Role of E2F3 expression in modulating cellular proliferation rate in human bladder and prostate cancer cells

Amplification and overexpression of the E2F3 gene at 6p22 in human bladder cancer is associated with increased tumour stage, grade and proliferation index, and in prostate cancer E2F3 overexpression is linked to tumour aggressiveness. We first used small interfering RNA technology to confirm the potential importance of E2F3 overexpression in bladder cancer development. Knockdown of E2F3 expression in bladder cells containing the 6p22 amplicon strongly reduced the extent of bromodeoxyuridine (BrdU) incorporation and the rate of cellular proliferation. In contrast, knockdown of CDKAL1/FLJ20342, another proposed oncogene, from this amplicon had no effect. Expression cDNA microarray analysis on bladder cancer cells following E2F3 knockdown was then used to identify genes regulated by E2F3, leading to the identification of known E2F3 targets such as Cyclin A and CDC2 and novel targets including pituitary tumour transforming gene 1, Polo-like kinase 1 (PLK1) and Caveolin-2. For both bladder and prostate cancer, we have proposed that E2F3 protein overexpression may cooperate with removal of the E2F inhibitor retinoblastoma tumor suppressor protein (pRB) to drive cellular proliferation. In support of this model, we found that ectopic expression of E2F3a enhanced the BrdU incorporation, a marker of cellular proliferation rate, of prostate cancer DU145 cells, which lack pRB, but had no effect on the proliferation rate of PC3 prostate cancer cells that express wild-type pRB. BrdU incorporation in PC3 cells could, however, be increased by overexpressing E2F3a in cells depleted of pRB. When taken together, these observations indicate that E2F3 levels have a critical role in modifying cellular proliferation rate in human bladder and prostate cancer.

Microarray comparative genomic hybridisation analysis of intraocular uveal melanomas identifies distinctive imbalances associated with loss of chromosome 3

Defining regions of genomic imbalance can identify genes involved in tumour development. Conventional cytogenetics has identified several nonrandom copy number alterations (CNA) in uveal melanomas (UVM), which include monosomy 3, chromosome 6 abnormalities and gain of 8q. To gain further insight into the CNAs and define the regions involved more precisely we analysed 18 primary UVMs using 1 Mb BAC microarray comparative genomic hybridisation (CGH). Our analysis showed that the most common genomic imbalances were 8q gain (78%), 6p gain (67%) and monosomy 3 (56%). Two distinct CGH profiles could be delineated on the basis of the chromosome 3 status. The most common genetic changes in monosomy 3 tumours, in our study, were gain of 8q11.21-q24.3, 6p25.1-p21.2, 21q21.2-q21.3 and 21q22.13-q22.3 and loss of 1p36.33-p34.3, 1p31.1-p21.2, 6q16.2-q25.3 and 8p23.3-p11.23. In contrast, disomy 3 tumours showed recurrent gains of only 6p25.3-p22.3 and 8q23.2-q24.3. Our approach allowed definition of the smallest overlapping regions of imbalance, which may be important in the development of UVM.

Expression analysis onto microarrays of randomly selected cDNA clones highlights HOXB13 as a marker of human prostate cancer

In a strategy aimed at identifying novel markers of human prostate cancer, we performed expression analysis using microarrays of clones randomly selected from a cDNA library prepared from the LNCaP prostate cancer cell line. Comparisons of expression profiles in primary human prostate cancer, adjacent normal prostate tissue, and a selection of other (nonprostate) normal human tissues, led to the identification of a set of clones that were judged as the best candidate markers of normal and/or malignant prostate tissue. DNA sequencing of the selected clones revealed that they included 10 genes that had previously been established as prostate markers: NKX3.1, KLK2, KLK3 (PSA), FOLH1 (PSMA), STEAP2, PSGR, PRAC, RDH11, Prostein and FASN. Following analysis of the expression patterns of all selected and sequenced genes through interrogation of SAGE databases, a further three genes from our clone set, HOXB13, SPON2 and NCAM2, emerged as additional candidate markers of human prostate cancer. Quantitative RT-PCR demonstrated the specificity of expression of HOXB13 in prostate tissue and revealed its ubiquitous expression in a series of 37 primary prostate cancers and 20 normal prostates. These results demonstrate the utility of this expression-microarray approach in hunting for new markers of individual human cancer types.

The role of the peripherin/RDS gene in retinal dystrophies

Peripherin/RDS is a transmembrane glycoprotein expressed in vertebrate photoreceptors. It is located at the rim of the disc membranes of the photoreceptor outer segments, where it is thought to play an important role in folding and stacking of the discs. Initially, the identification of a mutation in the rds mouse model defined the role of this gene in hereditary retinal dystrophies. To date over 60 different mutations have been reported in human retinal diseases, with most being restricted to single families. A characteristic of mutations in the peripherin/RDS gene is the broad phenotypic spectrum in patients, and the variability in clinical expression, even within families. Thus, genotype-phenotype correlations are difficult and only reliable for a minority of mutations.

Genomic differentiation of Neanderthals and anatomically modern man allows a fossil-DNA-based classification of morphologically indistinguishable hominid bones

Southern blot hybridizations of genomic DNA were introduced as a relatively simple fossil-DNA-based approach to classify remains of Neanderthals. When hybridized with genomic DNA of either human or Neanderthal origin, DNA extracted from two Neanderthal finds-the Os parietale, from Warendorf-Neuwarendorf, Germany, and a clavicula, from Krapina, Croatia-was shown to yield hybridization signals that differ by at least a factor of two compared to the signals obtained with the use of fossil DNA of an early Homo sapiens from the Vogelherd cave (Stetten I), Germany. When labeled chimpanzee DNA was used as a probe, Neanderthal and human DNA, however, revealed hybridization signals of similar intensity. Thus, the genome of Neanderthals is expected to differ significantly from the genome of anatomically modern man, because of the contrasting composition of repetitive DNA. These data support the hypothesis that Neanderthals were not ancestors of anatomically modern man.

Voltage-induced release of nucleic acids from palaeontological samples

Most of the protocols for the recovery of ancient DNA from palaeontological specimens are time-consuming and tend to yield inconsistent polymerase chain reaction (PCR) results. "Voltage-induced release" is a novel and rapid approach for the extraction of ancient DNA. Nucleic acids are directly electrophoresed out of powder derived from hard and soft tissues. This technique is much faster than other methods in which pulverized tissue conventionally undergoes time-consuming crude lysis steps. The total preparation time is 5-6 h. The reliability of the voltage-induced release method was validated by (i) measuring the ratio of D-to L-enantiomers of the amino acids aspartic acid, alanine, and leucine, and (ii) by specific PCR amplification of four single-copy markers of human chromosome 17 and 18. We compare voltage-induced release to a frequently used silica-based protocol. DNA extracted employing voltage-induced release was more effective in PCR amplifications, which may be attributed to the effective removal of PCR inhibitors.

Total colourblindness is caused by mutations in the gene encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel

Total colourblindness (OMIM 216900), also referred to as rod monochromacy (RM) or complete achromatopsia, is a rare, autosomal recessive inherited and congenital disorder characterized by photophobia, reduced visual acuity, nystagmus and the complete inability to discriminate between colours. Electroretinographic recordings show that in RM, rod photoreceptor function is normal, whereas cone photoreceptor responses are absent. The locus for RM has been mapped to chromosome 2q11 (ref. 2), however the gene underlying RM has not yet been identified. Recently, a suitable candidate gene, CNGA3, encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel, a key component of the phototransduction pathway, has been cloned and assigned to human chromosome 2q11 (refs 3,4). We report the identification of missense mutations in CNGA3 in five families with RM. Homozygous mutations are present in two families, whereas the remaining families show compound heterozygous mutations. In all cases, the segregation pattern of the mutations is consistent with the autosomal recessive inheritance of the disease and all mutations affect amino acids that are highly conserved among cyclic nucleotide gated channels (CNG) in various species. This is the first report of a colour vision disorder caused by defects other than mutations in the cone pigment genes, and implies at least in this instance a common genetic basis for phototransduction in the three different cone photoreceptors of the human retina.

Repair of degraded duplex DNA from prehistoric samples using Escherichia coli DNA polymerase I and T4 DNA ligase

The most notable feature of DNA extracted from prehistoric material is that it is of poor quality. Amplification of PCR products from such DNA is consequently an exception. Here we present a simple method for the repair of degraded duplex DNA using the enzymes Escherichia coli DNA polymerase I and T4 DNA ligase. Adjacent sequences separated by nicks do not split up into intact strands during the denaturation step of PCR. Thus the target DNA is refractory to amplification. The proposed repair of nicked, fragmented ancient DNA results in an increase of amplification efficiency, such that the correct base order of the respective nuclear DNA segment can be obtained.

Efficient retroviral infection of mammalian cells is blocked by inhibition of poly(ADP-ribose) polymerase activity

Integration of proviral DNA into the host cell genome is a characteristic feature of the retroviral life cycle. This process involves coordinate DNA strand break formation and rejoining reactions. The full details of the integration process are not yet fully understood. However, the endonuclease and DNA strand-joining activities of the virus-encoded integrase protein (IN) are thought to act in concert with other, as-yet-unidentified, endogenous nuclear components which are involved in the DNA repair process. The nuclear enzyme poly(ADP-ribose) polymerase (PARP), which is dependent on DNA strand breaks for its activity, is involved in the efficient repair of DNA strand breaks, and maintenance of genomic integrity, in nucleated eukaryotic cells. In the present work, we examine the possible involvement of PARP in the retroviral life cycle and demonstrate that inhibition of PARP activity, by any one of three independent mechanisms, blocks the infection of mammalian cells by recombinant retroviral vectors. This requirement for PARP activity appears to be restricted to processes involved in the integration of provirus into the host cell DNA. PARP inhibition does not affect viral entry into the host cell, reverse transcription of the viral RNA genome, postintegration synthesis of viral gene products, synthesis of the viral RNA genome, or the generation of infective virions. Therefore, efficient retroviral infection of mammalian cells is blocked by inhibition or PARP activity.