested deletions that would not be identified by traditional 22q11.2 FISH, thus requiring an orthogonal technology to diagnose. Major medical problems included immune dysfunction or allergies (77%), palatal abnormalities (67%), congenital heart disease (64%), gastrointestinal difficulties (65%), endocrine dysfunction (>50%), scoliosis (50%), renal anomalies (16%), and airway abnormalities. Median full-scale intelligence quotient was 76, with no significant difference between individuals with and without congenital heart disease or hypocalcemia. Characteristic dysmorphic facial features were present in most individuals, but dermatoglyphic patterns of our cohort are similar to normal controls. This is the largest longitudinal study of patients with 22q11.2DS, helping to further describe the condition and aid in diagnosis and management. Further surveillance will likely elucidate additional clinically relevant findings as they age.

Molecular genetics of 22q11.2 deletion syndrome.

The 22q11.2 deletion syndrome (22q11.2DS) is a congenital malformation and neuropsychiatric disorder caused by meiotic chromosome rearrangements. One of the goals of this review is to summarize the current state of basic research studies of 22q11.2DS. It highlights efforts to understand the mechanisms responsible for the 22q11.2 deletion that occurs in meiosis. This mechanism involves the four sets of low copy repeats (LCR22) that are dispersed in the 22q11.2 region and the deletion is mediated by nonallelic homologous recombination events. This review also highlights selected genes mapping to the 22q11.2 region that may contribute to the typical clinical findings associated with the disorder and explain that mutations in genes on the remaining allele can uncover rare recessive conditions. Another important aspect of 22q11.2DS is the existence of phenotypic heterogeneity. While some patients are mildly affected, others have severe medical, cognitive, and/or psychiatric challenges. Variability may be due in part to the presence of genetic modifiers. This review discusses current genome-wide efforts to identify such modifiers that could shed light on molecular pathways required for normal human development, cognition or behavior.

Congenital heart diseases and cardiovascular abnormalities in 22q11.2 deletion syndrome: From well-established knowledge to new frontiers.

Congenital heart diseases (CHDs) and cardiovascular abnormalities are one of the pillars of clinical diagnosis of 22q11.2 deletion syndrome (22q11.2DS) and still represent the main cause of mortality in the affected children. In the past 30 years, much progress has been made in describing the anatomical patterns of CHD, in improving their diagnosis, medical treatment, and surgical procedures for these conditions, as well as in understanding the underlying genetic and developmental mechanisms. However, further studies are still needed to better determine the true prevalence of CHDs in 22q11.2DS, including data from prenatal studies and on the adult population, to further clarify the genetic mechanisms behind the high variability of phenotypic expression of 22q11.2DS, and to fully understand the mechanism responsible for the increased postoperative morbidity and for the premature death of these patients. Moreover, the increased life expectancy of persons with 22q11.2DS allowed the expansion of the adult population that poses new challenges for clinicians such as acquired cardiovascular problems and complexity related to multisystemic comorbidity. In this review, we provide a comprehensive review of the existing literature about 22q11.2DS in order to summarize the knowledge gained in the past years of clinical experience and research, as well as to identify the remaining gaps in comprehension of this syndrome and the possible future research directions.

Reduction of CRKL expression in patients with partial DiGeorge syndrome is associated with impairment of T-cell functions.

BACKGROUND: Partial DiGeorge syndrome (pDGS) is caused by deletion of the 22q11.2 region. Within this region lies CrK-like (CRKL), a gene encoding an adapter protein belonging to the Crk family that is involved in the signaling cascade of IL-2, stromal cell-derived factor 1α, and type I interferon. Although recurrent infections can be observed in patients with deletion of chromosome 22 syndrome, the immune pathogenesis of this condition is yet not fully understood. OBJECTIVE: We aimed to investigate the role of CRKL in T-cell functional responses in patients affected with pDGS. METHODS: Protein expression levels and phosphorylation of CRKL were evaluated in patients with pDGS. T-cell functional assays in vitro and gene-silencing experiments were also performed. RESULTS: CRKL protein expression, as well as its phosphorylation, were reduced in all patients with pDGS, especially on IL-2 stimulation. Moreover, T cells presented impaired proliferation and reduced IL-2 production on anti-CD3/CD28 stimulation and decreased c-Fos expression. Finally, CRKL silencing in Jurkat T cells resulted in impaired T-cell proliferation and reduced c-Fos expression. CONCLUSIONS: The impaired T-cell proliferation and reduction of CRKL, phosphorylated CRKL, and c-Fos levels suggest a possible role of CRKL in functional deficiencies of T cells in patients with pDGS.

Assessment of Chromosome 22q11.2 Deletion in Patients with Isolated Cleft Palate: A Systematic Review of Prospective Studies.

Background: The prevalence of 22q11.2 deletion in patients presenting with isolated cleft palate has not been systematically assessed. Objective: To assess the evidence in the literature for the prevalence of 22q11.2 deletion in patients who were presenting with isolated cleft palate. Material and Method: A systematic literature search was conducted through PubMed between 1992 and June 2016 using search terms of 22q11.2 deletion OR 22q11 deletion AND cleft palate. Results: Of the six prospective studies reported, 328 patients with isolated cleft palate had been screened with FISH (Fluorescence In Situ Hybridization) test for 22q11.2 deletion. Among the 328 patients, there was one (0.3%) patient with positive FISH test for 22q11.2 deletion. This patient was clinically assessed and did not have an associated malformation or clinically recognized syndrome. Conclusion: The prevalence of 22q11.2 deletion among patients with isolated cleft palate is rather low. Of more than 400 genetic disorders involving occurrences of isolated cleft palate, FISH testing for 22q11.2 deletion in a patient with isolated cleft palate is recommended on clinical suspicion of additional clinical presentations of 22q11.2 deletion syndrome such as conotruncal congenital heart diseases, dysmorphic facies, velopharyngeal insufficiencies, immune deficiencies, hypoparathyroidisms, and neuropsychiatric disorders.

Synergistic interactions between Drosophila orthologues of genes spanned by de novo human CNVs support multiple-hit models of autism.

Autism spectrum disorders (ASDs) are highly heritable and characterised by deficits in social interaction and communication, as well as restricted and repetitive behaviours. Although a number of highly penetrant ASD gene variants have been identified, there is growing evidence to support a causal role for combinatorial effects arising from the contributions of multiple loci. By examining synaptic and circadian neurological phenotypes resulting from the dosage variants of unique human:fly orthologues in Drosophila, we observe numerous synergistic interactions between pairs of informatically-identified candidate genes whose orthologues are jointly affected by large de novo copy number variants (CNVs). These CNVs were found in the genomes of individuals with autism, including a patient carrying a 22q11.2 deletion. We first demonstrate that dosage alterations of the unique Drosophila orthologues of candidate genes from de novo CNVs that harbour only a single candidate gene display neurological defects similar to those previously reported in Drosophila models of ASD-associated variants. We then considered pairwise dosage changes within the set of orthologues of candidate genes that were affected by the same single human de novo CNV. For three of four CNVs with complete orthologous relationships, we observed significant synergistic effects following the simultaneous dosage change of gene pairs drawn from a single CNV. The phenotypic variation observed at the Drosophila synapse that results from these interacting genetic variants supports a concordant phenotypic outcome across all interacting gene pairs following the direction of human gene copy number change. We observe both specificity and transitivity between interactors, both within and between CNV candidate gene sets, supporting shared and distinct genetic aetiologies. We then show that different interactions affect divergent synaptic processes, demonstrating distinct molecular aetiologies. Our study illustrates mechanisms through which synergistic effects resulting from large structural variation can contribute to human disease.

Loss of Wnt5a disrupts second heart field cell deployment and may contribute to OFT malformations in DiGeorge syndrome.

Outflow tract (OFT) malformation accounts for ∼30% of human congenital heart defects and manifests frequently in TBX1 haplo-insufficiency associated DiGeorge (22q11.2 deletion) syndrome. OFT myocardium originates from second heart field (SHF) progenitors in the pharyngeal and splanchnic mesoderm (SpM), but how these progenitors are deployed to the OFT is unclear. We find that SHF progenitors in the SpM gradually gain epithelial character and are deployed to the OFT as a cohesive sheet. Wnt5a, a non-canonical Wnt, is expressed specifically in the caudal SpM and may regulate oriented cell intercalation to incorporate SHF progenitors into an epithelial-like sheet, thereby generating the pushing force to deploy SHF cells rostrally into the OFT. Using enhancer trap and Cre transgenes, our lineage tracing experiments show that in Wnt5a null mice, SHF progenitors are trapped in the SpM and fail to be deployed to the OFT efficiently, resulting in a reduction in the inferior OFT myocardial wall and its derivative, subpulmonary myocardium. Concomitantly, the superior OFT and subaortic myocardium are expanded. Finally, in chick embryos, blocking the Wnt5a function in the caudal SpM perturbs polarized elongation of SHF progenitors, and compromises their deployment to the OFT. Collectively, our results highlight a critical role for Wnt5a in deploying SHF progenitors from the SpM to the OFT. Given that Wnt5a is a putative transcriptional target of Tbx1, and the similar reduction of subpulmonary myocardium in Tbx1 mutant mice, our results suggest that perturbing Wnt5a-mediated SHF deployment may be an important pathogenic mechanism contributing to OFT malformations in DiGeorge syndrome.

Unilateral Möbius syndrome: two cases and a review of the literature.

IMPORTANCE: The Möbius sequence is a rare condition defined by the combination of congenital non-progressive facial and abducens nerve palsies. The etiology of the sequence is still unknown, but likely encompasses a group of heterogeneous disorders involving genetic maldevelopment of the brainstem, a fetal vascular insult and/or teratogen exposure. The clinical phenotype reported has expanded over the years, and may be associated with more extensive cranial nerve and oropharyngeal involvement, as well as limb defects. OBSERVATIONS: We describe two cases of children presenting with unilateral Möbius syndrome associated with ipsilateral unilateral palatal weakness. Investigations failed to identified a clear underlying etiology, but both cases shared phenotypic features of other more common cranial facial disorders such as craniofacial microsomia and the velocardiofacial syndrome. CONCLUSION AND RELEVANCE: These two cases highlight the clinical heterogeneity of the Möbius sequence. Although asymmetries are not uncommon, cases with strictly unilateral features are extremely rare, and as such these may represent a distinct subgroup that may pertain to a specific etiology. Although in many cases, evidence of an intrauterine vascular insult may be identified, a contributing genetic etiology should be considered, even in cases with strictly unilateral features. As such genes expressed in the developing rhombencephalon and its vasculature represent good candidates for future investigation.

Impaired acuity of the approximate number system in 22q11.2 microdeletion syndrome

A magnitude comparison deficit has been frequently observed in velocardiofacial syndrome (Del22q11.2). We hypothesized that this deficit extends to impairments in the acuity of the approximate number system (ANS). Three groups of children aged 8-14 years were investigated: Del22q11.2 children (n = 12), low cognitive ability children (LCA; n = 12), and matched typically developing children (TD; n = 28). All children were assessed with a simple reaction time task and symbolic and nonsymbolic number comparison tasks. To estimate the acuity of the ANS, the Weber fraction (w) was calculated from the nonsymbolic comparison task. The Del22q11.2 group exhibited a significantly higher w compared with the other groups. Importantly, no significant differences were found in w between the TD and LCA groups. The performance pattern of the Del22q11.2 group was similar to the TD group in the symbolic comparison task, and both of these groups had better performance than the LCA group. The impairment of ANS acuity observed in individuals with Del22q11.2 cannot be explained by deficits in general processing speed because no significant group differences were found in the simple reaction time task. These results suggest that lower acuity of the ANS should be added to the behavioral phenotype of Del22q11.2. The absence of impaired ANS acuity in the LCA group is consistent with the hypothesis that number sense is a relatively specific and autonomous domain. Investigations of low ANS acuity in mathematics learning difficulties and Del22q11.2 should be intensified.(AU)

Impaired acuity of the approximate number system in 22q11.2 microdeletion syndrome

A magnitude comparison deficit has been frequently observed in velocardiofacial syndrome (Del22q11.2). We hypothesized that this deficit extends to impairments in the acuity of the approximate number system (ANS). Three groups of children aged 8-14 years were investigated: Del22q11.2 children (n = 12), low cognitive ability children (LCA; n = 12), and matched typically developing children (TD; n = 28). All children were assessed with a simple reaction time task and symbolic and nonsymbolic number comparison tasks. To estimate the acuity of the ANS, the Weber fraction (w) was calculated from the nonsymbolic comparison task. The Del22q11.2 group exhibited a significantly higher w compared with the other groups. Importantly, no significant differences were found in w between the TD and LCA groups. The performance pattern of the Del22q11.2 group was similar to the TD group in the symbolic comparison task, and both of these groups had better performance than the LCA group. The impairment of ANS acuity observed in individuals with Del22q11.2 cannot be explained by deficits in general processing speed because no significant group differences were found in the simple reaction time task. These results suggest that lower acuity of the ANS should be added to the behavioral phenotype of Del22q11.2. The absence of impaired ANS acuity in the LCA group is consistent with the hypothesis that number sense is a relatively specific and autonomous domain. Investigations of low ANS acuity in mathematics learning difficulties and Del22q11.2 should be intensified...

Contribution of congenital heart disease to neuropsychiatric outcome in school-age children with 22q11.2 deletion syndrome.

Children with 22q11.2 deletion syndrome (22q11DS) present with congenital heart disease (CHD) and high prevalence of psychiatric disorders and neurocognitive deficits. Although CHD has been implicated in neurodevelopment, its role in the neuropsychiatric outcome in 22q11DS is poorly understood. We investigated whether CHD contributes to the high prevalence of psychiatric disorders and neurocognitive impairments in 22q11DS. Fifty-four children ages 8-14 years with 22q11DS and 16 age-matched non-deleted children with CHD participated. They were assessed using semi-structured interviews and a Computerized Neurocognitive Battery. CHD status was assessed using available medical records. Prevalence of psychiatric disorders and cognitive profiles were compared among the groups. There were no significant differences between the prevalence of psychiatric disorders in the 22q11DS with and without CHD. In 22q11DS with CHD, the prevalence rates were 41% anxiety disorders, 37% ADHD and 71% psychosis spectrum. In 22q11DS without CHD, the rates were 33% anxiety disorders, 41% ADHD and 64% psychosis spectrum. In comparison, the non-deleted CHD group had lower rates of psychopathology (25% anxiety disorders, 6% ADHD, and 13% psychosis spectrum). Similarly, the 22q11DS groups, regardless of CHD status, had significantly greater neurocognitive deficits across multiple domains, compared to the CHD-only group. We conclude that CHD in this sample of children with 22q11.2DS does not have a major impact on the prevalence of psychiatric disorders and is not associated with increased neurocognitive deficits. These findings suggest that the 22q11.2 deletion status itself may confer significant neuropsychiatric vulnerability in this population.

The 22q11 deletion: DiGeorge and velocardiofacial syndromes and the role of TBX1.

Hemizygous deletion of 22q11 affects approximately 1:4000 live births and may give rise to many different malformations but classically results in a constellation of phenotypes that receive a diagnosis of DiGeorge syndrome or velocardiofacial syndrome. Particularly affected are the heart and great vessels, the endocrine glands of the neck, the face, the soft palate, and cognitive development. Although up to 50 genes may be deleted, it is haploinsufficiency of the transcription factor TBX1 that is thought to make the greatest contribution to the disorder. Mouse embryos are exquisitely sensitive to varying levels of Tbx1 mRNA, and Tbx1 is required in all three germ layers of the embryonic pharyngeal region for normal development. TBX1 controls cell proliferation and affects cellular differentiation in a cell autonomous fashion, but it also directs non-cell autonomous effects, most notably in the signaling between pharyngeal surface ectoderm and the rostral neural crest. TBX1 interacts with several signaling pathways, including fibroblast growth factor, retinoic acid, CTNNB1 (formerly known as ß-catenin), and bone morphogenetic protein (BMP), and may regulate pathways by both DNA-binding and non-binding activity. In addition to the structural abnormalities seen in 22q11 deletion syndrome (DS) and Tbx1 mutant mouse models, patients reaching adolescence and adulthood have a predisposition to psychiatric illness. Whether this has a developmental basis and, if so, which genes are involved is an ongoing strand of research. Thus, knowledge of the genetic and developmental mechanisms underlying 22q11DS has the potential to inform about common disease as well as developmental defect.

Chapter 27: Approach to primary immunodeficiency.

Primary immunodeficiency diseases (PID) are inherited defects of the innate or adaptive arms of the immune system that lead to an increase in the incidence, frequency, or severity of infections. There may be defects in the adaptive arm of the immune system that include combined immunodeficiency and antibody deficiency syndromes or by abnormalities in innate immunity such as disorders of phagocytes, the complement pathway, or Toll-Like receptor (TLR) mediated signaling. Recurrent sinopulmonary infections with encapsulated bacteria such as Haemophilus influenza type B or Streptococcus pneumoniae may be characteristic of an IgG antibody deficiency or dysfunction. Frequent viral, fungal, or protozoal infections may suggest T lymphocyte dysfunction. Multiple staphylococcal skin infections and fungal infections may imply neutrophil dysfunction or the hyper-IgE syndrome, and recurrent neisserial infection is a characteristic manifestation of late complement component (C5-9, or the membrane attack complex) defects. Recurrent viral or pyogenic bacterial infections often without the presence of a significant inflammatory response suggest a defect in TLR signaling. Mycobacterial infections are characteristic of defects in interleukin (IL)-12, interferon (IFN) gamma, or their receptors. Screening of newborns for T-cell lymphopenia using a polymerase chain reaction to amplify T-cell receptor excision circles (TRECs), which are formed when a T cell rearranges the variable region of its receptor, serves as a surrogate for newly synthesized naïve T cells. Because of very low numbers of TRECs, severe combined immunodeficiency, DiGeorge syndrome, and other causes of T-cell lymphopenia have been identified in newborns.

DiGeorge anomaly in the absence of chromosome 22q11.2 deletion.

OBJECTIVE: To test the hypothesis that the prevalence of deletion 22q11.2 among individuals who meet criteria for DiGeorge anomaly (DGA) is lower than the 90% commonly cited. STUDY DESIGN: Participants were identified through retrospective chart reviews on all patients who underwent testing for deletion 22q11.2 and all patients with a diagnosis of "DiGeorge" or any of the major criteria associated with DGA at a large pediatric hospital over a period of 6 years. DGA was confirmed in 64 individuals, based on the presence of at least 2 of the following features: (1) cellular immune deficiency and/or absence of part or all of the thymus; (2) hypocalcemia and/or parathyroid deficiency; (3) congenital heart disease. RESULTS: Of the 64 individuals with DGA, 29 (45%) did not have a chromosome 22q11.2 deletion. Among this deletion-negative subset, diabetic embryopathy and other chromosome abnormalities were the most commonly recognized underlying etiologies. CONCLUSIONS: These findings challenge a widely held belief that nearly 90% of DGA is due to chromosome 22q11.2 deletion. This study also calls attention to the heterogeneity of DGA, highlights similarities and differences between those with and without a chromosome 22q11.2 deletion, and attempts to resolve some confusing features of conditions associated with DGA.

Combined immune deficiencies in children.

Combined immune deficiencies are a heterogeneous group of congenital disorders usually attributable to a single gene defect. The hallmark of these disorders is recurrent infections resulting from defects in both T- and B-cell function. This article reviews the basic components of the immune system as well as the clinical presentation, laboratory findings, and treatment for 3 distinct combined immune deficiencies.

Inactivation of TGFbeta signaling in neural crest stem cells leads to multiple defects reminiscent of DiGeorge syndrome.

Specific inactivation of TGFbeta signaling in neural crest stem cells (NCSCs) results in cardiovascular defects and thymic, parathyroid, and craniofacial anomalies. All these malformations characterize DiGeorge syndrome, the most common microdeletion syndrome in humans. Consistent with a role of TGFbeta in promoting non-neural lineages in NCSCs, mutant neural crest cells migrate into the pharyngeal apparatus but are unable to acquire non-neural cell fates. Moreover, in neural crest cells, TGFbeta signaling is both sufficient and required for phosphorylation of CrkL, a signal adaptor protein implicated in the development of DiGeorge syndrome. Thus, TGFbeta signal modulation in neural crest differentiation might play a crucial role in the etiology of DiGeorge syndrome.