Desmin mutation responsible for idiopathic dilated cardiomyopathy

BACKGROUND

Idiopathic dilated cardiomyopathy, of which approximately 20% of cases are familial (FDCM), is a primary myocardial disorder characterized by ventricular dilatation and impaired systolic function. It is a common cause of heart failure and the need for cardiac transplantation. Although 6 chromosomal loci responsible for autosomal dominant FDCM have been mapped by linkage analysis, none of these genes have been identified. By use of the candidate-gene approach, actin was identified recently as being responsible for dilated cardiomyopathy. Considerable evidence suggests desmin, a muscle-specific intermediate filament, plays a significant role in cardiac growth and development.

METHODS AND RESULTS

To determine whether a defect of desmin induces dilated cardiomyopathy, 44 probands with FDCM underwent clinical evaluation and DNA analysis. Diagnostic criteria, detected by echocardiography, consisted of ventricular dimension of >/=2.7 cm/m(2) with an ejection fraction </=50% in the absence of other potential causes. After amplification by polymerase chain reaction, the exons of the desmin gene were sequenced. A missense desmin mutation, Ile451Met, which cosegregates with FDCM without clinically evident skeletal muscle abnormalities, was identified in a 4-generation family but was not detected in 460 unrelated healthy individuals.

CONCLUSIONS

A novel missense mutation of desmin, Ile451Met, was identified as the genetic cause of idiopathic dilated cardiomyopathy. This finding is of particular significance because this is the first mutation detected in the desmin tail domain, and the function of the desmin tail remains unknown. Because this mutation leads to a restricted cardiac phenotype in the family studied in the present report, it suggests that the tail of desmin plays an important functional role in cardiac tissue.

Enhanced proportion of small adipose cells in insulin-resistant vs insulin-sensitive obese individuals implicates impaired adipogenesis

AIMS/HYPOTHESIS

The biological mechanism by which obesity predisposes to insulin resistance is unclear. One hypothesis is that larger adipose cells disturb metabolism via increased lipolysis. While studies have demonstrated that cell size increases in proportion to BMI, it has not been clearly shown that adipose cell size, independent of BMI, is associated with insulin resistance. The aim of this study was to test this widely held assumption by comparing adipose cell size distribution in 28 equally obese, otherwise healthy individuals who represented extreme ends of the spectrum of insulin sensitivity, as defined by the modified insulin suppression test.

SUBJECTS AND METHODS

Subcutaneous periumbilical adipose tissue biopsy samples were fixed in osmium tetroxide and passed through the Beckman Coulter Multisizer to obtain cell size distributions. Insulin sensitivity was quantified by the modified insulin suppression test. Quantitative real-time PCR for adipose cell differentiation genes was performed for 11 subjects.

RESULTS

All individuals exhibited a bimodal cell size distribution. Contrary to expectations, the mean diameter of the larger cells was not significantly different between the insulin-sensitive and insulin-resistant individuals. Moreover, insulin resistance was associated with a higher ratio of small to large cells (1.66 +/- 1.03 vs 0.94 +/- 0.50, p = 0.01). Similar cell size distributions were observed for isolated adipose cells. The real-time PCR results showed two- to threefold lower expression of genes encoding markers of adipose cell differentiation (peroxisome proliferator-activated receptor gamma1 [PPARgamma1], PPARgamma2, GLUT4, adiponectin, sterol receptor element binding protein 1c) in insulin-resistant compared with insulin-sensitive individuals.

CONCLUSIONS/INTERPRETATION

These results suggest that after controlling for obesity, insulin resistance is associated with an expanded population of small adipose cells and decreased expression of differentiation markers, suggesting that impairment in adipose cell differentiation may contribute to obesity-associated insulin resistance.

Global curvature, thickness, and the ideal shapes of knots

The global radius of curvature of a space curve is introduced. This function is related to, but distinct from, the standard local radius of curvature and is connected to various physically appealing properties of a curve. In particular, the global radius of curvature function provides a concise characterization of the thickness of a curve, and of certain ideal shapes of knots as have been investigated within the context of DNA.

Localization of a gene responsible for arrhythmogenic right ventricular dysplasia to chromosome 3p23

BACKGROUND

Arrhythmogenic right ventricular dysplasia (ARVD), a familial cardiomyopathy occurring with a prevalence of 1 in 5000, is characterized by replacement of myocytes with fatty and fibrous tissue. Clinical manifestations include structural and functional abnormalities of the right ventricle and arrhythmias, leading to a sudden death rate of 2.5% per year. Four loci have been mapped, but no gene has been identified as yet.

METHODS AND RESULTS

We identified a large family of >200 members with ARVD segregating as an autosomal dominant trait affecting 10 living individuals. The diagnosis of ARVD was based on international diagnostic criteria including history, physical examination, ECG, echocardiogram, right ventricular angiogram, endomyocardial biopsy, and 24-hour ambulatory ECG. Blood was collected for DNA from 149 family members. Analysis of 257 polymorphic microsatellite markers by genetic linkage excluded previously known loci for ARVD and identified a novel locus at 3p23. Analysis of an additional 20 markers further defined the region. A peak logarithm of the odds score of 6.91 was obtained with marker D3S3613 at theta=0% recombination. Haplotype analysis identified a shared region between markers D3S3610 and D3S3659 of 9. 3 cM.

CONCLUSIONS

A novel locus for ARVD has been mapped to 3p23 and the region narrowed to 9.3 cM. Identification of the gene will allow genetic screening and a specific diagnosis for a disease with protean nonspecific findings. It should also provide insight fundamental to understanding cardiac chamber-specific gene expression and/or the mechanism of myocyte apoptosis observed in this disease.

Budesonide enema in pouchitis--a double-blind, double-dummy, controlled trial

BACKGROUND

Pouchitis has been suggested to be a recurrence of ulcerative colitis in a colon-like mucosa. Topical steroids are a valid therapeutic alternative for distal forms of ulcerative colitis.

AIM

To investigate the efficacy and tolerability of budesonide enema in the treatment of pouchitis compared with oral metronidazole.

MATERIALS AND METHODS

Twenty-six patients with an active episode of pouchitis (defined as a pouchitis disease activity index score >or= 7) and no treatment during the previous month were randomized to receive either budesonide enema (2 mg/100 mL at bedtime) plus placebo tablets or oral metronidazole (0.5 g b.d.) plus placebo enema in a prospective, double-blind, double-dummy, 6-week, controlled trial.

RESULTS

Based on the intention-to-treat principle, we detected a significant improvement in disease activity at the end of the first week with both drugs (P < 0.01). After that, improvement was moderated until stabilization at 4 weeks in both treatments. The per protocol analysis showed that both drugs had similar efficacy in terms of disease activity, clinical and endoscopic findings. Fifty-eight per cent and 50% of patients improved (decrease in pouchitis disease activity index >or= 3) with budesonide enema and metronidazole, respectively (odds ratio, 1.4; confidence interval, 0.2-8.9). Adverse effects were observed in 57% of patients given metronidazole and in 25% of patients given budesonide.

CONCLUSIONS

Budesonide enemas are an alternative treatment for active pouchitis, with similar efficacy but better tolerability than oral metronidazole.

The locus of a novel gene responsible for arrhythmogenic right-ventricular dysplasia characterized by early onset and high penetrance maps to chromosome 10p12-p14

Arrhythmogenic right-ventricular dysplasia (ARVD), a cardiomyopathy inherited as an autosomal-dominant disease, is characterized by fibro-fatty infiltration of the right-ventricular myocardium. Four loci for ARVD have been mapped in the Italian population, and recently the first locus was mapped in inhabitants of North America. None of the genes have been identified. We have now identified another North American family with early onset of ARVD and high penetrance. All of the children with the disease haplotype had pathological or clinical evidence of the disease at age <10 years. The family spans five generations, having 10 living and 2 dead affected individuals, with ARVD segregating as an autosomal-dominant disorder. Genetic linkage analysis excluded known loci, and a novel locus was identified on chromosome 10p12-p14. A peak two-point LOD score of 3.92 was obtained with marker D10S1664, at a recombination fraction of 0. Additional genotyping and haplotype analysis identified a shared region of 10.6 cM between marker D10S547 and D10S1653. Thus, a novel gene responsible for ARVD resides on the short arm of chromosome 10. This disease is intriguing, since it initiates exclusively in the right ventricle and exhibits pathological features of apoptosis. Chromosomal localization of the ARVD gene is the first step in identification of the genetic defect and the unraveling of the molecular basis responsible for the pathogenesis of the disease.

Novel cardiac troponin T mutation as a cause of familial dilated cardiomyopathy

BACKGROUND

Familial dilated cardiomyopathy (FDCM) and hypertrophic cardiomyopathy (FHCM) are the 2 most common forms of primary cardiac muscle diseases. Studies indicate that mutations in sarcomeric proteins are responsible for FHCM and suggest that mutations in cytoskeletal proteins cause FDCM. Evidence is evolving, however, that such conclusions are premature.

METHODS AND RESULTS

A novel missense mutation in the cardiac troponin T gene was identified by direct sequencing and confirmed by endonuclease restriction analysis in a large family with FDCM that we had previously mapped to chromosome 1q32. The mutation substitutes tryptophan for a highly conserved amino acid, arginine, at amino acid residue 141 (Arg141Trp). The mutation occurs within the tropomyosin-binding domain of cardiac troponin T and alters the charge of the residue. This mutation cosegregates with the disease, being present in all 14 living affected individuals. The mutation was not found in 100 normal control subjects. Clinical features were congestive heart failure with premature deaths. The age of onset and severity of the disease are highly variable, with incomplete penetrance. Because 15 mutations in troponin T are known to cause FHCM, 219 probands with FHCM were screened, and none had the mutation.

CONCLUSIONS

Thus, the novel cardiac troponin T mutation Arg141Trp is responsible for FDCM in our family. Because several mutations in troponin T have already been recognized to be responsible for FHCM, it appears that the phenotype, whether it be hypertrophy or dilatation, is determined by the specific mutation rather than the gene.

On the parameterization of rigid base and basepair models of DNA from molecular dynamics simulations

A method is described to extract a complete set of sequence-dependent material parameters for rigid base and basepair models of DNA in solution from atomistic molecular dynamics simulations. The method is properly consistent with equilibrium statistical mechanics, leads to effective shape, stiffness and mass parameters, and employs special procedures for treating spontaneous torsion angle flips and H-bond breaks, both of which can have a significant effect on the results. The method is accompanied by various analytical consistency checks that can be used to assess the equilibration of statistical averages, and different modeling assumptions pertaining to the rigidity of the bases and basepairs and the locality of the quadratic internal energy. The practicability of the approach is verified by estimating complete parameter sets for the 16-basepair palindromic oligomer G(TA)(7)C simulated in explicit water and counterions. Our results indicate that the method is capable of resolving sequence-dependent variations in each of the material parameters. Moreover, they show that the assumptions of rigidity and locality hold rather well for the base model, but not for the basepair model. For the latter, it is shown that the non-local nature of the internal energy can be understood in terms of a certain compatibility relation involving Schur complements.

Effect of sex steroids on peak bone density of growing rabbits

To determine the effect of sex hormones on bone density (BD) during growth, longitudinal quantitative computed tomography (QCT) measurements were obtained in growing, castrated New Zealand White rabbits following administration of normal saline, testosterone, or estrogen from 6 wk of age until the time of skeletal maturity. Vertebral QCT densities increased during growth, were highest at the time of epiphyseal closure, and were significantly greater (P less than 0.001) in hormone-treated animals. In vivo QCT measurements in 12 vertebraes correlated strongly (r = 0.92) with percentage of calcium per weight assessed in vitro by neutron activation analysis.

Use of mental health services by formerly homeless adults residing in group and independent housing

OBJECTIVE

The study examined patterns of mental health service use among 112 formerly homeless mentally ill adults to determine whether clients in a staffed group living situation would need fewer types of services or lesser amounts of some services than those living independently in single apartments.

METHODS

Clients in the Boston McKinney demonstration project were randomly assigned to two housing types: individual apartments or a group living situation designed to teach residents to manage the house and their own affairs with minimal staff presence. The types and amounts of services these clients used during an 18-month period were documented and compared.

RESULTS

Service use by all clients was heavy, especially use of inpatient psychiatric services. It did not differ by housing type. The large majority of clients in both housing types were able to remain housed and avoid homelessness. Clients who did not stay in assigned housing for the duration of the study had higher levels of inpatient service use, including detoxification and substance abuse treatment.

CONCLUSIONS

When homeless mentally ill adults are provided permanent housing and accessible mental health treatment and specialized social services, they are likely to avoid unstable housing patterns, which are associated with higher use of inpatient services.

Is the frequency of multiple sclerosis increasing in Mexico?

Multiple sclerosis has steadily increased in Mexican mestizos from an apparently rare disorder in the 1970s to the second most frequent cause of admission to a neurology ward in the 1990s. Most patients belonged to high socioeconomic and educational groups. Familial incidence was low. Age at onset was younger than in other series and long term disability was milder than in patients from countries in which the disease is apparently more prevalent.

cgDNA: a software package for the prediction of sequence-dependent coarse-grain free energies of B-form DNA

cgDNA is a package for the prediction of sequence-dependent configuration-space free energies for B-form DNA at the coarse-grain level of rigid bases. For a fragment of any given length and sequence, cgDNA calculates the configuration of the associated free energy minimizer, i.e. the relative positions and orientations of each base, along with a stiffness matrix, which together govern differences in free energies. The model predicts non-local (i.e. beyond base-pair step) sequence dependence of the free energy minimizer. Configurations can be input or output in either the Curves+ definition of the usual helical DNA structural variables, or as a PDB file of coordinates of base atoms. We illustrate the cgDNA package by comparing predictions of free energy minimizers from (a) the cgDNA model, (b) time-averaged atomistic molecular dynamics (or MD) simulations, and (c) NMR or X-ray experimental observation, for (i) the Dickerson–Drew dodecamer and (ii) three oligomers containing A-tracts. The cgDNA predictions are rather close to those of the MD simulations, but many orders of magnitude faster to compute. Both the cgDNA and MD predictions are in reasonable agreement with the available experimental data. Our conclusion is that cgDNA can serve as a highly efficient tool for studying structural variations in B-form DNA over a wide range of sequences.

Changes in doxorubicin distribution and toxicity in mice pretreated with the cyclosporin analogue SDZ PSC 833

SDZ PSC 833 (PSC 833) is a cyclosporin A analogue that is under clinical investigation in combination with doxorubicin (Dx) or other anticancer agents as a type-1 multidrug resistance (MDR-1)-reversing agent. The present study was focused on the effects of PSC 833 on the distribution and toxicity of Dx in non-tumor-bearing CDF1 male mice. Mice were given PSC 833 i.p. at 30 min before i.v. Dx treatment. Dx levels were determined by a high-performance liquid chromatography (HPLC) assay at different times during a 72-h period following Dx treatment in the serum, heart, intestine, liver, kidney, and adrenals of mice. In all tissues, Dx area under the concentration-time curve (AUC) values were much greater in mice receiving 10 mg/kg Dx in combination with 12.5 or 25 mg/kg PSC 833 than in mice receiving Dx alone. The highest increase in Dx concentrations was found in the intestine, liver, kidney, and adrenals. Lower, albeit significant, differences were found in the heart. PSC 833 did not appear to influence either urinary or fecal Dx elimination or Dx metabolism to a great extent. Doses of PSC 833 devoid of any toxicity potentiated the acute and delayed toxicity of Dx dramatically. The mechanism responsible for this enhanced toxicity has not yet been elucidated but is likely to be related to an increased tissue retention of Dx due to inhibition of the P-glycoprotein (Pgp) pump by PSC 833, as has recently been proposed for cyclosporin A.

Human protein tyrosine phosphatase-like gene: expression profile, genomic structure, and mutation analysis in families with ARVD

The mouse protein tyrosine phosphatase-like gene (Ptpla) was recently cloned and data suggested that it plays a role in myogenesis and cardiogenesis. The human homologue (PTPLA) was mapped to chromosome 10p13-14, a region where we have mapped a locus responsible for arrhythmogenic right ventricular dysplasia (ARVD). As a positional candidate gene, we characterized PTPLA by determining its tissue expression, its genomic structure, and we also screened for mutations in the ARVD patients. Northern analysis demonstrated PTPLA is preferentially expressed in both adult and fetal heart. A much lower expression was detected in skeletal and smooth muscle tissues. Virtually no expression was observed in other tissues. The protein-encoding sequences of PTPLA consist of seven exons. A sequence variation (Lys64Gln) was found in all the affecteds in a large ARVD family. However, the same variant was also detected in normal control subjects (three alleles/100 chromosomes). Thus, the variant (Lys64Gln) is not responsible for ARVD in our family and is a benign polymorphism. Nevertheless, its tissue-specific expression in the developing and adult heart suggest PTPLA has a role in regulating cardiac development, differentiation, or other cellular events. The genomic structure and intragenic polymorphism of PTPLA should be useful for further clinical and genetic studies such as gene targeting of PTPLA.

Comparative efficacy of chloramphenicol, ampicillin, and co-trimoxazole in the treatment of typhoid fever

Two clinical trials were conducted to compare the efficacy of 3 antimicrobial agents often recommended for the treatment of typhoid fever. Chloramphenicol was more effective than parenteral ampicillin or oral co-trimoxazole (trimethaprim/sulphamethoxazole) in reducing the duration of fever. Oral chloramphenicol was more effective than parenteral chloramphenicol probably because oral doses resulted in higher blood concentrations of the drug. However, parenteral chloramphenicol was given during the initial period of acute illness, without loss of efficacy.

Immature teratomas: identification of patients at risk for malignant recurrence

We investigated the significance of immature elements in an otherwise benign teratoma in 28 patients with immature teratomas diagnosed and treated at the Childrens Hospital of Los Angeles from 1941 to 1986. Different characteristics, including age, sex, primary tumor site, type of surgery (complete resection vs. partial resection or biopsy), and preoperative levels of alpha-fetoprotein (AFP) were analyzed to evaluate their association with risk of subsequent local malignant recurrence. After a median follow-up of 6 years, 21 patients are alive with no recurrence of the tumor (72% event-free survival). One patient died from infection after surgery and six patients had local malignant tumor recurrence within 1 year from diagnosis. Of the 28 patients, 12 had AFP levels measured at diagnosis. Eight patients had normal levels with no further evidence of tumor recurrence, and four had elevated levels with three tumor recurrences. Our experience demonstrates that only at the time of diagnosis do AFP levels correlate with a subsequent malignant behavior of these tumors (P = .004). Those patients with immature teratomas and elevated AFP levels at diagnosis should receive adjuvant chemotherapy after the initial surgical resection.

Housing costs for adults who are mentally ill and formerly homeless

The goal of this study was to evaluate the costs, under two different housing conditions, to the state mental health agency of caring for adults who are homeless and mentally ill. One hundred and twelve clients of the Massachusetts Department of Mental Health, living in psychiatric shelters, were randomly assigned to one of two housing types: Evolving Consumer Households or Independent Living apartments. For the next 18 months each client was followed so that the cost of treatment, case management, and housing could be collected and compared. The authors found that treatment and case management costs did not vary by housing type, but housing costs were significantly higher for those assigned to Evolving Consumer Households. Regardless of original housing assignment, treatment costs were lower for clients who remained where they were originally placed. The authors conclude that providing support for clients that increases housing stability reduces their need for treatment and that independent living arrangements may be a more cost-effective policy choice.

Emergence of KPC-producing Klebsiella pneumoniae in Uruguay: infection control and molecular characterization

We describe the first outbreak of Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-KP), the infection control measures adopted and the shift in resistance patterns of isolates during antibiotic treatment. The ST258 KPC-KP strain exhibited a multiresistant antibiotic phenotype including co-resistance to gentamycin, colistin and tigecycline intermediate susceptibility. Isolates before and after treatment had different behaviour concerning their antibiotic susceptibility and the population analysis profile study. A progressive increase in the aminoglycosides (acquiring amicacin resistance) and β-lactam MICs, and a decreased susceptibility to fosfomycin was observed throughout the administration of combined antimicrobial regimens including meropenem. A high meropenem resistance KPC-KP homogeneous population (MIC 256 Jg/mL), could arise from the meropenem heterogeneous low-level resistance KPC-KP population (MIC 8 Jg/mL), by the selective pressure of the prolonged meropenem therapy. The kpc gene was inserted in a Tn4401 isoform a, and no transconjugants were detected. The core measures adopted were successful to prevent evolution towards resistance dissemination.

Efficacy of fine-needle aspiration biopsy of thyroid nodules: experience of a Mexican institution

In most centers only selected patients with high risk thyroid nodules undergo thyroid surgery, and fine needle aspiration biopsy (FNA) is used to select patients for surgical treatment. The aim of the present study was to evaluate the impact of FNA on the management of thyroid nodules at our institution. A total of 872 patients who underwent FNA over a period of 7 years were retrospectively analyzed. There were 66 men and 806 women with a mean age of 40 +/- 15 years. Altogether 549 patients presented with a thyroid nodule and 323 with multinodular disease. The sensitivity and specificity of FNA were 90.0% and 99.8%, respectively. The positive and negative predictive values were 98% and 99%, respectively, and the accuracy was 99%. Our results are in agreement with those of other reports establishing that FNA of the thyroid is safe, reliable, and effective for differentiating benign from malignant nodules.

In vitro evaluation of G1: a novel antimicrobial compound

G1 (1-[5-bromofur-2-il]-2-bromo-2-nitroethene) is a novel antimicrobial compound developed in Cuba with reported broadspectrum activity against Gram-positive and -negative bacteria, yeasts and fungi. A compound of this nature may have considerable therapeutic potential. We tested the in vitro activity of this novel compound against 3595 organisms using microbroth dilution. The following are MIC50, MIC90 and range respectively for some of the microorganisms tested: E. coli 16, 16, 4 32; Klebsiella sp. 16, 16, 8 32; Citrobacter sp. 16, 16, 8 16; Enterobacter sp. 16, 16, 8-16; Proteus sp. 16, 16, 8-16; Coagulase-negative staphylococci 16, 32, 4-32; Enterococcus sp. 16, 32, 2-32; Staphylococcus aureus 8, 16, 4-16; Streptococcus agalactiae 4, 8, 4 8; Streptococcus pyogenes 4, 8, 0.25-16; Candida albicans 2, 2, 1-4; Candida tropicalis 4, 4, 2-4; Candida sp. 2,4, 1-4. MIC values appear lower for Gram-positive microorganisms and yeasts. G1 appears to be a novel antimicrobial agent with broad spectrum activity against bacterial and fungal pathogens. Defining the activity of this compound against multi-resistant bacteria is a priority.

Identification and characterization of a novel gene (C4orf5) located on human chromosome 4q with specific expression in cardiac and skeletal muscle

The loci of several genes responsible for arrhythmogenic right ventricular dysplasia (ARVD) have been mapped. Since ARVD involves the right ventricle, we sought candidate genes preferentially expressed in the right ventricle utilizing differential display polymerase chain reaction (PCR) on mRNA from the chambers of an adult human heart. PCR products were cloned, sequenced, and used to screen an adult heart cDNA library. A novel 1.3-kb cDNA (HGMW-approved symbol C4orf5) with an open reading frame of 795 bp was identified. A probe designed from the 3' untranslated region of the 1.3-kb cDNA was hybridized to the 1.3-kb transcript and an alternatively spliced 2.5-kb transcript in the heart and skeletal muscle RNA lanes on a multitissue Northern blot. Analysis of a 39-kb partial genomic sequence identified three intronic splice sites in the 1.3-kb transcript. The gene was mapped to human chromosome 4q26-q27. Computer-based analysis indicated that this gene is novel with no known function.

Advanced UV/H₂O₂ oxidation of deca-bromo diphenyl ether in sediments

Removal of BDE-209 from contaminated sediments by UV/H2O2 treatment was investigated under different reaction conditions (different UV irradiance and H2O2 concentrations). After 10h of UV/H2O2 treatment, 90% of BDE-209 was removed with a half-life time (t1/2) of 3.5h and a kinetic constant (k) of 0.22 h(-1). Possible formation of OH-PBDEs and debrominated polybromodiphenyl ethers was investigated by GC-MS and LC-MS/MS. None of the abovementioned BDE-209 by-products was found after 2.5, 5.5 and 10h of UV/H2O2 treatment. Toxicity experiments carried out with zebrafish embryos exposed to the sediment before and after the UV/H2O2 treatment did not show any morphological or behavioural alterations, suggesting that no putative debrominated or oxidation products were originated by the treatment in concentrations high enough to elicit significant toxic effects in zebrafish embryos.

Molecular cloning, expression analysis, and chromosome mapping of WDR6, a novel human WD-repeat gene

The WD-repeat proteins are found in all eukaryotes and play an important role in the regulation of a wide variety of cellular functions such as signal transduction, transcription, and proliferation. Here we report on the cloning and characterization of a novel human WD-repeat gene, WDR6, which encodes a protein of 1121 amino acids and contains 11 WD-repeat units. WDR6 is unique since its 11 WD repeats are clustered into two distinct groups separated by a putative transmembrane domain. The WDR6 gene was mapped to chromosome 15q21 by fluorescence in situ hybridization. Northern analysis demonstrated that WDR6 is ubiquitously expressed in human adult and fetal tissues. WDR6 is not homologous to any previously identified human WD-repeat genes including WDR1 through WDR5. However, it was found to have significant sequence similarity with Arabidopsis thaliana hypothetical protein T7B11.12, yeast putative elongation factor G, and probable membrane protein YPL183c. All of them have been defined as WD-repeat proteins. Therefore, WDR6 is a novel protein and probably belongs to a highly conserved subfamily of WD-repeat proteins in which T7B11.12 and YPL183c are its distantly related members.