Citations

The genetic study of titin has been notoriously difficult because of its size and complicated alternative splicing routes. Here, we have used zebrafish as an animal model to investigate the functions of individual titin isoforms. We identified 2 titin orthologs in zebrafish, ttna and ttnb , and annotated the full-length genomic sequences for both genes. We found that ttna , but not ttnb , is required for sarcomere assembly in the heart as well as the subsequent establishment of cardiac contractility. In fact, ttna is the earliest sarcomeric mRNA that is expressed in the heart, which makes it an early molecular marker for cardiomyocyte differentiation. Surprisingly, ttna is required for later steps of sarcomere assembly, including the assembly of Z-discs and A-bands, but not for early steps such as the assembly of Z-bodies and nonstriated myosin filaments. Reduction of individual titin isoforms in vivo using morpholino-modified antisense oligonucleotides indicated that (1) both N2B exon–containing and N2A exon–containing isoforms of ttna are required for sarcomere assembly in the heart; (2) N2A exon–containing isoforms of both ttna and ttnb are required for sarcomere assembly in the somites; and (3) the N2B exon–containing isoforms of ttnb are expressed later than other titin isoforms and are probably involved in modulating their expression; however, these isoforms of ttnb are not required for sarcomere assembly. Collectively, our results reveal distinct functions of different titin isoforms and suggest that various phenotypes in “titinopathies” may be attributable to the disruption of different titin isoforms.

Nitric oxide (NO) is a highly diffusible and short-lived physiological messenger. Despite its diffusible nature, NO modifies thiol groups of specific cysteine residues in target proteins and alters protein function via S-nitrosylation. Although intracellular S-nitrosylation is a specific posttranslational modification, the defined localization of an NO source (nitric oxide synthase, NOS) with protein S-nitrosylation has never been directly demonstrated. Endothelial NOS (eNOS) is localized mainly on the Golgi apparatus and in plasma membrane caveolae. Here, we show by using eNOS targeted to either the Golgi or the nucleus that S-nitrosylation is concentrated at the primary site of eNOS localization. Furthermore, localization of eNOS on the Golgi enhances overall Golgi protein S-nitrosylation, the specific S-nitrosylation of N -ethylmaleimide-sensitive factor and reduces the speed of protein transport from the endoplasmic reticulum to the plasma membrane in a reversible manner. These data indicate that local NOS action generates organelle-specific protein S-nitrosylation reactions that can regulate intracellular transport processes.

Objective: Although the epidemiology of microscopic colitis has been described in Europe, no such data exist from North America. We studied the incidence, prevalence and temporal trends of microscopic colitis in a geographically defined US population. Design and setting: In this population based cohort study, residents of Olmsted County, Minnesota, with a new diagnosis of microscopic colitis, and all who had colon biopsies for evaluation of diarrhoea, between 1 January 1985 and 31 December 2001 were identified. Biopsies were reviewed for confirmation (cases) and to identify missed cases (diarrhoea biopsies). Main outcome measures: Incidence rates, age and sex adjusted to the 2000 US white population. Poisson regression assessed the association of calendar period, age and sex with incidence. Results: We identified 130 incident cases for an overall rate of 8.6 cases per 100 000 person-years. There was a significant secular trend, with incidence increasing from 1.1 per 100 000 early in the study to 19.6 per 100 000 by the end (p<0.001). Rates increased with age (p<0.001). By subtype, the incidence was 3.1 per 100 000 for collagenous colitis and 5.5 per 100 000 for lymphocytic colitis. Collagenous colitis was associated with female sex (p<0.001) but lymphocytic colitis was not. Prevalence (per 100 000 persons) on 31 December 2001 was 103.0 (39.3 for collagenous colitis and 63.7 for lymphocytic colitis). Conclusions: The incidence of microscopic colitis has increased significantly over time, and by the end of the study, the incidence and prevalence were significantly higher than reported previously. Microscopic colitis is associated with older age, and collagenous colitis is associated with female sex.

ABSTRACT Purpose. A widely advocated approach to increasing spectacle magnification in minus lenses is to increase center thickness and reduce vertex distance. Conventionally, a steeper base curve is to be avoided because of the accompanying increased vertex distance in a minus lens and the reduction of spectacle magnification that results. This approach works when small amounts of spectacle magnification are needed. However, when large amounts are needed for high minus lenses with flat base curves, the conventional approach does not provide sufficient magnification. Facial features such as eyelash length limit the contribution of reducing vertex distance, and the flat base curves limit the efficacy of increasing center thickness. Steeper base curves are required to increase the optical “leverage” of increasing center thickness. Methods. Through use of an example, a steeper base curve is shown to increase the spectacle magnification of a high minus lens. The gain in spectacle magnification is preserved by maintaining a nearly constant vertex distance through bevel location. Results. In the example, changing the base curve of a −6.50‐D lens by +4.50 D while increasing the center thickness by 4.1 mm resulted in a +4.4% increase in spectacle magnification. The lens bevel was kept as close as possible to the front surface, allowing the increased center thickness to keep the back vertex at essentially a constant vertex distance in the presence of the steeper base curve. Without the steeper base curve, it was not possible to attain the needed spectacle magnification. Conclusions. When large amounts of spectacle magnification are needed for high minus lenses, both steeper base curves and increased center thicknesses are necessary. The reduction in spectacle magnification from increased vertex distance that is expected with steeper base curves can be neutralized by keeping the bevel close to the front surface on the thicker lens.

Abstract Germ line mutations in several genes (BRCA1, BRCA2, and CHEK2) whose products are involved in the DNA damage–signaling pathway have been implicated in prostate cancer risk. To identify additional genes in this pathway that might confer susceptibility to this cancer, we analyzed a recently identified DNA damage–response gene, p53AIP1 (a gene encoding for p53-regulated apoptosis-inducing protein 1), for genetic variants in prostate cancer. Five novel germ line variants were identified. The two truncating variants (Ser32Stop and Arg21insG) were found in 3% (4 of 132) of unselected prostate tumor samples. Genotyping of the two variants in an additional 393 men with sporadic prostate cancer showed a frequency of 3.1% (12 of 393) in contrast to 0.6% (2 of 327) in 327 unaffected men (Fisher's exact test, P = 0.018), with an odds ratio (OR) of 5.1 [95% confidence interval (95% CI), 1.1-23.0]. In addition, two of six tumors carrying the truncating variants were associated with loss of heterozygosity of the wild-type alleles, suggesting that p53AIP1 may act as a tumor suppressor. We also showed that the truncated p53AIP1 was unable to induce apoptosis and suppress cell growth in HeLa and COS-7 cells. These results suggest that loss-of-function variants in p53AIP1 associated with the risk of sporadic prostate cancer and further support the concept that the genetic defects in the DNA damage–response genes play an important role in the development of prostate cancer. (Cancer Res 2006; 66(21): 10302-7)