X-exome sequencing of 405 unresolved families identifies seven novel intellectual disability genes

X-linked intellectual disability (XLID) is a clinically and genetically heterogeneous disorder. During the past two decades in excess of 100 X-chromosome ID genes have been identified. Yet, a large number of families mapping to the X-chromosome remained unresolved suggesting that more XLID genes or loci are yet to be identified. Here, we have investigated 405 unresolved families with XLID. We employed massively parallel sequencing of all X-chromosome exons in the index males. The majority of these males were previously tested negative for copy number variations and for mutations in a subset of known XLID genes by Sanger sequencing. In total, 745 X-chromosomal genes were screened. After stringent filtering, a total of 1297 non-recurrent exonic variants remained for prioritization. Co-segregation analysis of potential clinically relevant changes revealed that 80 families (20%) carried pathogenic variants in established XLID genes. In 19 families, we detected likely causative protein truncating and missense variants in 7 novel and validated XLID genes (CLCN4, CNKSR2, FRMPD4, KLHL15, LAS1L, RLIM and USP27X) and potentially deleterious variants in 2 novel candidate XLID genes (CDK16 and TAF1). We show that the CLCN4 and CNKSR2 variants impair protein functions as indicated by electrophysiological studies and altered differentiation of cultured primary neurons from Clcn4(-/-) mice or after mRNA knock-down. The newly identified and candidate XLID proteins belong to pathways and networks with established roles in cognitive function and intellectual disability in particular. We suggest that systematic sequencing of all X-chromosomal genes in a cohort of patients with genetic evidence for X-chromosome locus involvement may resolve up to 58% of Fragile X-negative cases.

Hand-assisted Laparoscopic Donor Nephrectomy and Cytokine Changes

BACKGROUND

Laparoscopic living-donor nephrectomy (LDN) exerts systemic effects causing transaminitis and increased urinary neutrophil gelatinase-associated lipocalm (NGAL) excretion. Hand-assisted laparoscopic donor nephrectomy, which tends to be shorter with less pneumoperitoneum, may be hypothesized to produce less systemic stimulation than total laparoscopic LDN.

METHODS

Serial urine and serum samples were collected from 15 patients undergoing HALDN. Samples were analyzed for NGAL and kidney injury molecule 1 (KIM-1) levels preoperatively and 24 hours post-surgery. Data relating to alanine aminotransferase, creatinine, and estimated glomerular filtration rate was also analyzed in 48 live donors preoperatively and at 24 hours and 48 hours post-surgery and compared to published data on LDN.

RESULTS

Expected changes to creatinine and estimated glomerular filtration rates were observed in the donors. Compared to the preoperative levels, alanine aminotransferase levels showed a significant decrease at 24 hours (P = .004) and were not significantly different from baseline levels at 48 hours (P = .08). Serum KIM-1 and NGAL levels remained unchanged (P = .89 and P = .14, respectively) at 24 hours after donation. Similarly, urinary levels of KIM-1 and NGAL were not statistically significantly different after donation. Mean operating time for this cohort was 1 hour, 36 minutes.

CONCLUSIONS

In contrast to other published data, our cohort did not exhibit changes to liver function tests or biomarker changes after donor nephrectomy. This could be because of the lower operative time (96 minutes vs. 216 minutes) or because of the intermittent release of the pneumoperitoneum in the hand-assisted method which may exert less of a systemic inflammatory response.

New insights into Brunner syndrome and potential for targeted therapy

We report two families with Brunner syndrome living in one state of Australia. The first family had a predicted protein-truncating variant of monoamine oxidase A (MAOA) (p.S251KfsX2). Affected males had mild intellectual disability (ID), obsessive behaviour, limited friendships and were introverted and placid during clinical interview. The family disclosed episodic explosive aggression after a diagnosis was made. The second family had a missense variant in MAOA (p.R45W). Affected males had borderline-mild ID, attention deficit disorder and limited friendships. One had a history of explosive aggression in childhood and episodic symptoms of flushing, headaches and diarrhoea. Their carrier mother had normal intelligence but similar episodic symptoms. Characteristic biochemical abnormalities included high serum serotonin and urinary metanephrines and low urinary 5-hydroxyindoleacetic acid (5-HIAA) and vanillylmandelic acid (VMA). Symptomatic individuals in the second family had particularly high serotonin levels, and treatment with a serotonin reuptake inhibitor and dietary modification resulted in reversal of biochemical abnormalities, reduction of 'serotonergic' symptoms and behavioural improvement. Brunner syndrome should be considered as a cause of mild ID with paroxysmal behavioural symptoms. It can be screened for with serum/urine metanephrine and serotonin measurement. Cautious treatment with a serotonin reuptake inhibitor, dietary modifications and avoidance of medications contraindicated in patients on monoamine oxidase inhibitors can improve symptoms.

An apical left ventricular aneurysm rupture presenting as left breast mass 11 years after surgical repair

Left ventricular (LV) pseudoaneurysm is a rare entity and, consequently, there is limited knowledge of the condition's natural history. The most frequent mode of presentation for LV pseudoaneurysm is heart failure with chest pain. However, the variable presentation of this condition requires a high index of suspicion for diagnosis. We report the case of a 75-year-old woman who had suffered an acute myocardial infarction 23 years previously, which resulted in a calcified LV apical aneurysm. Three weeks prior to being referred to our hospital, she was noted by her general practitioner to have a left-sided breast mass although mammography was negative. One week later, she attended the accident and emergency department; she was haemodynamically unstable but was resuscitated successfully. Contrast enhanced computed tomography showed a large haematoma located in the left chest wall communicating with the left ventricle. She underwent emergency cardiac surgical repair. On arrival at the intensive care unit following surgery, her haemodynamic status was unstable, and she deteriorated rapidly and died. With this report, we aim to raise the level of awareness for an apical LV pulsatile mass that could anatomically expand and present as a breast mass or tumour. An early diagnosis and timely surgical intervention is essential in order to achieve better outcomes and avoid detrimental complications.

The effects of histone deacetylase inhibitors on glioblastoma-derived stem cells

Glioblastoma multiforme (GBM) is the most malignant brain tumor with limited effective treatment options. Cancer stem cells (CSCs), a subpopulation of cancer cells with stem cell properties found in GBMs, have been shown to be extremely resistant to radiation and chemotherapeutic agents and have the ability to readily reform tumors. Therefore, the development of therapeutic agents targeting CSCs is extremely important. In this study, we isolated glioblastoma-derived stem cells (GDSCs) from GBM tissue removed from patients during surgery and analyzed their gene expression using quantitative real-time PCR and immunocytochemistry. We examined the effects of histone deacetylase inhibitors trichostatin A (TSA) and valproic acid (VPA) on the proliferation and gene expression profiles of GDSCs. The GDSCs expressed significantly higher levels of both neural and embryonic stem cell markers compared to GBM cells expanded in conventional monolayer cultures. Treatment of GDSCs with histone deacetylase inhibitors, TSA and VPA, significantly reduced proliferation rates of the cells and expression of the stem cell markers, indicating differentiation of the cells. Since differentiation into GBM makes them susceptible to the conventional cancer treatments, we posit that use of histone deacetylase inhibitors may increase efficacy of the conventional cancer treatments for eliminating GDSCs.

Genotype and clinical care correlations in craniosynostosis: findings from a cohort of 630 Australian and New Zealand patients

Craniosynostosis is one of the most common craniofacial disorders encountered in clinical genetics practice, with an overall incidence of 1 in 2,500. Between 30% and 70% of syndromic craniosynostoses are caused by mutations in hotspots in the fibroblast growth factor receptor (FGFR) genes or in the TWIST1 gene with the difference in detection rates likely to be related to different study populations within craniofacial centers. Here we present results from molecular testing of an Australia and New Zealand cohort of 630 individuals with a diagnosis of craniosynostosis. Data were obtained by Sanger sequencing of FGFR1, FGFR2, and FGFR3 hotspot exons and the TWIST1 gene, as well as copy number detection of TWIST1. Of the 630 probands, there were 231 who had one of 80 distinct mutations (36%). Among the 80 mutations, 17 novel sequence variants were detected in three of the four genes screened. In addition to the proband cohort there were 96 individuals who underwent predictive or prenatal testing as part of family studies. Dysmorphic features consistent with the known FGFR1-3/TWIST1-associated syndromes were predictive for mutation detection. We also show a statistically significant association between splice site mutations in FGFR2 and a clinical diagnosis of Pfeiffer syndrome, more severe clinical phenotypes associated with FGFR2 exon 10 versus exon 8 mutations, and more frequent surgical procedures in the presence of a pathogenic mutation. Targeting gene hot spot areas for mutation analysis is a useful strategy to maximize the success of molecular diagnosis for individuals with craniosynostosis.

Transcriptome profiling of UPF3B/NMD-deficient lymphoblastoid cells from patients with various forms of intellectual disability

The nonsense-mediated mRNA decay (NMD) pathway was originally discovered by virtue of its ability to rapidly degrade aberrant mRNAs with premature termination codons. More recently, it was shown that NMD also directly regulates subsets of normal transcripts, suggesting that NMD has roles in normal biological processes. Indeed, several NMD factors have been shown to regulate neurological events (for example, neurogenesis and synaptic plasticity) in numerous vertebrate species. In man, mutations in the NMD factor gene UPF3B, which disrupts a branch of the NMD pathway, cause various forms of intellectual disability (ID). Using Epstein Barr virus-immortalized B cells, also known as lymphoblastoid cell lines (LCLs), from ID patients that have loss-of-function mutations in UPF3B, we investigated the genome-wide consequences of compromised NMD and the role of NMD in neuronal development and function. We found that ~5% of the human transcriptome is impacted in UPF3B patients. The UPF3B paralog, UPF3A, is stabilized in all UPF3B patients, and partially compensates for the loss of UPF3B function. Interestingly, UPF3A protein, but not mRNA, was stabilised in a quantitative manner that inversely correlated with the severity of patients' phenotype. This suggested that the ability to stabilize the UPF3A protein is a crucial modifier of the neurological symptoms due to loss of UPF3B. We also identified ARHGAP24, which encodes a GTPase-activating protein, as a canonical target of NMD, and we provide evidence that deregulation of this gene inhibits axon and dendrite outgrowth and branching. Our results demonstrate that the UPF3B-dependent NMD pathway is a major regulator of the transcriptome and that its targets have important roles in neuronal cells.

Anti-tuberculosis prophylaxis following renal transplantation: acceptable variations?

BACKGROUND

Guidelines suggest tuberculosis (TB) prophylaxis in renal transplant recipients originating in endemic areas or in those at risk from non-endemic countries. Concern remains that these guidelines may fail to provide adequate prophylaxis for a cohort of patients who remain at potential risk. We aimed to determine variation patterns among different transplant units within the United Kingdom (UK) with regard to TB prophylaxis policy.

METHODS

The renal pharmacist at each of the 25 UK renal transplant centers was contacted. Specific information was obtained relating to drug prophylaxis given, duration of treatment, as well as which transplant recipients were eligible for treatment.

RESULTS

A 96% response rate (24/25 centers) was achieved. Prophylaxis regimens varied from no prophylaxis to isoniazid 300 mg given life-long. The most common duration of treatment was 6 months post transplantation (at 7 centers). Variations existed in the concurrent use of pyridoxine. A wide discrepancy was seen in the determination of who should receive prophylaxis, with no clear association with frequency of TB incidence in the region.

CONCLUSIONS

A marked discrepancy exists among national renal transplant units in pharmacologic prophylaxis for TB, as well in the selection of individuals for this treatment.