O-GlcNAc transferase missense mutations linked to X-linked intellectual disability deregulate genes involved in cell fate determination and signaling.

It is estimated that ∼1% of the world's population has intellectual disability, with males affected more often than females. OGT is an X-linked gene encoding for the enzyme O-GlcNAc transferase (OGT), which carries out the reversible addition of N-acetylglucosamine (GlcNAc) to Ser/Thr residues of its intracellular substrates. Three missense mutations in the tetratricopeptide (TPR) repeats of OGT have recently been reported to cause X-linked intellectual disability (XLID). Here, we report the discovery of two additional novel missense mutations (c.775 G>A, p.A259T, and c.1016 A>G, p.E339G) in the TPR domain of OGT that segregate with XLID in affected families. Characterization of all five of these XLID missense variants of OGT demonstrates modest declines in thermodynamic stability and/or activities of the variants. We engineered each of the mutations into a male human embryonic stem cell line using CRISPR/Cas9. Investigation of the global O-GlcNAc profile as well as OGT and O-GlcNAc hydrolase levels by Western blotting showed no gross changes in steady-state levels in the engineered lines. However, analyses of the differential transcriptomes of the OGT variant-expressing stem cells revealed shared deregulation of genes involved in cell fate determination and liver X receptor/retinoid X receptor signaling, which has been implicated in neuronal development. Thus, here we reveal two additional mutations encoding residues in the TPR regions of OGT that appear causal for XLID and provide evidence that the relatively stable and active TPR variants may share a common, unelucidated mechanism of altering gene expression profiles in human embryonic stem cells.

Clinical Benefit of NMDA Receptor Antagonists in a Patient With ATP1A2 Gene Mutation.

Mutations in the ATP1A2 gene cause familial hemiplegic migraine type 2, alternating hemiplegia of childhood, and cerebellar function deficits, epilepsy, and mental retardation. These symptoms are likely related to glutamatergic hyperexcitability. Our patient is a 12-year-old boy with a history of complex partial seizures, attention-deficit/hyperactivity disorder, and fine motor difficulty. During early childhood, he had episodes of a self-resolving right-sided hemiparesis and focal epilepsy. His seizures did not respond to several antiepileptic medications but stopped after he received valproate. His intermittent episodes of hemiplegia persisted. Additionally, he had pronounced bilateral fine motor impairment and significant executive deficits that gradually worsened. The whole exome sequencing revealed a de novo missense mutation in the ATP1A2 gene and a maternally inherited POLG gene mutation of unknown clinical significance. We hypothesized that glutamatergic excitotoxicity due to the ATP1A2 mutation contributed to the pathogenesis of our patient's condition. He was started on N-methyl-D-aspartate receptor antagonists (memantine and dextromethorphan), as well as coenzyme Q10 One year later, he showed significant improvement in sustained attention, learning efficiency, general cognitive efficiency, and fine motor dexterity. We postulate that N-methyl-D-aspartate receptor antagonists were effective for behavioral, cognitive, and cerebellar symptoms in our patient with ATP1A2 gene mutation.

Novel Presentation of Rosai-Dorfman Histiocytosis With a Prolonged Course of Cranial and Peripheral Neuropathies.

BACKGROUND: Rosai-Dorfman disease is a form of histiocytosis affecting the systemic lymph nodes. Intracranial Rosai-Dorfman disease is rare and presents with extra-parenchymal or intraparenchymal proliferative mass lesions. Cranial neuropathy has not been reported in Rosai-Dorfman disease except when caused by mass effect by an adjacent lesion. PATIENT DESCRIPTION: We describe a girl with Rosai-Dorfman disease who presented with peripheral and multiple cranial neuropathies. Detailed clinical, immunologic, neurophysiology, imaging, and genetic studies were performed. She had a prolonged course but recovered fully after immune therapies. She had increased titers of striated muscle and smooth muscle antibodies. Imaging studies revealed contrast enhancement of cranial nerves and striated muscles. Demyelination was evident in the nerve twigs from muscle biopsy. Exome sequencing did not reveal a genetic mutation. CONCLUSIONS: Most patients with Rosai-Dorfman disease have a benign course, but severe neurological dysfunction due to bulbar involvement and cranial and peripheral neuropathies may occur. Treatment with immunoglobulin and steroids may be of benefit.

Sibling response to initial antiepileptic medication predicts treatment success.

OBJECTIVE: A recent study focusing on a response to antiepileptic drugs (AED) among siblings for epilepsy showed a similar response among epileptic siblings to specific AEDs or AED combinations. Currently, however, family history of treatment response to AEDs is not readily employed in deciding which initial medication to use when treating patients with epilepsy. We tested the hypothesis that sibling response to initial AED predicts treatment success. METHODS: Presumed siblings were identified from a single-center database of patients diagnosed with epilepsy by matching last name, address, and name of parent(s). We identified 28 sibling pairs and two sibling trios with epilepsy. Seventeen of these sibling pairs were started on the same initial AED, with 15 sibling pairs having the same type of epilepsy. The remaining 11 pairs were started on a different initial AED, with 8 of these sibling pairs having the same type of epilepsy. Subjects with seizure freedom for a period of ≥1year were classified as a "responder". RESULTS: When at least one of the sibling pair responded to an initial AED, the proportion of the other siblings also responding to the initial AED was significantly higher if the siblings were treated with the same AED (8/11) compared to siblings who were treated with different AED (1/10) (Fisher's exact test, p-value=0.0075). SIGNIFICANCE: These findings suggest that sibling response to initial AED is predictive of the success of AED therapy. This study is limited by a small cohort and retrospective design. Future, larger prospective studies are needed to reproduce and further validate these findings.

Homozygous Mutation in Synaptic Vesicle Glycoprotein 2A Gene Results in Intractable Epilepsy, Involuntary Movements, Microcephaly, and Developmental and Growth Retardation.

BACKGROUND: Synaptic vesicle protein 2A (SV2a) is the binding site of the antiepileptic drug levetiracetam and the only known synaptic vesicle target of an epilepsy medication. To date, no pathogenic mutation in SV2A, which is the gene encoding synaptic vesicle glycoprotein 2A, has been identified in humans. We report a homozygous mutation in the SV2A gene in a patient with intractable epilepsy. METHODS: We investigated a patient with intractable epilepsy, involuntary movements, microcephaly, and developmental and growth retardation. Both parents were multiply consanguineous and an earlier-born brother of the proband had a similar course and died at 7 months of age. Detailed clinical history, imaging, electroencephalograph and metabolic testing were obtained. Full exome sequencing was performed using genomic DNA isolated from the patient and both parents. RESULTS: Exome sequencing identified a homozygous arginine to glutamine mutation in amino acid position 383 (R383Q) in exon 5 of the SV2A gene. Both parents were carriers for the R383Q variant, suggesting that R383Q is a recessive mutation. There were no other candidate alterations in the exome that could explain the phenotype in the proband. The amino acid arginine at position 383 of SV2a gene is evolutionally conserved throughout vertebrates. R383Q change is not observed in known healthy cohorts, exome databases, or the Database of Single Nucleotide Polymorphisms. The R383Q mutation is located in the second adenine binding domain in SV2a protein and may alter adenine nucleotides binding to SV2a. CONCLUSION: Our report provides the elusive evidence that an SV2A mutation can be a cause of epilepsy in humans. Levetiracetam, which binds to SV2A, was not effective as an antiepileptic medication. The location of the mutation in our patient supports an important role of adenine nucleotides binding in SV2A function.

Advances in Tourette syndrome: diagnoses and treatment.

Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder characterized by multiple motor tics and at least one vocal or phonic tic, and often one or more comorbid psychiatric disorders. Premonitory sensory urges before tic execution and desire for "just-right" perception are central features. The pathophysiology involves cortico-striato-thalamo-cortical circuits and possibly dopaminergic system. TS is considered a genetic disorder but the genetics is complex and likely involves rare mutations, common variants, and environmental and epigenetic factors. Treatment is multimodal and includes education and reassurance, behavioral interventions, pharmacologic, and rarely, surgical interventions.

Polymorphisms in xenobiotic metabolism genes and autism.

Autism is a neurodevelopmental syndrome defined by deficits in social reciprocity and communication and by unusual repetitive behaviors. Although there is an underlying genetic predisposition, the etiology of autism is currently unknown. A recent increase in prevalence suggests that genetically determined vulnerability to environmental exposure might contribute to the causation of autism. We performed family-based association studies of polymorphisms in metal-regulatory transcription factor 1(MTF1), a multispecific organic anion transporter (ABCC1), proton-coupled divalent metal ion transporters (SLC11A3 and SLC11A2), paraoxonase 1 (PON1), and glutathione S-transferase (GSTP1) genes in 196 autistic disorder families. There was deviation from the expected pattern of transmission for polymorphisms in MTF1 (Single nucleotide polymorphism database reference identification number, dbSNP rs3790625, P = .02) and divalent metal ion transporter SLC11A3 (dbSNP rs2304704, P = .07) genes. Although these results might represent chance finding, further investigations of genetic variations of metal metabolism in autism are warranted.

Posterior reversible encephalopathy and cerebral vasoconstriction in a patient with hemolytic uremic syndrome.

BACKGROUND: We report a patient with hemolytic uremic syndrome who presented with radiological manifestations suggestive of posterior reversible encephalopathy syndrome and reversible cerebral vasoconstriction syndrome. PATIENT: A 13-year-old girl presented with fever and bloody diarrhea and progressed to develop hemolytic uremic syndrome. She subsequently developed encephalopathy, aphasia, and right-sided weakness. RESULTS: Brain magnetic resonance imaging showed presence of vasogenic edema in the left frontal lobe, in addition to T2 and fluid-attenuated inversion recovery changes in white matter bilaterally, compatible with posterior reversible encephalopathy syndrome. Magnetic resonance angiography showed beading of the cerebral vessels. Neurological deficits reversed 8 days after symptom onset, with resolution of the beading pattern on follow-up magnetic resonance angiography after 3 weeks, suggesting reversible cerebral vasoconstriction syndrome. CONCLUSIONS: Both posterior reversible encephalopathy syndrome and reversible cerebral vasoconstriction syndrome may represent manifestations of similar underlying pathophysiologic mechanisms. Recognition of the co-existence of these processes in patients with hemolytic uremic syndrome may aid in judicious management of these patients and avoidance of inappropriate therapeutic interventions.

Association of Y chromosome haplotypes with autism.

There is significant male excess in autism. In this study, we investigated a possible Y chromosome effect by haplotype analysis. We investigated 12 single-nucleotide polymorphisms in Y-linked neuroligin 4, transducin beta-like 1, and eukaryotic translation initiation factor 1a genes in 146 autistic participants and 102 control participants of European American origin. The set of 12 single-nucleotide polymorphisms defined 9 Y chromosome haplotypes in autistic and control participants. Although the 2 most frequent haplotypes were equally distributed in the autistic and control participants, some haplotypes were overrepresented or underrepresented in autistic participants. The distribution of haplotypes between the autistic and control groups, as determined by Monte Carlo tests with Clump software, was significantly different (P = .0001 with 100,000 simulations). Our results are suggestive of a Y chromosome effect in autism.

Homozygous myotonic dystrophy with craniosynostosis.

Myotonic dystrophy is considered a true dominant condition with no difference in the phenotype between heterozygous and homozygous cases. The homozygous state is very rare and only a few patients have been reported in the literature. We report a 2.5-year-old boy from a nonconsanguineous marriage, with a unique combination of clinical and radiological findings: hypotonia, motor and language developmental delay, ventriculomegaly, subcortical white matter lesions, and craniosynostosis. Mutation analysis revealed 2 copies of expansion mutation of 1260 and 60 cytosine-thymine-guanine repeats in the myotonic dystrophy protein kinase gene. Both the mildly symptomatic (434 repeats) mother and the asymptomatic (37 repeats) father are heterozygous. Craniosynostosis has not been reported previously in myotonic dystrophy. This homozygous case expands the clinical spectrum of myotonic dystrophy type 1 and provides support to the hypothesis that myotonic dystrophy type 1 pathophysiology could be, in part, due to the loss of normal function of the wild-type protein.

Association of Reelin gene polymorphisms with autism.

Genome scans indicate a linkage of autism to the chromosome 7q21-q36 region. Recent studies suggest that the Reelin gene may be one of the loci contributing to the positive linkage between chromosome 7q and autism. However, these studies were relatively small scale, using a few markers in the gene. We investigated 34 single nucleotide polymorphisms (SNPs) in the Reelin gene with an average spacing between the SNPs of 15 kb for evidence of association with autism. There were significant differences in the transmission of the alleles of exon 22 and intron 59 SNP to autistic subjects. Our findings support a role for the Reelin gene in the susceptibility to autism.

No association between single nucleotide polymorphisms in DLX6 and Piccolo genes at 7q21-q22 and autism.

Several independent genome scans have revealed excess allele sharing in an overlapping 40 cM region of 7q21-34 in autism. DLX6 and Piccolo (PCLO) at 7q21-q22 are two positional and functional candidate genes in autism. We have investigated a single nucleotide polymorphism (SNP) in exon 4 of the PCLO gene and a SNP in intron 1 of the DLX6 gene for linkage and association in autistic disorder using both qualitative and quantitative analyses. One hundred ninety-six multiplex autistic disorder families were tested using transmission disequilibrium and two-point affected sib pair linkage analysis. We found no evidence of association or linkage with the two intragenic markers. In addition, there was also no linkage or association between language and stereotypic behavior quantitative traits in autism and the SNPs. In conclusion, our studies suggest that these two SNPs in DLX6 and PCLO genes are not in linkage disequilibrium with autism.

Association of tryptophan 2,3 dioxygenase gene polymorphism with autism.

Although elevation of blood and platelet serotonin has been documented in autism, genetic analyses of serotonin transporter gene have given conflicting results. Tryptophan 2,3 dioxygenase (TDO2) is the rate-limiting enzyme in the catabolism of tryptophan, the precursor of serotonin. A mutation that results in decreased activity of the TDO2 can decrease catabolism of tryptophan and increase the level of whole body serotonin. As such it is a potential candidate gene for autism. We have investigated five single nucleotide polymorphisms in the TDO2 gene for association with autistic disorder. One hundred and ninety six multiplex autistic disorder families were tested using transmission disequilibrium test. There was a significant difference in the transmission of a promoter variant to autistic subjects (P = 0.0006). Haplotype analysis also demonstrated significant difference in the transmission of TDO2 haplotypes to autistic subjects (P = 0.0027). Our results suggest the presence of a susceptibility mutation in the TDO2 or a nearby gene, but may also represent a chance finding.