Pinella Failla

A recurrent 15q13.3 microdeletion syndrome associated with mental retardation and seizures

We report a recurrent microdeletion syndrome causing mental retardation, epilepsy and variable facial and digital dysmorphisms. We describe nine affected individuals, including six probands: two with de novo deletions, two who inherited the deletion from an affected parent and two with unknown inheritance. The proximal breakpoint of the largest deletion is contiguous with breakpoint 3 (BP3) of the Prader-Willi and Angelman syndrome region, extending 3.95 Mb distally to BP5. A smaller 1.5-Mb deletion has a proximal breakpoint within the larger deletion (BP4) and shares the same distal BP5. This recurrent 1.5-Mb deletion contains six genes, including a candidate gene for epilepsy (CHRNA7) that is probably responsible for the observed seizure phenotype. The BP4–BP5 region undergoes frequent inversion, suggesting a possible link between this inversion polymorphism and recurrent deletion. The frequency of these microdeletions in mental retardation cases is ∼0.3% (6/2,082 tested), a prevalence comparable to that of Williams, Angelman and Prader-Willi syndromes.

Disruptive CHD8 mutations define a subtype of autism early in development.

Autism spectrum disorder (ASD) is a heterogeneous disease in which efforts to define subtypes behaviorally have met with limited success. Hypothesizing that genetically based subtype identification may prove more productive, we resequenced the ASD-associated gene CHD8 in 3,730 children with developmental delay or ASD. We identified a total of 15 independent mutations; no truncating events were identified in 8,792 controls, including 2,289 unaffected siblings. In addition to a high likelihood of an ASD diagnosis among patients bearing CHD8 mutations, characteristics enriched in this group included macrocephaly, distinct faces, and gastrointestinal complaints. chd8 disruption in zebrafish recapitulates features of the human phenotype, including increased head size as a result of expansion of the forebrain/midbrain and impairment of gastrointestinal motility due to a reduction in postmitotic enteric neurons. Our findings indicate that CHD8 disruptions define a distinct ASD subtype and reveal unexpected comorbidities between brain development and enteric innervation.

Prevalence and clinical picture of celiac disease in italian down syndrome patients: a multicenter study.

Background A multicenter research study of Down syndrome patients was carried out to estimate the prevalence of celiac disease in patients with Down syndrome and to show clinical characteristics and laboratory data of Down syndrome patients. Methods The authors studied 1,202 Down syndrome patients. Fifty-five celiac disease patients (group 1) were compared with 55 immunoglobulin A antigliadin–positive antiendomysium antibodies–negative patients (group 2) and with 57 immunoglobulin A antigliadin–negative antiendomysium antibodies–negative patients (group 3). Results Celiac disease was diagnosed in 55 of 1,202 Down syndrome patients (4.6%). In group 1, weight and height percentiles were shifted to the left, whereas these parameters were normally distributed in groups 2 and 3. In celiac patients, diarrhea, vomiting, failure to thrive, anorexia, constipation, and abdominal distension were higher than in the other two groups. Low levels of hemoglobinemia, serum iron, and calcium were observed more frequently in group 1. The diagnosis of celiac disease was made after a mean period of 3.8 years from the initiation of symptoms. Sixty-nine percent of patients showed a classic presentation, 11% had atypical symptoms, and 20% had silent celiac disease. Autoimmune disorders were more frequent (30.9%) in group 1 than in the other two groups examined (15%;P < 0.05). Conclusions This study reconfirms a high prevalence of celiac disease in Down syndrome. However, the diagnostic delay, the detection of atypical symptoms or silent form in one third of the cases, and the increased incidence of autoimmune disorders suggest the need for the screening of celiac disease in all Down syndrome patients.

Complex Segmental Duplications Mediate a Recurrent dup(X)(p11.22-p11.23) Associated with Mental Retardation, Speech Delay, and EEG Anomalies in Males and Females

Submicroscopic copy-number variations make a considerable contribution to the genetic etiology of human disease. We have analyzed subjects with idiopathic mental retardation (MR) by using whole-genome oligonucleotide-based array comparative genomic hybridization (aCGH) and identified familial and de novo recurrent Xp11.22-p11.23 duplications in males and females with MR, speech delay, and a peculiar electroencephalographic (EEG) pattern in childhood. The size of the duplications ranges from 0.8-9.2 Mb. Most affected females show preferential activation of the duplicated X chromosome. Carriers of the smallest duplication show X-linked recessive inheritance. All other affected individuals present dominant expression and comparable clinical phenotypes irrespective of sex, duplication size, and X-inactivation pattern. The majority of the rearrangements are mediated by recombination between flanking complex segmental duplications. The identification of common clinical features, including the typical EEG pattern, predisposing genomic structure, and peculiar X-inactivation pattern, suggests that duplication of Xp11.22-p11.23 constitutes a previously undescribed syndrome.

Identification of pathogenic gene variants in small families with intellectually disabled siblings by exome sequencing

Background Intellectual disability (ID) is a common neurodevelopmental disorder affecting 1–3% of the general population. Mutations in more than 10% of all human genes are considered to be involved in this disorder, although the majority of these genes are still unknown. Objectives We investigated 19 small non-consanguineous families with two to five affected siblings in order to identify pathogenic gene variants in known, novel and potential ID candidate genes. Non-consanguineous families have been largely ignored in gene identification studies as small family size precludes prior mapping of the genetic defect. Methods and results Using exome sequencing, we identified pathogenic mutations in three genes, DDHD2, SLC6A8, and SLC9A6, of which the latter two have previously been implicated in X-linked ID phenotypes. In addition, we identified potentially pathogenic mutations in BCORL1 on the X-chromosome and in MCM3AP, PTPRT, SYNE1, and ZNF528 on autosomes. Conclusions We show that potentially pathogenic gene variants can be identified in small, non-consanguineous families with as few as two affected siblings, thus emphasising their value in the identification of syndromic and non-syndromic ID genes.

Celiac disease in Down's syndrome with HLA serological and molecular studies

The association between Downs syndrome (DS) and celiac disease (CD) has been confirmed by several authors. The sensitivity and specificity of antigliadin antibodies (AGAs), the clinical features of subjects with DS and CD (DS-CD+), the incidence of CD, and the results of serological and molecular class I and II HLA typing were determined in a sample of 57 Sicilian subjects with DS. Six (10.5%) and 17 subjects (29.8%) showed high levels of IgA AGAs and IgG AGAs, respectively. AGAs sensitivity and specificity were lower than in the population without DS. Ten people with DS were submitted to jejunal biopsy, and seven (12.2%) showed CD according to ESPGAN criteria. All seven patients were put on gluten-free diet, followed by rapid disappearance of symptoms. Class I and II HLA serological and molecular typing was carried out in seven DS-CD + subjects, 22 people with DS without CD (DS-CD-), five subjects with CD without DS, and 20 controls. Between DS-CD + and DS-CD- subjects, no statistically significant difference regarding serum HLA class I antigens was found. DQA1*0101 allele appears significantly in DS-CD + patients and deserves to be searched for in a larger sample to assess its meaning in the DS-CD association.

The Koolen-de Vries syndrome: A phenotypic comparison of patients with a 17q21.31 microdeletion versus a KANSL1 sequence variant

The Koolen-de Vries syndrome (KdVS; OMIM #610443), also known as the 17q21.31 microdeletion syndrome, is a clinically heterogeneous disorder characterised by (neonatal) hypotonia, developmental delay, moderate intellectual disability, and characteristic facial dysmorphism. Expressive language development is particularly impaired compared with receptive language or motor skills. Other frequently reported features include social and friendly behaviour, epilepsy, musculoskeletal anomalies, congenital heart defects, urogenital malformations, and ectodermal anomalies. The syndrome is caused by a truncating variant in the KAT8 regulatory NSL complex unit 1 (KANSL1) gene or by a 17q21.31 microdeletion encompassing KANSL1. Herein we describe a novel cohort of 45 individuals with KdVS of whom 33 have a 17q21.31 microdeletion and 12 a single-nucleotide variant (SNV) in KANSL1 (19 males, 26 females; age range 7 months to 50 years). We provide guidance about the potential pitfalls in the laboratory testing and emphasise the challenges of KANSL1 variant calling and DNA copy number analysis in the complex 17q21.31 region. Moreover, we present detailed phenotypic information, including neuropsychological features, that contribute to the broad phenotypic spectrum of the syndrome. Comparison of the phenotype of both the microdeletion and SNV patients does not show differences of clinical importance, stressing that haploinsufficiency of KANSL1 is sufficient to cause the full KdVS phenotype.

How microsatellite analysis can be exploited for subtelomeric chromosomal rearrangement analysis in mental retardation

Editor—The genetic causes of mental retardation are still largely unknown so that about 34% of cases of severe to moderate and 80% of mild mental retardation remain unresolved.1 ,2 Consequently, genetic counselling is difficult in these cases. Chromosomal rearrangements are still the most frequent cause of mental retardation and cytogenetic analysis at 400-550 band resolution cannot detect rearrangements smaller than 5 Mb. Therefore, any new technologies to improve cytogenetic analysis would be of great benefit. In recent years, there has been evidence that the cause of 6-7% of mental retardation involves subtle chromosome rearrangements. Several molecular methodologies have been used successfully to investigate the integrity of telomeres, such as hypervariable polymorphisms (HVPs), FISH, and CGH, while others based on DNA array approaches are being developed.2 The choice of method rests on considerations of feasibility, cost, reproducibility, and sensitivity. FISH and microsatellite analyses are the techniques most commonly used by numerous laboratories and both of them are still being evaluated in terms of their performance and practicability. FISH based analysis with telomeric specific probes provides a simultaneous investigation of all chromosomes ends, resulting in total detection of chromosome rearrangements without requiring the examination of parental chromosomes.3-5 However, this method does not assign parental origin, it loses UPD events, and only gives information regarding abnormalities spanning the probes DNA region. Although now simplified by being available in kit form, the method not only requires considerable expertise in molecular cytogenetics, but is also expensive and time consuming. HVP analysis using microsatellites, which is both easy and inexpensive, has two main problems, as it requires both parental DNA samples and high informativeness, established by the number and frequencies of alleles. However, even for highly heterozygous loci ≅0.8, the detection rate for monosomy and trisomy is 0.64 and 0.5, …

Schizophrenia in a patient with subtelomeric duplication of chromosome 22q

To the Editor: Schizophrenia is a common and severe psychiatric condition. To date, only a few genes have been involved as risk factors (1). Chromosomal rearrangements associated with this disorder are a valuable resource (2). Here, we report on a girl with schizophrenia showing a 22q13.3-qter duplication, without any familial neuropsychiatric disease, documented by a three-generation family history. We were not able to establish a de novo origin of the duplication because the father and his parents were dead at the time of ascertainment. Developmental milestones were reached within normal range. Menarche (13 years) was the time of onset of initial behavioural problems (agitation, social closure and passivity), followed at the age of 15 years by auditory hallucinations, loss of self-control, dysfunction of self-awareness with temporary amnesia, disorientation, aggressive acting out and sleep disturbances. At the present age of 20 years, psychometric testing with Wechsler Adult Intelligence Scale-Revised shows a global intelligence quotient (IQ) of 73, a verbal IQ of 71 and a performance IQ of 80, whereas the score is 86 at Standard Progressive Matrices. The girl presents also with psychomotor restlessness and attention deficit. Ideation is severely impaired and speech is incoherent. Marked irritability, sexually related problems, unstable temper, and aggressive reaction to disappointment are also evident. General affectivity is compromised. Difficulties in accepting and following the rules in different social contexts highlight the adaptive area. Apathy and poor personal hygiene complete the clinical picture, which satisfies the Diagnostic statistical manual, 4th Ed., Text Revised (DSM IV-TR) (3) diagnostic criteria for borderline intellectual functioning and disorganized schizophrenia. The phenotype is also characterized by muscular hypotonia, microbrachycephaly (present also in the mother), hypertelorism, moderate myopia, downslanting palpebral fissures, deviation of the nasal septum, helix hyperplasia, thick lips, retrognathia, hypothenar eminence hypoplasia, scoliosis, splayfoot with valgus hallux, and joint hyperlaxity. The brain computerized tomography scan is normal. The electroencephalogram shows low-voltage sharp-wave complexes on the posterior areas of both hemispheres. A normal 46, XX karyotype from peripheral blood lymphocytes followed by a Multiprobe FISH Assay (Chromoprobe Multiprobe-T SystemCytocell Ltd, Oxford, UK) disclosed a third 22qter signal on the p arm of chromosome 22, not present in the clinically normal mother. Segregation pattern of the informative D22S1170 microsatellite revealed in our patient one maternal and two paternal alleles. The extent of the rearrangement was then assessed by array CGH assay using Human Genome CGH Microarray Kit 44B (Agilent Technologies, Palo Alto, CA), which showed a terminal 5.4 Mb duplication (Fig. 1). Among the 21 patients with terminal 22q duplications recently reviewed (4), only two (patients 2 and 3, respectively, father and son) have a duplication size comparable with that of our patient. Interestingly, this is the smallest duplication so far reported, and the patients show minor learning disabilities, psychiatric difficulties since early childhood and mild mental retardation’. The more severe degree of mental retardation, found in larger duplications, hampers the diagnosis of schizophrenia. Linkage findings for schizophrenia have been reported on chromosome 22q13 (5, 6), suggesting that one or more genes in this region could confer susceptibility to this psychiatric disorder. Among the several genes mapping there, we want to draw the attention on two of them: SHANK3 and WNT7B. The gene SHANK3 (7–9) codes for a scaffolding protein of the post-synaptic density of excitatory synapses in the mammalian brain, and its expression increases during post-natal development especially in the cerebellum and thalamus. WNT7B belongs to Wingless (Wnt) family members, secreted glycoproteins, which are intracellular signalling molecules both during neural development and in the mature nervous system (10). The Wnt signalling pathway has

Narrowing the candidate region for congenital diaphragmatic hernia in chromosome 15q26: contradictory results.

To the Editor: Subtelomeric screening and FISH analysis of a 13-year-old girl with severe mental retardation, intrauterine growth retardation, microcephaly, facial dysmorphisms, hypoplastic kidney, and short hands and feet but without congenital diaphragmatic hernia (CDH [MIM 142340]) allowed us to find a de novo deletion in 15q26.1–26.2. That region, as shown by Klaassens et al. (2005) in a study published in the May issue of the Journal, contains a candidate region for CDH, a condition that occurrs in ∼1 of 3,000 newborns and is associated with a 30%–60% mortality rate, with significant morbidity among survivors (Harrison et al. 1994; Nobuhara et al. 1996). The etiology of this condition is barely known and, in most cases, is considered idiopathic, whereas ∼15% of patients with CDH show chromosomal abnormalities. Recently, Biggio et al. (2004) reported on a child with a 15q26.1 deletion showing CDH, coarctation of the aorta, and dysmorphic features, suggesting this region as the possible candidate locus for CDH. Furthermore, the authors proposed myocyte-specific enhancer factor–2A (MEF2A [MIM 600660]) as a candidate gene for CDH, coding for a protein playing a critical role in the control of muscle differentiation and development. Klaassens et al. (2005) found 7% numerical and 5% structural chromosome abnormalities in 200 CDH patients. The most frequent chromosome abnormality was 15q deletion. Eventually, they determined the size of the deletions in seven patients with CDH. They incorporated data from two patients with terminal 15q deletions without CDH, and data from one patient with a small 15q interstitial deletion and CDH. A minimal deletion region, spanning ∼5 Mb at chromosome bands 15q26.1–15q26.2, has been suggested by these authors. Two of the known genes of this region, namely, NR2F2 (MIM 107773) and CDH2 (MIM 602119), were considered to be the best candidates for CDH. To better define the deletion in our patient, FISH experiments were carried out with a set of linearly ordered BACs selected by human NCBI Map Viewer (build 35.1) and provided by the Sanger Institute. This analysis showed that the BAC RP11-386M24, localized to chromosome band 15q26.1 (∼9.0 Mb from the end of the chromosome), was the closest to the telomere that hybridized on both chromosomes in all examined metaphases. The immediately more centromeric CTD—2313J17 BAC showed signals of different intensities on the 15q telomeres, suggesting that the breakpoint lay within this BAC, whereas the overlapping RP11-437B10 BAC and all the distally placed BACs showed no hybridization signal (data not shown). We thus compared our results with the most significant previously characterized 15q deletions, including ring chromosome 15, unbalanced translocations, and pure 15qter monosomies, either associated with the CDH phenotype or not. As shown in figure 1, no clear critical region can be drawn from these data, essentially because case 12 with CDH carried a ring (15) resulting in a smaller deletion than cases 1, 2, and 3, without CDH. At least two hypotheses can be made to explain these contradictory data. First, it is possible that haploinsufficiency of the CDH locus has a reduced penetrance and that data from patients without CDH could be useless in establishing the critical region. If this is true, the candidate region is restricted to ∼3.5 Mb (fig. 1) and includes the NR2F2 gene, but its telomeric limit is more distal than that defined by Klaassens et al. (2005), which was derived from a deletion of a patient without CDH (fig. 1, case 13). On the other hand, drawing genotype-phenotype relationships may be difficult in ring carriers because of the potential instability of ring chromosomes that can be associated with gain or loss of genetic material in other tissues (Tumer et al. 2004). If we omit ring cases from the analysis, then the critical region would be narrowed to a 0.7-Mb genomic portion (fig. 1). The NR2F2 gene, in this case, would be located outside this putative critical region. Figure  1 Graphical representation of 15q deletions in patients with and without CDH. The most significant BAC clones analyzed are shown on the left. Solid boxes represent deleted regions, hatched boxes indicate the uncertainty of the breakpoints, and open boxes ... The ST8 alpha-N-acetyl-neuraminide alpha-2, 8-sialyltransferase 2 gene (ST8SIA2 [MIM 602546]) is the unique known gene in this region and encodes for a type II membrane protein that catalyzes the transfer of sialic acid from CMP-sialic acid to the neural cell adhesion molecules (NCAMs) (Ong et al. 1998). The ST8SIA2 gene is expressed in many tissues during development (Angata et al. 1997). Evidence suggests that polysialylated NCAMs promote cell migration and, thus, they are thought to play a critical role in development. More specifically, it has been shown that, during diaphragmatic morphogenesis, the expression of polysialylated NCAMs is tightly modulated along each stage of myogenesis (Allan and Greer 1998). Finally, although it is less likely, we cannot exclude the possibility that both the mentioned hypotheses are true. In this case, the critical region would be represented by the extent of the deletion in patient 8 (fig. 1). Additional findings are needed to refine the search for a CDH gene in 15q chromosome. However, it seems likely that NR2F2 and ST8SIA2 are the best candidates.