CIAO1 and MMS19 deficiency: A lethal neurodegenerative phenotype caused by cytosolic Fe-S cluster protein assembly disorders.

PURPOSE: The functionality of many cellular proteins depends on cofactors; yet, they have only been implicated in a minority of Mendelian diseases. Here, we describe the first 2 inherited disorders of the cytosolic iron-sulfur protein assembly system. METHODS: Genetic testing via genome sequencing was applied to identify the underlying disease cause in 3 patients with microcephaly, congenital brain malformations, progressive developmental and neurologic impairments, recurrent infections, and a fatal outcome. Studies in patient-derived skin fibroblasts and zebrafish models were performed to investigate the biochemical and cellular consequences. RESULTS: Metabolic analysis showed elevated uracil and thymine levels in body fluids but no pathogenic variants in DPYD, encoding dihydropyrimidine dehydrogenase. Genome sequencing identified compound heterozygosity in 2 patients for missense variants in CIAO1, encoding cytosolic iron-sulfur assembly component 1, and homozygosity for an in-frame 3-nucleotide deletion in MMS19, encoding the MMS19 homolog, cytosolic iron-sulfur assembly component, in the third patient. Profound alterations in the proteome, metabolome, and lipidome were observed in patient-derived fibroblasts. We confirmed the detrimental effect of deficiencies in CIAO1 and MMS19 in zebrafish models. CONCLUSION: A general failure of cytosolic and nuclear iron-sulfur protein maturation caused pleiotropic effects. The critical function of the cytosolic iron-sulfur protein assembly machinery for antiviral host defense may well explain the recurrent severe infections occurring in our patients.

Identification of two 14q32 deletions involving DICER1 associated with the development of DICER1-related tumors.

DICER1 encodes an RNase III endonuclease protein that regulates the production of small non-coding RNAs. Germline mutations in DICER1 are associated with an autosomal dominant hereditary cancer predisposition syndrome that confers an increased risk for the development of several rare childhood and adult-onset tumors, the most frequent of which include pleuropulmonary blastoma, ovarian sex cord-stromal tumors, cystic nephroma, and thyroid gland neoplasia. The majority of reported germline DICER1 mutations are truncating sequence-level alterations, suggesting that a loss-of-function type mechanism drives tumor formation in DICER1 syndrome. However, reports of patients with germline DICER1 whole gene deletions are limited, and thus far, only two have reported an association with tumor development. Here we report the clinical findings of three patients from two unrelated families with 14q32 deletions that encompass the DICER1 locus. The deletion identified in Family I is 1.4 Mb and was initially identified in a 6-year-old male referred for developmental delay, hypotonia, macrocephaly, obesity, and behavioral problems. Subsequent testing revealed that this deletion was inherited from his mother, who had a clinical history that included bilateral multinodular goiter and papillary thyroid carcinoma. The second deletion is 5.0 Mb and was identified in a 15-year-old female who presented with autism, coarse facial features, Sertoli-Leydig cell tumor, and Wilms' tumor. These findings provide additional supportive evidence that germline deletion of DICER1 confers an increased risk for DICER1-related tumor development, and provide new insight into the clinical significance of deletions involving the 14q32 region.

Clinical features associated with copy number variations of the 14q32 imprinted gene cluster.

Uniparental disomy (UPD) for imprinted chromosomes can cause abnormal phenotypes due to absent or overexpression of imprinted genes. UPD(14)pat causes a unique constellation of features including thoracic skeletal anomalies, polyhydramnios, placentomegaly, and limited survival; its hypothesized cause is overexpression of paternally expressed RTL1, due to absent regulatory effects of maternally expressed RTL1as. UPD(14)mat causes a milder condition with hypotonia, growth failure, and precocious puberty; its hypothesized cause is absence of paternally expressed DLK1. To more clearly establish how gains and losses of imprinted genes can cause disease, we report six individuals with copy number variations of the imprinted 14q32 region identified through clinical microarray-based comparative genomic hybridization. Three individuals presented with UPD(14)mat-like phenotypes (Temple syndrome) and had apparently de novo deletions spanning the imprinted region, including DLK1. One of these deletions was shown to be on the paternal chromosome. Two individuals with UPD(14)pat-like phenotypes had 122-154kb deletions on their maternal chromosomes that included RTL1as but not the differentially methylated regions that regulate imprinted gene expression, providing further support for RTL1 overexpression as a cause for the UPD(14)pat phenotype. The sixth individual is tetrasomic for a 1.7Mb segment, including the imprinted region, and presents with intellectual disability and seizures but lacks significant phenotypic overlap with either UPD(14) syndrome. Therefore, the 14q32 imprinted region is dosage sensitive, with deletions of different critical regions causing UPD(14)mat- and UPD(14)pat-like phenotypes, while copy gains are likely insufficient to recapitulate these phenotypes.

Mutations in the intellectual disability gene KDM5C reduce protein stability and demethylase activity.

Mutations in KDM5C are an important cause of X-linked intellectual disability in males. KDM5C encodes a histone demethylase, suggesting that alterations in chromatin landscape may contribute to disease. We used primary patient cells and biochemical approaches to investigate the effects of patient mutations on KDM5C expression, stability and catalytic activity. We report and characterize a novel nonsense mutation, c.3223delG (p.V1075Yfs*2), which leads to loss of KDM5C protein. We also characterize two KDM5C missense mutations, c.1439C>T (p.P480L) and c.1204G>T (p.D402Y) that are compatible with protein production, but compromise stability and enzymatic activity. Finally, we demonstrate that a c.2T>C mutation in the translation initiation codon of KDM5C results in translation re-start and production of a N-terminally truncated protein (p.M1_E165del) that is unstable and lacks detectable demethylase activity. Patient fibroblasts do not show global changes in histone methylation but we identify several up-regulated genes, suggesting local changes in chromatin conformation and gene expression. This thorough examination of KDM5C patient mutations demonstrates the utility of examining the molecular consequences of patient mutations on several levels, ranging from enzyme production to catalytic activity, when assessing the functional outcomes of intellectual disability mutations.

6q22.1 microdeletion and susceptibility to pediatric epilepsy.

Genomic copy-number variations (CNVs) constitute an important cause of epilepsies and other human neurological disorders. Recent advancement of technologies integrating genome-wide CNV mapping and sequencing is rapidly expanding the molecular field of pediatric neurodevelopmental disorders. In a previous study, a novel epilepsy locus was identified on 6q16.3q22.31 by linkage analysis in a large pedigree. Subsequent array comparative genomic hybridization (array CGH) analysis of four unrelated cases narrowed this region to ∼5 Mb on 6q22.1q22.31. We sought to further narrow the critical region on chromosome 6q22. Array CGH analysis was used in genome-wide screen for CNVs of a large cohort of patients with neurological abnormalities. Long-range PCR and DNA sequencing were applied to precisely map chromosomal deletion breakpoints. Finally, real-time qPCR was used to estimate relative expression in the brain of the candidate genes. We identified six unrelated patients with overlapping microdeletions within 6q22.1q22.31 region, three of whom manifested seizures. Deletions were found to be de novo in 5/6 cases, including all subjects presenting with seizures. We sequenced the deletion breakpoints in four patients and narrowed the critical region to a ∼250-kb segment at 6q22.1 that includes NUS1, several expressed sequence tags (ESTs) that are highly expressed in the brain, and putative regulatory sequences of SLC35F1. Our findings indicate that dosage alteration in particular, of NUS1, EST AI858607, or SLC35F1 are important contributors to the neurodevelopmental phenotype associated with 6q22 deletion, including epilepsy and tremors.

Comprehensive evaluation of the child with intellectual disability or global developmental delays.

Global developmental delay and intellectual disability are relatively common pediatric conditions. This report describes the recommended clinical genetics diagnostic approach. The report is based on a review of published reports, most consisting of medium to large case series of diagnostic tests used, and the proportion of those that led to a diagnosis in such patients. Chromosome microarray is designated as a first-line test and replaces the standard karyotype and fluorescent in situ hybridization subtelomere tests for the child with intellectual disability of unknown etiology. Fragile X testing remains an important first-line test. The importance of considering testing for inborn errors of metabolism in this population is supported by a recent systematic review of the literature and several case series recently published. The role of brain MRI remains important in certain patients. There is also a discussion of the emerging literature on the use of whole-exome sequencing as a diagnostic test in this population. Finally, the importance of intentional comanagement among families, the medical home, and the clinical genetics specialty clinic is discussed.

The metabolic evaluation of the child with an intellectual developmental disorder: diagnostic algorithm for identification of treatable causes and new digital resource.

Intellectual developmental disorders (IDD), characterized by significant impairment of cognitive functions, with limitations of learning, adaptive behavior and skills, are frequent (2.5% of the population affected) and present with significant co-morbidity. The burden of IDD, in terms of emotional suffering and associated health care costs, is significant; prevention and treatment therefore are important. A systematic literature review, updated in 2013, identified 89 inborn errors of metabolism (IEMs), which present with IDD as prominent feature and are amenable to causal therapy. Therapeutic effects include improvement and/or stabilization of psychomotor/cognitive development, behavior/psychiatric disturbances, seizures, neurologic and systemic manifestations. The levels of available evidence for the various treatments range from Level 1b, c (n=5); Level 2a, b, c (n=14); Level 4 (n=53), and Levels 4-5 (n=27). For a target audience comprising clinical and biochemical geneticists, child neurologists and developmental pediatricians, five experts translated....this data into a 2-tiered diagnostic algorithm: The first tier comprises metabolic "screening" tests in urine and blood, which are relatively accessible, affordable, less invasive, and have the potential to identify 60% of all treatable IEMs. The second tier investigations for the remaining disorders are ordered based on individual clinical signs and symptoms. This algorithm is supported by an App www.treatable-id.org, which comprises up-to-date information on all 89 IEMs, relevant diagnostic tests, therapies and a search function based on signs and symptoms. These recommendations support the clinician in early identification of treatable IEMs in the child with IDD, allowing for timely initiation of therapy with the potential to improve neurodevelopmental outcomes. The need for future studies to determine yield and usefulness of these recommendations, with subsequent updates and improvements to developments in the field, is outlined.

Neurodevelopmental disorders and genetic testing: current approaches and future advances.

Genetic testing for intellectual disability, global developmental delay and other neurodevelopmental disorders has advanced considerably in the last five to ten years and can be an important diagnostic tool for clinicians. This article provides a clinical and ethical framework for understanding these advances, future directions and the current limitations of these approaches.

Haploinsufficiency of SOX5 at 12p12.1 is associated with developmental delays with prominent language delay, behavior problems, and mild dysmorphic features.

SOX5 encodes a transcription factor involved in the regulation of chondrogenesis and the development of the nervous system. Despite its important developmental roles, SOX5 disruption has yet to be associated with human disease. We report one individual with a reciprocal translocation breakpoint within SOX5, eight individuals with intragenic SOX5 deletions (four are apparently de novo and one inherited from an affected parent), and seven individuals with larger 12p12 deletions encompassing SOX5. Common features in these subjects include prominent speech delay, intellectual disability, behavior abnormalities, and dysmorphic features. The phenotypic impact of the deletions may depend on the location of the deletion and, consequently, which of the three major SOX5 protein isoforms are affected. One intragenic deletion, involving only untranslated exons, was present in a more mildly affected subject, was inherited from a healthy parent and grandparent, and is similar to a deletion found in a control cohort. Therefore, some intragenic SOX5 deletions may have minimal phenotypic effect. Based on the location of the deletions in the subjects compared to the controls, the de novo nature of most of these deletions, and the phenotypic similarities among cases, SOX5 appears to be a dosage-sensitive, developmentally important gene.

Recurrent deletions and reciprocal duplications of 10q11.21q11.23 including CHAT and SLC18A3 are likely mediated by complex low-copy repeats.

We report 24 unrelated individuals with deletions and 17 additional cases with duplications at 10q11.21q21.1 identified by chromosomal microarray analysis. The rearrangements range in size from 0.3 to 12 Mb. Nineteen of the deletions and eight duplications are flanked by large, directly oriented segmental duplications of >98% sequence identity, suggesting that nonallelic homologous recombination (NAHR) caused these genomic rearrangements. Nine individuals with deletions and five with duplications have additional copy number changes. Detailed clinical evaluation of 20 patients with deletions revealed variable clinical features, with developmental delay (DD) and/or intellectual disability (ID) as the only features common to a majority of individuals. We suggest that some of the other features present in more than one patient with deletion, including hypotonia, sleep apnea, chronic constipation, gastroesophageal and vesicoureteral refluxes, epilepsy, ataxia, dysphagia, nystagmus, and ptosis may result from deletion of the CHAT gene, encoding choline acetyltransferase, and the SLC18A3 gene, mapping in the first intron of CHAT and encoding vesicular acetylcholine transporter. The phenotypic diversity and presence of the deletion in apparently normal carrier parents suggest that subjects carrying 10q11.21q11.23 deletions may exhibit variable phenotypic expressivity and incomplete penetrance influenced by additional genetic and nongenetic modifiers.

National profile of children with Down syndrome: disease burden, access to care, and family impact.

OBJECTIVE: To measure the co-morbidities associated with Down syndrome compared with those in other children with special health care needs (CSHCN). Additionally, to examine reported access to care, family impact, and unmet needs for children with Down syndrome compared with other CSHCN. STUDY DESIGN: An analysis was conducted on the nationally representative 2005 to 2006 National Survey of Children with Special Health Care Needs. Bivariate analyses compared children with Down syndrome with all other CSHCN. Multivariate analyses examined the role of demographic, socioeconomic, and medical factors on measures of care receipt and family impact. RESULTS: An estimated 98,000 CSHCN have Down syndrome nationally. Compared with other CSHCN, children with Down syndrome had a greater number of co-morbid conditions, were more likely to have unmet needs, faced greater family impacts, and were less likely to have access to a medical home. These differences become more pronounced for children without insurance and from low socioeconomic status families. CONCLUSIONS: Children with Down syndrome disproportionately face greater disease burden, more negatively pronounced family impacts, and greater unmet needs than other CSHCN. Promoting medical homes at the practice level and use of those services by children with Down syndrome and other CSHCN may help mitigate these family impacts.

Behavioral features in young adults with FG syndrome (Opitz-Kaveggia syndrome).

Opitz and Kaveggia [Opitz and Kaveggia (1974); Z Kinderheilkd 117:1-18] reported on a family of five affected males with distinctive facial appearance, mental retardation, macrocephaly, imperforate anus, and hypotonia. Risheg et al. [Risheg et al. (2007); Nature Genetics 39:451-453] identified an identical mutation (p.R961W) in MED12 in six families with Opitz-Kaveggia syndrome, including a surviving affected man from the original family reported in 1974. The previously described behavior phenotype of hyperactivity, affability, and excessive talkativeness is very frequent in young boys with FG syndrome, along with socially oriented, attention-seeking behaviors. We present case studies of five adult males who were previously published with the clinical diagnosis of FG syndrome and then subsequently proven by Risheg et al. [Risheg et al. (2007); Nature Genetics 39:451-453] to have the recurrent p.R961W mutation. These individuals had episodic and longstanding behavior patterns, sometimes aggressive or self-abusing, that occurred more frequently in puberty and early adulthood. We try to describe the triggers for these behaviors, indicate how these behaviors change with advancing age, and suggest specific recommendations and interventional strategies based on the clinical histories of affected adolescent males with FG syndrome [Graham et al., 2008; Clark et al., 2009]. Young men who exhibit these behaviors may benefit from a careful examination to detect medical problems, use of mood stabilizers if needed, and/or behavioral intervention. The transition to a community living situation can be challenging without careful planning and timely behavioral intervention. They remain impulsive and can have aggressive outbursts when making the transition to adult life, but these challenges can be managed, as demonstrated by these clinical histories.

A recurrent 16p12.1 microdeletion supports a two-hit model for severe developmental delay.

We report the identification of a recurrent, 520-kb 16p12.1 microdeletion associated with childhood developmental delay. The microdeletion was detected in 20 of 11,873 cases compared with 2 of 8,540 controls (P = 0.0009, OR = 7.2) and replicated in a second series of 22 of 9,254 cases compared with 6 of 6,299 controls (P = 0.028, OR = 2.5). Most deletions were inherited, with carrier parents likely to manifest neuropsychiatric phenotypes compared to non-carrier parents (P = 0.037, OR = 6). Probands were more likely to carry an additional large copy-number variant when compared to matched controls (10 of 42 cases, P = 5.7 x 10(-5), OR = 6.6). The clinical features of individuals with two mutations were distinct from and/or more severe than those of individuals carrying only the co-occurring mutation. Our data support a two-hit model in which the 16p12.1 microdeletion both predisposes to neuropsychiatric phenotypes as a single event and exacerbates neurodevelopmental phenotypes in association with other large deletions or duplications. Analysis of other microdeletions with variable expressivity indicates that this two-hit model might be more generally applicable to neuropsychiatric disease.

Access to genetic counseling for children with autism, Down syndrome, and intellectual disabilities.

OBJECTIVE: We examined the need for genetic counseling services (GCS) for families of children with autism spectrum disorder (ASD), Down syndrome (DS), and/or mental retardation (MR) and factors that influence the receipt of needed GCS for those children relative to other children with special health care needs (CSHCN). METHODS: Analysis was conducted on the 2005-2006 National Survey of Children With Special Health Care Needs, a nationally representative sample. Bivariate analyses were conducted by examining need for and receipt of GCS for children with ASD, DS, and/or MR and other CSHCN as well as differences by contextual variables using the health belief model (HBM). Logistic regression analyses were conducted to assess the relative impact of receipt of needed GCS by HBM constructs. RESULTS: Families of children with diagnoses of ASD, DS, and/or MR perceive significantly higher need for GCS than other CSHCN. The presence of a medical home is the single most important factor in facilitating access to GCS, together with the presence of insurance, particularly private or a combination of private and public insurance. As income and education attainment decrease, barriers to GCS rise. CONCLUSIONS: This analysis supports strategies for improving linkages between specialty providers and the medical home at which primary care is delivered. Increased effort should be made to attend to those who experience barriers that result from lack of insurance, poverty, low education, or racial or ethnic differences. Health professionals need to collaborate in developing solutions to underinsurance or lack of insurance for CSHCN.

FG syndrome, an X-linked multiple congenital anomaly syndrome: the clinical phenotype and an algorithm for diagnostic testing.

FG syndrome is a rare X-linked multiple congenital anomaly-cognitive impairment disorder caused by the p.R961W mutation in the MED12 gene. We identified all known patients with this mutation to delineate their clinical phenotype and devise a clinical algorithm to facilitate molecular diagnosis. We ascertained 23 males with the p.R961W mutation in MED12 from 9 previously reported FG syndrome families and 1 new family. Six patients are reviewed in detail. These 23 patients were compared with 48 MED12 mutation-negative patients, who had the clinical diagnosis of FG syndrome. Traits that best discriminated between these two groups were chosen to develop an algorithm with high sensitivity and specificity for the p.R961W MED12 mutation. FG syndrome has a recognizable dysmorphic phenotype with a high incidence of congenital anomalies. A family history of X-linked mental retardation, deceased male infants, and/or multiple fetal losses was documented in all families. The algorithm identifies the p.R961W MED12 mutation-positive group with 100% sensitivity and 90% specificity. The clinical phenotype of FG syndrome defines a recognizable pattern of X-linked multiple congenital anomalies and cognitive impairment. This algorithm can assist the clinician in selecting the patients for testing who are most likely to have the recurrent p.R961W MED12 mutation.

Improving genetic health care: a Northern New England pilot project addressing the genetic evaluation of the child with developmental delays or intellectual disability.

In 2006, all clinical genetics practices in Northern New England (Vermont, New Hampshire, and Maine) formed a learning collaborative with the purpose of improving genetic health care and outcomes. This article describes the current status of this effort. The methodology is based on our own modifications of the Institute of Healthcare Improvement "Breakthrough Series" and the Northern New England Cystic Fibrosis Consortium. Because of similarities across practices and the availability of existing published practice parameters, the clinical genetics evaluation of the child with developmental delay or intellectual disability was chosen as the topic to be studied. The aim was to improve the rate of etiological diagnosis of those with developmental delays referred to each genetics center by improving the processes of care. Process and outcomes were evaluated. Four of five sites also evaluated the impact of array comparative genomic hybridization (a-CGH) laboratory testing of such patients. There was significant site-to-site variation in the rate of new diagnoses by a-CGH with the average new diagnosis rate of 11.8% (range 5.4-28.8%). Barriers to implementation of the process and outcome data collection and analysis were significant and related to time pressures, lack of personnel or staff to support this activity, and competing quality improvement initiatives at the institutional home of some genetics centers.

The genetic architecture of Down syndrome phenotypes revealed by high-resolution analysis of human segmental trisomies.

Down syndrome (DS), or trisomy 21, is a common disorder associated with several complex clinical phenotypes. Although several hypotheses have been put forward, it is unclear as to whether particular gene loci on chromosome 21 (HSA21) are sufficient to cause DS and its associated features. Here we present a high-resolution genetic map of DS phenotypes based on an analysis of 30 subjects carrying rare segmental trisomies of various regions of HSA21. By using state-of-the-art genomics technologies we mapped segmental trisomies at exon-level resolution and identified discrete regions of 1.8-16.3 Mb likely to be involved in the development of 8 DS phenotypes, 4 of which are congenital malformations, including acute megakaryocytic leukemia, transient myeloproliferative disorder, Hirschsprung disease, duodenal stenosis, imperforate anus, severe mental retardation, DS-Alzheimer Disease, and DS-specific congenital heart disease (DSCHD). Our DS-phenotypic maps located DSCHD to a <2-Mb interval. Furthermore, the map enabled us to present evidence against the necessary involvement of other loci as well as specific hypotheses that have been put forward in relation to the etiology of DS-i.e., the presence of a single DS consensus region and the sufficiency of DSCR1 and DYRK1A, or APP, in causing several severe DS phenotypes. Our study demonstrates the value of combining advanced genomics with cohorts of rare patients for studying DS, a prototype for the role of copy-number variation in complex disease.

Behavior of 10 patients with FG syndrome (Opitz-Kaveggia syndrome) and the p.R961W mutation in the MED12 gene.

Opitz and Kaveggia [Opitz and Kaveggia (1974); Z Kinderheilk 117:1-18] reported on a family of five affected males with distinctive facial appearance, mental retardation, macrocephaly, imperforate anus and hypotonia. Risheg et al. [Risheg et al. (2007); Nat Genet 39:451-453] identified an identical mutation (p.R961W) in MED12 in six families with Opitz-Kaveggia syndrome, including a surviving affected man from the family reported in 1974. The previously defined behavior phenotype of hyperactivity, affability, and excessive talkativeness is very frequent in young boys with this mutation, along with socially oriented, attention-seeking behaviors. We present case studies of two older males with FG syndrome and the p.R961W mutation to illustrate how their behavior changes with age. We also characterize the behavior of eight additional individuals with FG syndrome and this recurrent mutation in MED12 using the Vineland Adaptive Behavior Scales 2nd edition, the Reiss Profile of Fundamental Goals and Motivation Sensitivities, and the Achenbach Child Behavior Checklist. Males with this MED12 mutation had deficits in communication skills compared to their socialization and daily living skills. In addition, they were at increased risk for maladaptive behavior, with a propensity towards aggression, anxiety, and inattention. Based on the behavior phenotype in 10 males with this recurrent MED12 mutation, we offer specific recommendations and interventional strategies. Our findings reinforce the importance of testing for the p.R961W MED12 mutation in males who are suspected of having developmental and behavioral problems with a clinical phenotype that is consistent with FG syndrome.