Selective analysis of cell-free DNA in maternal blood for evaluation of fetal trisomy.

OBJECTIVE: To develop a novel prenatal assay based on selective analysis of cell-free DNA in maternal blood for evaluation of fetal Trisomy 21 (T21) and Trisomy 18 (T18). METHODS: Two hundred ninety-eight pregnancies, including 39 T21 and seven T18 confirmed fetal aneuploidies, were analyzed using a novel, highly multiplexed assay, termed digital analysis of selected regions (DANSR™). Cell-free DNA from maternal blood samples was analyzed using DANSR assays for loci on chromosomes 21 and 18. Products from 96 separate patients were pooled and sequenced together. A standard Z-test of chromosomal proportions was used to distinguish aneuploid samples from average-risk pregnancy samples. DANSR aneuploidy discrimination was evaluated at various sequence depths. RESULTS: At the lowest sequencing depth, corresponding to 204,000 sequencing counts per sample, average-risk cases where distinguished from T21 and T18 cases, with Z statistics for all cases exceeding 3.6. Increasing the sequencing depth to 410,000 counts per sample substantially improved separation of aneuploid and average-risk cases. A further increase to 620,000 counts per sample resulted in only marginal improvement. This depth of sequencing represents less than 5% of that required by massively parallel shotgun sequencing approaches. CONCLUSION: Digital analysis of selected regions enables highly accurate, cost efficient, and scalable noninvasive fetal aneuploidy assessment.

A novel EWS-WT1 gene fusion product in desmoplastic small round cell tumor is a potent transactivator of the insulin-like growth factor-I receptor (IGF-IR) gene.

Desmoplastic small round cell tumor (DSRCT) is a primitive sarcoma characterized by a recurrent chromosomal translocation, t(11;22)(p13;q12), which fuses the 5' exons of the EWS gene to the 3' exons of the WT1 gene. EWS-WT1 chimeras are heterogeneous as a result of fusions of different regions of the EWS gene to the WT1 gene. We report here a rare and novel EWS-WT1 variant, EWS-WT1 5/10, in a 6-year-old boy diagnosed with DSRCT and analyze the potential transactivation effect of the fusion oncoprotein. The predicted product is comprised of the N-terminal transactivation domain of EWS and lacks any sequence derived from the WT1 gene product. Nonetheless, the truncated protein was able to stimulate expression of the insulin-like growth factor-I receptor gene, a potent antiapoptotic receptor tyrosine kinase with potentially important roles in DSRCT etiology. These findings raise the possibility that the oncogenic potential of EWS-WT1 fusions is not necessarily a consequence of the fusion protein product per se.

Genotoxicants target distinct molecular networks in neonatal neurons.

BACKGROUND: Exposure of the brain to environmental agents during critical periods of neuronal development is considered a key factor underlying many neurologic disorders. OBJECTIVES: In this study we examined the influence of genotoxicants on cerebellar function during early development by measuring global gene expression changes. METHODS: We measured global gene expression in immature cerebellar neurons (i.e., granule cells) after treatment with two distinct alkylating agents, methylazoxymethanol (MAM) and nitrogen mustard (HN2). Granule cell cultures were treated for 24 hr with MAM (10-1,000 microM) or HN2 (0.1-20 microM) and examined for cell viability, DNA damage, and markers of apoptosis. RESULTS: Neuronal viability was significantly reduced (p < 0.01) at concentrations > 500 microM for MAM and > 1.0 microM for HN2; this correlated with an increase in both DNA damage and markers of apoptosis. Neuronal cultures treated with sublethal concentrations of MAM (100 microM) or HN2 (1.0 microM) were then examined for gene expression using large-scale mouse cDNA microarrays (27,648). Gene expression results revealed that a) global gene expression was predominantly up-regulated by both genotoxicants; b) the number of down-regulated genes was approximately 3-fold greater for HN2 than for MAM; and c) distinct classes of molecules were influenced by MAM (i.e, neuronal differentiation, the stress and immune response, and signal transduction) and HN2 (i.e, protein synthesis and apoptosis). CONCLUSIONS: These studies demonstrate that individual genotoxicants induce distinct gene expression signatures. Further study of these molecular networks may explain the variable response of the developing brain to different types of environmental genotoxicants.

GABAergic system gene expression predicts clinical outcome in patients with neuroblastoma.

PURPOSE: Neuroblastoma (NB) is a common childhood malignancy characterized by heterogeneous clinical behavior. The purpose of this study was to identify potential NB biomarkers that may improve outcome prediction. PATIENTS AND METHODS: The suppression subtractive hybridization (SSH) technique was used to identify the genes differentially expressed between NB and control tissue. RNA isolated from 235 primary NB tumor samples obtained from the Children's Cancer Group was evaluated for expression of the candidate markers using quantitative reverse transcriptase polymerase chain reaction (Taqman assays). The association between the mRNA expression levels in the identified candidate genes and clinical outcome was evaluated. RESULTS: SSH analysis identified differential expression of members of the GABAergic gene family in NB. Lower levels of gamma-aminobutyric acid (GABA) receptor-associated protein (GABARAP) gene expression predict decreased survival among all patients. GABA(A) delta receptor subunit gene expression was predictive of a poor outcome among Evans stage IV-S patients. An index of five coexpressed GABA(A) receptor subunits was identified (GABA(A) profile [GAP score]). Patients with a higher GAP score (> -1) had a survival advantage. Multivariate analysis showed that GABARAP and GABA(A) alpha2 receptor subunit gene expression levels and GAP score remained predictors of clinical outcome after accounting for current prognostic indicators. CONCLUSION: Dysregulation of the GABAergic system may constitute a fundamental event in the development of NB, and assessment of GABAergic system gene expression could provide improved patient stratification and potential new therapies.

Proteomic identification of urinary biomarkers of diabetic nephropathy.

OBJECTIVE: Diabetic nephropathy is a serious complication of both type 1 and type 2 diabetes, and, unless arrested, leads to end-stage renal disease. Current diagnosis consists of urine assays of microalbuminuria, which have inadequate specificity and sensitivity. RESEARCH DESIGN AND METHODS: We used proteomic analyses to identify novel biomarkers of nephropathy in urine from type 2 diabetic patients with demonstrated normo-, micro-, or macroalbuminuria. Samples were analyzed by fluorescence two-dimensional (2-D) differential in-gel electrophoresis (DIGE), and protein identification was performed by liquid chromatography-tandem mass spectrometry. RESULTS: 2-D DIGE analysis of the urinary proteome in diabetes with nephropathy identified 195 protein spots representing 62 unique proteins. These proteins belonged to several functional groups, i.e., cell development, cell organization, defense response, metabolism, and signal transduction. Comparisons between control and diabetic subjects with different stages of renal dysfunction revealed the differential expression of several proteins. Spot volume quantification identified 7 proteins that were progressively upregulated with increasing albuminuria and 4 proteins that exhibited progressive downregulation. The majority of these potential candidate biomarkers were glycoproteins. CONCLUSIONS: These data demonstrate the ability of proteomic analyses to reveal potential biomarkers for diabetic nephropathy in urine, an important step forward in advancing accurate diagnosis and our understanding of disease mechanisms.

Standardizing global gene expression analysis between laboratories and across platforms.

To facilitate collaborative research efforts between multi-investigator teams using DNA microarrays, we identified sources of error and data variability between laboratories and across microarray platforms, and methods to accommodate this variability. RNA expression data were generated in seven laboratories, which compared two standard RNA samples using 12 microarray platforms. At least two standard microarray types (one spotted, one commercial) were used by all laboratories. Reproducibility for most platforms within any laboratory was typically good, but reproducibility between platforms and across laboratories was generally poor. Reproducibility between laboratories increased markedly when standardized protocols were implemented for RNA labeling, hybridization, microarray processing, data acquisition and data normalization. Reproducibility was highest when analysis was based on biological themes defined by enriched Gene Ontology (GO) categories. These findings indicate that microarray results can be comparable across multiple laboratories, especially when a common platform and set of procedures are used.

Cloning and characterization of Xen-dorphin prohormone from Xenopus laevis: a new opioid-like prohormone distinct from proenkephalin and prodynorphin.

Opioid-like peptides mediate analgesia and induce behavioral effects such as tolerance and dependence by ligand-receptor-mediated mechanisms. The classical opioid prohormones can generate several bioactive peptides, and these divergent families of prohormones share a common well conserved ancestral opioid motif (Tyr-Gly-Gly-Phe). Evidence from pharmacological and molecular cloning studies indicates the presence of multiple isoforms of opioid ligands and receptors that are as yet uncharacterized. To identify potential new members we used the opioid motif as an anchor sequence and isolated two distinct isoforms (Xen-dorphins A and B) of an opioid prohormone from Xenopus laevis brain cDNA library. Xen-dorphin prohormones can generate multiple novel opioid ligands distinct from the known members of this family. Both isoforms are present in a wide variety of tissues including the brain. Two potential bioactive peptides, Xen-dorphin-1A and -1B, that were chemically synthesized showed opioid agonist activity in frog and rat brain membranes using a [35S]GTPgammaS assay. Initial radioligand binding experiments demonstrated that Xen-dorphin-1B binds with high affinity to opioid receptor(s) and with potential preference to the kappa-opioid receptor subtype. Cloning of the Xen-dorphin prohormone provides new evidence for the potential presence of other members in the opioid peptide superfamily.

Suppression subtractive hybridization and microarray identification of estrogen-regulated hypothalamic genes.

The gonadal steroid estrogen is a pleiotropic hormone that has multiple effects on numerous cellular functions. One of estrogen's major targets is the brain, where the steroid not only affects growth, differentiation, and survival of neurons, but also regulates cell excitability. Because estrogen modulates multiple, overlapping signaling pathways, it has been difficult to scrutinize the transcriptional activity of the steroid. Therefore, we still lack a global picture of how different genes interact and are regulated by estrogen. Herein we report the use of suppression subtractive hybridization followed by custom microarray analysis of thousands of genes that are differentially expressed during the negative feedback phase of the female reproductive cycle. We have found a number of key transcripts that are regulated by estrogen and contribute to the alteration in synaptic transmission and hence excitability of hypothalamic neurons (e.g., GABA neurons). These include gec-1, GABA(B)R2, PI3 kinase subunit p55gamma, and a number of proteins containing pleckstrin homology domains that are critical for plasma membrane targeting. Studies are underway to refine our analysis to individual nuclei and individual cells. However, what has emerged from this highly sensitive microarray analysis is that estrogen affects neuronal plasticity in hypothalamic neurons not only by transcription of new membrane proteins (e.g., receptors and channels), but also by altering expression of downstream signaling molecules and proteins involved in neurosecretory pathways.

Identification of STAT-1 as a molecular target of IGFBP-3 in the process of chondrogenesis.

The chondrogenesis process requires the ordered proliferation and differentiation of chondrocytes. Insulin-like growth factor-binding protein (IGFBP)-3, well characterized as the carrier of insulin-like growth factor (IGF), has been reported to have intrinsic bioactivity that is independent of IGF binding. The mechanisms involved in this IGF-independent action are still unclear. Using the RCJ3.1C5.18 chondrogenic cells, which in culture progresses from undifferentiated to terminally differentiated chondrocytes, we have shown previously that IGFBP-3 has an IGF-independent, antiproliferative effect in undifferentiated and early differentiated but not in terminally differentiated chondrocytes. In the present study, cDNA microarray analysis was used to screen for genes: 1) that were regulated by IGFBP-3 in early but not in terminally differentiated chondrocytes; 2) that were regulated specifically by IGFBP-3, but not by IGF-I; and 3) whose regulation was abolished by coincubation of IGFBP-3 with IGF-I. Signal transducer and activator of transcription (STAT)-1 was the gene that, fulfilling the screening criteria, exhibited the greatest up-regulation by IGFBP-3 (>40-fold). STAT-1 gene up-regulation was confirmed by Northern analysis of cells treated with IGFBP-3 or transfected with an IGFBP-3 expression vector. Remarkably, similar results were obtained when cells were transfected with an IGFBP-3 mutant unable to bind IGFs, definitively demonstrating the IGF-independent action of IGFBP-3. Consistent with the up-regulation of STAT-1 mRNA, IGFBP-3 also increased STAT-1 protein expression. Furthermore, both IGFBP-3 and the IGFBP-3 mutant induced STAT-1 phosphorylation and its nuclear localization. An antisense STAT-1 oligonucleotide abolished the IGF-independent cell apoptosis induced by IGFBP-3. We have demonstrated that STAT-1 is a major intracellular signaling and transcriptional target of the IGF-independent apoptotic effect of IGFBP-3 in chondrogenesis.