Fetal exome sequencing for isolated increased nuchal translucency: should we be doing it?

OBJECTIVE: To evaluate the utility of prenatal exome sequencing (ES) for isolated increased nuchal translucency (NT) and to investigate factors that increase diagnostic yield. DESIGN: Retrospective analysis of data from two prospective cohort studies. SETTING: Fetal medicine centres in the UK and USA. POPULATION: Fetuses with increased NT ≥3.5 mm at 11-14 weeks of gestation recruited to the Prenatal Assessment of Genomes and Exomes (PAGE) and Columbia fetal whole exome sequencing studies (n = 213). METHODS: We grouped cases based on (1) the presence of additional structural abnormalities at presentation in the first trimester or later in pregnancy, and (2) NT measurement at presentation. We compared diagnostic rates between groups using Fisher exact test. MAIN OUTCOME MEASURES: Detection of diagnostic genetic variants considered to have caused the observed fetal structural anomaly. RESULTS: Diagnostic variants were detected in 12 (22.2%) of 54 fetuses presenting with non-isolated increased NT, 12 (32.4%) of 37 fetuses with isolated increased NT in the first trimester and additional abnormalities later in pregnancy, and 2 (1.8%) of 111 fetuses with isolated increased NT in the first trimester and no other abnormalities on subsequent scans. Diagnostic rate also increased with increasing size of NT. CONCLUSIONS: The diagnostic yield of prenatal ES is low for fetuses with isolated increased NT but significantly higher where there are additional structural anomalies. Prenatal ES may not be appropriate for truly isolated increased NT but timely, careful ultrasound scanning to identify other anomalies emerging later can direct testing to focus where there is a higher likelihood of diagnosis.

Fetal hydrops and the Incremental yield of Next-generation sequencing over standard prenatal Diagnostic testing (FIND) study: prospective cohort study and meta-analysis.

OBJECTIVE: To determine the incremental yield of exome sequencing (ES) over chromosomal microarray analysis (CMA) or karyotyping in prenatally diagnosed non-immune hydrops fetalis (NIHF). METHODS: A prospective cohort study (comprising an extended group of the Prenatal Assessment of Genomes and Exomes (PAGE) study) was performed which included 28 cases of prenatally diagnosed NIHF undergoing trio ES following negative CMA or karyotyping. These cases were combined with data from a systematic review of the literature. MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov databases were searched electronically (January 2000 to October 2020) for studies reporting on the incremental yield of ES over CMA or karyotyping in fetuses with prenatally detected NIHF. Inclusion criteria for the systematic review were: (i) at least two cases of NIHF undergoing sequencing; (ii) testing initiated based on prenatal ultrasound-based phenotype; and (iii) negative CMA or karyotyping result. The incremental diagnostic yield of ES was assessed in: (i) all cases of NIHF; (ii) isolated NIHF; (iii) NIHF associated with an additional fetal structural anomaly; and (iv) NIHF according to severity (i.e. two vs three or more cavities affected). RESULTS: In the extended PAGE study cohort, the additional diagnostic yield of ES over CMA or karyotyping was 25.0% (7/28) in all NIHF cases, 21.4% (3/14) in those with isolated NIHF and 28.6% (4/14) in those with non-isolated NIHF. In the meta-analysis, the pooled incremental yield based on 21 studies (306 cases) was 29% (95% CI, 24-34%; P < 0.00001; I2 = 0%) in all NIHF, 21% (95% CI, 13-30%; P < 0.00001; I2 = 0%) in isolated NIHF and 39% (95% CI, 30-49%; P < 0.00001; I2 = 1%) in NIHF associated with an additional fetal structural anomaly. In the latter group, congenital limb contractures were the most prevalent additional structural anomaly associated with a causative pathogenic variant, occurring in 17.3% (19/110) of cases. The incremental yield did not differ significantly according to hydrops severity. The most common genetic disorders identified were RASopathies, occurring in 30.3% (27/89) of cases with a causative pathogenic variant, most frequently due to a PTPN11 variant (44.4%; 12/27). The predominant inheritance pattern in causative pathogenic variants was autosomal dominant in monoallelic disease genes (57.3%; 51/89), with most being de novo (86.3%; 44/51). CONCLUSIONS: Use of prenatal next-generation sequencing in both isolated and non-isolated NIHF should be considered in the development of clinical pathways. Given the wide range of potential syndromic diagnoses and heterogeneity in the prenatal phenotype of NIHF, exome or whole-genome sequencing may prove to be a more appropriate testing approach than a targeted gene panel testing strategy. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Evidence to Support the Clinical Utility of Prenatal Exome Sequencing in Evaluation of the Fetus with Congenital Anomalies: Scientific Impact Paper No. 64 [February] 2021.

Structural differences (congenital anomalies) in the makeup of the baby's heart, brain and other organs are found on antenatal ultrasound scans in up to 3% of pregnancies. These often have a genetic cause, arising because of changes in the chromosomes (which store our genetic material) or the DNA code that make up the genes. The more differences a baby has the more likely the risk of underlying genetic disease. If a structural difference is found, parents are usually offered a genetic test, which may be carried out on cells taken either from the placenta (chorionic villous sampling) or the fluid surrounding the baby (amniocentesis). At the moment, these cells are only tested for changes in the chromosomes and are only able to reveal the underlying cause in about 40% of unborn babies. Prenatal exome sequencing (ES) is a new genetic test, which, when combined with testing the DNA of both parents can find changes in the baby's genetic code. If a DNA change is found that can explain the structural changes seen on ultrasound, specific information about the underlying diagnosis can be given to the parents. Having this information can help parents make important decisions about their ongoing pregnancy, as well as help doctors to care for the mother and baby. Finding a genetic change can also help to understand how the condition has arisen and whether it might happen again in another pregnancy. It may also be possible to test for the genetic condition in future pregnancies. Although prenatal ES is an exciting new way to improve diagnosis rates for structural differences, it has some challenges. While the test is very detailed, it may not always find a genetic explanation and sometimes the results are difficult to interpret. For example, genetic changes can be found where their significance for the pregnancy is unclear. More recently, two studies have now shown that prenatal ES can find a genetic diagnosis in at least 10% of pregnancies with structural differences where standard chromosome testing has been negative. This paper reviews these studies, along with earlier evidence on ES and provides clinicians with guidance for future practice.

COngenital heart disease and the Diagnostic yield with Exome sequencing (CODE) study: prospective cohort study and systematic review.

OBJECTIVE: To determine the incremental yield of antenatal exome sequencing (ES) over chromosomal microarray analysis (CMA) or conventional karyotyping in prenatally diagnosed congenital heart disease (CHD). METHODS: A prospective cohort study of 197 trios undergoing ES following CMA or karyotyping owing to CHD identified prenatally and a systematic review of the literature were performed. MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov (January 2000 to October 2019) databases were searched electronically for studies reporting on the diagnostic yield of ES in prenatally diagnosed CHD. Selected studies included those with more than three cases, with initiation of testing based upon prenatal phenotype only and that included cases in which CMA or karyotyping was negative. The incremental diagnostic yield of ES was assessed in: (1) all cases of CHD; (2) isolated CHD; (3) CHD associated with extracardiac anomaly (ECA); and (4) CHD according to phenotypic subgroup. RESULTS: In our cohort, ES had an additional diagnostic yield in all CHD, isolated CHD and CHD associated with ECA of 12.7% (25/197), 11.5% (14/122) and 14.7% (11/75), respectively (P = 0.81). The corresponding pooled incremental yields from 18 studies (encompassing 636 CHD cases) included in the systematic review were 21% (95% CI, 15-27%), 11% (95% CI, 7-15%) and 37% (95% CI, 18-56%), respectively. The results did not differ significantly when subanalysis was limited to studies including more than 20 cases, except for CHD associated with ECA, in which the incremental yield was greater (49% (95% CI, 17-80%)). In cases of CHD associated with ECA in the primary analysis, the most common extracardiac anomalies associated with a pathogenic variant were those affecting the genitourinary system (23/52 (44.2%)). The greatest incremental yield was in cardiac shunt lesions (41% (95% CI, 19-63%)), followed by right-sided lesions (26% (95% CI, 9-43%)). In the majority (68/96 (70.8%)) of instances, pathogenic variants occurred de novo and in autosomal dominant (monoallelic) disease genes. The most common (19/96 (19.8%)) monogenic syndrome identified was Kabuki syndrome. CONCLUSIONS: There is an apparent incremental yield of prenatal ES in CHD. While the greatest yield is in CHD associated with ECA, consideration could also be given to performing ES in the presence of an isolated cardiac abnormality. A policy of routine application of ES would require the adoption of robust bioinformatic, clinical and ethical pathways. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Rapid disease progression in a patient with mismatch repair-deficient and cortisol secreting adrenocortical carcinoma treated with pembrolizumab.

CONTEXT: Metastatic adrenocortical carcinoma (ACC) is an aggressive malignancy with a poor prognosis and limited therapeutic options. A subset of ACC is due to Lynch syndrome, an inherited tumor syndrome resulting from germline mutations in mismatch repair (MMR) genes. It has been demonstrated that several cancers characterized by MMR deficiency are sensitive to immune checkpoint inhibitors that target PD-1. Here, we provide the first report of PD-1 blockade with pembrolizumab in a patient with Lynch syndrome and progressive cortisol-secreting metastatic ACC. CASE REPORT: A 58-year-old female with known Lynch syndrome presented with severe Cushing's syndrome and was diagnosed with a cortisol-secreting ACC. Three months following surgical resection and adjuvant mitotane therapy the patient developed metastatic disease and persistent hypercortisolemia. She commenced pembrolizumab, but her second cycle was delayed due to a transient transaminitis. Computed tomography performed after 12 weeks and 2 cycles of pembrolizumab administration revealed significant disease progression and treatment was discontinued. After 7 weeks, the patient became jaundiced and soon died due to fulminant liver failure. CONCLUSION: Treatment of MMR-deficient cortisol-secreting ACC with pembrolizumab may be ineffective due to supraphysiological levels of circulating corticosteroids, which may in turn mask severe drug-induced organ damage.

Recent Advances in Imprinting Disorders.

Imprinting disorders (ImpDis) are a group of currently 12 congenital diseases with common underlying (epi)genetic etiologies and overlapping clinical features affecting growth, development and metabolism. In the last years it has emerged that ImpDis are characterized by the same types of mutations and epimutations, i.e. uniparental disomies, copy number variations, epimutations, and point mutations. Each ImpDis is associated with a specific imprinted locus, but the same imprinted region can be involved in different ImpDis. Additionally, even the same aberrant methylation patterns are observed in different phenotypes. As some ImpDis share clinical features, clinical diagnosis is difficult in some cases. The advances in molecular and clinical diagnosis of ImpDis help to circumvent these issues, and they are accompanied by an increasing understanding of the pathomechanism behind them. As these mechanisms have important roles for the etiology of other common conditions, the results in ImpDis research have a wider effect beyond the borders of ImpDis. For patients and their families, the growing knowledge contributes to a more directed genetic counseling of the families and personalized therapeutic approaches.

Genome-wide DNA methylation profiling of recurrent and non-recurrent chordomas.

Chordomas are an aggressive rare type of malignant bone tumors arising from the remnant of the notochord. Chordomas occur mainly in vertebral bones and account for 1-4% of malignant bone tumors. Management and treatment of chordomas are difficult as they are resistant to conventional chemotherapy; therefore, they are mainly treated with surgery and radiation therapy. In this study, we performed DNA methylation profiling of 26 chordomas and normal nucleus pulposus samples plus UCH-1 chordoma cell line using the Illumina Infinium HumanMethylation450 BeadChips. Combined bisulfite restriction analysis and bisulfite sequencing was used to confirm the methylation data. Gene expression was analyzed using RT-PCR before and after 5-aza-2'-deoxycytidine (5-azaDC) treatment of chordoma cell lines. Analysis of the HumanMethylation450 BeadChip data led to the identification of 8,819 loci (2.9%) that were significantly differentially methylated (>0.2 average ß-value difference) between chordomas and nucleus pulposus samples (adjusted P < 0.05). Among these, 5,868 probes (66.5%) were hypomethylated, compared to 2,951 (33.5%) loci that were hypermethylated in chordomas compared to controls. From the 2,951 differentially hypermethylated probes, 33.3% were localized in the promoter region (982 probes) and, among these, 104 probes showed cancer-specific hypermethylation. Ingenuity Pathway Analysis indicates that the cancer-specific differentially methylated loci are involved in various networks including cancer disease, nervous system development and function, cell death and survival, cellular growth, cellular development, and proliferation. Furthermore, we identified a subset of probes that were differentially methylated between recurrent and non-recurrent chordomas. BeadChip methylation data was confirmed for these genes and gene expression was shown to be upregulated in methylated chordoma cell lines after treatment with 5-azaDC. Understanding epigenetic changes in chordomas may provide insights into chordoma tumorigenesis and development of epigenetic biomarkers.

The tumor susceptibility gene TMEM127 is mutated in renal cell carcinomas and modulates endolysosomal function.

TMEM127 is an endosome-associated tumor suppressor gene in pheochromocytomas, neuroendocrine tumors that can co-occur with renal cell carcinomas (RCCs). TMEM127 loss leads to increased mTOR signaling. However, the spectrum of tumors with TMEM127 mutation and how TMEM127 and mTOR interact in tumorigenesis remains unknown. Here, we report that germline TMEM127 mutations occur in RCCs and that some mutant proteins, unlike wild-type (WT) TMEM127, fail to cooperate with activated early endosomal GTPase, Rab5, to inhibit mTOR signaling. Tmem127-null mouse embryonic fibroblasts (MEFs) are deficient in generating early-to-late hybrid endosomes upon constitutive Rab5 activation, a defect rescued by WT, but not mutant, TMEM127. This endosomal dysfunction results in diminished mTOR colocalization with Rab5-positive vesicles. Conversely, active, lysosomal-bound mTOR is increased in Tmem127-null MEFs, which also display enhanced lysosomal biogenesis. Our data map the tumor-suppressive properties of TMEM127 to modulation of mTOR function in the endolysosome, a feature that may contribute to both pheochromocytoma and RCC pathogenesis.

Knockdown of Slingshot 2 (SSH2) serine phosphatase induces Caspase3 activation in human carcinoma cell lines with the loss of the Birt-Hogg-Dubé tumour suppressor gene (FLCN).

Birt-Hogg-Dubé (BHD) syndrome, is a dominantly inherited familial cancer syndrome associated with susceptibility to renal cell carcinoma (RCC) caused by inactivating mutations in the folliculin (FLCN) gene. The precise functions of the FLCN gene product are still under investigation but RCC from BHD patients show loss of the wild-type allele consistent with a tumor suppressor gene function. In a search for potential synthetic-lethal targets for FLCN using a phosphatase siRNA library screening approach, we found that knockdown of SSH2 serine phosphatase (one of the three members of Slingshot family and previously implicated in actin reorganization) specifically induced Caspase3/7 activity in a dose-dependent manner (up to six-fold increase, 10 nM, 72 h) in two human FLCN-deficient cell lines (BHD-origin renal cell carcinoma UOK257 and thyroid carcinoma FTC133) but not in their folliculin expressing isogenic cell lines. SSH2 siRNA-induced knockdown was accompanied by increased expression of SSH1 and SSH3 (suggesting a compensatory regulatory mechanism among members of SSH family). FLCN-null cells exhibited evidence of dysregulated cofilin de/phosphorylation pathways. Knockdown of SSH2 in FLCN-null cells was associated with an alteration in cell cycle kinetics (20% increase in G1, 30% and 40% decrease in S and G2M, respectively). Combination treatment of multiple SSH family (SSH2 plus SSH1 and/or SSH3) siRNAs potentiated induction of Caspase3/7 activity and changes in the cell cycle kinetics. These data indicate that: (a) apoptotic cell death in FLCN-null cells can be triggered by SSH2 knockdown through cell cycle arrest; (b) SSH2 represents a potential therapeutic target for the development of agents for the treatment of BHD syndrome and, possibly, related tumors.

How does altering the resolution of chromosomal microarray analysis in the prenatal setting affect the rates of pathological and uncertain findings?

OBJECTIVE: Chromosomal Microarray Analysis (CMA) has a higher detection rate of pathogenic chromosome abnormalities over conventional (G-band) karyotyping. The optimum resolution of CMA in the prenatal setting remains debatable. Our objective was to determine if an increased detection rate was obtained by performing differing resolution of CMA on the same fetal samples and whether this resulted in an increase in variants of uncertain clinical significance (VOUS). METHODS: Sixty-two fetal cases initially underwent a 1 Mb targeted BAC microarray within a clinical diagnostic setting in addition to conventional karyotyping. At the conclusion of pregnancy, a higher resolution 60 K oligonucleotide microarray was performed. RESULTS: The 1 Mb BAC analysis demonstrated a detection rate of pathogenic copy number variations (CNVs) in 4.1% (95% CI 2.1-7.6) of cases and a variation of unknown significance (VOUS) rate of 0.4% (95% CI 0.07-2.2) over conventional G-band karyotyping. The 60 K array had an additional pathogenic detection rate of 4.8% (95% CI 1.6-13.3) over the BAC array but also detected an additional 8% (95% CI 1.3-14.8) VOUS. CONCLUSION: As the CMA platform resolution increases detection rates increase but are associated with an increase in VOUS rates. Our findings support the need for further large scale studies to inform the national consensus on the resolution required and on reporting of VOUS in the antenatal setting.

Use of prenatal chromosomal microarray: prospective cohort study and systematic review and meta-analysis.

OBJECTIVES: Chromosomal microarray analysis (CMA) is utilized in prenatal diagnosis to detect chromosomal abnormalities not visible by conventional karyotyping. A prospective cohort of women undergoing fetal CMA and karyotyping following abnormal prenatal ultrasound findings is presented in the context of a systematic review and meta-analysis of the literature describing detection rates by CMA and karyotyping. METHODS: We performed a prospective cohort study of 243 women undergoing CMA alongside karyotyping when a structural abnormality was detected on prenatal ultrasound. A systematic review of the literature was also performed. MEDLINE (1970-Dec 2012), EMBASE (1980-Dec 2012) and CINAHL (1982-June 2012) databases were searched electronically. Selected studies included > 10 cases and prenatal CMA in addition to karyotyping. The search yielded 560 citations. Full papers were retrieved for 86, and 25 primary studies were included in the systematic review. RESULTS: Our cohort study found an excess detection rate of abnormalities by CMA of 4.1% over conventional karyotyping when the clinical indication for testing was an abnormal fetal ultrasound finding; this was lower than the detection rate of 10% (95% CI, 8-13%) by meta-analysis. The rate of detection for variants of unknown significance (VOUS) was 2.1% (95% CI, 1.3-3.3%) when the indication for CMA was an abnormal scan finding. The VOUS detection rate was lower (1.4%; 95% CI, 0.5-3.7%) when any indication for prenatal CMA was meta-analyzed. CONCLUSION: We present evidence for a higher detection rate by CMA than by karyotyping not just in the case of abnormal ultrasound findings but also in cases of other indications for invasive testing. It is likely that CMA will replace karyotyping in high-risk pregnancies.

Microarray comparative genomic hybridization in prenatal diagnosis: a review.

G-band chromosomal karyotyping of fetal cells obtained by invasive prenatal testing has been used since the 1960s to identify structural chromosomal anomalies. Prenatal testing is usually performed in response to parental request, increased risk of fetal chromosomal abnormality associated with advanced maternal age, a high-risk screening test and/or the presence of a congenital malformation identified by ultrasonography. The results of karyotyping may inform the long-term prognosis (e.g. aneuploidy being associated with a poor outcome or microscopic chromosomal anomalies predicting global neurodevelopmental morbidity). Relatively recent advances in microarray technology are now enabling high-resolution genome-wide evaluation for DNA copy number abnormalities (e.g. deletions or duplications). While such technological advances promise increased sensitivity and specificity they can also pose difficult challenges of interpretation and clinical management. This review aims to give interested clinicians without an extensive prior knowledge of microarray technology, an overview of its use in prenatal diagnosis, the literature to date, advantages, potential pitfalls and experience from our own tertiary center.

Risk of cancer other than breast or ovarian in individuals with BRCA1 and BRCA2 mutations.

The risks of cancers other than breast and ovarian amongst BRCA1 and BRCA2 mutation carriers are based on relatively few family based studies with the risk of specific cancers tested in population based samples of cancers from founder populations. We assessed risks of "other cancers" in 268 BRCA1 families and 222 BRCA2 families using a person years at risk analysis from 1975 to 2005. Cancer confirmations were overall higher than in previous family based studies at 64%. There was no overall increase in risk for BRCA1 carriers although oesophagus had a significant increased RR of 2.9 (95% CI 1.1-6.0) and stomach at 2.4 (95% CI 1.2-4.3), these were based mainly on unconfirmed cases. For BRCA2 increased risks for cancers of the pancreas (RR 4.1, 95% CI 1.9-7.8) and prostate (RR 6.3, 95% CI 4.3-9.0) and uveal melanoma (RR 99.4, 95% CI 11.1-359.8) were confirmed. Possible new associations with oesophagus (RR 4.1, 95% CI 1.9-7.8) and stomach (RR 2.7, 95% CI 1.3-4.8) were detected but these findings should be treated with caution due to lower confirmation rates. In contrast to previous research a higher risk of prostate cancer was found in males with mutations in the BRCA2 OCCR region. The present study strengthens the known links between BRCA2 and pancreatic and prostate cancer, but throws further doubt onto any association with BRCA1. New associations with upper gastro-intestinal malignancy need to be treated with caution and confirmed by large prospective studies.

A Novel ABCA12 Mutation in Two Families with Congenital Ichthyosis.

Autosomal recessive congenital ichthyosis (ARCI) is a rare genetically heterogeneous disorder characterized by hyperkeratosis in addition to dry, scaly skin. There are six genes currently known to be associated with the disease. Exome sequencing data for two affected individuals with ichthyosis from two apparently unrelated consanguineous Pakistani families was analysed. Potential candidate mutations were analysed in additional family members to determine if the putative mutation segregated with disease status. A novel mutation (c.G4676T, p.Gly1559Val) in ABCA12 occurred at a highly conserved residue, segregated with disease status in both families, and was not detected in 143 control chromosomes. Genotyping with microsatellite markers demonstrated a partial common haplotype in the two families, and a common founder mutation could not be excluded. Comparison to previously reported cases was consistent with the hypothesis that severe loss of function ABCA12 mutations are associated with Harlequin Ichthyosis and missense mutations are preferentially associated with milder phenotypes. In addition to identifying a possible founder mutation, this paper illustrates how advances in genome sequencing technologies could be utilised to rapidly elucidate the molecular basis of inherited skin diseases which can be caused by mutations in multiple disease genes.

Promoter mutation is a common variant in GJC2-associated Pelizaeus-Merzbacher-like disease.

Pelizaeus-Merzbacher-like disease (PMLD) is a clinically and genetically heterogeneous neurological disorder of cerebral hypomyelination. It is clinically characterised by early onset (usually infantile) nystagmus, impaired motor development, ataxia, choreoathetoid movements, dysarthria and progressive limb spasticity. We undertook autozygosity mapping studies in a large consanguineous family of Pakistani origin in which affected children had progressive lower limb spasticity and features of cerebral hypomyelination on MR brain imaging. SNP microarray and microsatellite marker analysis demonstrated linkage to chromosome 1q42.13-1q42.2. Direct sequencing of the gap junction protein gamma-2 gene, GJC2, identified a promoter region mutation (c.-167A>G) in the non-coding exon 1. The c.-167A>G promoter mutation was identified in a further 4 individuals from two families (who were also of Pakistani origin) with clinical and radiological features of PMLD in whom previous routine diagnostic screening of GJC2 had been reported as negative. A common haplotype was identified at the GJC2 locus in the three mutation-positive families, consistent with a common origin for the mutation and likely founder effect. This promoter mutation has only recently been reported in GJC2-PMLD but it has been postulated to affect the binding of the transcription factor SOX10 and appears to be a prevalent mutation, accounting for ~29% of reported patients with GJC2-PMLD. We propose that diagnostic screening of GJC2 should include sequence analysis of the non-coding exon 1, as well as the coding regions to avoid misdiagnosis or diagnostic delay in suspected PMLD.

Epigenetic inactivation of the RASSF10 candidate tumor suppressor gene is a frequent and an early event in gliomagenesis.

We have recently described the N-terminal RAS association domain family of genes, RASSF7-10. Previously, we cloned the N-terminal RASSF10 gene and demonstrated frequent methylation of the associated 5'-CpG island in acute lymphoblastic leukemia. To characterize RASSF10 gene expression, we demonstrate that in developing Xenopus embryos, RASSF10 shows a very striking pattern in the rhombencephalon (hind brain). It is also expressed in other parts of the brain and other organs. Due to the well-defined expression pattern in the brain of Xenopus embryos, we analyzed the methylation status of the RASSF10-associated 5'-CpG island in astrocytic gliomas. RASSF10 was frequently methylated in WHO grade II-III astrocytomas and WHO grade IV primary glioblastomas (67.5%), but was unmethylated in grade I astrocytomas and in DNA from age matched control brain samples. RASSF10 gene expression both at the mRNA and protein levels could be switched back on in methylated glioma cell lines after treatment with 5-aza-2'-deoxycytidine. In secondary glioblastomas (sGBM), RASSF10 methylation was an independent prognostic factor associated with worst progression-free survival and overall survival and occurred at an early stage in their development. In cell culture experiments, overexpression of RASSF10 mediated a reduction in the colony forming ability of two RASSF10-methylated glioma cell lines. Conversely, RNAi-mediated knockdown of RASSF10-stimulated anchorage-independent growth of U87 glioma cells, increased their viability and caused an increase in the cells' proliferative ability. We generated and characterized a RASSF10-specific antibody and demonstrated for the first time that RASSF10 subcellular localization is cell-cycle dependent with RASSF10 colocalizing to centrosomes and associated microtubules during mitosis. This is the first report demonstrating that RASSF10 can act as a tumor suppressor gene and is frequently methylated in gliomas and can potentially be developed into a prognostic marker for sGBM.

Genome-wide methylation analysis identifies epigenetically inactivated candidate tumour suppressor genes in renal cell carcinoma.

The detection of promoter region hypermethylation and transcriptional silencing has facilitated the identification of candidate renal cell carcinoma (RCC) tumour suppressor genes (TSGs). We have used a genome-wide strategy (methylated DNA immunoprecipitation (MeDIP) and whole-genome array analysis in combination with high-density expression array analysis) to identify genes that are frequently methylated and silenced in RCC. MeDIP analysis on 9 RCC tumours and 3 non-malignant normal kidney tissue samples was performed, and an initial shortlist of 56 candidate genes that were methylated by array analysis was further investigated; 9 genes were confirmed to show frequent promoter region methylation in primary RCC tumour samples (KLHL35 (39%), QPCT (19%), SCUBE3 (19%), ZSCAN18 (32%), CCDC8 (35%), FBN2 (34%), ATP5G2 (36%), PCDH8 (58%) and CORO6 (22%)). RNAi knockdown for KLHL35, QPCT, SCUBE3, ZSCAN18, CCDC8 and FBN2 resulted in an anchorage-independent growth advantage. Tumour methylation of SCUBE3 was associated with a significantly increased risk of cancer death or relapse (P=0.0046). The identification of candidate epigenetically inactivated RCC TSGs provides new insights into renal tumourigenesis.

Additional information from array comparative genomic hybridization technology over conventional karyotyping in prenatal diagnosis: a systematic review and meta-analysis.

OBJECTIVE: Array comparative genomic hybridization (CGH) is transforming clinical cytogenetics with its ability to interrogate the human genome at increasingly high resolution. The aim of this study was to determine whether array CGH testing in the prenatal population provides diagnostic information over conventional karyotyping. METHODS: MEDLINE (1970 to December 2009), EMBASE (1980 to December 2009) and CINAHL (1982 to December 2009) databases were searched electronically. Studies were selected if array CGH was used on prenatal samples or if array CGH was used on postnatal samples following termination of pregnancy for structural abnormalities that were detected on an ultrasound scan. Of the 135 potential articles, 10 were included in this systematic review and eight were included in the meta-analysis. The pooled rate of extra information detected by array CGH when the prenatal karyotype was normal was meta-analyzed using a random-effects model. The pooled rate of receiving an array CGH result of unknown significance was also meta-analyzed. RESULTS: Array CGH detected 3.6% (95% CI, 1.5-8.5) additional genomic imbalances when conventional karyo-typing was 'normal', regardless of referral indication. This increased to 5.2% (95% CI, 1.9-13.9) more than karyotyping when the referral indication was a structural malformation on ultrasound. CONCLUSIONS: There appears to be an increased detection rate of chromosomal imbalances, compared with conventional karyotyping, when array CGH techniques are employed in the prenatal population. However, some are copy number imbalances that are not clinically significant. This carries implications for prenatal counseling and maternal anxiety.