A definitive haplotype map as determined by genotyping duplicated haploid genomes finds a predominant haplotype preference at copy-number variation events.

The majority of complete hydatidiform moles (CHMs) harbor duplicated haploid genomes that originate from sperm. This makes CHMs more advantageous than conventional diploid cells for determining haplotypes of SNPs and copy-number variations (CNVs), because all of the genetic variants in a CHM genome are homozygous. Here we report SNP and CNV haplotype structures determined by analysis of 100 CHMs from Japanese subjects via high-density DNA arrays. The obtained haplotype map should be useful as a reference for the haplotype structure of Asian populations. We resolved common CNV regions (merged CNV segments across the examined samples) into CNV events (clusters of CNV segments) on the basis of mutual overlap and found that the haplotype backgrounds of different CNV events within the same CNV region were predominantly similar, perhaps because of inherent structural instability.

Population Pharmacokinetics and Exposure-Response of Lithium Carbonate in Patients Based on Tubular Reabsorption Mechanisms.

BACKGROUND AND OBJECTIVE: Lithium, which is used to treat bipolar disorder, has a narrow therapeutic blood concentration range and quickly reaches clinically toxic levels. We performed a population pharmacokinetic analysis with a lithium tubular reabsorption model including urinary pH and investigated the relationship between blood lithium concentration and tremor as a side effect. METHODS: Routine clinical data, including 389 serum concentrations, were collected from 214 patients orally administered an adjusted amount of lithium carbonate. Pharmacokinetics were described using a one-compartment distribution model with first-order absorption and elimination. The fractions of the MID (Li+ + LiCO3-) and ION (2Li+ + CO32-) forms were calculated using the Henderson-Hasselbalch equation, and the influences of these fractions on clearance (CL) were evaluated. The rate of tremor development was analyzed using a logit model. RESULTS: Oral apparent CL (CL/F) was explained by nonrenal CL and renal CL, and renal CL was varied by the fractions of lithium forms influenced by urinary pH. The contribution of MID to CL was slightly larger than that of ION. The rate of tremor development was estimated to be more than 30% when the trough lithium concentration was greater than 1.26 mEq L-1. CONCLUSION: Renal function and urinary pH are important indices in lithium treatment, so the serum concentration of lithium may be predicted based on the renal function and urinary pH.

Stomach cancer-derived del223V-226L mutation of the STCH gene causes loss of sensitization to TRAIL-mediated apoptosis.

The stress 70 protein chaperone (STCH), a member of the heat shock protein 70 (HSP70) superfamily, is a microsomal protein that contains a N-terminal ATPase domain but lacks a C-terminal protein binding domain. Although cell-protective functions of HSP70 members are well characterized, the biological relevance of STCH remains unclear. We previously identified STCH as a candidate gene for susceptibility to stomach cancer by genetic analyses. In this study, we searched somatic mutations of STCH in human stomach cancer and identified the 668del12bp mutation in exon 4, resulting in a four amino acid deletion (del223V-226L) in the conserved ATP-binding domain. In vitro binding assays revealed that this mutant lacks ATP-binding activity. Overexpression of wild-type STCH sensitized cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death, whereas del223V-226L mutant did not show any effect. These results suggest that STCH has a role in cell survival via modulation of the TRAIL-mediated cell death pathway.

Association of Polycomb group SUZ12 with WD-repeat protein MEP50 that binds to histone H2A selectively in vitro.

SUZ12 is a Polycomb group protein that forms Polycomb repressive complexes (PRC2/3) together with EED and histone methyltransferase EZH2. Although the essential role of SUZ12 in regulating the activity of the PRC2/3 complexes has been demonstrated, additional function of this protein was suggested. Here, we show that SUZ12 interacts with WD-repeat protein MEP50 in vitro and in vivo. We show that the MEP50 binds histone H2A selectively among core histones, and mediates transcriptional repression of protein arginine methyltransferase PRMT5, which is known to methylate H2A and H4. These results suggest that SUZ12 might have a role in transcriptional regulation through physical interaction with MEP50 that can be an adaptor between PRMT5 and its substrate H2A.

Self-interaction of heterochromatin protein 1 is required for direct binding to histone methyltransferase, SUV39H1.

Heterochromatin protein 1 (HP1) binds to the nucleosome via a methylated lysine residue 9 of histone H3 which is catalyzed by a histone methyltransferase such as SUV39H1. Although co-localization of HP1 and SUV39H1 has been evident in immunostaining and immunoprecipitation experiments, direct protein-protein interactions have remained to be characterized. We examined interactions between mouse HP1 alpha (mHP1 alpha) and SUV39H1 in yeast and in vitro. A yeast two-hybrid and a glutathione S-transferase pull-down study indicated that the chromo shadow domain of mHP1 alpha directly interacts with the N-terminal 39 amino acid stretch of SUV39H1. The IY165/168EE mutation in the chromo shadow domain of mHP1 alpha abrogated a self-interaction and this mutant did not interact with SUV39H1. The 13-mer peptide containing a consensus sequence for binding to the dimer surface formed by the chromo shadow domains inhibited interaction between mHP1 alpha and SUV39H1. It seems that self-interaction through the chromo shadow domain of HP1 is crucial for recruitment of SUV39H1 onto nucleosomes.

Polycomb group suppressor of zeste 12 links heterochromatin protein 1alpha and enhancer of zeste 2.

Drosophila suppressor of zeste 12 (Su(z)12) is a Polycomb group (PcG) transcriptional repressor and is present in E(z)-ESC, a multiprotein complex with methylation activity specific for lysine 9 and 27 of histone H3. Although PcG- and heterochromatin-mediated gene silencing have been considered distinct, mutant flies of Su(z)12 showed not only homeotic transformation but also position effect variegation. We now report that the mammalian SU(Z)12 directly interacts with heterochromatin protein 1alpha (HP1alpha) and PcG enhancer of zeste 2 (EZH2), the mammalian counterpart of E(z), in vitro and in vivo. Two distinct domains in SU(Z)12 are involved in these interactions, the region between the zinc finger motif and the VEFS (VRN2-EMF2-FIS2-Su(z)12) box for HP1alpha (amino acid residues 479-536) and the VEFS box for EZH2 (amino acid residues 600-639), which are not mutually exclusive. Interestingly this region of the VEFS box has been shown to be critical for the phenotype of the Su(z)12 mutant fly. In addition SU(Z)12 represses transcription activity in the presence of HP1alpha in a reporter assay. These results provide a molecular explanation for the functional link of these epigenetic silencing processes mediated by Su(z)12.