The Human GCAP1 and GCAP2 Genes Are Arranged in a Tail-to-Tail Array on the Short Arm of Chromosome 6 (p21.1)

GCAP1 and GCAP2 are related Ca²⁺-binding proteins that activate photoreceptor guanylate cyclase(s). We showed previously that the human GCAP1 gene, consisting of four exons, is located at 6p21.1 (locus designation GUCA). To identify the chromosomal location of the GCAP2 gene, we first cloned its cDNA and determined its intron–exon distribution by PCR analysis. The results show that the introns of the GCAP2 gene are positioned exactly as in the GCAP1 gene and are nearly double in size. Sequence similarity between the two genes, however, is limited to portions of exons 1 and 2. The GCAP1 and GCAP2 genes are transcribed into single mRNA species (1.7 and 2.2 kb, respectively) and are detectable only in the retina by Northern blotting. The GCAP2 gene was found by somatic human–hamster hybrid panel analysis and FISH to reside at GUCA in a region indistinguishable from that of GCAP1. PCR analysis with exon 4-specific primers showed that the genes are in a tail-to-tail array less than 5 kb apart and altogether span less than 20 kb of genomic DNA. The identical gene structures and loci of GCAP1 and GCAP2, and the identical function of the gene products, are consistent with a gene duplication event.     

Rescue of cyclin D1 deficiency by knockin cyclin E.

D-type cyclins and cyclin E represent two very distinct classes of mammalian G1 cyclins. We have generated a mouse strain in which the coding sequences of the cyclin D1 gene (Ccnd1) have been deleted and replaced by those of human cyclin E (CCNE). In the tissues and cells of these mice, the expression pattern of human cyclin E faithfully reproduces that normally associated with mouse cyclin D1. The replacement of cyclin D1 with cyclin E rescues all phenotypic manifestations of cyclin D1 deficiency and restores normal development in cyclin D1-dependent tissues. Thus, cyclin E can functionally replace cyclin D1. Our analyses suggest that cyclin E is the major downstream target of cyclin D1.     

Ultrawideband radiation and pentylenetetrazol-induced convulsions in rats.

New non-ionizing pulsed systems using ultrawideband (UWB) require safety assessment before they can be used by either military or civilian communities. The development of directed energy weaponry intended for use against electronically vulnerable targets, as well as ground-probing radar systems, have used fast-rise-time high-peak-power electromagnetic pulses characteristic of UWB emitters. It has been postulated that these ultrashort pulses might produce electromagnetic transients resulting in tissue damage. Several challenges to this notion have been posed, however. One report found that rats exposed to UWB after receiving a convulsant drug tended toward longer latency to the onset of convulsions than the no-exposure group. Although not statistically significant, the presence of this trend prompted the present study. An ED99 dose of the convulsant pentylenetetrazol (PTZ) or saline was given just before UWB or sham exposure and resultant seizure activity was recorded. The data from the current study show no effect of UWB exposure on PTZ-induced seizure activity, thereby not supporting the tissue damage concerns, at least for the exposure parameters used here.     

Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size–island age model in the Pacific

Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr⁻¹) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.

     

Rapid conditional targeted ablation of cells expressing human CD59 in transgenic mice by intermedilysin

Conditional targeted cell ablation is a powerful approach for investigating the pathogenesis of human diseases and in vivo cellular functions. Intermedilysin (ILY) is a cytolytic pore-forming toxin secreted by Streptococcus intermedius that lyses human cells exclusively, owing to its receptor specificity for human CD59. We generated two transgenic mouse strains that express human CD59 either on erythrocytes (strain ThCD59(RBC)) or on endothelia (strain ThCD59(END)). Intravenous injection of ILY in ThCD59(RBC) mice induced acute intravascular hemolysis, leading to reduced nitric oxide bioavailability, increased platelet activation and rapid death. In ThCD59(END) mice, ILY induced rapid endothelial damage, leading to acute death and disseminated intravascular coagulation. Additionally, we show that human serum contains ILY-specific neutralizing antibodies not found in any other animal species. Together, these results suggest that this new rapid conditional targeted ILY-mediated cell ablation technique can be used in combination with any available transgenic expression system to study the physiologic role of specific cell populations.