Germline mutations of the POU6F2 gene in Wilms tumors with loss of heterozygosity on chromosome 7p14

Genomics, Transcriptomics, and Epigenetics of Sporadic Pituitary Tumors

Pituitary tumors (PT) are highly heterogeneous neoplasms, comprising functioning and nonfunctioning lesions. Functioning PT include prolactinomas, causing amenorrhea-galactorrhea in women and sexual dysfunction in men; GH-secreting adenomas causing acromegaly-gigantism; ACTH-secreting corticotrophinomas causing Cushing disease (CD); and the rare TSH-secreting thyrotrophinomas that result in central hyperthyroidism. Nonfunctioning PT do not result in a hormonal hypersecretion syndrome and most of them are of gonadotrope differentiation; other non-functioning PT include null cell adenomas and silent ACTH-, GH- and PRL-adenomas. Less than 5% of PT occur in a familial or syndromic context whereby germline mutations of specific genes account for their molecular pathogenesis. In contrast, the more common sporadic PT do not result from a single molecular abnormality but rather emerge from several oncogenic events that culminate in an increased proliferation of pituitary cells, and in the case of functioning tumors, in a non-regulated hormonal hypersecretion. In recent years, important advances in the understanding of the molecular pathogenesis of PT have been made, including the genomic, transcriptomic, epigenetic, and proteomic characterization of these neoplasms. In this review, we summarize the available molecular information pertaining the oncogenesis of PT.

POU6F2 mutation in humans with pubertal failure alters GnRH transcript expression

Idiopathic hypogonadotropic hypogonadism (IHH) is characterized by the absence of pubertal development and subsequent impaired fertility often due to gonadotropin-releasing hormone (GnRH) deficits. Exome sequencing of two independent cohorts of IHH patients identified 12 rare missense variants in POU6F2 in 15 patients. POU6F2 encodes two distinct isoforms. In the adult mouse, expression of both isoform1 and isoform2 was detected in the brain, pituitary, and gonads. However, only isoform1 was detected in mouse primary GnRH cells and three immortalized GnRH cell lines, two mouse and one human. To date, the function of isoform2 has been verified as a transcription factor, while the function of isoform1 has been unknown. In the present report, bioinformatics and cell assays on a human-derived GnRH cell line reveal a novel function for isoform1, demonstrating it can act as a transcriptional regulator, decreasing GNRH1 expression. In addition, the impact of the two most prevalent POU6F2 variants, identified in five IHH patients, that were located at/or close to the DNA-binding domain was examined. Notably, one of these mutations prevented the repression of GnRH transcripts by isoform1. Normally, GnRH transcription increases as GnRH cells mature as they near migrate into the brain. Augmentation earlier during development can disrupt normal GnRH cell migration, consistent with some POU6F2 variants contributing to the IHH pathogenesis.

Exploring the Potential Driver Gene Mutations That Promote Renal Cancer Cell Metastasis and Implantation Based on Circulating Tumor Cells Culture

Studies have shown that the circulating tumor cell (CTC) is a necessary condition for the invasion and distant metastasis of renal cell carcimona (RCC). However, few CTCs-related gene mutations have been developed which could promote the metastasis and implantation of RCC. The objective of this study is to explore the potential driver gene mutations that promote RCC metastasis and implantation based on CTCs culture. Fifteen patients with primary mRCC and three healthy subjects were included, and peripheral blood was obtained. After the preparation of synthetic biological scaffolds, peripheral blood CTCs were cultured. Successful cultured CTCs were applied to construct CTCs-derived xenograft (CDX) models, followed by DNA extraction, whole exome sequencing (WES) and bioinformatics analysis. Synthetic biological scaffolds were constructed based on previously applied techniques, and peripheral blood CTCs culture was successfully performed. We then constructed CDX models and performed WES, and explored the potential driver gene mutations that may promote RCC metastasis and implantation. Bioinformatics analysis showed that KAZN and POU6F2 may be closely related to the prognosis of RCC. We successfully performed the culture of peripheral blood CTCs and, on this basis we initially explored the potential driver mutations for the metastasis and implantation of RCC.

Identification of novel prognostic markers of survival time in high-risk neuroblastoma using gene expression profiles

Neuroblastoma is the most common extracranial solid tumor in childhood. Patients in high-risk group often have poor outcomes with low survival rates despite several treatment options. This study aimed to identify a genetic signature from gene expression profiles that can serve as prognostic indicators of survival time in patients of high-risk neuroblastoma, and that could be potential therapeutic targets. RNA-seq count data was downloaded from UCSC Xena browser and samples grouped into Short Survival (SS) and Long Survival (LS) groups. Differential gene expression (DGE) analysis, enrichment analyses, regulatory network analysis and machine learning (ML) prediction of survival group were performed. Forty differentially expressed genes (DEGs) were identified including genes involved in molecular function activities essential for tumor proliferation. DEGs used as features for prediction of survival groups included EVX2, NHLH2, PRSS12, POU6F2, HOXD10, MAPK15, RTL1, LGR5, CYP17A1, OR10AB1P, MYH14, LRRTM3, GRIN3A, HS3ST5, CRYAB and NXPH3. An accuracy score of 82% was obtained by the ML classification models. SMIM28 was revealed to possibly have a role in tumor proliferation and aggressiveness. Our results indicate that these DEGs can serve as prognostic indicators of survival in high-risk neuroblastoma patients and will assist clinicians in making better therapeutic and patient management decisions.

Identification of a novel somatic mutation of POU6F2 by whole-genome sequencing in prolactinoma

BACKGROUND

Pituitary adenomas (PAs) are one of the most common intracranial tumors; approximately half of PAs are prolactin (PRL)-secreting PAs (prolactinomas). The genetic alterations prevalent in prolactinomas are unknown.

METHODS

Here, we present a patient with an extremely aggressive and giant prolactinoma accompanied by serious destruction of the surrounding bone mass. This patient exhibited resistance to dopaminergic drugs. Through whole-genome sequencing, we identified two novel somatic mutations in the POU6F2 gene (NM_001166018.2: c. 839 C>T; NM_001166018.2: c. 875A>G).

RESULTS

This report is the first to identify these somatic mutations in the POU6F2 gene in a prolactinoma. We found that these two mutations obviously decreased the expression level of POU6F2. Inhibition of POU6F2 activity increased the cell proliferation and PRL secretion in rat pituitary cells, but proliferation and PRL secretion were decreased in cells with POU6F2 overexpression.

CONCLUSIONS

POU6F2 might play a crucial role in the development of prolactinomas and may be a promising target for developing new therapies against prolactinomas.

Genome-Wide Analysis Reveals Four Novel Loci for Attention-Deficit Hyperactivity Disorder in Korean Youths

Objectives:

The molecular mechanisms underlying attention-deficit hyperactivity disorder (ADHD) remain unclear. Therefore, this study aimed to identify the genetic susceptibility loci for ADHD in Korean children with ADHD. We performed a case-control and a family-based genome-wide association study (GWAS), as well as genome-wide quantitative trait locus (QTL) analyses, for two symptom traits.

Methods:

A total of 135 subjects (71 cases and 64 controls), for the case-control analysis, and 54 subjects (27 probands and 27 unaffected siblings), for the family-based analysis, were included.

Results:

The genome-wide QTL analysis identified four single nucleotide polymorphisms (SNPs) (rs7684645 near APELA, rs12538843 near YAE1D1 and POU6F2, rs11074258 near MCTP2, and rs34396552 near CIDEA) that were significantly associated with the number of inattention symptoms in ADHD. These SNPs showed possible association with ADHD in the family-based GWAS, and with hyperactivity-impulsivity in genome-wide QTL analyses. Moreover, association signals in the family-based QTL analysis for the number of inattention symptoms were clustered near genes IL10, IL19, SCL5A9, and SKINTL.

Conclusion:

We have identified four QTLs with genome-wide significance and several promising candidates that could potentially be associated with ADHD (CXCR4, UPF1, SETD5, NALCN-AS1, ERC1, SOX2-OT, FGFR2, ANO4, and TBL1XR1). Further replication studies with larger sample sizes are needed.

Retina-derived POU domain factor 1 coordinates expression of genes relevant to renal and neuronal development

Retina-derived POU domain Factor 1 (RPF-1), a member of POU transcription factor family, is encoded by POU6F2 gene, addressed by interstitial deletions at chromosome 7p14 in Wilms tumor (WT). Its expression has been detected in developing kidney and nervous system, suggesting an early role for this gene in regulating development of these organs. To investigate into its functions and determine its role in transcriptional regulation, we generated an inducible stable transfectant from HEK293 cells. RPF-1 showed nuclear localization, elevated stability, and transactivation of promoters featuring POU consensus sites, and led to reduced cell proliferation and in vivo tumor growth. By addressing the whole transcriptome regulated by its induction, we could detect a gross alteration of gene expression that is consistent with promoter occupancy predicted by genome-wide Chip-chip analysis. Comparison of bound regulatory regions with differentially expressed genes allowed identification of 217 candidate targets. Enrichment of divergent octamers in predicted regulatory regions revealed promiscuous binding to bipartite POUS and POUH consensus half-sites with intervening spacers. Gel-shift competition assay confirmed the specificity of RPF-1 binding to consensus motifs, and demonstrated that the Ser-rich region upstream of the POU domain is indispensable to achieve DNA-binding. Promoter-reporter activity addressing a few target genes indicated a dependence by RPF-1 on transcriptional response. In agreement with its expression in developing kidney and nervous system, the induced transcriptome appears to indicate a function for this protein in early renal differentiation and neuronal cell fate, providing a resource for understanding its role in the processes thereby regulated.

Whole-Exome Sequencing of Salivary Gland Mucoepidermoid Carcinoma

PURPOSE

Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. To explore the genetic origins of MEC, we performed systematic genomic analyses of these tumors.

EXPERIMENTAL DESIGN

Whole-exome sequencing and gene copy-number analyses were performed for 18 primary cancers with matched normal tissue. FISH was used to determine the presence or absence of the MECT1-MAML2 translocation in 17 tumors.

RESULTS

TP53 was the most commonly mutated gene in MEC (28%), and mutations were found only in intermediate- and high-grade tumors. Tumors with TP53 mutations had more mutations overall than tumors without TP53 mutations (P = 0.006). POU6F2 was the second most frequently mutated gene, found in three low-grade MECs with the same in-frame deletion. Somatic alterations in IRAK1, MAP3K9, ITGAL, ERBB4, OTOGL, KMT2C, and OBSCN were identified in at least two of the 18 tumors sequenced. FISH analysis confirmed the presence of the MECT1-MAML2 translocation in 15 of 17 tumors (88%).

CONCLUSIONS

Through these integrated genomic analyses, MECT1-MAML2 translocation and somatic TP53 and POU6F2 mutations appear to be the main drivers of MEC. Clin Cancer Res; 23(1); 283-8. ©2016 AACR.

Evaluation of chromosome 11p imbalances in aniridia and Wilms tumor patients

Newborn sporadic aniridia patients with an 11p13 deletion including the WT1 gene have an increased risk to develop Wilms tumor. At present a risk for Wilms tumor cannot be estimated in patients with deletions not extending into, but ending close to WT1. Therefore, it is important to determine the distance of deletion endpoints from the WT1 gene and survey these patients for a longer follow-up time to obtain a more defined risk estimation. Using molecular methods, such as Multiplex Ligation-dependent Probe Amplification (MLPA), deletion endpoints can be mapped more accurately than with FISH. We describe here the analysis of six aniridia patients, in two of these the deletions extend close to the 3' end of WT1. At the ages of 3.8 and 4 years they have not developed a Wilms tumor, suggesting a low tumor risk in such patients. In addition we have studied 24 non-AN cases with a higher likelihood for WT1 alterations with MLPA and found no deletions. In conclusion newborns with aniridia should be studied with molecular methods that can determine deletion endpoints in 11p13 exactly. For a better Wilms tumor risk estimation cases with deletion endpoints close to WT1 should be followed for at least 4-5 years. Furthermore germ line intragenic deletions affecting WT1 in patients with a higher likelihood for a WT1 association, for example, bilateral tumors, genitourinary aberrations, or nephrotic syndrome, were not found in this study, suggesting that deletions are rare events.

Loss of heterozygosity analysis at different chromosome regions in Wilms tumor confirms 1p allelic loss as a marker of worse prognosis: a study from the Italian Association of Pediatric Hematology and Oncology

PURPOSE

The specific aims of the AIEOP-TW-2003 protocol included prospectively investigating a possible association of tumor loss of heterozygosity with outcomes in children treated for Wilms tumor.

MATERIALS AND METHODS

We analyzed 125 unilateral favorable histology Wilms tumors registered between 2003 and 2008 in the Italian cooperative protocol for microsatellite markers mapped to chromosomes 1p, 7p, 11q, 16q and 22q.

RESULTS

The 3-year disease-free survival and overall survival probabilities were 0.87 (95% CI 0.81-0.93) and 0.98 (95% CI 0.96-1.0), respectively. Loss of heterozygosity at 1p was significantly associated with a worse disease-free survival (probability 0.67 for patients with and 0.92 for those without 1p loss of heterozygosity, p = 0.0009), as confirmed also by multivariate analysis adjusting for tumor stage and patient age at diagnosis. There was no difference in disease-free survival probability among children with loss of heterozygosity in the other chromosomal regions tested. The worse outlook for children older than 2 years at diagnosis did not seem to be influenced by the loss of heterozygosity patterns considered.

CONCLUSIONS

Chromosome 1p loss of heterozygosity seems to be a risk factor for nonanaplastic Wilms tumor, possibly regardless of other clinical factors. Our findings were uninformative regarding loss of heterozygosity in the other chromosomal regions tested.

Genomic profiling by whole-genome single nucleotide polymorphism arrays in Wilms tumor and association with relapse

Despite the excellent survival rate of Wilms tumor (WT) patients, only approximately one-half of children who suffer tumor recurrence reach second durable remission. This underlines the need for novel markers to optimize initial treatment. We investigated 77 tumors using Illumina 370CNV-QUAD genotyping BeadChip arrays and compared their genomic profiles to detect copy number (CN) abnormalities and allelic ratio anomalies associated with the following clinicopathological variables: relapse (yes vs. no), age at diagnosis (≤ 24 months vs. >24 months), and disease stage (low stage, I and II, vs. high stage, III and IV). We found that CN gains at chromosome region 1q21.1-q31.3 were significantly associated with relapse. Additional genetic events, including allelic imbalances at chromosome arms 1p, 1q, 3p, 3q, and 14q were also found to occur at higher frequency in relapsing tumors. Interestingly, allelic imbalances at 1p and 14q also showed a borderline association with higher tumor stages. No genetic events were found to be associated with age at diagnosis. This is the first genome wide analysis with single nucleotide polymorphism (SNP) arrays specifically investigating the role of genetic anomalies in predicting WT relapse on cases prospectively enrolled in the same clinical trial. Our study, besides confirming the role of 1q gains, identified a number of additional candidate genetic markers, warranting further molecular investigations.

Clinical and molecular description of a Wilms tumor in a patient with tuberous sclerosis complex

We report on a girl affected with tuberous sclerosis, carrying a germline de novo TSC2 mutation, c.4934-4935delTT, leading to a p.F1645CfsX7, who developed a unilateral Wilms tumor (WT). Molecular investigation of the tumor biopsy at diagnosis revealed the loss of the constitutional wild-type TSC2 allele, and loss of heterozygosity for the WT1 gene. Deletion of the WTX gene was also present, but it involved the functionally inactive X chromosome. No mutation affecting the remaining WT1 and WTX alleles, as well as the CTNNB1 gene was found. Pathological examination of the surgical specimen documented the presence of diffuse anaplasia and p53 immunoreactivity. To the best of our knowledge, this is the second report of a patient with tuberous sclerosis who developed a WT, and it represents the first case in which a detailed clinical and molecular description is provided.

Genes, mutations, and human inherited disease at the dawn of the age of personalized genomics

The number of reported germline mutations in human nuclear genes, either underlying or associated with inherited disease, has now exceeded 100,000 in more than 3,700 different genes. The availability of these data has both revolutionized the study of the morbid anatomy of the human genome and facilitated "personalized genomics." With approximately 300 new "inherited disease genes" (and approximately 10,000 new mutations) being identified annually, it is pertinent to ask how many "inherited disease genes" there are in the human genome, how many mutations reside within them, and where such lesions are likely to be located? To address these questions, it is necessary not only to reconsider how we define human genes but also to explore notions of gene "essentiality" and "dispensability."Answers to these questions are now emerging from recent novel insights into genome structure and function and through complete genome sequence information derived from multiple individual human genomes. However, a change in focus toward screening functional genomic elements as opposed to genes sensu stricto will be required if we are to capitalize fully on recent technical and conceptual advances and identify new types of disease-associated mutation within noncoding regions remote from the genes whose function they disrupt.

Candidate genes and potential targets for therapeutics in Wilms' tumour

Wilms' tumour (WT) is the most common malignant renal tumour of childhood. During the past two decades or so, molecular studies carried out on biopsy specimens and tumour-derived cell lines have identified a multitude of chromosomal and epigenetic alterations in WT. In addition, a significant amount of evidence has been gathered to identify the genes and signalling pathways that play a defining role in its genesis, growth, survival and treatment responsiveness. As such, these molecules and mechanisms constitute potential targets for novel therapeutic strategies for refractory WT. In this report we aim to review some of the many candidate genes and intersecting pathways that underlie the complexities of WT biology.

Two candidate tumor suppressor genes, MEOX2 and SOSTDC1, identified in a 7p21 homozygous deletion region in a Wilms tumor

A SNP-based array analysis of 100 Wilms tumors (WT) from 97 patients identified 7p alterations (hemizygous and homozygous deletions and uniparental disomy) in nine tumors. The homozygous deletion (HD) region of 7p21 found in one tumor partially overlapped with another HD region reported previously, and was narrowed down to a 2.1-Mb region. Based on an expression analysis of 10 genes located in the HD region in 3 WT lines and previous studies on tumorigenic roles of MEOX2 and SOSTDC1, we further analyzed these two genes. Sequencing showed no mutation in MEOX2, but two missense mutations (L50F and Q129L) in SOSTDC1 in four tumors; L50F in two tumors was of germline origin. Expression levels (0, 1+ and 2+) of MEOX2 were lower in four tumors with 7p alterations than in 18 tumors with no 7p alterations (P = 0.017), and those of SOSTDC1 tended to be lower in five tumors with 7p alterations or SOSTDC1 mutation than in 17 tumors with no 7p alterations or SOSTDC1 mutation (P = 0.056). There were no significant differences in clinical characteristics between nine patients with 7p alterations and 88 patients with no 7p alterations; however, there was a difference in the status of IGF2 (uniparental disomy, loss of imprinting, or retention of imprinting) between the two patient groups (P = 0.028). Losses of MEOX2 and SOSTDC1 may accelerate angiogenesis and augment signals in the Wnt pathway, respectively. Both genes may be prime candidates for 7p tumor suppressor genes, which may have a role in the progression of Wilms tumorigenesis.

Loss of heterozygosity at 2q37 in sporadic Wilms' tumor: putative role for miR-562

PURPOSE

Wilms' tumor is a childhood cancer of the kidney with an incidence of approximately 1 in 10,000. Cooccurrence of Wilms' tumor with 2q37 deletion syndrome, an uncommon constitutional chromosome abnormality, has been reported previously in three children. Given these are independently rare clinical entities, we hypothesized that 2q37 harbors a tumor suppressor gene important in Wilms' tumor pathogenesis.

EXPERIMENTAL DESIGN

To test this, we performed loss of heterozygosity analysis in a panel of 226 sporadic Wilms' tumor samples and mutation analysis of candidate genes.

RESULTS

Loss of heterozygosity was present in at least 4% of cases. Two tumors harbored homozygous deletions at 2q37.1, supporting the presence of a tumor suppressor gene that follows a classic two-hit model. However, no other evidence of second mutations was found, suggesting that heterozygous deletion alone may be sufficient to promote tumorigenesis in concert with other genomic abnormalities. We show that miR-562, a microRNA within the candidate region, is expressed only in kidney and colon and regulates EYA1, a critical gene for renal development. miR-562 expression is reduced in Wilms' tumor and may contribute to tumorigenesis by deregulating EYA1. Two other candidate regions were localized at 2q37.3 and 2qter, but available data from patients with constitutional deletions suggest that these probably do not confer a high risk for Wilms' tumor.

CONCLUSIONS

Our data support the presence of a tumor suppressor gene at 2q37.1 and suggest that, in individuals with constitutional 2q37 deletions, any increased risk for developing Wilms' tumor likely correlates with deletions encompassing 2q37.1.

Duplication of paternal IGF2 or loss of maternal IGF2 imprinting occurs in half of Wilms tumors with various structural WT1 abnormalities

The WT1 gene essential for the embryonic kidney development is mutated in 15-25% of Wilms tumors (WTs). To clarify whether genetic subtypes of WT1 abnormalities are correlated with IGF2 or CTNNB1 alterations or clinicopathological characteristics, we performed comprehensive WT1, IGF2, and CTNNB1 analyses of 36 WTs with WT1 abnormalities using single nucleotide polymorphism arrays, and methylation analysis of the IGF2-H19 differentially methylated region. The tumors were classified into three subtypes based on WT1 abnormalities: 13 with WT1 deletion, 12 with WT1 mutation, and 11 with both deletion and mutation. IGF2 alterations were found in 50% (18/36), paternal uniparental disomy (UPD) of 11p13-11p15 in 13 tumors, UPD limited to 11p15 in 3, and loss of IGF2 imprinting in 2. Quantitative RT-PCR analysis showed that tumors with IGF2 alteration had higher levels of IGF2 mRNA than tumors without IGF2 alteration (P = 0.02). WT1 mRNA levels were very low in six of eight WTs with WT1 deletion, whereas four of eight WTs with WT1 mutation or both deletion and mutation showed higher levels of WT1 mRNA than fetal kidneys. WTs with WT1 mutations occurred in younger patients (P < 0.01), and WTs with mutations or both deletion and mutation (12/23) were more frequent in syndromic patients than WTs (1/13) with the deletion (P = 0.02). WTs with WT1 mutations or both deletion and mutation had the triphasic histological-type (15/23; P = 0.03) and CTNNB1 mutation (17/23; P = 0.03) more frequently than WTs with the deletion (2/13 and 4/13). Thus, three WT1 subtypes were correlated with certain genetic and clinicopathological characteristics.

In silico regulatory analysis for exploring human disease progression

Background

An important goal in bioinformatics is to unravel the network of transcription factors (TFs) and their targets. This is important in the human genome, where many TFs are involved in disease progression. Here, classification methods are applied to identify new targets for 152 transcriptional regulators using publicly-available targets as training examples. Three types of sequence information are used: composition, conservation, and overrepresentation.

Results

Starting with 8817 TF-target interactions we predict an additional 9333 targets for 152 TFs. Randomized classifiers make few predictions (~2/18660) indicating that our predictions for many TFs are significantly enriched for true targets. An enrichment score is calculated and used to filter new predictions.

Two case-studies for the TFs OCT4 and WT1 illustrate the usefulness of our predictions:

• Many predicted OCT4 targets fall into the Wnt-pathway. This is consistent with known biology as OCT4 is developmentally related and Wnt pathway plays a role in early development.

• Beginning with 15 known targets, 354 predictions are made for WT1. WT1 has a role in formation of Wilms' tumor. Chromosomal regions previously implicated in Wilms' tumor by cytological evidence are statistically enriched in predicted WT1 targets. These findings may shed light on Wilms' tumor progression, suggesting that the tumor progresses either by loss of WT1 or by loss of regions harbouring its targets.

• Targets of WT1 are statistically enriched for cancer related functions including metastasis and apoptosis. Among new targets are BAX and PDE4B, which may help mediate the established anti-apoptotic effects of WT1.

• Of the thirteen TFs found which co-regulate genes with WT1 (p ≤ 0.02), 8 have been previously implicated in cancer. The regulatory-network for WT1 targets in genomic regions relevant to Wilms' tumor is provided.

Conclusion

We have assembled a set of features for the targets of human TFs and used them to develop classifiers for the determination of new regulatory targets. Many predicted targets are consistent with the known biology of their regulators, and new targets for the Wilms' tumor regulator, WT1, are proposed. We speculate that Wilms' tumor development is mediated by chromosomal rearrangements in the location of WT1 targets.

Reviewers

This article was reviewed by Trey Ideker, Vladimir A. Kuznetsov(nominated by Frank Eisenhaber), and Tzachi Pilpel.

Functional inactivation of the WTX gene is not a frequent event in Wilms' tumors

For many years the precise genetic etiology of the majority of Wilms' tumors has remained unexplained. Recently, the WTX gene, mapped to chromosome Xq11.1, has been reported to be lost or mutated in approximately one-third of Wilms' tumors. Moreover, in female cases, the somatically inactivated alleles were found to invariantly derive from the active chromosome X. Consequently, WTX has been proposed as a 'one-hit' tumor suppressor gene. To provide further insights on the contribution of WTX to the development of the disease, we have examined 102 Wilms' tumors, obtained from 43 male and 57 female patients. Quantitative PCR analyses detected WTX deletions in 5 of 45 (11%) tumors from males, whereas loss of heterozygosity at WTX-linked microsatellites was observed in 9 tumors from 50 informative females (19%). However, in the latter group, using a combination of HUMARA assay and bisulfite-modified DNA sequencing, we found that the deletion affected the active chromosome X only in two cases (4%). Sequence analyses detected an inactivating somatic mutation of WTX in a single tumor, in which a strongly reduced expression of the mutant allele respect to the wild-type allele was observed, a finding not consistent with its localization on the active chromosome X. Overall, a functional somatic nullizygosity of the WTX gene was ascertained only in seven of the Wilms' tumors included in the study (approximately 7%). Our findings indicate that previously reported estimates on the proportion of Wilms' tumors due to WTX alterations should be reconsidered.

Greig cephalopolysyndactyly (GCPS) contiguous gene syndrome in a boy with a 14 Mb deletion in region 7p13-14 caused by a paternal balanced insertion (5; 7)

We report on a six years old boy with several features of Greig cephalopolysyndactyly syndrome (GCPS) including craniofacial dysmorphism, hypertelorism, heart defect, preaxial hexadactyly of toes, partial agenesis of corpus callosum, and severe developmental delay. Greig cephalopolysyndactyly (GCPS) can be caused by GLI3 deletions. In patients with large deletions which include additional genes, it is termed Greig cephalopolysyndactyly-contiguous gene syndrome (GCPS-CGS). It is generally believed that the deletion size correlates with disease severity. Nearly all cases appear to be a result of GLI3 de novo deletions. Chromosome analysis of our patient revealed a large deletion in chromosome 7(p13-p14). Unlike most previously described cases, we found that this deletion resulted from a paternal balanced insertional translocation of 7p13-14 into the long arm of chromosome 5.

Allogeneic transplantation and the risk for transmission of genetic disease: the heritable cancer disorders

With the development of new approaches to transplantation therapy, such as those building upon the potential found in stem cells, it is vital to pursue a clear understanding of transplantation risks. Allogeneic transplantation presents risk for the transmission of disease of various types, including genetic disease. Predisposition to develop cancer is a feature of numerous genetic disorders, and it may be transmissible by transplantation. Some genetic disorders predisposing to cancer are remarkably common, either worldwide or in specific populations, and they could pose significant risk. Hence, to reduce risk to recipients, there is reason to exclude from donation those potential donors (including embryos) harboring certain germ-line mutations. However, the frequent absence of readily identifiable features might confound the effort to exclude those who harbor mutation. Thus, it is also important to consider the magnitude of risk that they represent. For some disorders, life-threatening cancer is highly likely to develop in those individuals born with germ-line mutation, but whether recipients would face the same risk from transplanted mutation is not always evident. Given the diversity of pathways that lead to cancer, there may be diverse factors that impact the likelihood for cancer to develop in the recipient, with some factors decreasing and others increasing the risk. One factor of special concern is the possibility that manipulation of donor cells, prior to transplantation, might introduce additional genetic or epigenetic abnormality, thereby increasing the risk.

Normal distribution and medullary-to-cortical shift of Nestin-expressing cells in acute renal ischemia

Nestin, a marker of multi-lineage stem and progenitor cells, is a member of intermediate filament family, which is expressed in neuroepithelial stem cells, several embryonic cell types, including mesonephric mesenchyme, endothelial cells of developing blood vessels, and in the adult kidney. We used Nestin-green fluorescent protein (GFP) transgenic mice to characterize its expression in normal and post-ischemic kidneys. Nestin-GFP-expressing cells were detected in large clusters within the papilla, along the vasa rectae, and, less prominently, in the glomeruli and juxta-glomerular arterioles. In mice subjected to 30 min bilateral renal ischemia, glomerular, endothelial, and perivascular cells showed increased Nestin expression. In the post-ischemic period, there was an increase in fluorescence intensity with no significant changes in the total number of Nestin-GFP-expressing cells. Time-lapse fluorescence microscopy performed before and after ischemia ruled out the possibility of engraftment by the circulating Nestin-expressing cells, at least within the first 3 h post-ischemia. Incubation of non-perfused kidney sections resulted in a medullary-to-cortical migration of Nestin-GFP-positive cells with the rate of expansion of their front averaging 40 microm/30 min during the first 3 h and was detectable already after 30 min of incubation. Explant matrigel cultures of the kidney and aorta exhibited sprouting angiogenesis with cells co-expressing Nestin and endothelial marker, Tie-2. In conclusion, several lines of circumstantial evidence identify a sub-population of Nestin-expressing cells with the mural cells, which are recruited in the post-ischemic period to migrate from the medulla toward the renal cortex. These migrating Nestin-positive cells may be involved in the process of post-ischemic tissue regeneration.

The murine Pou6f2 gene is temporally and spatially regulated during kidney embryogenesis and its human homolog is overexpressed in a subset of Wilms tumors

We have previously suggested the transcription factor gene POU6F2 as a novel tumor suppressor involved in Wilms tumor (WT) predisposition. Since WT arises from pluripotent embryonic renal precursors, in this study we analyzed the expression of the murine homolog Pou6f2 during kidney embryogenesis and compared it to that of Wt1, the homolog of WT1, a known WT related gene involved in mesenchyme to epithelium conversion. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) performed for Pou6f2 on kidney specimens from embryos, pups, and adult mice, showed that the Pou6f2 mRNA was more abundant in the earliest analyzed phase of kidney organogenesis (E13) than in more advanced fetal stages and in adult animal. In situ RT-PCR demonstrated that Pou6f2 expression parallels the centripetal differentiation of renal morphogenesis. In addition, in E18 kidney, most structures exhibiting Pou6f2 expression stained positively in immunohistochemistry for the Wt1 protein. Finally, quantitative real-time RT-PCR revealed an overexpression (>/=80 times) of POU6F2 compared with normal kidney in 5 of 22 (23%) WTs. The finding of a highly regulated temporal and spatial Pou6f2 expression during renal organogenesis, of its coexpression with Wt1 and of POU6F2 overexpression in a subset of WTs are consistent with a role of POU6F2 in kidney development and provide further support to its involvement in WT.

Wilms tumor in monozygous twins: clinical, pathological, cytogenetic and molecular case report

The concomitant occurrence of Wilms tumor (WT) was observed in two monozygotic twin sisters without evidence of congenital malformations. Twin 1 was diagnosed with a stage I WT at 11 months of age, whereas twin 2 developed a bilateral (stage V) WT at 13 months of age. In both cases pathologic examination showed a nonanaplastic stromal type WT, with marked rhabdomyomatous elements. Cytogenetic analyses performed on blood samples and on tumor specimens revealed no karyotypic abnormality. No alteration of the WT1 and POU6F2 genes was identified in constitutional and tumor DNA of both sisters, and no anomaly in WT1 expression was evidenced in the normal kidney of one of them. However, loss of heterozygosity on chromosome 11p, involving the alleles of maternal origin, was detected both in the single tumor of twin 1 and in the two distinct tumors of twin 2, thus suggesting a common etiology of the diseases. To the authors' knowledge, this is the first report describing at both the clinical and genetic level a couple of monozygotic twins concordant for WT development.