Localization of a gene for non-syndromic hearing loss (DFNA5) to chromosome 7p15

Insight into the structure, function and the tumor suppression effect of gasdermin E

Gasdermin E (GSDME), which is also known as DFNA5, was first identified as a deafness-related gene that is expressed in cochlear hair cells, and mutation of this gene causes autosomal dominant neurogenic hearing loss. Later studies revealed that GSDME is mostly expressed in the kidney, placenta, muscle and brain cells, but it is expressed at low levels in tumor cells. The GSDME gene encodes the GSDME protein, which is a member of the gasdermin (GSDM) family and has been shown to participate in the induction of apoptosis and pyroptosis. The current literature suggests that Caspase-3 and Granzyme B (Gzm B) can cleave GSDME to generate the active N-terminal fragment (GSDME-NT), which integrates with the cell membrane and forms pores in this membrane to induce pyroptosis. Furthermore, GSDME also forms pores in mitochondrial membranes to release apoptosis factors, such as cytochrome c (Cyt c) and high-temperature requirement protein A2 (HtrA2/Omi), and subsequently activates the intrinsic apoptosis pathway. In recent years, GSDME has been shown to exert tumor-suppressive effects, suggesting that it has potential therapeutic effects on tumors. In this review, we introduce the structure and function of GSDME and the mechanism by which it induces cell death, and we discuss its tumor suppressive effect.

Novel, pathogenic insertion variant of GSDME associates with autosomal dominant hearing loss in a large Chinese pedigree

Nonsyndromic hearing loss (NSHL) is a genetically diverse, highly heterogeneous condition characterised by deafness, and Gasdermin E (GSDME) variants have been identified as directly inducing autosomal dominant NSHL. While many NSHL cases associated with GSDME involve the skipping of exon 8, there is another, less understood pathogenic insertion variant specifically found in Chinese pedigrees that causes deafness, known as autosomal dominant 5 (DFNA5) hearing loss. In this study, we recruited a large Chinese pedigree, conducted whole-exome and Sanger sequencing to serve as a comprehensive clinical examination, and extracted genomic DNA samples for co-segregation analysis of the members. Conservation and expression analyses for GSDME were also conducted. Our clinical examinations revealed an autosomal dominant phenotype of hearing loss in the family. Genetic analysis identified a novel insertion variant in GSDME exon 8 (GSDME: NM_004403.3: c.1113_1114insGGGGTGCAGCTTACAGGGTGGGTGT: p. P372fs*36). This variant is segregated with the deafness phenotype of this pedigree. The GSDME gene was highly conserved in the different species we analysed, and its mRNA expression was ubiquitously low in different human tissues. In conclusion, we have successfully identified a novel pathogenic insertion variant of GSDME in a Chinese pedigree that causes deafness, shedding light on the genetic basis of hearing loss within this specific family. Our findings expand the spectrum of known variants associated with GSDME-related deafness and may further support both the underlying gain-of-function mechanism and functional associations of GSDME hearing loss variants.

Triggering pyroptosis enhances the antitumor efficacy of PARP inhibitors in prostate cancer

PURPOSE

PARP inhibitors have revolutionized the treatment landscape for advanced prostate cancer (PCa) patients who harboring mutations in homologous recombination repair (HRR) genes. However, the molecular mechanisms underlying PARP inhibitors function beyond DNA damage repair pathways remain elusive, and identifying novel predictive targets that favorably respond to PARP inhibitors in PCa is an active area of research.

METHODS

The expression of GSDME in PCa cell lines and human PCa samples was determined by western blotting. Targeted bisulfite sequencing, gene enrichment analysis (GSEA), clone formation, construction of the stably transfected cell lines, lactate dehydrogenase (LDH) assay, western blotting as well as a mouse model of subcutaneous xenografts were used to investigate the role of GSDME in PCa. The combinational therapeutic effect of olaparib and decitabine was determined using both in vitro and in vivo experiments.

RESULTS

We have found low expression of GSDME in PCa. Interestingly, we demonstrated that GSDME activity is robustly induced in olaparib-treated cells undergoing pyroptosis, and that high methylation of the GSDME promoter dampens its activity in PCa cells. Intriguingly, genetically overexpressing GSDME does not inhibit tumor cell proliferation but instead confers sensitivity to olaparib. Furthermore, pharmacological treatment with the combination of olaparib and decitabine synergistically induces GSDME expression and cleavage through caspase-3 activation, thus promoting pyroptosis and enhancing anti-tumor response, ultimately resulting in tumor remission.

CONCLUSION

Our findings highlight a novel therapeutic strategy for enhancing the long-term response to olaparib beyond HRR-deficient tumors in PCa, underscoring the critical role of GSDME in regulating tumorigenesis.

Integrated analysis of diagnostic, prognostic value and potential drug treatment of GSDME in head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSC) poses a global health challenge. Effective biomarkers for early detection are necessary to improve the survival rate of HNSC patient. The purpose of this study was using integrated bioinformatic analysis to investigate the potential biological roles of GSDME in HNSC.

METHODS

The Gene Expression Omnibus (GEO) and Cancer Gnome Atlas (TCGA) databases were used to analyze the expression of GSDME in different cancer types. The correlation between GSDME expression and immune cell infiltration or immune checkpoint genes was examined by Spearman correlation analysis. DNA methylation analysis of the GSDME gene was conducted using the MethSurv database. Kaplan-Meier (K-M) survival curves, diagnostic receiver operating characteristic (ROC) curves, nomogram model, and Cox regression analysis were chosen to evaluate the diagnostic and prognostic predictive value of GSDME. Connectivity Map (Cmap) online platform, Protein Data Bank (PDB) database and Chem3D, AutoDock Tool and PyMol software were used to predict and visualize potential molecular drugs aimed for GSDME.

RESULTS

GSDME expression level in HNSC was significantly higher than in the controls (p < 0.001). Differentially expressed genes (DEGs) correlation with GSDME were enriched in the GO pathways, such as protein activation cascade, complement activation and classical pathway (p < 0.05). According to GSEA, GSDME-associated differentially expressed genes were significantly enriched in KRAS signaling pathway and cytokine signaling molecule (p < 0.05). There is a significant relation between GSDME expression and immune cell infiltration in HNSC tissues, as well as immune checkpoint genes expression (p < 0.001). DNA methylation status of cg17790129 CpG islands of GSDME gene is correlated with HNSC prognosis (p < 0.05). Based on Cox regression analysis of HNSC patients, GSDME as a potential risk gene has high correlation with overall survival (OS) and disease specific survival (DSS) (p < 0.05). In a ROC curve analysis, HNSC tissues were differentiated from adjacent peritumoral tissues based on GSDME expression levels (AUC = 0.928). Totally six potential drugs targeted for GSDME were screened and the molecular docking tests between GSDME protein and candidate drugs were conducted.

CONCLUSIONS

GSDME is a promising therapeutic target as well as a potential clinical biomarker in HNSC patients.

Promoting GSDME expression through DNA demethylation to increase chemosensitivity of breast cancer MCF-7 / Taxol cells

OBJECTIVE

Breast cancer is the most common and high-incidence cancer in women. It is mainly treated by surgery combined with chemoradiation. The main challenge in treating breast cancer patients is developing resistance to chemotherapeutics, so it is urgent to find potential strategies that can improve the chemotherapy effect of patients. In this study, we aimed to explore the role of GSDME methylation in the sensitivity of chemotherapy for breast cancer.

METHODS

Here, we identified breast cancer MCF-7 / Taxol cells models using quantitative real-time PCR (qRT-PCR), Western blotting (WB), and cell counting kit-8 (CCK-8) analyses. Epigenetic changes in it were detected by Methylated DNA immunoprecipitation-sequencing and methylation-specific PCR. The expression level of GSDME in breast cancer cells was observed by qPCR and WB analyses. CCK-8 and colony formation assay were used to detect cell proliferation. Finally, pyroptosis was detected by LDH assay, flow cytometry, and WB analyses.

RESULTS

Our results indicate that ABCB1 mRNA and p-GP expression are significantly increased in breast cancer MCF-7 / Taxol cells. GSDME enhancer methylation was found in drug-resistant cells and was associated with the down-regulation of GSDME expression. After treatment with decitabine (5-Aza-2'-deoxycytidine), the demethylation of GSDME induced the occurrence of pyroptosis and thereby inhibited the proliferation of MCF-7 / Taxol cells. We found that the upregulation of GSDME enhances the chemosensitivity of MCF-7 / Taxol cells to paclitaxel by inducing pyroptosis.

CONCLUSION

Taken together, we identified decitabine increases GSDME expression through DNA demethylation and induces pyroptosis, thus increasing the chemosensitivity of MCF-7 / Taxol cells to Taxol. Use of decitabine / GSDME / pyroptosis-based treatment strategies may be a new way to overcome the resistance of breast cancer to paclitaxel chemotherapy.

Mutation analysis of the GSDME gene in a Chinese family with non-syndromic hearing loss

Background

Hearing loss is considered one of the most common sensory nervous system defects, about 60% of which are caused by genetic factors. Mutations in the GSDME gene are responsible for post-lingual, progressive, autosomal dominant hearing loss. This study aimed to characterize the genetic mutations and clinical features of a Chinese GSDME family.

Methods

After clinical evaluations, high-throughput DNA sequencing was conducted using DNA samples from this family. Sanger sequencing was performed to verify the suspected variants. A detailed genotype and phenotype analysis were carried out. Gene set enrichment analysis (GSEA) was performed to identify the signaling pathway associated with GSDME expression.

Results

A known hotspot heterozygous splice-site variation (c.991-15_991_13delTTC) was identified and shown to segregate with the hearing loss phenotype in the family. This pathogenic splice-site variant results in skipping of exon 8. GSEA analysis identified changes in regulation of the cell cycle checkpoint, peroxisome, and amino acid metabolism signaling pathways.

Conclusions

We identified a reported mutation in the GSDME gene. Our findings support the 3 bp deletion (c.991-15_991-13del) was a hotspot variation, and it emerged as an essential contributor to autosomal dominant progressive hearing loss in East Asians. GSDME gene is closely associated with a range of signaling pathways. These characterized findings may provide new evidence for pathogenesis.

Role of gasdermin family proteins in the occurrence and progression of hepatocellular carcinoma

Primary liver cancer is the sixth most common cancer and the third leading cause of cancer mortality worldwide, hepatocellular carcinoma (HCC) is the most common type of liver cancer, accounting for 75%–85% of cases. The occurrence and progression of HCC involve multiple events. Pyroptosis is a gasdermins mediated programmed cell death and is intricately associated with cancerogenesis, including HCC. This review mainly concerns the recent research advances of the gasdermin family members in HCC. The biological roles and specific expression patterns of the family members are discussed, especially those that are involved in the regulatory pathways in the occurrence and progression of HCC. We provide the latest progress into the distinct molecular mechanisms of gasdermin family members involved in the occurrence and development of HCC.

Pyroptosis and Its Role in the Modulation of Cancer Progression and Antitumor Immunity

Pyroptosis is a type of programmed cell death (PCD) accompanied by an inflammatory reaction and the rupture of a membrane. Pyroptosis is divided into a canonical pathway triggered by caspase-1, and a non-canonical pathway independent of caspase-1. More and more pyroptosis-related participants, pathways, and regulatory mechanisms have been exploited in recent years. Pyroptosis plays crucial roles in the initiation, progression, and metastasis of cancer and it affects the immunotherapeutic outcome by influencing immune cell infiltration as well. Extensive studies are required to elucidate the molecular mechanisms between pyroptosis and cancer. In this review, we introduce the discovery history of pyroptosis, delineate the signaling pathways of pyroptosis, and then make comparisons between pyroptosis and other types of PCD. Finally, we provide an overview of pyroptosis in different cancer types. With the progression in the field of pyroptosis, new therapeutic targets and strategies can be explored to combat cancer.

DFNA5 inhibits colorectal cancer proliferation by suppressing the mTORC1/2 signaling pathways via upregulation of DEPTOR

The human deafness, autosomal dominant 5 gene (DFNA5), a newly discovered executor of pyroptosis, has been strongly implicated in the tumorigenesis of several human cancers. However, an understanding of the functional role of DFNA5 in the development and progression of colorectal cancer (CRC) is limited. In this study, we demonstrated that DFNA5 was downregulated in CRC tissues. Ectopic expression of DFNA5 inhibited tumor cell growth in vitro, retarded tumor formation in vivo, and blocked a cell-cycle transition from the G0/G1 to the S phase, whereas a DFNA5 knockdown promoted cell proliferation. Western blotting showed that the levels of cell cycle-related proteins, including cyclin D1, cyclin E, CDK2, and p21, were accordingly altered upon DFNA5 overexpression or DFNA5 knockdown. Mechanistic studies indicated that DFNA5 exerted its tumor suppressor functions by antagonizing mTORC1/2 signaling via upregulation of DEPTOR. In addition, blockage of mTORC1/2 signaling by Torin-1 abolished the accelerative proliferation by DFNA5 knockdown. In conclusion, these results indicated that DFNA5 inhibits the proliferation and tumor formation of colon cancer cells by suppressing mTORC1/2 signaling.

A novel splice site variant c.1183 + 1 G > C in DFNA5 causing autosomal dominant nonsyndromic hearing loss in a Chinese family

BACKGROUND

The most frequent clinical presentation of autosomal dominant nonsyndromic hearing loss (ADNSHL) is bilateral, symmetrical, postlingual progressive sensorineural hearing loss, which begins with impairment at high frequencies and eventually progresses to hearing loss at all frequencies. Autosomal dominant deafness-5 (DFNA5) is a subtype of ADNSHL caused by heterozygous variants in the gasdermin E (GSDME, also known as DFNA5) gene.

METHODS

Deafness gene NGS panel analysis were performed on the proband of a six-generation Chinese family with hearing loss. The co-segregation analysis between the hearing loss and the novel variant was analyzed by Sanger sequencing and pure-tone audiometry. The minigene splicing assay was performed to evaluate the potential effect of the variant on messenger RNA splicing in vitro.

RESULTS

The family exhibited autosomal dominant, progressive, postlingual, nonsyndromic sensorineural hearing loss, which was similar to that of the previously reported DFNA5 families. A novel heterozygous splice site variant in GSDME gene intron 8 was identified, which co-segregated with the hearing loss phenotype of the family. The variant caused skipping of exon 8 in the mutant transcript, leading to the direct linking of exons 7 and 9.

CONCLUSIONS

We identified a novel GSDME splice site variant c.1183 + 1 G > C in an extended Chinese family, which led to the skipping of exon 8. The results extended the pathogenic variants spectrum of the GSDME gene, provided further support for the 'gain-of-function' mechanism of DFNA5, and afforded a molecular interpretation for these patients with ADNSHL.

Identification of a novel DFNA5 mutation, IVS7-2 a > G, in a Chinese family with non-syndromic sensorineural hearing loss

BACKGROUND

To date, seven DFNA5 mutations have been reported in families with autosomal dominant non-syndromic hearing loss worldwide. All the mutations cause exon 8 skipping at the mRNA level, that led to the protein truncated and the protein could exert a gain of ototoxic function.

OBJECTIVE

In this study, we found an autosomal-dominant non-syndromic hearing loss Chinese pedigree which spanned four generations and comprised 43 members. We want to identify the causative gene and mutation.

METHODS

Application of microsatellite markers on DFNA 23 loci preliminary screening of 25 genes, data were analyzed by linkage analysis.

RESULTS

We mapped the locus to the region between D7S629 and D7S516 (two-point lod-score of 5.39) with the application of 8 microsatellite markers. By direct sequencing of candidate genes in mapping region, we identified a novel missense mutation ivs7-2 A > G in DFNA5 gene, which was faithfully cosegregated with hearing loss in the family.

CONCLUSION AND SIGNIFICANCE

The missense mutation in intron 7 of DFNA5 causes skipping of exon 8, resulting in premature termination of the open reading frame. This type of mutation has repeatedly confirmed that it provides more evidence for the previous view and provides a more solid foundation for future research.

Gasdermin E: A Prospective Target for Therapy of Diseases

Gasdermin E (GSDME) is a member of the gasdermin protein family, which mediates programmed cell death including apoptosis and pyroptosis. Recently, it was suggested that GSDME is activated by chemotherapeutic drugs to stimulate pyroptosis of cancer cells and trigger anti-tumor immunity, which is identified as a tumor suppressor. However, GSDME-mediated pyroptosis contributes to normal tissue damage, leading to pathological inflammations. Inhibiting GSDME-mediated pyroptosis might be a potential target in ameliorating inflammatory diseases. Therefore, targeting GSDME is a promising option for the treatment of diseases in the future. In this review, we introduce the roles of GSDME-driven programmed cell death in different diseases and the potential targeted therapies of GSDME, so as to provide a foundation for future research.

Chemical Modulation of Gasdermin-Mediated Pyroptosis and Therapeutic Potential

Pyroptosis, a lytic form of programmed cell death, both stimulates effective immune responses and causes tissue damage. Gasdermin (GSDM) proteins are a family of pore-forming executors of pyroptosis. While the most-studied member, GSDMD, exerts critical functions in inflammasome biology, emerging evidence demonstrates potential broad relevance for GSDM-mediated pyroptosis across diverse pathologies. In this review, we describe GSDM biology, outline conditions where inflammasomes and GSDM-mediated pyroptosis represent rational therapeutic targets, and delineate strategies to manipulate these central immunologic processes for the treatment of human disease.

A pan-cancer analysis of molecular characteristics and oncogenic role of gasdermins

Background

The gasdermins (GSDMs) family is proposed to be pore-forming effector proteins that cause cell membrane permeabilization and pyroptosis. Despite our increasing knowledge of GSDMD, GSDME and GSDMB, the biological functions and the regulation of GSDM expression and activation remain elusive for most GSDMs. In this study, we analyzed the molecular characteristics and oncogenic role of GSDM family genes systematically.

Methods

TCGA, CCLE, cBioPortal, GEPIA, CellMiner and BioGRID databases were utilized in this study. Immunohistochemical analysis and a series of in vitro experiments were conducted.

Results

We found that, in cancer, GSDM genes and their expressions extensively changed, which were associated with patient survival. The expression of GSDMs was widely associated with cancer-related pathways, drug resistance, immune subtypes, tumor microenvironment and cancer cell stemness. However, an intra- and inter-cancer heterogeneity was discovered regarding the corresponding GSDM gene. We found that GSDMA and GSDMB regulated drug resistance to the opposite direction of GSDME. In colorectal cancer, GSDME might be a positive regulator in cell invasion and metastasis through cell migration and angiogenesis, while GSDMA, GSDMB and GSDMD might be a negatively regulator of cell migration.

Conclusions

GSDM family genes might play important roles in cancer other than pyroptosis. We suggest more efforts be made to investigate the GSDM family and each GSDM gene be studied as an entity in each type of cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02483-4.

The pyroptosis-related gene signature predicts prognosis and indicates immune activity in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) remains one of the most common malignant tumors with poor survival. Pyroptosis is a kind of programmed cell death that can regulate the proliferation, invasion, and metastasis of tumor cells. However, the expression levels of pyroptosis-related genes (PRGs) in HCC and their relationship with prognosis are still unclear.

Methods

Our study identified 35 PRGs through bioinformatics analysis that were differentially expressed between tumor samples and nontumor samples. According to these differentially expressed genes, HCC patients could be divided into two groups, cluster 1 and cluster 2. The least absolute shrinkage and selection operator (LASSO) Cox regression method was performed to construct a 10-gene signature that classified HCC patients in the cancer genome atlas (TCGA) database into low-risk and high-risk groups.

Results

The results showed that the survival rate of HCC patients in the low-risk group was significantly higher than that in the high-risk group (p < 0.001). The validation cohort, the Gene Expression Omnibus (GEO) cohort, was divided into two risk groups based on the median risk score calculated by the TCGA cohort. The overall survival (OS) of the low-risk group was significantly better than that of the high-risk group (p = 0.007). Univariate and multivariate Cox regression analyses revealed that the risk score was an independent factor in predicting OS in HCC patients. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that immune-related high-risk groups were rich in genes and had reduced immune status.

Conclusions

PRGs play a significant role in tumor immunity and have the potential capability to predict the prognosis of HCC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00445-0.

Gasdermin E permits interleukin-1 beta release in distinct sublytic and pyroptotic phases

Cellular inflammasome activation causes caspase-1 cleavage of the pore-forming protein gasdermin D (GSDMD) with subsequent pyroptotic cell death and cytokine release. Here, we clarify the ambiguous role of the related family member gasdermin E (GSDME) in this process. Inflammasome stimulation in GSDMD-deficient cells led to apoptotic caspase cleavage of GSDME. Endogenous GSDME activation permitted sublytic, continuous interleukin-1β (IL-1β) release and membrane leakage, even in GSDMD-sufficient cells, whereas ectopic expression led to pyroptosis with GSDME oligomerization and complete liberation of IL-1β akin to GSDMD pyroptosis. We find that NLRP3 and NLRP1 inflammasomes ultimately rely concurrently on both gasdermins for IL-1β processing and release separately from their ability to induce cell lysis. Our study thus identifies GSDME as a conduit for IL-1β release independent of its ability to cause cell death.

Gasdermins: pore-forming activities and beyond

Gasdermins (GSDMs) belong to a protein superfamily that is found only in vertebrates and consists of GSDMA, GSDMB, GSDMC, GSDMD, DFNA5 (a.k.a. GSDME) and DFNB59 (a.k.a. Pejvakin (PJVK)) in humans. Except for DFNB59, all members of the GSDM superfamily contain a conserved two-domain structure (N-terminal and C-terminal domains) and share an autoinhibitory mechanism. When the N-terminal domain of these GSDMs is released, it possesses pore-forming activity that causes inflammatory death associated with the loss of cell membrane integrity and release of inflammatory mediators. It has also been found that spontaneous mutations occurring in the genes of GSDMs have been associated with the development of certain autoimmune disorders, as well as cancers. Here, we review the current knowledge of the expression profile and regulation of GSDMs and the important roles of this protein family in inflammatory cell death, tumorigenesis and other related diseases.

Genetics of Postlingual Sensorineural Hearing Loss

Literature and clinical practice around adult-onset hearing loss (HL) has traditionally focused on environmental risk factors, including noise exposure, ototoxic drug exposure, and cardiovascular disease. The most common diagnosis in adult-onset HL is presbycusis. However, the age of onset of presbycusis varies, and patients often describe family history of HL as well as individual variation in progression and severity. In recent years, there has been accumulating evidence of gene-environment interactions underlying adult cases of HL. Susceptibility loci for age-related HL have been identified, and genes related to postlingual nonsyndromic HL continue to be discovered through individual reports and genome-wide association studies. This review will outline main concepts in genetics as related to HL, identify implicated genes, and discuss clinical implications. Laryngoscope, 131:401-409, 2021.

Gasdermin family: a promising therapeutic target for cancers and inflammation-driven diseases

This review focuses on current advances in researches of gasdermin family. The distinctive expression patterns and biological roles of members in this family were discussed. Most of them exhibit pore-forming activity on cell membranes and are executors for programmed cell death with cytokines release, and play roles in cancers and inflammation-driven diseases. Therefore, they can be used as potential therapeutic targets to treat related diseases.

Research progresses of molecular mechanism of pyroptosis and its related diseases

Pyroptosis is a newly discovered untypical form of programmed cell death by inflammatory response, which is dependent on the classic pathway of Caspase-1 and the non-canonical pathway of Caspase-11 in mice or orthologue Caspase-4/-5 in Humans. It has been found that the Gasdermin family of protein is a key molecule in the formation of membrane pores of pyroptosis. After being cleaved by inflammatory caspases, it releases a N-terminal fragment with perforating activity to trigger pyroptosis. That pyroptosis is closely related to the occurrence and development of certain diseases. Now, the molecular mechanism of pyroptosis and pyroptosis-related diseases are reviewed.

A PLK1 kinase inhibitor enhances the chemosensitivity of cisplatin by inducing pyroptosis in oesophageal squamous cell carcinoma

BACKGROUND

Targeting PLK1 has recently been proven as a viable therapeutic strategy against oesophageal squamous cell carcinom (ESCC). Therefore, this study aimed to explore whether the PLK1 inhibitor BI2536 is able to sensitize ESCC cells to cisplatin (DDP) and determine the underlying mechanisms.

METHODS

Viability, clonogenicity, cell cycle distribution and apoptosis were assessed in ESCC cells treated with BI2536 or DDP alone or in combination. Checkpoint activation was examined by immunoblotting and immunohistochemistry. Xenograft model was used to assess the efficacy of the co-treatment. The expression level of GSDME in tissue samples were examined by immunohistochemistry.

FINDINGS

We found that the combination of BI2536 and DDP was synergistic in ESCC cells, which induced pyroptosis in ESCC cells at low doses. Mechanistic studies revealed that BI2536 significantly induced DNA damage and impaired the DNA damage repair pathway in DDP-treated cells both in vitro and in vivo. Interestingly, we found that co-treatment with BI2536 and DDP induced pyroptosis in ESCC cells depending on the caspase-3/GSDME pathway. Importantly, our study found that GSDME was more highly expressed in tumour tissue than that in normal adjacent tissues, and could serve as a prognostic factor.

INTERPRETATION

BI2536 sensitizes ESCC cells to DDP by inhibiting the DNA damage repair pathway and inducing pyroptosis, which provides new information for understanding pyroptosis. Our study also reveals that the PLK1 inhibitor BI2536 may be an attractive candidate for ESCC targeted therapy, especially when combined with DDP for treating the GSDME overexpression subtype. FUND: National 973 Program and National Natural Science Fundation of China.

Genetic Hearing Loss and Gene Therapy

Genetic hearing loss crosses almost all the categories of hearing loss which includes the following: conductive, sensory, and neural; syndromic and nonsyndromic; congenital, progressive, and adult onset; high-frequency, low-frequency, or mixed frequency; mild or profound; and recessive, dominant, or sex-linked. Genes play a role in almost half of all cases of hearing loss but effective treatment options are very limited. Genetic hearing loss is considered to be extremely genetically heterogeneous. The advancements in genomics have been instrumental to the identification of more than 6,000 causative variants in more than 150 genes causing hearing loss. Identification of genes for hearing impairment provides an increased insight into the normal development and function of cells in the auditory system. These defective genes will ultimately be important therapeutic targets. However, the auditory system is extremely complex which requires tremendous advances in gene therapy including gene vectors, routes of administration, and therapeutic approaches. This review summarizes and discusses recent advances in elucidating the genomics of genetic hearing loss and technologies aimed at developing a gene therapy that may become a treatment option for in the near future.

IVS8+1 DelG, a Novel Splice Site Mutation Causing DFNA5 Deafness in a Chinese Family

BACKGROUND

Nonsyndromic hearing loss (NSHL) is highly heterogeneous, in which more than 90 causative genes have currently been identified. DFNA5 is one of the deafness genes that known to cause autosomal dominant NSHL. Until date, only five DFNA5 mutations have been described in eight families worldwide. In this study, we reported the identification of a novel pathogenic mutation causing DFNA5 deafness in a five-generation Chinese family.

METHODS

After detailed clinical evaluations of this family, the genomic DNA of three affected individuals was selected for targeted exome sequencing of 101 known deafness genes, as well as mitochondrial DNA and microRNA regions. Co-segregation analysis between the hearing loss and the candidate variant was confirmed in available family members by direct polymerase chain reaction (PCR)-Sanger sequencing. Real-time PCR (RT-PCR) was performed to investigate the potential effect of the pathogenic mutation on messenger RNA splicing.

RESULTS

Clinical evaluations revealed a similar deafness phenotype in this family to that of previously reported DFNA5 families with autosomal dominant, late-onset hearing loss. Molecular analysis identified a novel splice site mutation in DFNA5 intron 8 (IVS8+1 delG). The mutation segregated with the hearing loss of the family and was absent in 120 unrelated control DNA samples of Chinese origin. RT-PCR showed skipping of exon 8 in the mutant transcript.

CONCLUSIONS

We identified a novel DFNA5 mutation IVS8+1 delG in a Chinese family which led to skipping of exon 8. This is the sixth DFNA5 mutation relates to hearing loss and the second one in DFNA5 intron 8. Our findings provide further support to the hypothesis that the DFNA5-associated hearing loss represents a mechanism of gain-of-function.

Targeted Exome Sequencing of Deafness Genes After Failure of Auditory Phenotype-Driven Candidate Gene Screening

OBJECTIVE

To demonstrate the efficacy and advantages of targeted exome sequencing (TES) of known deafness genes in cases with failed or misleading auditory phenotype-driven candidate gene screening.

STUDY DESIGN

Prospective cohort survey.

SETTING

Otolaryngology department of a tertiary referral hospital.

PATIENTS

Six hearing-impaired probands with seemingly non-syndromic features from six deaf families were enrolled in this study after failure of genetic diagnosis using auditory phenotype-driven candidate gene screening.

INTERVENTION

TES of known deafness genes was performed in the six probands, and a final causative variant was pursued using subsequent filtering steps.

MAIN OUTCOME MEASURE

Potential causative variants determined using TES were confirmed by previously introduced filtering steps.

RESULTS

We detected causative variants in three (50%) of six families, and these variants were in the COCH, PAX3, and GJB2 genes. Additionally, we also recapitulated the recent finding from other report arguing for the non-pathogenic potential of MYO1A variant.

CONCLUSIONS

TES of a deafness panel provides a comprehensive genetic screening tool that can be implemented without being misled by the audiogram configuration information and can complement incomplete clinical physical examinations. In addition, the secondary incidental finding obtained by TES contributes useful information regarding the deafness field.

A DFNA5 mutation identified in Japanese families with autosomal dominant hereditary hearing loss

Mutations in DFNA5 lead to autosomal dominant nonsyndromic hereditary hearing loss (NSHHL). To date, four different mutations in DFNA5 have been reported to cause hearing loss. A 3 bp deletion mutation (c.991-15_991-13del) was identified in Chinese and Korean families with autosomal dominant NSHHL, which suggested that the 3 bp deletion mutation was derived from a single origin. In the present study, we performed genetic screening of mutations in the interval between intron 6 and exon 9 of DFNA5 in 65 Japanese patients with autosomal dominant NSHHL and identified the c.991-15_991-13del mutation in two patients. Furthermore, we compared the DFNA5-linked haplotypes consisting of intragenic SNPs between the reported Chinese and Korean families and found that the Japanese patients showed a shared region spanning 41,874 bp. This is the first report of DFNA5 mutations in Japanese patients with autosomal dominant NSHHL, supporting the suggestion that the 3 bp deletion mutation occurred in their ancestors.

Optimization of simultaneous screening of the main mutations involved in non-syndromic deafness using the TaqMan® OpenArray™ Genotyping platform

Background

Hearing loss is the most common sensory deficit in humans, affecting approximately 10% of the global population. In developed countries, one in every 500 individuals suffers from severe to profound bilateral sensorineural hearing loss. For those up to 5 years old, the proportion is higher, at 2.7 in 1000 individuals, and for adolescents the average is 3.5 in 1000. Among the causes of hearing loss, more than 50% are related to genetic factors. To date, nearly 150 loci and 64 genes have been associated with hearing loss. Mutations in the GJB2 gene, which encodes connexin 26, constitute the main genetic cause. So far, more than 300 variations have been described in this gene.

As a response to the clinical and genetic heterogeneity of hearing loss and the importance of correct molecular diagnosis of individuals with hereditary hearing loss, this study worked in the optimization for a diagnostic protocol employing a high-throughput genotyping technology.

Methods

For this work, was used the TaqMan® OpenArray™ Genotyping platform. This is a high performance, high-throughput technology based on real-time PCR, which enables the evaluation of up to 3072 SNPs (Single Nucleotide Polymorphisms), point mutations, small deletions, and insertions, using a single genotyping plate. For the study, were selected the layout allowing to analyze 32 alterations in 96 individuals simultaneously. In the end, the generated results were validated by conventional techniques, as direct sequencing, Multiplex PCR and RFLP-PCR.

Results

A total of 376 individuals were analyzed, of which 94 were healthy controls, totaling 4 plates in duplicate. All 31 of the changes analyzed were present in the nuclear genes GJB2, GJB6, CRYL1, TMC1, SLC26A4, miR-96, and OTOF, and in the mitochondrial genes MT-RNR1 and MT-TS1. The reactions were subsequently validated by established techniques (direct sequencing, multiplex PCR, and RFLP-PCR) that had previously been used to perform molecular screening of hearing loss at the Human Genetics Laboratory of the Center for Molecular Biology and Genetic Engineering (CBMEG), at the State University of Campinas (UNICAMP). In total, 11,656 genotyping reactions were performed. Of these, only 351 reactions failed, representing approximately 3.01% of the total. The average accuracy of genotyping using the OpenArray™ plates was 96.99%.

Conclusions

The results demonstrated the accuracy, low cost, and good reproducibility of the technique, indicating that the TaqMan® OpenArray™ Genotyping Platform is a useful and reliable tool for application in molecular diagnostic testing of hearing loss.

DFNA5, a Gene Involved in Hearing Loss and Cancer: A Review

Objectives:

The DFNA5 gene was identified in 1998 as a gene that causes an autosomal dominant form of hearing impairment. Five different DFNA5 mutations have been found; each results in skipping of exon 8 at the messenger RNA level. This finding indicates that DFNA5-associated hearing loss is attributable to a highly specific gain-of-function mutation. Interestingly, later reports revealed that DFNA5 also plays a role in tumor biology.

Methods:

Recent data have shed more light on the biological function of DFNA5. Through a literature search, the current knowledge of this gene is reviewed.

Results:

DFNA5 is the first gene for monogenic deafness that is known to involve apoptosis as a disease mechanism — A mechanism that was shown to be involved in frequent types of hearing loss caused by age, noise, or drugs. In line with its apoptosis-inducing properties, DFNA5 is a tumor suppressor gene with an important role in major types of tumors.

Conclusions:

DFNA5 is a tumor suppressor gene that is involved in apoptosis pathways and as such performs a basic role in cell survival. In view of the known role of apoptosis in several forms of hearing loss, DFNA5 may be a player in the underlying disease mechanisms.

A powerful and flexible statistical framework for testing hypotheses of allele-specific gene expression from RNA-seq data

Variation in gene expression is thought to make a significant contribution to phenotypic diversity among individuals within populations. Although high-throughput cDNA sequencing offers a unique opportunity to delineate the genome-wide architecture of regulatory variation, new statistical methods need to be developed to capitalize on the wealth of information contained in RNA-seq data sets. To this end, we developed a powerful and flexible hierarchical Bayesian model that combines information across loci to allow both global and locus-specific inferences about allele-specific expression (ASE). We applied our methodology to a large RNA-seq data set obtained in a diploid hybrid of two diverse Saccharomyces cerevisiae strains, as well as to RNA-seq data from an individual human genome. Our statistical framework accurately quantifies levels of ASE with specified false-discovery rates, achieving high reproducibility between independent sequencing platforms. We pinpoint loci that show unusual and biologically interesting patterns of ASE, including allele-specific alternative splicing and transcription termination sites. Our methodology provides a rigorous, quantitative, and high-resolution tool for profiling ASE across whole genomes.

Evidence for a founder mutation causing DFNA5 hearing loss in East Asians

Mutations in the DFNA5 gene are known to cause autosomal dominant non-syndromic hearing loss (ADNSHL). To date, five DFNA5 mutations have been reported, all of which were different in the genomic level. In this study, we ascertained a Korean family with autosomal dominant, progressive and sensorineural hearing loss and performed linkage analysis that revealed linkage to the DFNA5 locus on chromosome 7. Sequence analysis of DFNA5 identified a 3-bp deletion in intron 7 (c.991-15_991-13del) as the cause of hearing loss in this family. As the same mutation had been reported in a large Chinese family segregating DFNA5 hearing loss, we compared their DFNA5 mutation-linked haplotype with that of the Korean family. We found a conserved haplotype, suggesting that the 3-bp deletion is derived from a single origin in these families. Our observation raises the possibility that this mutation may be a common cause of autosomal dominant progressive hearing loss in East Asians.

The genetic bases for non-syndromic hearing loss among Chinese

Deafness is an etiologically heterogeneous trait with many known genetic, environmental causes or a combination thereof. The identification of more than 120 independent genes for deafness has provided profound new insights into the pathophysiology of hearing. However, recent findings indicate that a large proportion of both syndromic and non-syndromic forms of deafness in the Chinese population are caused by defects in a small number of genes. Studies of the genetic epidemiology and molecular genetic features revealed that there is a clear relevance of genes causing deafness in Chinese deaf patients as well as a unique spectrum of common and rare deafness gene mutations in the Chinese population. This review is focused on the genetic aspects of non-syndromic and mitochondrial deafness, in which unique molecular genetic features of hearing impairment have been identified in the Chinese population. The current China population is approximately 1.3 billion. It is estimated that 30,000 infants are born with congenital sensorineural hearing loss each year. Better understanding of the genetic causes of deafness in the Chinese population is important for accurate genetics counseling and early diagnosis for timely intervention and treatment options.

Methylation of the DFNA5 increases risk of lymph node metastasis in human breast cancer

The pathogenesis of breast cancer involves multiple genetic and epigenetic events. In this study, we report an epigenetic alteration of DFNA5 in human breast cancer. DFNA5 gene was silenced in breast cancer cell lines that were methylated in the DFNA5 promoter, and restored by treatment with the demethylating agent, 5-aza-dC, and gene knock-down of DFNA5 increased cellular invasiveness in vitro. The mRNA expression of DFNA5 in breast cancer tissues was down-regulated as compared to normal tissues. Moreover, the DFNA5 promoter was found to be methylated in primary tumor tissues with high frequency (53%, 18/34). Quantitative methylation-specific PCR of DFNA5 clearly discriminated primary breast cancer tissues from normal breast tissues (15.3%, 2/13). Moreover, methylation status of DFNA5 was correlated with lymph node metastasis in breast cancer patients. Our data implicate DFNA5 promoter methylation as a novel molecular biomarker in human breast cancer.

Aberrant promoter methylation and tumor suppressive activity of the DFNA5 gene in colorectal carcinoma

To identify novel methylated gene promoters, we compared differential RNA expression profiles of colorectal cancer (CRC) cell lines with or without treatment of 5-aza-2'-deoxycytidine (5-aza-dC). Out of 1776 genes that were initially 'absent (that is, silenced)' by gene expression array analysis, we selected 163 genes that were increased after 5-aza-dC treatment in at least two of three CRC cell lines. The microarray results were confirmed by Reverse Transcription-PCR, and CpG island of the gene promoters were amplified and sequenced for examination of cancer-specific methylation. Among the genes identified, the deafness, autosomal dominant 5 gene, DFNA5, promoter was found to be methylated in primary tumor tissues with high frequency (65%, 65/100). Quantitative methylation-specific PCR of DFNA5 clearly discriminated primary CRC tissues from normal colon tissues (3%, 3/100). The mRNA expression of DFNA5 in four of five colon cancer tissues was significantly downregulated as compared to normal tissues. Moreover, forced expression of full-length DFNA5 in CRC cell lines markedly decreased the cell growth and colony-forming ability whereas knockdown of DFNA5 increased cell growth in culture. Our data implicate DFNA5 as a novel tumor suppressor gene in CRC and a valuable molecular marker for human cancer.

In CEM cells the autosomal deafness gene dfna5 is regulated by glucocorticoids and forskolin

Certain mutations of the dfna5 gene result in a form of autosomal deafness that holds special interest because its phenotype resembles the hearing loss often seen during aging. Little is known of the function or regulation of dfna5 or its encoded protein. However dfna5 has recently been shown to be induced by p53. It also is epigenetically repressed in gastric cancer. We have discovered that dfna5 can be induced by glucocorticoids (GCs) and that this regulation is influenced by crosstalk with the protein kinase A (PKA) system. We show that GCs induce dfna5 mRNA and that its expression appears to be repressed in the basal state. Induction of dfna5 mRNA correlates with GC-dependent apoptosis of CEM cells, though dfna5 expression alone is not sufficient for apoptosis.

A novel DFNA5 mutation, IVS8+4 A>G, in the splice donor site of intron 8 causes late-onset non-syndromic hearing loss in a Chinese family

We report here the clinical, genetic, and molecular characteristics of a large Chinese family exhibiting non-syndromic, late-onset autosomal dominant sensorineural hearing loss. Clinical evaluation revealed variable phenotypes of hearing loss in terms of severity and age-at-onset of disease in these subjects. Genome-wide linkage analysis mapped the disease gene to the DFNA5 locus with a maximum two-point log odds score of 5.39 at [theta] = 0 for marker D7S2457. DNA sequencing of DFNA5 revealed a novel heterozygous IVS8+4 A>G substitution in the splice donor site of intron 8. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed skipping of exon 8 in the mutant transcript. This mutation faithfully cosegregated with hearing loss in the family. In addition, the mutation was absent in 100 unrelated control DNA samples of Chinese origin. The IVS8+4 A>G mutation is predicted to create a shift in the reading frame and introduce a stop codon at position 372, thereby resulting in a prematurely truncated DFNA5 protein. Up to date, a total of four mutations in DFNA5 have been reported to lead to hearing impairment, all of them result in skipping of exon 8 at the mRNA level. Our findings provide further support for the hypothesis that DFNA5-associated hearing loss is caused by a very specific gain-of-function mutation.

Mice lacking Dfna5 show a diverging number of cochlear fourth row outer hair cells

A complex mutation in DFNA5, resulting in exon 8 skipping, causes autosomal dominant hearing impairment, which starts in the high frequencies between 5 and 15 years of age and progressively affects all frequencies. To study its function in vivo, Dfna5 knockout mice were generated through the deletion of exon 8, simultaneously mimicking the human mutation. To test the hearing impairment, frequency-specific Auditory Brainstem Response (ABR) measurements were performed at different ages in two genetic backgrounds (C57Bl/6J and CBA/Ca), but no differences between Dfna5-/- and Dfna5+/+ mice could be demonstrated. Morphological studies demonstrated significant differences in the number of fourth row outer hair cells between Dfna5-/- mice and their wild-type littermates. These results were obtained in both genetic backgrounds, albeit with opposite effects. In contrast to the results obtained in Dfna5-/- zebrafish, we did not observe different UDP-glucose dehydrogenase and hyaluronic acid levels in Dfna5-/- mice when compared to Dfna5+/+ mice.

HUMANNONSYNDROMICSENSORINEURALDEAFNESS

Given the unique biological requirements of sound transduction and the selective advantage conferred upon a species capable of sensitive sound detection, it is not surprising that up to 1% of the approximately 30,000 or more human genes are necessary for hearing. There are hundreds of monogenic disorders for which hearing loss is one manifestation of a syndrome or the only disorder and therefore is nonsyndromic. Herein we review the supporting evidence for identifying over 30 genes for dominantly and recessively inherited, nonsyndromic, sensorineural deafness. The state of knowledge concerning their biological roles is discussed in the context of the controversies within an evolving understanding of the intricate molecular machinery of the inner ear.

Disease associated balanced chromosome rearrangements (DBCR): report of two new cases

Disease associated balanced chromosome rearrangements (DBCR) causing truncation, deletion, inactivation or over-expression of specific genes are instrumental in identifying and cloning several disease genes and are estimated to be much more common than anticipated. In one survey, the minimal frequency of combined balanced de novo reciprocal translocations and inversions causing abnormal phenotype is estimated to be 0.17%, a sixfold increase compared to the general population suggesting a causative linkage between the abnormality and the observed phenotypic traits. Here, we report two new cases of apparently balanced de novo translocations resulting in developmental delay and dysmorphic features.

Non-syndromic autosomal-dominant deafness

Non-syndromic deafness is a paradigm of genetic heterogeneity. More than 70 loci have been mapped, and 25 of the nuclear genes responsible for non-syndromic deafness have been identified. Autosomal-dominant genes are responsible for about 20% of the cases of hereditary non-syndromic deafness, with 16 different genes identified to date. In the present article we review these 16 genes, their function and their contribution to deafness in different populations. The complexity is underlined by the fact that several of the genes are involved in both dominant and recessive non-syndromic deafness or in both non-syndromic and syndromic deafness. Mutations in eight of the genes have so far been detected in only single dominant deafness families, and their contribution to deafness on a population base might therefore be limited, or is currently unknown. Identification of all genes involved in hereditary hearing loss will help in the understanding of the basic mechanisms underlying normal hearing, will facilitate early diagnosis and intervention and might offer opportunities for rational therapy.

Further delineation of the DFNA5 phenotype: results of speech recognition tests

Speech recognition scores were analyzed in 34 carriers of a DFNA5 mutation. Cross-sectional linear regression analysis (last visit, maximum recognition score in %Correct on age or PTA1,2,4 kHz) established onset age (score 90%) at 16 years and onset PTA1,2,4 kHz level (score 90%) at 41 dB hearing level. The deterioration rate was 0.7%/y in the plot of maximum score against age, whereas the deterioration gradient was 0.4%/dB in the plot of maximum score against PTA1,2,4 kHz. Given the previously demonstrated rapid progression of hearing impairment, speech recognition was relatively good: at age 70, the score was still >50%.

Molecular genetics of hearing loss

Hereditary isolated hearing loss is genetically highly heterogeneous. Over 100 genes are predicted to cause this disorder in humans. Sixty loci have been reported and 24 genes underlying 28 deafness forms have been identified. The present epistemic stage in the realm consists in a preliminary characterization of the encoded proteins and the associated defective biological processes. Since for several of the deafness forms we still only have fuzzy notions of their pathogenesis, we here adopt a presentation of the various deafness forms based on the site of the primary defect: hair cell defects, nonsensory cell defects, and tectorial membrane anomalies. The various deafness forms so far studied appear as monogenic disorders. They are all rare with the exception of one, caused by mutations in the gene encoding the gap junction protein connexin26, which accounts for between one third to one half of the cases of prelingual inherited deafness in Caucasian populations.

Mapping of a new autosomal dominant nonsyndromic hearing loss locus (DFNA30) to chromosome 15q25-26

Hearing impairment is the most common inherited human sensory defect. Nonsyndromic Hearing Impairment (NSHI) is the most genetically heterogeneous trait known. Over 70 loci have been mapped and a total of 19 genes have been identified. We report here a novel locus (DFNA 30) for autosomal dominant NSHI that we mapped to chromosome 15q25-26 in an Italian four-generation family. The haplotype analysis has identified a critical interval of 18 cM between markers D15S151 and D15S130. This region does not overlap with DFNB16 locus but partially coincides with the otosclerosis (OTS) locus. Localisation of the locus DFNA30 is a first step towards the identification of the gene.

A Dutch family with progressive autosomal dominant non-syndromic sensorineural hearing impairment linked to DFNA13

We present a Dutch family with autosomal dominantly inherited mid-frequency and high-frequency sensorineural hearing impairment. Genetic linkage analysis in this family indicated linkage to DFNA13 with logarithm of the odds ratio (LOD) scores > +4. The majority of the affected persons presented with hearing impairment from the age of 30 years onwards, although hearing impairment was noted at about 10 years of age in two affected persons. Three individuals represent phenocopies. After correction for presbyacusis, hearing impairment was most marked at 1-2 kHz and showed an annual progression of 0.8 dB per year. By the age of 60 years, the configuration of the audiogram was flat, reflecting the combined effects of the inherited progressive hearing loss and presbyacusis. Vestibular function was intact. Recently, mutations in the COL11A2 gene were found in two other families with non-syndromic hearing impairment linked to DFNA13. Further mutation analysis of the COL11A2 gene will show whether this family also contains a COL11A2 mutation.

Audiologic aspects of the search for DFNA20: a gene causing late-onset, progressive, sensorineural hearing loss

OBJECTIVE

The purpose of this research was to identify the gene responsible for a novel form of nonsyndromic, late-onset, bilateral, progressive, sensorineural hearing loss in a Michigan family of English descent. This report describes the audiologic aspects of the search.

DESIGN

Fifty-eight members of the family served as subjects for the study. Family pedigree information was gathered from family interviews, family records, birth and death registration records and census data. Audiologic evaluation was used to describe the hearing loss (phenotype) and classify family members as affected or unaffected based on hearing status. These data then were used in a linkage analysis, a process in which the inheritance of a trait is compared with the inheritance of genetic markers and statistically significant associations are sought.

RESULTS

The team mapped the hearing loss to the long arm of chromosome 17 at band 17q25. The pattern of inheritance is autosomal dominant. The search for the gene is continuing using a candidate gene approach.

CONCLUSIONS

The hearing loss demonstrated by this mid-Michigan family is a novel form of nonsyndromic, genetic, late-onset, bilateral, progressive, sensorineural hearing loss. The locus of the gene, the 20th for autosomal dominant hearing loss, is at band 17q25 of chromosome 17.

DFNA5 (ICERE-1) contributes to acquired etoposide resistance in melanoma cells

Resistance to drug treatment is a common observation in malignant melanoma. In order to analyze alterations in mRNA expression profiles associated with drug resistance in melanoma cells we previously established a panel of various drug-resistant cell variants derived from the human melanoma line MeWo and compared the mRNA expression profiles by a differential display technique. By that approach it could be demonstrated that the expression level of a mRNA encoded by a gene found to be mutated in non-syndromic hearing impairment, DFNA5 (ICERE-1), was distinctly decreased in the 33-fold etoposide-resistant melanoma cell line MeWo ETO 1. To evaluate the hypothesis that a decrease in DFNA5 mRNA expression level contributes to the acquired etoposide resistance phenotype exhibited by MeWo ETO 1 cells, this drug-resistant line was stably transfected with the DFNA5-encoding cDNA. Transfected clones showed a 30-35% reduced etoposide susceptibility by comparing the IC(25), IC(50) and IC(75) values of these clones with those displayed by the non-transfected, etoposide-resistant melanoma cell line MeWo ETO 1 and controls. Furthermore, etoposide exposure of stable DFNA5 transfectants resulted in an increase of caspase-3-mediated apoptotic events in DFNA5-transfected clones in comparison to MeWo ETO 1 cells and controls. The data therefore demonstrate that a decrease in DNFA5 mRNA expression level is associated with an increased etoposide resistance in melanoma cells due to an elevated cellular susceptibility to trigger a caspase-3-depending signal pathway leading to programmed cell death.

"New" autosomal-dominant infantile sensorineural non-progressive high-frequency hearing loss: report on a Brazilian family

We report on a three-generation Brazilian family with seven patients affected with non-progressive high-frequency sensorineural hearing loss with no associated anomalies first noted in early infancy. To our knowledge this is the first report on this autosomal-dominant condition. Clinical, audiological, and genetic aspects are discussed.

Identification of a transcriptional repressor related to the noncatalytic domain of histone deacetylases 4 and 5

Histone deacetylases (HDACs) are involved in regulating transcription by modifying the core histones of the nucleosome. To date, six HDACs have been identified in mammalian cells: the yeast RPD3 homologs HDAC1, 2, and 3 and the yeast HDA1 homologs HDAC4, 5, and 6. HDAC4 and HDAC5 contain a noncatalytic N-terminal domain. Herein, we report the identification of a protein HDRP (HDAC-related protein) that shares 50% identity in deduced amino acid sequence to the noncatalytic N-terminal domain of HDAC4 and 5. The steady-state levels of HDRP mRNA are high in human brain, heart, and skeletal muscle and low in the several other tissues. HDRP has an apparent molecular mass of approximately 75 kDa. HDRP does not possess intrinsic HDAC activity but forms complexes with both HDAC1 and HDAC3. HDRP represses both basal and activated transcription in transient transfection assays when tethered to DNA as a Gal4-fusion protein. HDAC inhibitors do not reverse transcriptional repression mediated by Gal4-HDRP. Thus, HDRP is a transcriptional repressor and can repress transcription in the presence of HDAC inhibitors.

Non-syndromal autosomal dominant hearing impairment: ongoing phenotypical characterization of genotypes

This review is concerned with the present state of phenotypical characterization of known genotypes of non-syndromal autosomal dominant hearing impairment. A brief outline of history and context of phenotyping and genotyping of hearing impairment is given with particular reference to the most recent developments in this field, followed by descriptions of DFNA1, DFNA2, DFNA5, DFNA6/14, DFNA8/12, DFNA9, DFNA 13, DFNA17 and DFNA21. Phenotyping those known genotypes may support the ongoing search for mutations in the corresponding gene and enhance genetic counselling. It is recommended that sufficient attention is given to a detailed description of the phenotype in each (newly) described hereditary hearing impairment disorder.