The role of IQSEC2 in syndromic intellectual disability: Narrowing the diagnostic odyssey.

While X-linked intellectual disability (XLID) syndromes pose a diagnostic challenge for clinicians, an increasing number of recognized disorders and their genetic etiologies are providing answers for patients and their families. The availability of clinical exome sequencing is broadening the ability to identify mutations in genes previously unrecognized as causing XLID. In recent years, the IQSEC2 gene, located at Xp11.22, has emerged as the cause of multiple cases of both nonsyndromic and syndromic XLID. Herein we present a case series of six individuals (five males, one female) with intellectual disability and seizures found to have alterations in IQSEC2. In all cases, the diagnostic odyssey was extensive and expensive, often including invasive testing such as muscle biopsies, before ultimately reaching the diagnosis. We report these cases to demonstrate the exhaustive work-up prior to finding the changes in IQSEC2 gene, recommend that this gene be considered earlier in the diagnostic evaluation of individuals with global developmental delay, microcephaly, and severe, intractable epilepsy, and support the use of intellectual disability panels including IQSEC2 in the first-line evaluation of these patients.

Secondary complex chromosome rearrangement identified by chromosome analysis and FISH subsequent to detection of an unbalanced derivative chromosome 12 by SNP array analysis.

Microarray analysis is used to detect small copy number changes (deletions and duplications) that may be associated with genetic syndromes and phenotypic abnormalities. However, there are limitations to what microarrays are able to detect. We present a patient referred for microarray in whom chromosome analysis identified a more complex structural rearrangement than was indicated by the microarray. Our studies included Affymetrix Cytoscan HD array, chromosome analysis and fluorescence in situ hybridization (FISH) using a subtelomere probe targeting chromosome 3. Array analysis revealed a 6.45-Mb terminal duplication of 3q28q29 and a 1.02-Mb terminal deletion of 12p13.33. This suggested an unbalanced translocation derivative. In order to investigate visibility of the rearrangement, chromosome analysis was performed, revealing an additional balanced complex chromosome rearrangement involving chromosomes 3 and 11, including a translocation with breakpoints at 3p13 and 11p11.2, as well as a paracentric inversion of segment 3p25p13 translocated onto chromosome 11. Subtelomere FISH confirmed that the duplicated chromosome 3q material observed in the array analysis was localized to distal 12p. This case clearly illustrates the combined utilization of classic cytogenetics, FISH and array technologies to better characterize chromosomal abnormalities.

Genotypic and phenotypic analysis of 396 individuals with mutations in Sonic Hedgehog.

BACKGROUND: Holoprosencephaly (HPE), the most common malformation of the human forebrain, may result from mutations in over 12 genes. Sonic Hedgehog (SHH) was the first such gene discovered; mutations in SHH remain the most common cause of non-chromosomal HPE. The severity spectrum is wide, ranging from incompatibility with extrauterine life to isolated midline facial differences. OBJECTIVE: To characterise genetic and clinical findings in individuals with SHH mutations. METHODS: Through the National Institutes of Health and collaborating centres, DNA from approximately 2000 individuals with HPE spectrum disorders were analysed for SHH variations. Clinical details were examined and combined with published cases. RESULTS: This study describes 396 individuals, representing 157 unrelated kindreds, with SHH mutations; 141 (36%) have not been previously reported. SHH mutations more commonly resulted in non-HPE (64%) than frank HPE (36%), and non-HPE was significantly more common in patients with SHH than in those with mutations in the other common HPE related genes (p<0.0001 compared to ZIC2 or SIX3). Individuals with truncating mutations were significantly more likely to have frank HPE than those with non-truncating mutations (49% vs 35%, respectively; p=0.012). While mutations were significantly more common in the N-terminus than in the C-terminus (including accounting for the relative size of the coding regions, p=0.00010), no specific genotype-phenotype correlations could be established regarding mutation location. CONCLUSIONS: SHH mutations overall result in milder disease than mutations in other common HPE related genes. HPE is more frequent in individuals with truncating mutations, but clinical predictions at the individual level remain elusive.

Postterm closure of the cavum septi pellucidi and developmental outcome in premature infants.

The authors report the natural history of closure of the cavum Septi pellucidi in premature infants 26 to 27 weeks postconception at birth and compare the developmental outcome in these infants who had closure by 42 weeks postconception to those who still had a cavum septum pellucidi visualized on ultrasound at approximately term (35-42 weeks). Of 72 patients, 35 patients still had a cavum septum pellucidi visualized on the last ultrasound done between 35 and 42 weeks postconception, and the developmental outcome of these patients was no different from those with earlier closure. The authors conclude that persistence of a cavum septi pellucidi through term is not an independent risk factor for developmental delay.

Multiple mechanisms are implicated in the generation of 5q35 microdeletions in Sotos syndrome.

BACKGROUND: Sotos syndrome is characterised by learning difficulties, overgrowth, and a typical facial appearance. Microdeletions at 5q35.3, encompassing NSD1, are responsible for approximately 10% of non-Japanese cases of Sotos. In contrast, a recurrent approximately 2 Mb microdeletion has been reported as responsible for approximately 50% of Japanese cases of Sotos. METHODS: We screened 471 cases for NSD1 mutations and deletions and identified 23 with 5q35 microdeletions. We investigated the deletion size, parent of origin, and mechanism of generation in these and a further 10 cases identified from published reports. We used "in silico" analyses to investigate whether repetitive elements that could generate microdeletions flank NSD1. RESULTS: Three repetitive elements flanking NSD1, designated REPcen, REPmid, and REPtel, were identified. Up to 18 cases may have the same sized deletion, but at least eight unique deletion sizes were identified, ranging from 0.4 to 5 Mb. In most instances, the microdeletion arose through interchromosomal rearrangements of the paternally inherited chromosome. CONCLUSIONS: Frequency, size, and mechanism of generation of 5q35 microdeletions differ between Japanese and non-Japanese cases of Sotos. Our microdeletions were identified from a large case series with a broad range of phenotypes, suggesting that sample selection variability is unlikely as a sole explanation for these differences and that variation in genomic architecture might be a contributory factor. Non-allelic homologous recombination between REPcen and REPtel may have generated up to 18 microdeletion cases in our series. However, at least 15 cannot be mediated by these repeats, including at least seven deletions of different sizes, implicating multiple mechanisms in the generation of 5q35 microdeletions.

Clinical and morphometric analysis of the hypoplastic corpus callosum.

A total of 307 children were evaluated over a 3-year period in our neurogenetics clinic. Review of their medical records demonstrated 26 patients with diagnoses of anomalies of the corpus callosum. Morphometric analysis was performed on those 23 patients qualitatively assessed as having a hypoplastic (small, but morphologically intact) corpus callosum. Morphometric data were compared with clinical correlates for each patient. From these data, we conclude that the hypoplastic corpus callosum is not a normal variant of development but rather an indicator of a more fundamental abnormality of cerebral development.

Midline cerebral dysgenesis, dysfunction of the hypothalamic-pituitary axis, and fetal alcohol effects.

OBJECTIVE: Neuropathologic evaluation was performed on an infant with fetal alcohol effects. DESIGN: Coronal brain sections and representative tissue blocks stained with hematoxylin-eosin, silver stain, and immunocytochemical stains for hypothalamic and pituitary hormones were evaluated for neuropathologic abnormalities. PATIENT: A 2.5-month-old American Indian girl who had been exposed to first-trimester maternal binge alcohol abuse died after persistent problems of growth failure, sodium imbalance, aberrant temperature regulation, respiratory distress, and seizures. RESULTS: Autopsy revealed severe microcephaly, hypertelorism, midfacial hypoplasia, a high-arched palate, shortened palpebral fissures, and a small brain. The frontal lobes were fused anteriorly; olfactory bulbs and tracts were absent; and optic nerves were hypoplastic. An enlarged and bulbous hypothalamus obscured the pituitary gland. The thalamus and caudate nuclei were fused across the midline. Posteriorly, the single ventricle split to form rudimentary lateral horns. The anterior corpus callosum, septum pellucidum, fimbria, and fornices could not be identified. The anterior commissure and supraoptic nuclei were microscopically present. Many Purkinje cells were horizontally positioned, with abnormal dendritic structure. The posterior pituitary lobe was absent, and the infundibulum was flanked by a hypoplastic adenohypophysis and a large subarachnoid heterotopia. Immunocytochemical studies identified only vasopressin and neurophysin in the hypothalamus and only growth hormone and prolactin in the pituitary gland. CONCLUSION: To our knowledge, an association between fetal alcohol effects and a complex cerebral anomaly with features of incomplete holoprosencephaly and septo-optic dysplasia has not previously been reported and suggests a possible common pathogenesis needing further study.

Interleukin-1beta upregulates MMP-9 expression in stromal cells of human giant cell tumor of bone.

Giant cell tumor (GCT) of bone is a progressive, potentially malignant process that destroys skeletal tissue. It consists of multinucleated giant cells, which are hypothesized to be derived from a monocyte/macrophage lineage and mononuclear stromal cells, and the precise relationship of these cells is not fully understood. Recently, we demonstrated that the production of matrix metalloproteinase-9 (MMP-9) in GCT stromal cells is regulated by certain factor(s) secreted by the multinucleated giant cells. In the present study, we evaluated for the presence of interleukin-1beta (IL-1beta) and attempted to establish its possible role for the induction of MMP-9 in GCT stromal cells. Using enzyme-linked immunosorbent assay (ELISA), we have demonstrated that the primary GCT cultures secrete both IL-1beta and MMP-9. The addition of monoclonal antibody (mAb) against IL-1beta partially abrogated, but did not abolish, MMP-9 expression. Our results on gelatin zymography, reverse transcriptase-polymerase chain reaction (RT-PCR), and immunofluorescence showed that GCT stromal cells did not express MMP-9, although treatment with IL-1beta induced MMP-9 expression in a dose-dependent manner, and the secretion peaked 24 h after stimulation and then plateaued. Studies with cycloheximide, a protein synthesis inhibitor, demonstrated that de novo protein synthesis is required for IL-1beta induced MMP-9 expression. Moreover, nuclear run-on analysis has revealed that IL-1beta significantly increased MMP-9 gene transcription in GCT stromal cells. The data suggest that IL-1beta secreted by the multinucleated giant cells in GCT may be one of the factors responsible for the induction of MMP-9 at the transcriptional level in GCT stromal cells in vivo. We conclude that GCT has a self-stimulatory system for the production of MMP-9, and the ability of stromal cells to produce MMP-9 with appropriate stimuli, such as IL-1beta, and possibly in concert with other cytokines may contribute to the aggressive and potentially malignant behavior of GCT.

Expression of 72 kDa and 92 kDa type IV collagenases from human giant-cell tumor of bone.

Basement membrane forms widespread barriers to tumor invasion. It has been shown that tumor-secreted, basement membrane-degrading enzymes, namely metalloproteinases (MMPs) play an important role in tumor invasion and metastasis. In this study, we determined the enzymatic activity, content, and mRNA of both the 72 kDa (MMP-2) and 92 kDa (MMP-9) MMPs in primary cultures of human giant-cell tumor of bone (GCT) in vitro and in tissue extracts (in vivo). Gelatin zymography showed the presence of lytic bands at M(r) 121,000, 92,000, and 72,000, and these enzymatic activities were inhibited by EDTA, an inhibitor of MMPs. Western blots with antibodies specific for MMP-2 and MMP-9 confirmed the presence of MMP-2 and MMP-9 both in vitro and in vivo, but GCT cells at late passage showed only MMP-2. Northern blots using labeled cDNA probes specific for these molecules revealed the presence of 3.1 kb transcript for MMP-2 and a 2.9 kb transcript for MMP-9. Using specific antibodies to 72 kDa and 92 kDa type IV collagenases, we studied their cellular distribution by immunohistochemical means. Stronger immunoreactivity was found for 92 kDa type IV collagenase than 72 kDa type IV collagenase in the giant cells. It appears, therefore, that MMP-9 may play an important role in the malignant behavior of GCTs and suggests a potential therapeutic role for protease inhibitors in attempting to minimize the invasive behavior of GCTs.

Regulation of MMP-9 (92 kDa type IV collagenase/gelatinase B) expression in stromal cells of human giant cell tumor of bone.

Matrix metalloproteinases (MMPs) play an important regulatory role in tissue morphogenesis, cell differentiation, tumor invasion and metastasis. Several authors have reported a direct correlation between the production of 72 kDa (MMP-2) and 92 kDa (MMP-9) type IV collagenases/gelatinases and the metastatic potential of cancer cells. Recently, we have identified the expression of both MMP-2 and MMP-9 in primary cultures of human giant cell tumor (GCT) of bone in vitro, and in tissue extracts in vivo. Interestingly, MMP-9 is not secreted by late-passaged GCT cells. It is possible that the production of MMP-9 is regulated by certain factor(s) secreted by the multinucleated giant cells in the primary culture. In order to test this hypothesis, the effect of primary-culture-conditioned medium on the expression of MMP-9 by late-passaged mononuclear stromal cells was examined. Adding conditioned medium from the primary GCT culture to the late-passaged stromal cells induced MMP-9, as evidenced by the presence of lytic bands at M(r) 92,000 and 72,000 on a gelatin zymogram. These enzyme activities were inhibited by EDTA, a well-known inhibitor of the MMPs. We confirmed these results by Western blotting using specific antibodies and RT-PCR for MMP-2 and MMP-9. Immunofluorescence studies with specific antibodies to MMP-9 further confirmed its expression by the passaged stromal cells cultured in the primary-culture-conditioned medium. The data indicate that MMP-2 and MMP-9 are produced by the mononuclear stromal cells when cultured in GCT primary-culture-conditioned medium. This suggests that multinucleated giant cells in primary cultures secrete a factor(s) that stimulates stromal cells to produce MMP-9, which, in turn, may contribute to the aggressive behavior of GCT.

Marshall-Stickler phenotype associated with von Willebrand disease.

We report on 6 individuals from three different kindreds with Marshall-Stickler (MS) phenotype, with characteristic orofacial abnormalities, arthropathy, deafness, and eye findings, all of whom were discovered to have a mild bleeding diathesis and coagulation-study findings consistent with mild von Willebrand disease (vWD). MS syndrome has been linked in some cases to the type II procollagen gene (COL2A1) on chromosome 12q, and to the collagen XI gene (COL11A2) on chromosome 6. The von Willebrand factor (vWF) is encoded by a 180-Kb gene located on the short arm of chromosome 12. This is the first reported association of these two disorders.

Patient with double heterozygosity for achondroplasia and pseudoachondroplasia, with comments on these conditions and the relationship between pseudoachondroplasia and multiple epiphyseal dysplasia, Fairbank type.

We present a 7 1/2-year-old girl with achondroplasia and pseudoachondroplasia. Her mother has achondroplasia and her father has pseudoachondroplasia. Radiographic manifestations of these two conditions from infancy to age 6 years are outlined. The findings in this patient are compared with those of achondroplastic patients and pseudoachondroplastic patients of similar ages. Our review of radiographs of many pseudoachondroplastic patients and subsequently of those of patients with multiple epiphyseal dysplasia (MED), Fairbank type, reinforced our opinion that pseudoachondroplasia and multiple epiphyseal dysplasia, Fairbank type, are closely related conditions. MED, Fairbank type, may be the mildest form of pseudoachondroplasia. Recently published electron microscopic findings also suggest this.

The neuroimaging findings in Sotos syndrome.

We reviewed the neuroimaging studies of 40 patients with classic Sotos syndrome. The studies consisted of CT scans only in 4 patients and one or more MRI scans in 36 patients. The diagnosis of Sotos syndrome was made using well-established clinical criteria. The neuroimaging studies of each patient were evaluated subjectively by visual inspection and the chief findings were tabulated and grouped into five categories: 1) ventricular abnormalities, 2) extracerebral fluid spaces, 3) midline abnormalities, 4) migrational abnormalities, and 5) others. The most common abnormality of the cerebral ventricles was prominence of the trigone (90%), followed by prominence of the occipital horns (75%) and ventriculomegaly (63%). The supratentorial extracerebral fluid spaces were increased for age in 70% of the patients and the fluid spaces in the posterior fossa were increased in 70% also. A variety of midline abnormalities were noted but anomalies of the corpus callosum were almost universal. Gray matter heterotopias occurred in only 3 (8%) of 36 patients. Periventricular leukomalacia, presumably the result of prenatal or perinatal difficulties and unrelated to the basic condition, was the most common of the miscellaneous other abnormalities noted. The neuroimaging findings of Sotos syndrome are distinct enough to allow differentiation of this syndrome from other mental retardation syndromes with macrocephaly.

Tetrasomy of the short arm of chromosome 9: prenatal diagnosis and further delineation of the phenotype.

A fetus with multiple malformations was identified by prenatal ultrasound investigation. Cordocentesis and fetal lymphocyte chromosome analysis demonstrated a model number of 47 chromosomes. The extra chromosome material was identified as an isochromosome of the entire short arm of chromosome 9 with no involvement of the heterochromatic region of the long arm [47,XY, + i(9p)]. This represents the first report of prenatal diagnosis of tetrasomy 9p. Further delineation of the phenotype is discussed.

Volumetric neuroimaging in Usher syndrome: evidence of global involvement.

Usher syndrome is a group of genetic disorders consisting of congenital sensorineural hearing loss and retinitis pigmentosa of variable onset and severity depending on the genetic type. It was suggested that the psychosis of Usher syndrome might be secondary to a metabolic degeneration involving the brain more diffusely. There have been reports of focal and diffuse atrophic changes in the supratentorial brain as well as atrophy of some of the structures of the posterior fossa. We previously performed quantitative analysis of magnetic resonance imaging studies of 19 Usher syndrome patients (12 with type I and 7 with type II) looking at the cerebellum and various cerebellar components. We found atrophy of the cerebellum in both types and sparing of cerebellar vermis lobules I-V in type II Usher syndrome patients only. We now have studied another group of 19 patients (with some overlap in the patients studied from the previous report) with Usher syndrome (8 with type I, 11 with type II). We performed quantitative volumetric measurements of various brain structures compared to age- and sex-matched controls. We found a significant decrease in intracranial volume and in size of the brain and cerebellum with a trend toward an increase in the size of the subarachnoid spaces. These data suggest that the disease process in Usher syndrome involves the entire brain and is not limited to the posterior fossa or auditory and visual systems.

Hypoplasia of the cerebellar vermis and corpus callosum in thrombocytopenia with absent radius syndrome on MRI studies.

Thrombocytopenia with absent radius (TAR) syndrome is infrequently (7%) associated with mental retardation. In those cases, the mental deficiency is presumed to be a consequence of intracranial hemorrhage due to the thrombocytopenia. We report on 2 infants with TAR syndrome. One had developmental delay with evidence of cerebral dysgenesis by magnetic resonance imaging (MRI). Such findings have not been noted in the literature, but may not have been investigated in most cases. The other infant with TAR syndrome, who has had normal psychomotor development, has a normal brain on MRI scan. Detailed neuroimaging studies, preferably MRI, should be considered in the evaluation of patients with TAR syndrome, especially when there are documented signs of developmental delay, with or without a history of intracranial hemorrhage.

Agnathia, holoprosencephaly, and situs inversus: report of a case.

We present the first documented case of agnathia-holoprosencephaly (an uncommon form of craniofacial anomaly) associated with situs inversus. This case may represent the concordance of multiple field complex anomalies, but the possibility of a major midline malformation (situs inversus) caused by a timed insult (environmental or genetic) which affects multiple structures and occurs concurrently with a major field defect during early embryogenesis cannot be excluded.

Brain magnetic resonance imaging findings in the Opitz G/BBB syndrome: extension of the spectrum of midline brain anomalies.

We report the brain magnetic resonance imaging findings in 4 patients with the Opitz BBB/G syndrome. The scans were assessed by subjective interpretation and computerized image analysis. Findings noted in 3 of the 4 patients include hypoplasia or agenesis of the corpus callosum (3 patients), cerebellar vermal hypoplasia (2 patients), cortical atrophy and ventriculomegaly (3 patients), macro cisterna magna (3 patients), and a wide cavum septum pellucidum (1 patient). One patient had a normal scan. The demonstration of a wide cavum septum pellucidum extends the spectrum of midline brain anomalies (ventral induction defects) reported in this condition. This study along with other recent reports suggests that midline brain anomalies may be frequent findings in Opitz syndrome.

Identical twins discordant for Sotos syndrome.

The cause of Sotos syndrome is unknown but it usually occurs sporadically. Recent studies have shown no evidence of uniparental disomy. One set of concordant monozygotic twins has been reported. We have identified the Sotos syndrome in one of two 5-year-old male monozygotic twins. Our finding of discordance in these identical twins suggests that a postconceptual mutation, or epigenetic change and/or an environmental factor may be involved in the cause of Sotos syndrome.