Targeted next-generation sequencing of 21 candidate genes in hereditary ovarian cancer patients from the Republic of Bashkortostan

About 5-10% of all ovarian cancer cases show familial clustering, and some 15-25% of familial ovarian cancer cases are mediated by high-penetrance mutations in the BRCA1 and BRCA2 genes. Only few other genes have been identified for familial ovarian cancer.We conducted targeted next-generation sequencing of the protein coding region of 21 candidate genes, including UTR regions, in genomic DNA samples of 48 patients with familial ovarian cancer from the Republic of Bashkortostan. We identified deleterious variants in BRCA1, BRCA2, CHEK2, MSH6 and NBN in a total of 16 patients (33%). The NBN truncating variant, p.W143X, had not previously been reported. Seven patients (15%) were carriers of the c.5266dupC variant in BRCA1, supporting a Russian origin of this founder allele. An additional 15 variants of uncertain clinical significance were observed. We conclude that our gene panel explains about one-third of familial ovarian cancer risk in the Republic of Bashkortostan.

FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium

BACKGROUND

Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium.

METHODS

Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression.

RESULTS

Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95% confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2.

CONCLUSION

Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2.

CD34(+) lineage specific donor cell chimerism for the diagnosis and treatment of impending relapse of AML or myelodysplastic syndrome after allo-SCT

After allo-SCT, analysis of CD34(+) lineage-specific donor cell chimerism (DCC) is a sensitive method for monitoring minimal residual disease in patients with AML or myelodysplastic syndrome (MDS) with CD34 expression. To substantiate evidence of whether immune interventions in patients with impending relapse, defined by incomplete lineage-specific DCC, may prevent hematological relapse, we performed a retrospective nested case control study. Unsorted and lineage-specific DCC were measured in 134 patients. Forty-three patients had an incomplete CD34(+)-DCC with no other evidence of relapse. After immediate tapering of immunosuppressive treatment (30 patients) and/or infusion of donor lymphocytes (10 patients), 21 patients remained in remission (conversion to complete lineage-specific DCC) and 22 relapsed. Relapse-free survival at 3 years of the 91 patients with stable DCC and of the 43 patients with incomplete DCC was 74% (95% confidence interval (CI), 64-83%) and 40% (95% CI, 24-58%), respectively. OS rates were 79% (95% CI, 70-88%) and 52% (95% CI, 35-69%), respectively. These results, with 49% of patients with impending relapse successfully treated with immune intervention, highly suggest that analysis of CD34(+)-DCC is an important tool for monitoring and the management of AML and MDS patients after allo-SCT.

A randomized, double-blind, multicenter, phase 2 study of a human monoclonal antibody to human αν integrins (intetumumab) in combination with docetaxel and prednisone for the first-line treatment of patients with metastatic castration-resistant prostate cancer

BACKGROUND

Intetumumab is a fully human mAb with antiangiogenic, antitumor properties which has shown potential therapeutic effect in castration-resistant prostate cancer (CRPC) patients.

PATIENTS AND METHODS

In a phase 2, randomized, double-blind, multicenter study, men with metastatic CRPC without prior systemic nonhormonal therapy were randomly assigned to 75-mg/m(2) docetaxel (Taxotere) and 5-mg prednisone plus placebo (N = 65) or 10-mg/kg intetumumab (N = 66) q3w. Placebo patients with progressive disease (PD) could cross over to 10-mg/kg intetumumab alone or with docetaxel. The primary end-point was progression-free survival (PFS). The secondary end-points included tumor response (complete response + partial response, CR + PR), prostate-specific antigen (PSA) response, and overall survival (OS).

RESULTS

All efficacy end-points favored placebo over intetumumab, including PFS (median 11.0 versus 7.6 months, P = 0.014), tumor response (20% versus 16%, P = 0.795), PSA response (68% versus 47%, P = 0.018), OS (median 20.6 versus 17.2 months, P = 0.163). Common all-grade adverse events (AEs) with placebo and intetumumab were alopecia (43% versus 26%); diarrhea, leukopenia (both 34% versus 27%); neutropenia (35% versus 23%). Grade ≥ 3 leukopenia (28% versus 17%) and neutropenia (26% versus 18%) occurred more often with placebo than with intetumumab. Intetumumab serum concentrations increased with repeated dosing and did not reach steady-state. Greater decreases in N-telopeptide of type I collagen (NTx), C-telopeptide (CTx) and CTCs occurred with intetumumab than with placebo.

CONCLUSION

The addition of intetumumab to docetaxel resulted in shorter PFS without additional toxicity among CRPC patients.

The annexin A5 protective shield model revisited: inherited carriage of the M2/ANXA5 haplotype in placenta as a predisposing factor for the development of obstetric antiphospholipid antibodies

This concise review summarizes the role of reduced ANXA5 expression through carriage of the M2/ANXA5 haplotype as a predisposing factor for various thrombophilia related obstetric complications. A revised ANXA5 'protective shield' model is emphasized, where decreased coverage resulting of M2 carriage at placental villi could lead directly to the observed pathology and on the other hand through exposing of antiphospholipid antigenic determinants, to the development of antiphospholipid antibodies (aPL). The aPL then can further disrupt the ANXA5 protective shield. Available and prospective evidence for this revised model is discussed. Conclusions are made about the diagnostic implications of M2 carriage and possible therapeutic strategies with anticoagulants, proven successful in obstetric antiphospholipid syndrome (APS) treatment.

First-line bevacizumab-containing therapy for breast cancer: results in patients aged≥70 years treated in the ATHENA study

BACKGROUND

There are limited data on treatment outcomes in the growing population of elderly patients with locally recurrent/metastatic breast cancer (LR/mBC). To gain information on first-line bevacizumab combined with chemotherapy in the elderly, we analyzed data from the ATHENA trial in routine oncology practice.

PATIENTS AND METHODS

Patients with human epidermal growth factor receptor-2-negative LR/mBC received first-line bevacizumab with standard chemotherapy until disease progression, unacceptable toxicity, or physician/patient decision. We carried out a subgroup analysis of safety and efficacy in patients aged≥70 years. Possible correlations between tolerability and baseline comorbidities or Eastern Cooperative Oncology Group status were explored.

RESULTS

Bevacizumab was combined with single-agent paclitaxel in 46% of older patients. Only hypertension and proteinuria were more common in older than in younger patients (grade≥3 hypertension: 6.9% versus 4.2%, respectively; grade≥3 proteinuria: 4.0% versus 1.5%, respectively). Grade≥3 arterial/venous thromboembolism occurred in 2.9% versus 3.3%, respectively. Further analysis revealed no relationship between baseline presence and severity of hypertension and risk of developing hypertension during bevacizumab-containing therapy. Median time to progression was 10.4 months in patients aged≥70 years.

CONCLUSIONS

These findings suggest that bevacizumab-containing therapy is tolerable and active in patients aged≥70 years. Hypertension was more common than in younger patients but was manageable. We find no evidence precluding the use of bevacizumab in older patients, including those with hypertension, although age may influence chemotherapy choice.

Inhibitor-immunology-study. Evaluation of inhibitor development in haemophilia B

The development of inhibitors in haemophilia B is one of the most important complications of replacement therapy, affecting mortality and morbidity. Inhibitor development is based on complex immunological factors, and to date, only little is known about its underlying mechanisms. Here, we present first results of the haemophilia B group of our Inhibitor-Immunology study.

PATIENTS, METHODS

So far we have analysed 15 patients with haemophilia B. Four of them developed a high titre inhibitor; the remaining 11 had no inhibitor. We evaluated 9 SNPs in 8 genes (CD40, CTLA-4 , IL-1β, IL-10, TLR2 , TLR4, TLR9, TNF-α). We compared the distribution of these alleles between inhibitor and non-inhibitor haemophilia B patients and between haemophilia B patients and a normal male control population. HLA typing was performed in all patients. Results, discussion: There appears to be a trend towards a skewed distribution of TLR 9, IL-10 and CTLA4 alleles in haemophilia B patients. Due to the limited number these differences are, however, not statistically significant. The t-test of all patients with inhibitor versus without inhibitor was significant for HLA-A*03 and DPB1*0401 and borderline for DRB1*0201.

Reduced allele specific annexin A5 mRNA levels in placentas carrying the M2/ANXA5 allele

We aimed to trace the allele specific expression of ANXA5 mRNA in placentas carrying the M2 haplotype, conferring higher recurrent pregnancy loss risk, in order to verify directly the role of M2 in the relevant organ. The M2 allele in heterozygous placentas results in an average of 42% reduced ANXA5 mRNA levels as compared to the normal allele. Protein levels in these samples show considerable variations, impossible for statistical interpretation. The M2 allele of ANXA5 can be linked to reduced mRNA levels in heterozygous placentas and could result in more confined protein levels (lowered expression dynamics) of annexin A5.

Inhibitor-Immunology-Study

The development of inhibitors in haemophilia B is one of the most important complications of replacement therapy, affecting mortality and morbidity. Inhibitor development is based on complex immunological factors, and to date, only little is known about its underlying mechanisms. Here, we present first results of the haemophilia B group of our Inhibitor-Immunology study.

Patients, methods So far we have analysed 15 patients with haemophilia B. Four of them developed a high titre inhibitor; the remaining 11 had no inhibitor. We evaluated 9 SNPs in 8 genes (CD40, CTLA-4, IL-1β, IL-10, TLR2, TLR4, TLR9, TNF-α). We compared the distribution of these alleles between inhibitor and non-inhibitor haemophilia B patients and between haemophilia B patients and a normal male control population. HLA typing was performed in all patients.

Results, discussion There appears to be a trend towards a skewed distribution of TLR 9, IL-10 and CTLA4 alleles in haemophilia B patients. Due to the limited number these differences are, however, not statistically significant.The t-test of all patients with inhibitor versus without inhibitor was significant for HLA-A*03 and DPB1*0401 and borderline for DRB1*0201.

Blood chimerism in a girl with Down syndrome and possible freemartin effect leading to aplasia of the Müllerian derivatives

Cytogenetic and molecular genetic analysis in a case of sex-discordant dizygotic twins revealed blood chimerism in the girl (46,XY in blood and 47,XX, + 21 in fibroblasts) caused by feto-fetal transfusion from her healthy brother. The girl presented with Down syndrome, aplasia of the uterus and the Fallopian tubes and normal female external genitalia. We propose that the lack of Müllerian structures is caused by the effect of the Müllerian inhibiting substance transferred from the male to the female twin in early pregnancy. This disorder of sex development is known as freemartin phenomenon in female cattle from sex-discordant twin pairs.

Syntaxin 3B is essential for the exocytosis of synaptic vesicles in ribbon synapses of the retina

Ribbon synapses of the vertebrate retina are specialized synapses that release neurotransmitter by synaptic vesicle exocytosis in a manner that is proportional to the level of depolarization of the cell. This release property is different from conventional neurons, in which the release of neurotransmitter occurs as a short-lived burst triggered by an action potential. Synaptic vesicle exocytosis is a calcium regulated process that is dependent on a set of interacting synaptic proteins that form the so-called SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) complex. Syntaxin 3B has been identified as a specialized SNARE molecule in ribbon synapses of the rodent retina. However, the best physiologically-characterized neuron that forms ribbon-style synapses is the rod-dominant or Mb1 bipolar cell of the goldfish retina. We report here the molecular characterization of syntaxin 3B from the goldfish retina. Using a combination of reverse transcription (RT) polymerase chain reaction (PCR) and immunostaining with a specific antibody, we show that syntaxin 3B is highly enriched in the plasma membrane of bipolar cell synaptic terminals of the goldfish retina. Using membrane capacitance measurements we demonstrate that a peptide derived from goldfish syntaxin 3B inhibits synaptic vesicle exocytosis. These experiments demonstrate that syntaxin 3B is an important factor for synaptic vesicle exocytosis in ribbon synapses of the vertebrate retina.

Combined homology modelling and evolutionary significance evaluation of missense mutations in blood clotting factor VIII to highlight aspects of structure and function

Most small lesions in the factor VIII (FVIII) gene that cause haemophilia A (HA) are single nucleotide substitutions resulting in amino acid replacing (missense) mutations and leading to various phenotypes, ranging from mild to severe. We took a combined approach of homology modelling and quantitative evaluation of evolutionary significance of amino acid replacing alterations using the Grantham Matrix Score (GMS) to assess their structural effects and significance of pathological expression. Comparative homology models of all amino acid substitutions summarized in the FVIII mutations database plus these identified and reported lately by us or by our collaborators were evaluated. Altogether 640 amino acid replacing mutations were scored for potential distant or local conformation changes, influence on the molecular stability and predicted contact residues, using available FVIII domain models. The average propensity to substitute amino acid residues by mutation was found comparable to the overall probability of de novo mutations. Missense changes reported with various HA phenotypes were all confirmed significant using GMS. The fraction of these, comprising residues apparently involved in intermolecular interactions, exceeds the average proportion of such residues for FVIII. Predicted contact residues changed through mutation were visualized on the surface of FVIII domains and their possible functional implications were verified from the literature and are discussed considering available structural information. Our predictive modelling adds on the current view of domain interface molecular contacts. This structural insight could aid in part to the design of engineered FVIII constructs for therapy, to possibly enhance their stability and prolong circulating lifetime.

Complete cystic fibrosis transmembrane conductance regulator gene sequencing in patients with idiopathic chronic pancreatitis and controls

BACKGROUND

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene-many of which cause cystic fibrosis-have also been reported in patients with chronic pancreatitis. The authors examine whether mild or severe CFTR mutations, homozygous or compound heterozygous CFTR mutations, or even simple cystic fibrosis carrier status alone increases the risk of developing pancreatitis.

METHODS

After exclusion of patients with trypsinogen (PRSS1) mutations, cystic fibrosis, or pulmonary disease, and with known risk factors for pancreatitis 67 patients with idiopathic chronic pancreatitis (ICP) from northwest Germany and 60 geographically and ethnically matched controls were recruited. The entire coding region of the CFTR gene was sequenced in all patients and controls. ICP patients were also analysed for serine protease inhibitor Kazal type 1 (SPINK1) gene mutations.

RESULTS

Abnormal CFTR alleles were found to be twice as frequent in ICP patients as in controls (25/134 v 11/120; p<0.05). Three of four severe CFTR mutations detected in patients were compound heterozygous with another abnormal CFTR allele, whereas among controls three severe CFTR mutations were found in heterozygous cystic fibrosis carriers. In ICP patients 19 uncommon/mild mutations, including combinations of the 5T allele with 12TG repeats, were identified compared with only five in controls (p = 0.012). Heterozygous SPINK1 mutations were detected in eight ICP patients (15% v 1% in controls) but only one also carried an additional mild CFTR mutation.

CONCLUSIONS

These data show that not only compound heterozygosity, but also cystic fibrosis carrier status for different types of CFTR mutations, including uncommon/mild mutations, significantly increase the risk of developing pancreatitis. Although 45% of the study's ICP patients carried predisposing genetic risk factors (for example, mutations in CFTR or SPINK1), the authors found no evidence that the risk conveyed by CFTR mutations depends on co-inherited SPINK1 mutations.

Angiotensin-converting enzyme activity and the ACE Alu polymorphism in autosomal dominant polycystic kidney disease

BACKGROUND

Previous studies concerning Alu I/D polymorphism in the ACE gene and ADPKD severity have used the Alu genotypes as a representative of the true biological variable, namely ACE activity. However, wide individual and ethnic differences in the proportion of variance in ACE activity explained by the I/D genotype may have confounded these studies. This investigation examines the association between ADPKD severity and ACE in terms of plasma enzyme activity and I/D genotypes in individuals from three different countries.

METHODS

Blood samples were collected from 307 ADPKD patients (116 Australian, 124 Bulgarian and 67 Polish) for determination of ACE activity levels and I/D genotypes. Chronic renal failure (CRF) was present in 117 patients and end-stage renal failure (ESRF) in 68 patients.

RESULTS

ACE activity was related to the I/D genotype, showing a dosage effect of the D allele (P=0.006). The proportion of variance due to the Alu polymorphism was 14%. No difference in ACE activity and I/D genotype distribution was found between patients with CRF versus normal renal function (P=0.494; P=0.576) or between those with ESRF versus those without ESRF (P=0.872; P=0.825). No effect of the I/D genotype on age at development and progression to renal failure (CRF; ESRF) was detected in the overall group, and in subgroups based on ethnic origin, linkage status and sex.

CONCLUSION

ACE is not likely to play a role as a determinant of ADPKD phenotype severity.

Seven novel and four recurrent point mutations in the factor VIII (F8C) gene

Haemophilia A is a X-linked bleeding disorder, caused by deficiency in the activity of coagulation factor VIII due to mutations in the corresponding gene. The most common defect in patients is an inversion of the factor VIII gene that accounts for nearly 45% of individuals with severe hemophilia A. Point mutations and small deletions/insertions are responsible for the majority of cases with moderate to mild clinical course and for half of the severe hemophilia A occurrences. The majority of these mutations are "private", because of the high mutation rate for this particular gene. We report on eleven pathological changes in the factor VIII sequence detected in male patients with haemophilia A or in female obligate carriers. Seven of these mutations are novel [E204N, E265X, M320T, F436C, S535C, N2129M and R2307P] and four have been previously identified [V162M, R527W, R1966X, and R2159C]. Genotype-phenotype correlations and computer prediction analysis on the effect of missense mutations on the secondary structure of the factor VIII protein are performed and the relationships evaluated.

Homologues to the first gene for autosomal dominant polycystic kidney disease are pseudogenes

PKD1 is the first gene identified to be causative for the condition of autosomal dominant polycystic kidney disease. There are several genes homologous to PKD1 that are located proximal to the master gene on the same chromosome. Two of these genes have been recently covered in a large sequencing work on chromosome 16, and their structure has been broadly analyzed. However, the major question whether homologous genes (HG) code for functionally active polypeptides has not been resolved so far. The current study identifies and partially characterizes four more homologues of PKD1, different from the previously published sequence, two of which were found by screening of a BAC library and the other two contained in available databases. Analysis of HG transcripts shows that they are not translated in the model cell line T98G. Taken together, these findings suggest that homologues to PKD1 form a family of pseudogenes.

Screening the 3' region of the polycystic kidney disease 1 (PKD1) gene in 41 Bulgarian and Australian kindreds reveals a prevalence of protein truncating mutations

Screening for disease-causing mutations in the unique region of the polycystic kidney disease 1 (PKD1) gene was performed in 41 unrelated individuals with autosomal dominant polycystic kidney disease. Exons 34-41 and 43-46 were assayed using PCR amplification and SSCP analysis followed by direct sequencing of amplicons presenting variant SSCP patterns. We have identified seven disease-causing mutations of which five are novel [c.10634-10656del; c.11587delG; IVS37-10C>A; c.11669-11674del; c.13069-13070ins39] and two have been reported previously [Q4010X; Q4041X]. Defects in this part of the gene thus account for 17% of our group of patients. Five of the seven sequence alterations detected are protein-truncating which is in agreement with mutation screening data for this part of the gene by other groups. The two other mutations are in-frame deletions or insertions which could destroy important functional properties of polycystin 1. These findings suggest that the first step toward cyst formation in PKD1 patients is the loss of one functional copy of polycystin 1, which indirectly supports the "two-hit" model of cystogenesis where a second somatic mutation inactivating the normal allele is necessary to occur for development of the disease condition.

Screening for mutations in the peripheral myelin genes PMP22, MPZ and Cx32 (GJB1) in russian charcot-marie-tooth neuropathy patients; irina V. Mersiyanova, sookhrat M. Ismailov, alexandr V. Polyakov, elena L. Dadali, valeriy P. Fedotov, eva nelis, ann Lofgren, vincent timmerman, christine van broeckhoven, and oleg V. Evgrafov (Article was originally published in human mutation 15:340-347, 2000)

The authors wish to correct a mistake which occurred in the reporting of one of the mutations. The mutation in Cx32 Met34Lys is wrongly described as 100A>G. The correct description of the mutation should be 101T>A (Met34Lys).

Location of mutations within the PKD2 gene influences clinical outcome

BACKGROUND

Since the cloning of the gene for autosomal dominant polycystic kidney disease type 2 (PKD2), approximately 40 different mutations of that gene have been reported to be associated with the disease. The relationship between the PKD2 genotype and phenotype, however, remains unclear.

METHODS

Detailed clinical information was collected for PKD2 families in which the underlying mutation had been identified. Logistic regression analysis was employed to assess the influence of age and sex on hypertension, hematuria, renal calculi, and urinary tract infections, and a clinical phenotype score was computed. Patients were then grouped according to the relative location of their mutation within the cDNA sequence, and differences in the mean phenotypic score between groups were tested for statistical significance by means of a multiple pairwise t-test.

RESULTS

While phenotypic scores for each mutational group revealed a considerable degree of intragroup variability, the variability in phenotypic scores was significantly higher between mutational groups than within groups. A group-wise comparison of the mean phenotypic scores confirmed the observation of significant nonlinear variation in disease severity, with high- and low-scoring mutational groups interspersed along the gene sequence.

CONCLUSION

The identification of groups of mutations in the PKD2 gene, which differ significantly with respect to clinical outcome, is to our knowledge the first description of a genotype/phenotype correlation in autosomal dominant polycystic kidney disease. It also provides evidence against complete loss of function of the mutant PKD2 gene product.

Comparison of phenotypes of polycystic kidney disease types 1 and 2. European PKD1-PKD2 Study Group

BACKGROUND

Although autosomal dominant polycystic kidney disease type 2 (PKD2) is known to have a milder clinical phenotype than PKD1, neither disorder has been compared with an unaffected control population in terms of survival. We report the findings of a multicentre survey that aimed to define more precisely the survival and clinical expression of PKD1 and PKD2.

METHODS

Clinical data from 333 people with PKD1 (31 families) were compared with data from 291 people with PKD2 (31 families) and 398 geographically matched controls. Survival analysis was used to compare age-at-event data. Differences in the prevalence of complications were assessed by logistic regression.

FINDINGS

Median age at death or onset of end-stage renal disease was 53.0 years (95% CI 51.2-54.8) in individuals with PKD1, 69.1 years (66.9-71.3) in those with PKD2, and 78.0 years (73.8-82.2) in controls. Women with PKD2 had a significantly longer median survival than men (71.0 [67.4-74.8] vs 67.3 [64.9-69.7] years), but no sex influence was apparent in PKD1. Age at presentation with kidney failure was later in PKD2 than in PKD1 (median age 74.0 [67.2-80.8] vs 54.3 [52.7-55.9] years). PKD2 patients were less likely to have hypertension (odds ratio 0.25 [95% CI 0.15-0.42]), a history of urinary-tract infection (0.50 [0.31-0.83]), or haematuria (0.59 [0.35-0.98]).

INTERPRETATION

Although PKD2 is clinically milder than PKD1, it has a deleterious impact on overall life expectancy and cannot be regarded as a benign disorder.

Characterization of the murine polycystic kidney disease (Pkd2) gene

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most frequent genetically transmitted disorders among Europeans with an attributed frequency of 0.1%. The two most common genetic determinants for ADPKD are the PKD1 and PKD2 genes. In this study we report the genomic structure and pattern of expression of the Pkd2 gene, the murine homolog of the human PKD2 gene. Pkd2 is localized on mouse Chromosome (Chr) 5 proximal to anchor marker D5Mit175, spans at least 35 kb of the mouse genome, and consists of 15 exons. Its translation product consists of 966 amino acids, and the peptide shows a 95% homology to human polycystin2. Functional domains are particularly well conserved in the mouse homolog. The expression of mouse polycystin2 in the developing embryo at day 12.5 post conception is localized in mesenchymally derived structures. In the adult mouse, the protein is mostly expressed in kidney, which suggests its functional relevance for this organ.

Comparison of conformation-sensitive gel electrophoresis and single-strand conformation polymorphism analysis for detection of mutations in the BRCA1 gene using optimized conformation analysis protocols

In order to develop a selective mutation screening strategy for BRCA1, one of the gene responsible for hereditary predisposition to breast cancer, we analysed by single-strand conformation polymorphism (SSCP) and conformation-sensitive gel electrophoresis (CSGE) a cohort of 20 Bulgarian breast cancer patients, prescreened for nonsense mutations by the protein truncation test. By assaying the complete coding sequence of the gene applying both methods, we were able to detect 12 sequence alterations: 11 nucleotide substitutions and one deletion. Two of the alterations are intronic polymorphisms, the rest are exon sequence variants. Of the 12 polymorphisms identified, 11 are described and one is new. All sequence changes were detected by CSGE and eight of them were also shown by SSCP analysis. There was no sequence alterations which could be detected by SSCP analysis only. We propose that because of the specificity of most sequence variants detected (nucleotide substitutions) and the comparatively high percentage of AT content of the BRCA1 gene (58.4%), CSGE turned out to be the more sensitive technique in our assay. This observation is in agreement with other accepted analysis strategies for BRCA1 and it may prove useful for mutation screening of AT-rich, multi-exon genes.

A spectrum of mutations in the second gene for autosomal dominant polycystic kidney disease (PKD2)

Recently the second gene for autosomal dominant polycystic kidney disease (ADPKD), located on chromosome 4q21-q22, has been cloned and characterized. The gene encodes an integral membrane protein, polycystin-2, that shows amino acid similarity to the PKD1 gene product and to the family of voltage-activated calcium (and sodium) channels. We have systematically screened the gene for mutations by single-strand conformation-polymorphism analysis in 35 families with the second type of ADPKD and have identified 20 mutations. So far, most mutations found seem to be unique and occur throughout the gene, without any evidence of clustering. In addition to small deletions, insertions, and substitutions leading to premature translation stops, one amino acid substitution and five possible splice-site mutations have been found. These findings suggest that the first step toward cyst formation in PKD2 patients is the loss of one functional copy of polycystin-2.

Developmental regulation of Zbu1, a DNA-binding member of the SWI2/SNF2 family

The SWI2/SNF2 gene family has been implicated in a wide variety of processes, involving regulation of DNA structure and chromatin configuration, mitotic chromosome segregation, and DNA repair. Here we report the characterization of the Zbu1 gene, also known as HIP116, located on human chromosome band 3q25, which encodes a DNA-binding member of this superfamily. Zbu1 was isolated in this study by its affinity for a site in the myosin light chain 1/3 enhancer. The protein has single-stranded DNA-dependent ATPase activity, includes seven helicase motifs, and a RING finger motif that is shared exclusively by the RAD5, spRAD8, and RAD16 family members. During mouse embryogenesis, Zbu1 transcripts are detected relatively late in fetal development and increase in neonatal stages, whereas the protein accumulates asynchronously in heart, skeletal muscle, and brain. In adult human tissues, alternatively spliced Zbu1 transcripts are ubiquitous with highest expression in these tissues. Gene expression is also dramatically induced in human tumor lines and in Li-Fraumeni fibroblast cultures, suggesting that it is aberrantly regulated in malignant cells. The developmental profile of Zbu1 gene expression and the association of the protein with a tissue-specific transcriptional regulatory element distinguish it from other members of the SWI2/SNF2 family and suggest novel roles for the Zbu1 gene product.