Human Papillomavirus Type 16 E6 and E7 Cause Polyploidy in Human Keratinocytes and Up-Regulation of G2-M-phase Proteins

Human papillomavirus type 16 proteins E6 and E7 have been shown to cause centrosome amplification and lagging chromosomes during mitosis. These abnormalities during mitosis can result in missegregation of the chromosomes, leading to chromosomal instability. Genomic instability is thought to be an essential part of the conversion of a normal cell to a cancer cell. We now show that E6 and E7 together cause polyploidy in primary human keratinocytes soon after these genes are introduced into the cells. Polyploidy seems to result from a spindle checkpoint failure arising from abrogation of the normal functions of p53 and retinoblastoma family members by E6 and E7, respectively. In addition, E6 and E7 cause deregulation of cellular genes such as Plk1, Aurora-A, cdk1, and Nek2, which are known to control the G2-M-phase transition and the ordered progression through mitosis.

Deletion of complement factor H-related genes CFHR1 and CFHR3 is associated with atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Disease-associated mutations have been described in the genes encoding the complement regulators complement factor H, membrane cofactor protein, factor B, and factor I. In this study, we show in two independent cohorts of aHUS patients that deletion of two closely related genes, complement factor H-related 1 (CFHR1) and complement factor H-related 3 (CFHR3), increases the risk of aHUS. Amplification analysis and sequencing of genomic DNA of three affected individuals revealed a chromosomal deletion of approximately 84 kb in the RCA gene cluster, resulting in loss of the genes coding for CFHR1 and CFHR3, but leaving the genomic structure of factor H intact. The CFHR1 and CFHR3 genes are flanked by long homologous repeats with long interspersed nuclear elements (retrotransposons) and we suggest that nonallelic homologous recombination between these repeats results in the loss of the two genes. Impaired protection of erythrocytes from complement activation is observed in the serum of aHUS patients deficient in CFHR1 and CFHR3, thus suggesting a regulatory role for CFHR1 and CFHR3 in complement activation. The identification of CFHR1/CFHR3 deficiency in aHUS patients may lead to the design of new diagnostic approaches, such as enhanced testing for these genes.

Suppressing mitotic catastrophe: identifying mcs3 in Schizosaccharomyces pombe

In Schizosaccharomyces pombe (fission yeast), the transition from G2 phase of the cell cycle to mitosis is under strict regulation. The activation of Cdc2, a cyclin dependent serine/threonine protein kinase, is the critical control step in this process. The Cdc2/Cyclin-B (Cdc13) complex is regulated by Wee1 tyrosine kinase and Cdc25 tyrosine phosphatase, which work antagonistically to control progression into mitosis. Hyperactivation of the Cdc2/Cdc13 complex by phosphorylation results in premature mitosis, and as a consequence leads to genome instability. This is referred to as mitotic catastrophe, a lethal phenotype associated with chromosomal segregation abnormalities including chromosome breakage. Six mitotic catastrophe loci were found, five of which have been characterized and identified as various activators and repressors of the core mitotic control. The locus for mcs3 remains unknown. I used tetrad analysis in this study to determine the linkage distance between three genes suspected of flanking the region in which mcs3 is located. Linkage distances obtained in this study confirm that the SPBC428.10 and met17, as well as SPBC428.10 and wpl1 are tightly linked, suggesting this is an area of low recombination. Further linkage analysis should be conducted to determine the precise location of mcs3-12.

Annotated Chromosome Maps for Renal Disease

A combination of linkage analyses and association studies are currently employed to promote the identification of genetic factors contributing to inherited renal disease. We have standardized and merged complex genetic data from disparate sources, creating unique chromosomal maps to enhance genetic epidemiological investigations. This database and novel renal maps effectively summarize genomic regions of suggested linkage, association, or chromosomal abnormalities implicated in renal disease. Chromosomal regions associated with potential intermediate clinical phenotypes have been integrated, adding support for particular genomic intervals. More than 500 reports from medical databases, published scientific literature, and the World Wide Web were interrogated for relevant renal-related information. Chromosomal regions highlighted for prioritized investigation of renal complications include 3q13-26, 6q22-27, 10p11-15, 16p11-13, and 18q22. Combined genetic and physical maps are effective tools to organize genetic data for complex diseases. These renal chromosome maps provide insights into renal phenotype-genotype relationships and act as a template for future genetic investigations into complex renal diseases. New data from individual researchers and/or future publications can be readily incorporated to this resource via a user-friendly web-form accessed from the website: www.qub.ac.uk/neph-res/CORGI/index.php.

HOX genes: seductive science, mysterious mechanisms

HOX genes are evolutionarily highly conserved. The HOX proteins which they encode are master regulators of embryonic development and continue to be expressed throughout postnatal life. The 39 human HOX genes are located in four clusters (A-D) on different chromosomes at 7p15, 17q21 [corrected] 12q13, and 2q31 respectively and are assumed to have arisen by duplication and divergence from a primordial homeobox gene. Disorders of limb formation, such as hand-foot-genital syndrome, have been traced to mutations in HOXA13 and HOXD13. Evolutionary conservation provides unlimited scope for experimental investigation of the functional control of the Hox gene network which is providing important insights into human disease. Chromosomal translocations involving the MLL gene, the human homologue of the Drosophila gene trithorax, create fusion genes which exhibit gain of function and are associated with aggressive leukaemias in both adults and children. To date 39 partner genes for MLL have been cloned from patients with leukaemia. Models based on specific translocations of MLL and individual HOX genes are now the subject of intense research aimed at understanding the molecular programs involved, and ultimately the design of chemotherapeutic agents for leukaemia. Investigation of the role of HOX genes in cancer has led to the concept that oncology may recapitulate ontology, a challenging postulate for experimentalists in view of the functional redundancy implicit in the HOX gene network.

The pathophysiology of HOX genes and their role in cancer

The HOM-C clustered prototype homeobox genes of Drosophila, and their counterparts, the HOX genes in humans, are highly conserved at the genomic level. These master regulators of development continue to be expressed throughout adulthood in various tissues and organs. The physiological and patho-physiological functions of this network of genes are being avidly pursued within the scientific community, but defined roles for them remain elusive. The order of expression of HOX genes within a cluster is co-ordinated during development, so that the 3' genes are expressed more anteriorly and earlier than the 5' genes. Mutations in HOXA13 and HOXD13 are associated with disorders of limb formation such as hand-foot-genital syndrome (HFGS), synpolydactyly (SPD), and brachydactyly. Haematopoietic progenitors express HOX genes in a pattern characteristic of the lineage and stage of differentiation of the cells. In leukaemia, dysregulated HOX gene expression can occur due to chromosomal translocations involving upstream regulators such as the MLL gene, or the fusion of a HOX gene to another gene such as the nucleoporin, NUP98. Recent investigations of HOX gene expression in leukaemia are providing important insights into disease classification and prediction of clinical outcome. Whereas the oncogenic potential of certain HOX genes in leukaemia has already been defined, their role in other neoplasms is currently being studied. Progress has been hampered by the experimental approach used in many studies in which the expression of small subsets of HOX genes was analysed, and complicated by the functional redundancy implicit in the HOX gene system. Attempts to elucidate the function of HOX genes in malignant transformation will be enhanced by a better understanding of their upstream regulators and downstream target genes.

Microsatellite analysis for determination of the mutagenicity of extremely low-frequency electromagnetic fields and ionising radiation in vitro.

Extremely low-frequency electromagnetic fields (ELF-EMF) have been reported to induce lesions in DNA and to enhance the mutagenicity of ionising radiation. However, the significance of these findings is uncertain because the determination of the carcinogenic potential of EMFs has largely been based on investigations of large chromosomal aberrations. Using a more sensitive method of detecting DNA damage involving microsatellite sequences, we observed that exposure of UVW human glioma cells to ELF-EMF alone at a field strength of 1 mT (50 Hz) for 12 h gave rise to 0.011 mutations/locus/cell. This was equivalent to a 3.75-fold increase in mutation induction compared with unexposed controls. Furthermore, ELF-EMF increased the mutagenic capacity of 0.3 and 3 Gy gamma-irradiation by factors of 2.6 and 2.75, respectively. These results suggest not only that ELF-EMF is mutagenic as a single agent but also that it can potentiate the mutagenicity of ionising radiation. Treatment with 0.3 Gy induced more than 10 times more mutations per unit dose than irradiation with 3 Gy, indicating hypermutability at low dose.

A retrospective analysis of spring barley germplasm development from 'foundation genotypes' to currently successful cultivars

Twenty-eight mapped barley SSRs were used to examine changes in the level and pattern of variability in northern European spring barley over time. Comparing the most recently introduced cultivars with a group of 19 landraces and key progenitors termed 'foundation genotypes' we observed a reduction in the spectrum of alleles at 28 loci over time, and highlighted chromosomal regions with limited SSR allelic variation. The 19 'foundation genotypes' contained 72% of the alleles present in all the cultivars sampled. The smallest number of genotypes required to encompass all of the alleles detected in this study was 44, several of which were recently introduced cultivars. The level of diversity within modern cultivars was lower (0.484) than in the 'foundation genotypes' (0.597), although the values varied with the SSR locus. A total of 74 rare alleles (frequency

Genomic instability after targeted irradiation of human lymphocytes: Evidence for inter-individual differences under bystander conditions

Environmental (222)radon exposure is a human health concern, and many studies demonstrate that very low doses of high LET alpha-particle irradiation initiate deleterious genetic consequences in both radiated and non-irradiated bystander cells. One consequence, radiation-induced genomic instability (RIGI), is a hallmark of tumorigenesis and is often assessed by measuring delayed chromosomal aberrations We utilised a technique that facilitates transient immobilization of primary lymphocytes for targeted microbeam irradiation and have reported that environmentally relevant doses, e.g. a single He-3(2+) particle traversal to a single cell, are sufficient to Induce RIGI Herein we sought to determine differences in radiation response in lymphocytes isolated from five healthy male donors Primary lymphocytes were irradiated with a single particle per cell nucleus. We found evidence for inter-individual variation in radiation response (Rid, measured as delayed chromosome aberrations) Although this was not highly significant, it was possibly masked by high levels of intra-individual variation While there are many studies showing a link between genetic predisposition and RIGI, there are few studies linking genetic background with bystander effects in normal human lymphocytes In an attempt to investigate inter-individual variation in the induction of bystander effects, primary lymphocytes were irradiated with a single particle under conditions where fractions of the population were traversed We showed a marked genotype-dependent bystander response in one donor after exposure to 15% of the population The findings may also be regarded as a radiation-induced genotype-dependent bystander effect triggering an instability phenotype (C) 2010 Elsevier B.V. All rights reserved.

Twenty-eight divergent polysaccharide loci specifying within and amongst strain capsule diversity in three strains of Bacteroides fragilis

Comparison of the complete genome sequence of Bacteroides fragilis 638R, originally isolated in the USA, was made with two previously sequenced strains isolated in the UK (NCTC 9343) and Japan (YCH46). The presence of 10 loci containing genes associated with polysaccharide (PS) biosynthesis, each including a putative Wzx flippase and Wzy polymerase, was confirmed in all three strains, despite a lack of cross-reactivity between NCTC 9343 and 638R surface PS-specific antibodies by immunolabelling and microscopy. Genomic comparisons revealed an exceptional level of PS biosynthesis locus diversity. Of the 10 divergent PS-associated loci apparent in each strain, none is similar between NCTC 9343 and 638R. YCH46 shares one locus with NCTC 9343, confirmed by mAb labelling, and a second different locus with 638R, making a total of 28 divergent PS biosynthesis loci amongst the three strains. The lack of expression of the phase-variable large capsule (LC) in strain 638R, observed in NCTC 9343, is likely to be due to a point mutation that generates a stop codon within a putative initiating glycosyltransferase, necessary for the expression of the LC in NCTC 9343. Other major sequence differences were observed to arise from different numbers and variety of inserted extra-chromosomal elements, in particular prophages. Extensive horizontal gene transfer has occurred within these strains, despite the presence of a significant number of divergent DNA restriction and modification systems that act to prevent acquisition of foreign DNA. The level of amongst-strain diversity in PS biosynthesis loci is unprecedented.

Monozygotic twins discordant for phacomatosis pigmentovascularis: evidence for the concept of twin spotting.

The term phacomatosis pigmentovascularis (PPV) refers to the occurrence of vascular nevi with melanocytic or epidermal nevi. We report on monozygotic twins (MZTs) discordant for phacomatosis cesioflammea (PPV type II) providing evidence for the mechanism of twin spotting in the development of PPV. The affected twin had a nevus flammeus on the right arm and the right maxilla, and a pigmented area on the trunk in keeping with a persistent, aberrant Mongolian spot. The affected twin had bilateral ocular melanocytosis with abnormal scleral pigmentation, iris mamillations, increased pigmentation of the trabecular meshwork, and increased fundal pigmentation and secondary glaucoma. DNA testing confirmed monozygosity. This case of MZTs discordant for PPV supports the hypothesis that PPV results from mosaicism due to a post-zygotic mutational event and the concept of twin spotting.

Delineation of a recognisable phenotype of interstitial deletion 3 (q22.3q25.1) in a case with previously unreported truncus arteriosus

Interstitial deletions of chromosome 3q22.3e25.1 are very rare with only five previous reports of deletions in this region [1,2,4,7,9]. We describe a case of a female infant with a de novo deletion. Dysmorphic features and congenital heart disease led to a clinical genetics assessment on day 1 of life. Chromosomal analysis showed an interstitial deletion with a female karyotype 46,XX,del (3)(q23q25.1) dn. Subsequent array CGH demonstrated the breakpoints as 3q22.3q25.1. This is the first documented association with a truncus arteriosus. We identify an emerging clinical phenotype of microphthalmia, microcephaly, congenital heart disease, slow feeding, skeletal abnormalities, with an abnormal facies and developmental delay. Array CGH demonstrated that the FOXL2 gene responsible for BPES was not deleted in this patient. (C) 2010 Elsevier Masson SAS. All rights reserved.

Identification of a Second Kindred with Familial Hypocalciuric Hypercalcemia Type 3 (FHH3) Narrows Localization to a

Context: Familial hypocalciuric hypercalcemia (FHH) is a genetically heterogenous disorder that consists of three defined types, FHH1, FHH2, and FHH3 whose chromosomal locations are 3q21.1, 19p, and 19q13, respectively. FHH1, caused by mutations of the calcium-sensing receptor (CASR), occurs in more than 65% of patients, whereas the abnormalities underlying FHH2 and FHH3, which have each been described in single North American kindreds, are unknown.

Trisomy 10p with clinical features of facio-auriculo-vertebral spectrum: a case report

We report a male child born with complete absence of his external ear, hemifacial microsomia of the right side, high arched palate, a down-turned upper lip and slightly upslanting palpebral fissures. The features were suggestive of facio-auriculo-vertebral spectrum. Investigations showed a tandem duplication of the short arm of one chromosome 10 with apparent breakpoints at p14 and p15. This case extends the list of chromosomal abnormalities associated with the facio-auriculo-vertebral phenotype and also adds useful clinical information to possible trisomy 10p phenotypes.

Mosaic monosomy 14: clinical features and recognizable facies

A 1-year-old child with clinical features of monosomy 14 is reported. She has dysmorphic facial features including ocular colobomata, dolichocephaly and microcephaly, retinal pigmentation, severe seizures, fair curly hair and tapering fingers. There was severe mental retardation. This is the first reported case of severe mosaic monosomy 14, with up to 30% mosaicism. A recognizable facial gestalt is present in children with 14q deletions or partial monosomy 14, as well as susceptibility to infection, feeding difficulties, seizures and retinal pigmentation. (C) 2004 Lippincott Williams Wilkins.