Prostaglandin F 2 ␣, but Not Latanoprost, Increases the Ca 2؉ Sensitivity of the Pig Iris Sphincter Muscle

PURPOSE. To determine the mechanisms underlying prostaglandin (PG) F 2 ␣-, carbachol (CCh)-, or latanoprost (a PGF 2 ␣ analogue)-induced contraction of the pig iris sphincter muscle. METHODS. Effects of these agents on myofilament Ca 2ϩ sensitivity were evaluated and compared with the use of receptorcoupled permeabilized preparations by ␣-toxin. The effects of PGF 2 ␣ and CCh on the phosphorylation of myosin light chain (MLC) were also analyzed. RESULTS. In the intact strips, all three of these agents induced contractions. CONCLUSIONS. PGF 2 ␣, but not latanoprost, induced Ca 2ϩ sensitization of the pig iris sphincter muscle in an MLC phosphorylation-dependent manner through the rho-rho kinase pathway. The effect of latanoprost on the Ca 2ϩ sensitization mechanism was different from that of PGF 2 ␣ and was thought to play a beneficial role in glaucoma treatment. (Invest Ophthalmol Vis Sci

Genome-wide DNA methylation analysis in cohesin mutant human cell lines

The cohesin complex has recently been shown to be a key regulator of eukaryotic gene expression, although the mechanisms by which it exerts its effects are poorly understood. We have undertaken a genome-wide analysis of DNA methylation in cohesin-deficient cell lines from probands with Cornelia de Lange syndrome (CdLS). Heterozygous mutations in NIPBL, SMC1A and SMC3 genes account for ∼65% of individuals with CdLS. SMC1A and SMC3 are subunits of the cohesin complex that controls sister chromatid cohesion, whereas NIPBL facilitates cohesin loading and unloading. We have examined the methylation status of 27 578 CpG dinucleotides in 72 CdLS and control samples. We have documented the DNA methylation pattern in human lymphoblastoid cell lines (LCLs) as well as identified specific differential DNA methylation in CdLS. Subgroups of CdLS probands and controls can be classified using selected CpG loci. The X chromosome was also found to have a unique DNA methylation pattern in CdLS. Cohesin preferentially binds to hypo-methylated DNA in control LCLs, whereas the differential DNA methylation alters cohesin binding in CdLS. Our results suggest that in addition to DNA methylation multiple mechanisms may be involved in transcriptional regulation in human cells and in the resultant gene misexpression in CdLS