The molecular diversity of voltage-activated calcium channels was established by studies showing that channels could be distinguished by their voltage-dependence, deactivation and single-channel conductance. Low-voltage-activated channels are called 'T' type because their currents are both transient (owing to fast inactivation) and tiny (owing to small conductance). T-type channels are thought to be involved in pacemaker activity, low-threshold calcium spikes, neuronal oscillations and resonance, and rebound burst firing. Here we report the identification of a neuronal T-type channel. Our cloning strategy began with an analysis of Genbank sequences defined as sharing homology with calcium channels. We sequenced an expressed sequence tag (EST), then used it to clone a full-length complementary DNA from rat brain. Northern blot analysis indicated that this gene is expressed predominantly in brain, in particular the amygdala, cerebellum and thalamus. We mapped the human gene to chromosome 17q22, and the mouse gene to chromosome 11. Functional expression of the channel was measured in Xenopus oocytes. Based on the channel's distinctive voltage dependence, slow deactivation kinetics, and 7.5-pS single-channel conductance, we conclude that this channel is a low-voltage-activated T-type calcium channel.

Voltage-activated Ca2+ channels exist as multigene families that share common structural features. Different Ca2+ channels are distinguished by their electrophysiology and pharmacology and can be classified as either low or high voltage-activated channels. Six alpha1 subunit genes cloned previously code for high voltage-activated Ca2+ channels; therefore, we have used a database search strategy to identify new Ca2+ channel genes, possibly including low voltage-activated (T-type) channels. A novel expressed sequence-tagged cDNA clone of alpha1G was used to screen a cDNA library, and in the present study, we report the cloning of alpha1H (or CavT.2), a low voltage-activated Ca2+ channel from human heart. Northern blots of human mRNA detected more alpha1H expression in peripheral tissues, such as kidney and heart, than in brain. We mapped the gene, CACNA1H, to human chromosome 16p13.3 and mouse chromosome 17. Expression of alpha1H in HEK-293 cells resulted in Ca2+ channel currents displaying voltage dependence, kinetics, and unitary conductance characteristic of native T-type Ca2+ channels. The alpha1H channel is sensitive to mibefradil, a nondihydropyridine Ca2+ channel blocker, with an IC50 of 1.4 micromol/L, consistent with the reported potency of mibefradil for T-type Ca2+ channels. Together with alpha1G, a rat brain T-type Ca2+ channel also cloned in our laboratory, these genes define a unique family of Ca2+ channels.

Real-time quantitative PCR allows the sensitive, specific and reproducible quantitation of nucleic acids. Since its introduction, real-time quantitative PCR has revolutionized the field of molecular diagnostics and the technique is being used in a rapidly expanding number of applications. This exciting technology has enabled the shift of molecular diagnostics toward a high-throughput, automated technology with lower turnaround times. This article reviews the basic principles of real-time PCR and describes the various chemistries available: the double-stranded DNA-intercalating agent SYBR Green 1, hydrolysis probes, dual hybridization probes, molecular beacons and scorpion probes. Quantitation methods are discussed in addition to the competing instruments available on the market. Examples of applications of this important and versatile technique are provided throughout the review.

The epilepsies are a group of disorders characterised by recurrent seizures caused by episodes of abnormal neuronal hyperexcitability involving the brain. Up to 60 million people are affected worldwide and genetic factors may contribute to the aetiology in up to 40% of patients. The most common human genetic epilepsies display a complex pattern of inheritance. These are categorised as idiopathic in the absence of detectable structural or metabolic abnormalities. Juvenile myoclonic epilepsy (JME) is a distinctive and common variety of familial idiopathic generalised epilepsy (IGE) with a prevalence of 0.5-1.0 per 1000 and a ratio of sibling risk to population prevalence (lambda(s)) of 42. The molecular genetic basis of these familial idiopathic epilepsies is entirely unknown, but a mutation in the gene CHRNA4, encoding the alpha4 subunit of the neuronal nicotinic acetylcholine receptor (nAChR), was recently identified in a rare Mendelian variety of idiopathic epilepsy. Chromosomal regions harbouring genes for nAChR subunits were therefore tested for linkage to the JME trait in 34 pedigrees. Significant evidence for linkage with heterogeneity was found to polymorphic loci encompassing the region in which the gene encoding the alpha7 subunit of nAChR (CHRNA7) maps on chromosome 15q14 (HLOD = 4.4 at alpha = 0.65; Z(all) = 2.94, P = 0.0005). This major locus contributes to genetic susceptibility to JME in a majority of the families studied.

The p16 gene has been identified as a candidate tumour suppressor gene at 9p21, a region commonly deleted in bladder cancer. We screened 140 bladder tumours and 16 cell lines for deletions and sequence variants of p16. Eight cell lines showed homozygous deletion of p16 and two had small sequence variations. All 13 tumours with small defined deletions of 9p21, 18/31 (58%) of tumours with monosomy 9 and 9/91 (10%) of tumours with no chromosome 9 loss of heterozygosity had homozygous deletion of p16. No tumour-specific sequence variants were identified. Deletion mapping revealed a nested set of deletions focused on p16. Six deletions involved p16 but not the related and adjacent gene p15 and one tumour had an intragenic deletion of p16. All other deletions involved both p16 and p15. We conclude that p16 represents the major target for deletion at 9p21 in bladder cancer.

No abstract

Semaphorins are a large class of secreted or membrane-associated proteins that act as chemotactic cues for cell movement via their transmembrane receptors, plexins. We hypothesized that the function of the semaphorin signaling pathway in the control of cell migration could be harnessed by cancer cells during invasion and metastasis. We now report 13 somatic missense mutations in the cytoplasmic domain of the Plexin-B1 gene. Mutations were found in 89% (8 of 9) of prostate cancer bone metastases, in 41% (7 of 17) of lymph node metastases, and in 46% (41 of 89) of primary cancers. Forty percent of prostate cancers contained the same mutation. Overexpression of the Plexin-B1 protein was found in the majority of primary tumors. The mutations hinder Rac and R-Ras binding and R-RasGAP activity, resulting in an increase in cell motility, invasion, adhesion, and lamellipodia extension. These results identify a key role for Plexin-B1 and the semaphorin signaling pathway it mediates in prostate cancer.adhesion ͉ migration ͉ R-Ras ͉ Rac ͉ semaphorin

Oligoarray analysis of a matched pair of prostate cancer and normal cell lines derived from the same radical prostatectomy specimen identified 113 candidate hypomethylated genes that were overexpressed in the cancer cells and contained CpG islands. Hypomethylation of wingless-related MMTV integration site 5A (WNT5A), S100 calcium-binding protein P (S100P) and cysteine-rich protein 1(CRIP1) was confirmed in the cancer cells by bisulfite sequencing. Treatment of the corresponding normal prostate epithelial cells 1542-NPTX with the DNA methyltransferase inhibitor 5-Aza-2 0 -deoxycytidine (5-aza-CdR) induced higher levels of mRNA expression and partial loss of methylation on these genes. Primary prostate cancers were tested using methylation-specific polymerase chain reaction. WNT5A was hypomethylated in 11/17 (65%) tumors, S100P in 8/16 (50%) and CRIP1 in 13/20 (65%). Bisulfite sequencing of a section of the 5 0 untranslated region (UTR) of WNT5A revealed that three CpG sites (15, 24 and 35) were consistently methylated (93%) in the normal cell line and normal tissues, but not in the prostate cancer cell line and eight primary prostate cancers. Multiple putative binding sites for the transcription factors SP1 and AP-2 were found adjacent to CpG sites 15 and 24. A putative c-Myb binding site was located within the CpG site 35. Anti-c-Myb antibody co-precipitation with WNT5A was methylation-sensitive in 1542-NPTX cells. It is likely that an epigenetic mechanism regulates WNT5A expression in prostate cancer.