Search

Deletions of the long arm of chromosome 20 (20q) are rare, with only 16 reported patients displaying a proximal interstitial 20q deletion. A 1.62 Mb minimal critical region at 20q11.2, encompassing three genes GDF5, EPB41L1, and SAMHD1, is proposed to be responsible for this syndrome. The leading clinical features include growth retardation, intractable feeding difficulties with gastroesophageal reflux, hypotonia and psychomotor developmental delay. Common facial dysmorphisms including triangular face, hypertelorism, and hypoplastic alae nasi were additionally reported. Here, we present the clinical and molecular findings of five new patients with proximal interstitial 20q deletions. We analyzed the phenotype and molecular data of all previously reported patients with 20q11.2q12 microdeletions, along with our five new cases. Copy number variation analysis of patients in our cohort has enabled us to identify the second critical region in the 20q11.2q12 region and redefine the first region that is initially identified. The first critical region spans 359 kb at 20q11.2, containing six MIM genes, including two disease‐causing genes, GDF5 and CEP250. The second critical region spans 706 kb at 20q12, encompassing four MIM genes, including two disease‐causing genes, MAFB and TOP1. We propose GDF5 to be the primary candidate gene generating the phenotype of patients with 20q11.2 deletions. Moreover, we hypothesize TOP1 as a potential candidate gene for the second critical region at 20q12. Of note, we cannot exclude the possibility of a synergistic role of other genes involved in the deletion, including a contiguous gene deletion syndrome or position effect affecting both critical regions. Further studies focusing on patients with proximal 20q deletions are required to support our hypothesis. [ABSTRACT FROM AUTHOR]

We report the clinical and molecular cytogenetic characterization of four unrelated patients from France and Spain, carrying 2p14 microdeletions and presenting with intellectual disability and dysmorphisms. 2p14 microdeletions are very rare. Seven patients have been reported so far harboring deletions including 2p14p15 and encompassing OTX1, whose haploinsufficiency is frequently associated with genitourinary defects. To date, only one patient has been reported carrying a more proximal 2p14 microdeletion which does not include OTX1. Here, we report three further patients carrying proximal 2p14 microdeletions not including OTX1 and one patient carrying a more distal 2p14p15 microdeletion including this gene, providing new insights into the associated phenotypic spectrum. First, our study and a review of the literature showed that 3/4 patients carrying proximal 2p14 microdeletions had sensorineural hearing loss, suggesting the presence of a previously unreported deafness-causing gene in this chromosomal region. Second, one patient developed a progressive cardiomyopathy, suggesting that a cardiac follow-up should be systematically warranted even in the absence of congenital heart disease. We speculate that ACTR2 and MEIS1 might respectively play a role in the pathogenesis of the observed deafness and cardiomyopathy. Third, we observed other previously unreported features such as glaucoma, retinopathy, and mild midline abnormalities including short corpus callosum, hypospadias and anteriorly placed anus. Finally, the patient carrying a 2p14p15 deletion including OTX1 had normal kidneys and genitalia, thus confirming that OTX1 haploinsufficiency is not invariably associated with genitourinary defects. In conclusion, our study contributes significantly to delineate the phenotypic spectrum of 2p14 microdeletions. [ABSTRACT FROM AUTHOR]

We report a novel syndromic disorder of sex development observed in three male siblings, presenting with the association of micropenis without hypospadias, cryptorchidism, very low level of antimüllerian hormone in the neonatal period, and no persistent müllerian duct structures, suggesting a progressive regression of testicular function. The patients described here showed a striking neurological involvement including bilateral periventricular cysts observed in the anterior part of the frontal horns prenatally and increasing in size and number over time, associated with infra and supratentorial parenchymal atrophy, dilated ventricular system, corpus callosum hypoplasia, severe intellectual disability, and epilepsy. Associated features included a distinctive facies, joint contractures, retinopathy, and hearing loss. Pathological examination was consistent with testicular dysgenesis and leukoencephalopathy with spongiosis and microcalcifications. To the best of our knowledge, this disease, characterized by a recognizable pattern of malformations, has not been previously reported. An exhaustive genetic and metabolic evaluation was normal. Autosomal recessive inheritance was considered to be likely, on the basis of SNP studies. We hope that the detailed description provided here of the clinical, radiological, and pathological findings observed in this family will help to identify further unrelated patients, and ultimately, to clarify the genetic basis of this condition. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Interstitial microdeletions of 20q chromosome are rare, only 17 patients have been reported in the literature to date. Among them, only six carried a proximal 20q11.21-q11.23 deletion, with a size ranging from 2.6 to 6.8 Mb. The existence of a 20q11.2 microdeletion syndrome has been proposed, based on five previously reported cases that displayed anomalies of the extremities, intellectual disability, feeding difficulties, craniofacial dysmorphism and variable malformations. To further characterize this syndrome, we report on six new patients with 20q11.2 microdeletions diagnosed by whole-genome array-based comparative genomic hybridization. These patient reports more precisely refined the phenotype and narrowed the minimal critical region involved in this syndrome. Careful clinical assessment confirms the distinctive clinical phenotype. The craniofacial dysmorphism consists of high forehead, frontal bossing, enophthalmos, and midface hypoplasia. We have identified a 1.62 megabase minimal critical region involved in this syndrome encompassing three genes - GDF5, EPB41L1, and SAMHD1- which are strong candidates for different aspects of the phenotype. These results support that 20q11.2 microdeletion syndrome is a new contiguous gene deletion syndrome with a recognizable phenotype. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We report here on an 8-year-old girl and her mother, both displaying similar facial dysmorphism, speech delay, and mild to moderate intellectual disability. Array-CGH studies revealed the same interstitial 3q26.32 microdeletion encompassing a single coding gene, TBL1XR1, in both patients. The TBL1XR1 protein, which has four WD40 repeats, has been shown to bind the nuclear corepressor (NCOR) and histone deacetylase-3 complexes (HDAC3). TBL1XR1 mutations have recently been implicated in autism spectrum disorders, but our patients displayed no autistic behavior. Our findings suggest that TBL1XR1 haploinsufficiency can cause intellectual disability with a recognizable dysmorphism, without necessarily causing autistic behavior. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Mutations of the CDKL5 gene cause early epileptic encephalopathy. Patients manifest refractory epilepsy, beginning before the age of 3 months, which is associated with severe psychomotor delay and features that overlap with Rett syndrome. We report here a patient with mosaicism for CDKL5 exonic deletion, with the presence of two mutant alleles. The affected 4-year-old girl presented with infantile spasms, beginning at the age of 9 months, but subsequent progression of the disease was consistent with the classical CDKL5-related phenotype. A deletion of exons 17 and 18 was suspected on the basis of Multiplex Ligation Probe Amplification analysis, but unexpected results for cDNA analysis, which showed the presence of an abnormal transcript with the deletion of exon 18 only, led us to suspect that two distinct events might have occurred. We used custom array-CGH to determine the size and breakpoints of these deletions. Exon 18 was deleted from one of the abnormal alleles, and exon 17 was deleted from the other. A Fork Stalling and Template Switching (FoSTeS) mechanism was proposed to explain the two events, given the presence of regions of microhomology at the breakpoints. We propose here an original involvement of the FoSTeS mechanism to explain the co-occurrence of these two events in the CDKL5 gene in a single patient. This patient highlights the difficulties involved in the detection of such abnormalities, particularly when they occur in a mosaic state and involve two distinct mutational events in a single gene. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A girl patient born to healthy nonconsanguineous parents was referred at age 3 years and 2 months to our genetics department for testing due to developmental delay and postnatal microcephaly. Initial clinical evaluation revealed an overall developmental delay, mildly dysmorphic features, thin, sparse fair hair, and fair skin. Postnatal microcephaly and progressive ataxia and spasticity appeared later. Array CGH karyotyping showed a 333 kb de novo microdeletion on 3p22 covering the entire genomic sequence of a single gene, CTNNB1, which codes for β-catenin. β-catenin is a sub-unit of a multiprotein complex, which is part of the Wnt signaling pathway. In mice, a conditional homozygous β-catenin knockout displays loss of neurons, impaired craniofacial development, and hair follicle defects, which is similar to the phenotype presented by the patient described in this clinical report. Thus, CTNNB1 haploinsufficiency causes neuronal loss, craniofacial anomalies and hair follicle defects in both humans and mice. Point mutations in CTNNB1 in human have recently been reported but this is the first observation of a new recognizable multiple congenital anomaly/mental retardation syndrome caused by CTNNB1 haploinsufficiency. This clinical report should prompt a search for point mutations in CTNNB1 in patients presenting developmental delay, mild hair, skin and facial anomalies, and neurodegeneration characterized by postnatal microcephaly, and progressive ataxia and spasticity. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Neuroblastoma is the most frequent extra cranial solid tumor in infants and children. Genetic predisposition to neuroblastoma has been suspected previously due to familial cases of sporadic NB and predisposition to NB in several syndromes. Here, we report on a de novo 14q23.1-q23.3 microdeletion in a male presenting with a neuroblastoma diagnosed at 9 months, and spherocytosis, congenital heart defect, cryptorchidism, hypoplasia of corpus callosum, epilepsy, and developmental delay. Myc-associated-factor X ( MAX) haploinsufficiency could be regarded as the predisposing factor to NB. Indeed 14q deletion is a recurrent somatic rearrangement in NB and MAX somatic and germline loss of function mutation have recently been described in pheochromocytoma and paraganglioma. However, MAX was expressed in the tumor of the patient we report on and, accordingly, loss of heterozygosity, mutation, or promoter methylation were excluded. In addition, we discuss the potential involvement in the clinical spectrum presented by the patient of five of the deleted genes, namely DAAM1, PLEKHG3, SPTB, AKAP5, and ARID4A. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

FG syndrome, Lujan syndrome, and Ohdo syndrome, the Maat-Kievit-Brunner type, have been described as distinct syndromes with overlapping non-specific features and different missense mutations of the MED12 gene have been reported in all of them. We report a family including 10 males and 1 female affected with profound non-specific intellectual disability (ID) which was linked to a 30-cM region extending from Xp11.21 (ALAS2) to Xq22.3 (COL4A5). Parallel sequencing of all X-chromosome exons identified a frameshift mutation (c.5898dupC) of MED12. Mutated mRNA was not affected by non-sense mediated RNA decay and induced an additional abnormal isoform due to activation of cryptic splice-sites in exon 41. Dysmorphic features common to most affected males were long narrow face, high forehead, flat malar area, high nasal bridge, and short philtrum. Language was absent or very limited. Most patients had a friendly personality. Cognitive impairment, varying from borderline to profound ID was similarly observed in seven heterozygous females. There was no correlation between cognitive function and X-chromosome inactivation profiles in blood cells. The severe degree of ID in male patients, as well as variable cognitive impairment in heterozygous females suggests that the duplication observed in the present family may have a more severe effect on MED12 function than missense mutations. In a cognitively impaired male from this family, who also presented with tall stature and dysmorphism and did not have the MED12 mutation, a 600-kb duplication at 17p13.3 including the YWHAE gene, was found in a mosaic state. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We report on three patients presenting moderate intellectual disability, delayed language acquisition, and mild facial dysmorphia. Array-CGH studies revealed overlapping interstitial 12p13.1 microdeletions encompassing all or part of GRIN2B. GRIN2B encodes the NR2B subunit of the N-methyl- D-aspartate (NMDA) receptor. This receptor is a heteromeric glutamate-activated ion channel, present throughout the central nervous system. It plays a critical role in corticogenesis, neuronal migration, and synaptogenesis during brain development. GRIN2B alterations, including mutation and gene disruption by apparently balanced chromosomal rearrangements, have been described in patients with intellectual disability and autism spectrum disorder. We report here on the first cases of GRIN2B deletion, enlarging the spectrum of GRIN2B abnormalities. Our findings confirm the involvement of this gene in neurodevelopmental disorders. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We report on a child with Jacobsen syndrome (JBS, OMIM 147791) and abnormalities consistent with Beckwith-Wiedemann syndrome (BWS, OMIM 130650). The constitutional karyotype was apparently normal, but FISH analysis with probes specific for the short and long arms of chromosome 11 found 11qter deletion with 11pter trisomy in 80% of the cells studied. Array-CGH identified breakpoints in the 11p15.3 and 11q24.1 regions consistent with Jacobsen and Beckwith-Wiedemann syndromes. We suggest that this chromosome imbalance results from a pericentric inversion of chromosome 11 inherited from the father, with mosaicism resulting from meiotic recombination of a paternal inversion followed by mitotic recombination during the first embryonic divisions. This hypothesis is supported by the results of microsatellite marker analysis. Three previous cases of pericentric inversion and recombination of chromosome 11 have been reported. Our case is unusual in that it combines the Jacobsen and Beckwith-Wiedemann syndromes with mosaicism. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Pitt-Hopkins syndrome (PTHS) is characterized by distinctive facial dysmorphism, profound intellectual disability, and the possible occurrence of epilepsy and breathing anomalies. It is caused by haploinsufficiency of the TCF4 gene. No significant difference in clinical severity has been reported to date between PTHS patients carrying 18q21 deletions including the TCF4 gene, and those harboring TCF4 point mutations, suggesting a lack of genotype/phenotype correlation. Moreover, the size of 18q21 deletions including the TCF4 gene does not appear to have a significant effect on the phenotypic severity, suggesting that TCF4 haploinsufficiency is the most important prognostic factor in 18q deletions. We describe two unrelated patients presenting with clinical features reminiscent of PTHS and carrying mosaic interstitial 18q21 deletions characterized by array comparative genomic hybridization. One of the patients presented the lowest level of mosaic 18q21 deletion reported to date (5-10%). Our report and a review of the literature show that the mosaic status does not appear to have a significant effect on the clinical severity of 18q21 deletions, which are associated with a poor neurological outcome, whereas a mosaic TCF4 point mutation can result in a significantly milder phenotype. Malformations of internal organs are currently considered to be rare in PTHS. The patients described here had visceral anomalies, suggesting that a full morphological assessment, including heart and abdominal ultrasound scans, should be performed systematically in PTHS patients. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Floating-Harbor syndrome (FHS) is characterized by characteristic facial dysmorphism, short stature with delayed bone age, and expressive language delay. To date, the gene(s) responsible for FHS is (are) unknown and the diagnosis is only made on the basis of the clinical phenotype. The majority of cases appeared to be sporadic but rare cases following autosomal dominant inheritance have been reported. We identified a 4.7 Mb de novo 12q15-q21.1 microdeletion in a patient with FHS and intellectual deficiency. Pangenomic 244K array-CGH performed in a series of 12 patients with FHS failed to identify overlapping deletions. We hypothesized that FHS is caused by haploinsufficiency of one of the 19 genes or predictions located in the deletion found in our index patient. Since none of them appeared to be good candidate gene by their function, a high-throughput sequencing approach of the region of interest was used in eight FHS patients. No pathogenic mutation was found in these patients. This approach failed to identify the gene responsible for FHS, and this can be explained by at least four reasons: (i) our index patient could be a phenocopy of FHS; (ii) the disease may be clinically heterogeneous (since the diagnosis relies exclusively on clinical features), (iii) these could be genetic heterogeneity of the disease, (iv) the patient could carry a mutation in a gene located elsewhere. Recent descriptions of patients with 12q15-q21.1 microdeletions argue in favor of the phenocopy hypothesis. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We report on clinical and cytogenetic studies in a 7-year-old child with moderate intellectual disability, short stature, mild dysmorphism, and hearing loss. R-chromosome banding showed a de novo autosomal marker originating from the 17p chromosome segment in all cells analyzed. Array comparative genome hybridization (aCGH) was used to determine the gene content and proximal and distal breakpoints of the small supernumerary marker chromosome (SMC). These breakpoints mapped to the centromere of chromosome 17 and the 17p11.2 region, respectively. Unexpectedly, aCGH analysis also revealed a de novo deletion of 800 kb encompassing six genes in the 17q23.2 region, including MED13 (also known as THRAP1). We compared our patient with other reported cases of SMC(17), to determine the respective contributions of the duplication and the deletion to the phenotype. We cannot entirely exclude a minor role for the SMC(17), but we suggest that MED13 haploinsufficiency was responsible for the phenotype of the patient particularly the cataract, hearing loss and semicircular canal dysplasia. Moreover, this report highlights the usefulness of aCGH for the specification of gene content in cases of abnormality, facilitating the establishment of accurate phenotype-genotype correlations and the detection of other, complex rearrangements. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Partial trisomy 9p is one of the most common detected autosomal structural anomalies, so the phenotype-genotype correlation of this rearrangement has been well described. Despite variation in size of the 9p duplications, trisomy 9p syndrome is characterized by typical dysmorphic features and a variable but constant psychomotor and mental retardation. Previously reported phenotype genotype correlation studies proposed that the critical region for phenotype is located in 9p22. We report here on a new patient with partial trisomy 9p13.3→9pter in an 8-year-old boy with typical trisomy 9p dysmorphic features but a normal mental development. Cytogenetics investigations showed that our patient karyotype was 47,XY,+ der(22)t(9;22)(p13.q11) inherited by a 3:1 disjunction of a maternal reciprocal translocation t(9;22)(p13.q11). FISH and array CGH analysis were used to better characterize duplicated chromosomal regions and showed a large duplication of chromosome 9p13.3→9pter associated to microduplication in 22q11.1. The size of the duplications in chromosomes 9p and 22q were estimated about 33.9 and 2.67 Mb, respectively. The comparison between this case and those reported in the literature allows us to support that all syndromes show variability and that not all partial trisomies 9p are associated with intellectual disability. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

We report on a novel Xq11.11 microdeletion in a patient presenting with severe mental retardation (MR), focal epilepsy, tall stature, macrocephaly, and dysmorphism. This 1.3 Mb deletion, identified using array CGH, includes a single gene with known function- ARHGEF9-plus 1 gene with unknown function and three putative genes. ARHGEF9 encodes collybistin (Cb) that plays an important role in the localization of gephyrin which is the key protein of the scaffolding system of inhibitory synapses and is essential for postsynaptic clustering of both GABAA and glycine receptors. Cb-deficient male mice show reduced exploratory behavior, impaired spatial learning, increased anxiety scores, and reduction of gephyrin-dependent GABA receptor clusters in amygdala and hippocampus. Mutations or disruption of ARHGEF9 due to chromosomal rearrangements have been found in three patients with various clinical presentations: nevertheless, all 3 presented with MR and 2 with epilepsy. The case we report on provides further evidence for the role of ARHGEF9 in cognitive development. The other phenotypic features in our patient, including macrosomia and dysmorphism, may also be related to the loss of this gene. Alternatively, they may be consequences of the loss of one or more of the other genes located within the deletion or of the disruption of sequences regulating neighboring genes. Additional case reports with identical or overlapping deletions would help in defining the phenotype associated with ARHGEF9 haploinsufficiency. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]