Mutations in the transmembrane protease, serine 3 (TMPRSS3) gene, encoding a transmembrane serine protease, cause autosomal recessive deafness childhood (DFNB8) or congenital onset (DFNB10). TMPRSS3 mutations have been mainly identified in patients from Asian and Mediterranean countries and seem to be a rare finding in the Northern European population so far. The identification of two novel pathogenic TMPRSS3 mutations (c.646C→T − R216C; c.916G→A − A306T) is described in four affected siblings of German origin with postlingual hearing loss, treated by bilateral cochlear implantation with good results. Although TMPRSS3 mutations are supposed to be a rare cause of autosomal recessive hearing loss, in families with postlingual disease onset TMPRSS3 is the most favourable candidate gene after exclusion of GJB2 mutations.
Autosomal recessive nonsyndromic deafness is one of the most frequent forms of inherited hearing impairment. Over 30 autosomal recessive nonsyndromic hearing loss loci have been mapped, and 15 genes have been isolated. Of the over 30 reported autosomal recessive nonsyndromic hearing loss (NSHL) loci, the typical phenotype is prelingual non-progressive severe to profound hearing loss with the exception of DFNB8, which displays postlingual onset and DFNB13, which is progressive. In this report we describe a large inbred kindred from a remote area of Pakistan, comprising six generations and segregating autosomal recessive nonsyndromic prelingual deafness. DNA samples from 24 individuals were used for genome wide screen and fine mapping. Linkage analysis indicates that in this family the NSHL locus, (DFNB35) maps to a 17.54 cM region on chromosome 14 flanked by markers D14S57 and D14S59. Examination of haplotypes reveals a region that is homozygous for 11.75 cM spanning between markers D14S588 and D14S59. A maximum two-point LOD score of 5.3 and multipoint LOD score of 7.6 was obtained at marker D14S53. The interval for DFNB35 does not overlap with the regions for DFNA9, DFNA23 or DFNB5.
autosomal recessive nonsyndromic hearing loss; DFNA9; DFNA23; DFNB5; DFNB35; 14q24.1—14q24.3 prelingual; Pakistan
We studied a consanguineous family (Family A) from the island of Newfoundland with an autosomal recessive form of prelingual, profound, nonsyndromic sensorineural hearing loss. A genome-wide scan mapped the deafness trait to 10q21-22 (max LOD score of 4.0; D10S196) and fine mapping revealed a 16 Mb ancestral haplotype in deaf relatives. The PCDH15 gene was mapped within the critical region and was an interesting candidate because truncating mutations cause Usher syndrome type IF (USH1F) and two missense mutations have been previously associated with isolated deafness (DFNB23). Sequencing of the PCDH15 gene revealed 33 sequencing variants. Three of these variants were homozygous exclusively in deaf siblings but only one of them was not seen in ethnically matched controls. This novel c.1583 T>A transversion predicts an amino-acid substitution of a valine with an aspartic acid at codon 528 (V528D). Like the two DFNB23 mutations, the V528D mutation in Family A occurs in a highly conserved extracellular cadherin (EC) domain of PCDH15 and is predicted to be more deleterious than the previously identified DFNB23 missense mutations (R134G and G262D). Physical assessment, vestibular and visual function testing in deaf adults ruled out syndromic deafness because of Usher syndrome. This study validates the DFNB23 designation and supports the hypothesis that missense mutations in conserved motifs of PCDH15 cause nonsyndromic hearing loss. This emerging genotype–phenotype correlation in USH1F is similar to that in several other USH1 genes and cautions against a prognosis of a dual sensory loss in deaf children found to be homozygous for hypomorphic mutations at the USH1F locus.
PCDH15; isolated deafness; usher syndrome type IF; hypomorphic alleles
Recessive mutations of the myosin VIIA (MYO7A) gene are reported to be responsible for both a deaf–blindness syndrome (Usher type 1B [USH1B] and atypical Usher syndrome) and nonsyndromic hearing loss (HL; Deafness, Neurosensory, Autosomal Recessive 2 [DFNB2]). The existence of DFNB2 is controversial, and often there is no relationship between the type and location of the MYO7A mutations corresponding to the USH1B and DFNB2 phenotype. We investigated the molecular determinant of a mild form of retinopathy in association with a subtle splicing modulation of MYO7A mRNA.
Affected members underwent detailed audiologic and ocular characterization. DNA samples from family members were genotyped with polymorphic microsatellite markers. Sequencing of MYO7A was performed. Endogenous lymphoid RNA analysis and a splicing minigene assay were used to study the effect of the c.1935G>A mutation.
Funduscopy showed mild retinitis pigmentosa in adults with HL. Microsatellite analysis showed linkage to markers in the region on chromosome 11q13.5. Sequencing of MYO7A revealed a mutation in the last nucleotide of exon 16 (c.1935G>A), which corresponds to a substitution of a methionine to an isoleucine residue at amino acid 645 of the myosin VIIA. However, structural prediction of the molecular model of myosin VIIA shows that this amino acid replacement induces only minor structural changes in the immediate environment of the mutation and thus does not alter the overall native structure. We found that, although predominantly included in mature mRNA, exon 16 is in fact alternatively spliced in control cells and that the mutation at the very last position is associated with a switch toward a predominant exclusion of that exon. This observation was further supported using a splicing minigene transfection assay; the c.1935G>A mutation was found to trigger a partial impairment of the adjacent donor splice site, suggesting that the unique change at the last position of the exon is responsible for the enhanced exon exclusion in this family.
This study shows how an exonic mutation that weakens the 5′ splice site enhances a minor alternative splicing without abolishing a complete exclusion of the exon and therefore causes a less severe retinitis pigmentosa than the USH1B-associated alleles. It would be interesting to examine a possible correlation between intrafamilial phenotypic variability and the subtle variation in exon 16 inclusion, probably related to genetic background specificities.
TMPRSS2-Ets gene fusions were identified in prostate cancers where the promoter of transmembrane protease, serine 2 (TMPRSS2) fused with coding sequence of the erythroblastosis virus E26 (Ets) gene family members. TMPRSS2 is an androgen responsive transmembrane serine protease. Ets family members are oncogenic transcription factors that contain a highly conserved Ets DNA binding domain and an N-terminal regulatory domain.
Fusion of these gene results in androgen dependent transcription of Ets factor in prostate tumor cells. The ERG is the most common fusion partner with TMPRSS2 promoter in prostate cancer patients. The high prevalence of these gene fusions, in particular TMPRSS2-ERG, makes them attractive as potential diagnostic and prognostic indicators, as well as making them a potential target for tailored therapies.
This review focuses on the clinical and biological significance of TMPRSS2-ERG fusions and their role in PC development and progression.
TMPRSS2-ERG; Prostate Cancer; Clinical; Biological significance
Abstract Autosomal recessive nonsyndromic hearing impairment (ARNSHI) is the most frequent form of prelingual hereditary hearing loss in humans. Between 75 and 80% of all nonsyndromic deafness is inherited in an autosomal recessive pattern. Using linkage analysis, we have mapped a novel gene responsible for this form of nonsyndromic hearing impairment, DFNB65, in a consanguineous family from the Azad Jammu and Kashmir regions, which border Pakistan and India. A maximum multipoint LOD score of 3.3 was obtained at marker D20S840. The three-unit support interval is contained between markers D20S902 and D20S430, while the region of homozygosity is flanked by markers D20S480 and D20S430. The novel locus maps to a 10.5-cM region on chromosome 20q13.2–q13.32 and corresponds to a physical map distance of 4.3 Mb. DFNB65 represents the first ARNSHI locus to map to chromosome 20.
Autosomal recessive nonsyndromic hearing impairment; DFNB65; Pakistan; 20q13.2–q13.32
IRIDA (iron-refractory iron-deficiency anaemia) is a rare autosomal-recessive disorder hallmarked by hypochromic microcytic anaemia, low transferrin saturation and high levels of the iron-regulated hormone hepcidin. The disease is caused by mutations in the transmembrane serine protease TMPRSS6 (transmembrane protease serine 6) that prevent inactivation of HJV (haemojuvelin), an activator of hepcidin transcription. In the present paper, we describe a patient with IRIDA who carries a novel mutation (Y141C) in the SEA domain of the TMPRSS6 gene. Functional characterization of the TMPRSS6(Y141C) mutant protein in cultured cells showed that it localizes to similar subcellular compartments as wild-type TMPRSS6 and binds HJV, but fails to auto-catalytically activate itself. As a consequence, hepcidin mRNA expression is increased, causing the clinical symptoms observed in this IRIDA patient. The present study provides important mechanistic insight into how TMPRSS6 is activated.
haemojuvelin; hepcidin; iron-refractory irondeficiency anaemia (IRIDA); matriptase-2; transmembrane protease serine 6 (TMPRSS6); ALAS2, aminolevulinate δ synthase 2; BMP, bone morphogenetic protein; CUB domain, complement factor C1s/C1r, urchin embryonic growth factor and BMP domain; CMV, cytomegalovirus; DMEM, Dulbecco's modified Eagle's medium; EGFP, enhanced green fluorescent protein; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HJV, haemojuvelin; IRIDA, iron-refractory iron-deficiency anaemia; LDLR domain, low-density-lipoprotein receptor class A domain; ORF, open reading frame; PIC, phosphoinositidase C; qRT-PCR, quantitative real-time PCR; SEA domain, sea urchin sperm protein, enteropeptidase and agrin domain; SELDI–TOF, surface-enhanced laser-desorption ionization–time-of-flight; SLC11A2, solute carrier family 11, member 2; SLC25A28, solute carrier family 25, member 28; TMPRSS6, transmembrane protease serine 6; cdTMPRSS6, catalytic domain of TMPRSS6; TTSP, type II transmembrane serine protease
Hepcidin, a liver-derived protein that restricts enteric iron absorption, is the key regulator of body iron content. Several proteins induce expression of the hepcidin-encoding gene Hamp in response to infection or high levels of iron. However, mechanism(s) of Hamp suppression during iron depletion are poorly understood. Here we describe mask, a recessive, chemically induced mutant mouse phenotype, characterized by progressive loss of body but not facial hair and microcytic anemia. The mask phenotype results from reduced absorption of dietary iron caused by high levels of hepcidin, and is due to a splicing defect in the transmembrane serine protease 6 gene Tmprss6. Overexpression of normal TMPRSS6 protein suppresses activation of the Hamp promoter, and the TMPRSS6 cytoplasmic domain mediates Hamp suppression via proximal promoter element(s). TMPRSS6 is an essential component of a pathway that detects iron deficiency and blocks Hamp transcription, permitting enhanced dietary iron absorption.
A consanguineous family with autosomal recessive nonsyndromic hearing impairment (NSHI) was ascertained in Pakistan and displayed significant evidence of linkage to 3q13.31-q22.3. The novel locus (DFNB42) segregating in this kindred, maps to a 21.6 cM region according to a genetic map constructed using data from both the deCode and Marshfield genetic maps. This region of homozygosity is flanked by markers D3S1278 and D3S2453. A maximum multipoint LOD score of 3.72 was obtained at marker D3S4523. DFNB42 represents the third autosomal recessive NSHI locus to map to chromosome 3.
3q13.31-q22.3; DFNB42; nonsyndromic hearing impairment; Pakistan
TMPRSS2-ERG fusion is the most common oncogenic rearrangement in prostate cancer (CaP). Due to this chromosomal rearrangement one TMPRSS2 allele loses its promoter, and one of the ERG alleles gains that promoter leading to its overexpression in these tumor cells. Some studies suggest that TMPRSS2, an androgen regulated type II trans-membrane serine protease, may have an effect on CaP progression. We hypothesized that a difference in TMPRSS2 expression may be present in vivo between CaP cells with and without TMPRSS2-ERG fusion, or a compensatory mechanism for the allelic loss of TMPRSS2 may balance that expression difference. Therefore, TMPRSS2 mRNA expression was evaluated in micro-dissected CaP cells with and without TMPRSS2-ERG fusion in 132 CaP patients and analyzed for its correlation with other androgen receptor (AR) regulated genes and clinico-pathologic features. In vivo TMPRSS2 expression correlated with that of other AR-regulated genes, including PSA/KLK3 and PMEPA1, offering potential as AR surrogates. A significantly reduced expression of TMPRSS2 was evident in malignant cells harboring TMPRSS2-ERG fusion, but not in CaP cells without TMPRSS2-ERG fusion, further defining these two genetically distinct types of CaP.
prostate cancer; TMPRSS2; quantitative expression; TMPRSS2-ERG fusion
Approximately half the cases of prelingual hearing loss are caused by genetic factors. Identification of genes causing deafness is a crucial first step in understanding the normal function of these genes in the auditory system. Recently, a mutant allele of Tmhs was reported to be associated with deafness and circling behaviour in the hurry‐scurry mouse. Tmhs encodes a predicted tetraspan protein of unknown function, which is expressed in inner ear hair cells. The human homologue of Tmhs is located on chromosome 6p.
To determine the cause of deafness in four consanguineous families segregating recessive deafness linked to markers on chromosome 6p21.1‐p22.3 defining a novel DFNB locus.
A novel locus for non‐syndromic deafness DFNB67 was mapped in an interval of approximately 28.51 cM on human chromosome 6p21.1‐p22.3. DNA sequence analysis of TMHS revealed a homozygous frameshift mutation (246delC) and a missense mutation (Y127C) in affected individuals of two families segregating non‐syndromic deafness, one of which showed significant evidence of linkage to markers in the DFNB67 interval. The localisation of mTMHS in developing mouse inner ear hair cells was refined and found to be expressed briefly from E16.5 to P3.
These findings establish the importance of TMHS for normal sound transduction in humans.
The majority of prostate cancers harbor gene fusions of the 5′-untranslated region of the androgen-regulated transmembrane protease, serine 2 (TMPRSS2) promoter with erythroblast transformation specific (ETS) transcription factor family members. The common v-ets erythroblastosis virus E26 oncogene homolog [avian] (TMPRSS2–ERG) fusion is associated with a more aggressive clinical phenotype, implying the existence of a distinct subclass of prostate cancer defined by this fusion.
We used cDNA-mediated annealing, selection, ligation, and extension to determine the expression profiles of 6144 transcriptionally informative genes in archived biopsy samples from 455 prostate cancer patients in the Swedish Watchful Waiting cohort (1987–1999) and the US-based Physicians Health Study cohort (1983–2003). A gene expression signature for prostate cancers with the TMPRSS2-ERG fusion was determined using partitioning and classification models and used in computational functional analysis. Cell proliferation and TMPRSS2-ERG expression in androgen receptor–negative (NCI-H660) and –positive (VCaP-ERβ) prostate cancer cells after treatment with vehicle or estrogenic compounds were assessed by viability assays and quantitative polymerase chain reaction, respectively. All statistical tests were two-sided.
We identified an 87-gene expression signature that distinguishes TMPRSS2-ERG fusion prostate cancer as a discrete molecular entity (area under the curve = 0.80, 95% confidence interval [CI] = 0.792 to 0.81; P<.001). Computational analysis suggested that this fusion signature was associated with estrogen receptor (ER) signaling. Viability of NCI-H660 cells decreased after treatment with estrogen (viability normalized to day 0, estrogen vs vehicle at day 8, mean = 2.04 vs 3.40, difference = 1.36, 95% CI = 1.12 to 1.62) or ERβ agonist (ERβ agonist vs vehicle at day 8, mean = 1.86 vs 3.40, difference = 1.54, 95% CI = 1.39 to 1.69) but increased after ERα agonist treatment (ERα agonist vs vehicle at day 8, mean = 4.36 vs 3.40, difference = 0.96, 95% CI = 0.68 to 1.23). Similarly, expression of TMPRSS2-ERG decreased after ERβ agonist treatment (fold change over internal control, ERβ agonist vs vehicle at 24 hours, NCI H660, mean = 0.57-fold vs 1.0-fold, difference = 0.43, 95% CI = 0.29-fold to 0.57-fold) and increased after ERα agonist treatment (ERα agonist vs vehicle at 24 hours, mean = 5.63-fold vs 1.0-fold, difference = 4.63-fold, 95% CI = 4.34-fold to 4.92-fold).
TMPRSS2-ERG fusion prostate cancer is a distinct molecular subclass. TMPRSS2-ERG expression is regulated by a novel ER-dependent mechanism.
Mutations in OTOF, encoding otoferlin, cause non-syndromic recessive hearing loss. The goal of our study was to define the identities and frequencies of OTOF mutations in a model population. We screened a cohort of 557 large consanguineous Pakistani families segregating recessive, severe-to-profound, prelingual-onset deafness for linkage to DFNB9. There were 13 families segregating deafness consistent with linkage to markers for DFNB9. We analyzed the genomic nucleotide sequence of OTOF and detected probable pathogenic sequence variants among all 13 families. These include the previously reported nonsense mutation p.R708X and 10 novel variants: 3 nonsense mutations (p.R425X, p.W536X, and p.Y1603X), 1 frameshift (c.1103_1104delinsC), 1 single amino acid deletion (p.E766del) and 5 missense substitutions of conserved residues (p.L573R, p.A1090E, p.E1733K, p.R1856Q and p.R1939W). OTOF mutations thus account for deafness in 13 (2.3%) of 557 Pakistani families. This overall prevalence is similar, but the mutation spectrum is different from those for Western populations. In addition, we demonstrate the existence of an alternative splice isoform of OTOF expressed in the human cochlea. This isoform must be required for human hearing because it encodes a unique alternative C-terminus affected by some DFNB9 mutations.
DFNB9; hearing; OTOF; otoferlin
For autosomal recessive nonsyndromic hearing impairment over 30 loci have been mapped and 19 genes have been identified. DFNB38, a novel locus for autosomal recessive nonsyndromic hearing impairment, was localized in a consanguineous Pakistani kindred to 6q26–q27. The affected family members present with profound prelingual sensorineural hearing impairment and use sign language for communications. Linkage was established to microsatellite markers located on chromosome 6q26–q27 (Multipoint lod score 3.6). The genetic region for DFNB38 spans 10.1 cM according to the Marshfield genetic map and is bounded by markers D6S980 and D6S1719. This genetic region corresponds to 3.4 MB on the sequence-based physical map.
Autosomal recessive hearing impairment; DFNB38; Gene mapping; Pakistan; 6q26–q27
Mutations in MYO15A are associated with deafness in humans, and shaker 2 mice also exhibit a hearing loss due to defects of unconventional myosin 15a. We ascertained a consanguineous Pakistani family with recessively inherited moderate to severe hearing loss, which putatively segregated with markers linked to the DFNB3 locus. Prioritized sequencing of the second exon of MYO15A from the DNA of all affected individuals of family revealed a duplication of Cytosine in a stretch of seven repetitive C nucleotides (c.1185dupC). This mutation results in a frameshift and incorporates a stop codon in the open reading frame of MYO15A (p.E396fsX431). The findings of less severe hearing loss in families with linkage to DFNB3 are only reported for some individuals with mutations in exon 2 of MYO15A, which are further supported by this study. Therefore, on basis of linkage data and the presence of a less severe hearing loss phenotype, sequencing of a single exon of MYO15A can efficiently identify the causative mutations in patients from these families.
MYO15A; unconventional myosins; DFNB3; hearing loss; deafness; Pakistan
Genetic analysis of inbred Pakistani family PKDF280, segregating prelingual severe to profound sensorineural hearing loss, provided evidence for a DFNB locus on human chromosome 9q34.3. Co-segregation of the deafness trait with marker D9SH159 was determined by a two-point linkage analysis (LOD score 9.43 at θ=0). Two additional large families, PKDF517 and PKDF741, co-segregate recessive deafness with markers linked to the same interval. Haplotype analyses of these three families refined the interval to 3.84 Mb defined by D9S1818 (centromeric) and D9SH6 (telomeric). This interval overlaps with the previously reported DFNB33 locus whose chromosomal map position has been recently revised and assigned to a new position on chromosome 10p11.23-q21.1. The nonsyndromic deafness locus on chromosome 9q segregating in family PKDF280 was designated DFNB79. We are currently screening the 113 candidate DFNB79 genes for mutations and have excluded CACNA1B, EDF1, PTGDS, EHMT1, QSOX2, NOTCH1, MIR126 and MIR602.
hereditary deafness; DFNB79; DFNB33; Pakistan; chromosome 9q34.3
Genetic analysis of an inbred Pakistani family PKDF280, segregating prelingual severe to profound sensorineural hearing loss, provided evidence for a DFNB locus on human chromosome 9q34.3. Co-segregation of the deafness trait with marker D9SH159 was determined by a two-point linkage analysis (LOD score 9.43 at θ=0). Two additional large families, PKDF517 and PKDF741, co-segregate recessive deafness with markers linked to the same interval. Haplotype analyses of these three families refined the interval to 3.84 Mb defined by D9S1818 (centromeric) and D9SH6 (telomeric). This interval overlaps with the previously reported DFNB33 locus whose chromosomal map position has been recently revised and assigned to a new position on chromosome 10p11.23–q21.1. The nonsyndromic deafness locus on chromosome 9q segregating in family PKDF280 was designated DFNB79. We are currently screening the 113 candidate DFNB79 genes for mutations and have excluded CACNA1B, EDF1, PTGDS, EHMT1, QSOX2, NOTCH1, MIR126 and MIR602.
hereditary deafness; DFNB79; DFNB33; Pakistan; chromosome 9q34.3
Complete deficiency of a member of the type II transmembrane serine protease family, tmprss1 (also known as hepsin), is associated with severe to profound hearing loss in mice and a gross enlargement of the tectorial membrane in the cochlea. Levels of thyroxine in these mice have been shown to be significantly lower compared to wild type controls. Since thyroxine is critical for inner ear development, we delivered thyroxine to these mice during the prenatal or postnatal stage of development. Both treatments could not ameliorate hearing loss or correct deformities in the tectorial membrane of these mutant mice, suggesting that a deficiency in tmprss1 affects thyroxine responsiveness in the inner ear in vivo.
transmembrane serine protease; hepsin; tectorial membrane; hypothyroidism; cochlea; thyroid hormones; resistance to thyroid hormones
Genetic rearrangement of TMPRSS2 regulatory sequences and coding sequences of the ERG gene has been detected in nearly half of prostate cancers. Quantitative assays to detect such TMPRSS2-ERG gene fusion have been limited to real time PCR techniques that rely on reverse transcriptase-based amplification. We sought to develop a novel assay that uses branched DNA (bDNA) technology to measure TMPRSS2-ERG fusion.
Branched DNA probes were designed to detect TMPRSS2-ERG gene fusion in prostate cancer cell lines. Non-quantitative, nested reverse transcription (RT)-PCR and fluorescence in situ hybridization (FISH) were used to ascertain TMPRSS2-ERG gene fusion status in prostate tissues.
The branched DNA assay detected TMPRSS2-ERG gene fusion from less than 200 picogram of prostate cancer RNA, whereas more than 600 picogram of RNA was required for fusion gene detection by one step real time RT-PCR. In evaluation of clinical prostatectomy specimens, the branched DNA assay showed concordant detectable fusion signal in all 9 clinical samples that had fusion detected by nested RT-PCR or FISH. Moreover, branched DNA detected gene fusion in 2 of 16 prostate cancer tissue specimens that was not detected by FISH nor nested RT-PCR.
Our findings demonstrate a branched DNA assay that is effective for detection of TMPRSS2-ERG gene fusion in prostate cancer clinical specimens, thus providing an alternative method to ascertain the TMPRSS2-ERG gene fusion in human prostate cancer tissue.
branched DNA; prostate cancer; ERG; biomarker
Pendred syndrome is the association between congenital sensorineural deafness and goitre. The disorder is characterised by the incomplete discharge of radioiodide from a primed thyroid following perchlorate challenge. However, the molecular basis of the association between hearing loss and a defect in organification of iodide remains unclear. Pendred syndrome is inherited as an autosomal recessive trait and has recently been mapped to 7q31 coincident with the non-syndromic deafness locus DFNB4. To define the critical linkage interval for Pendred syndrome we have studied five kindreds, each with members affected by Pendred syndrome. All families support linkage to the chromosome 7 region, defined by the microsatellite markers D7S501-D7S523. Detailed haplotype analysis refines the Pendred syndrome linkage interval to a region flanked by the marker loci D7S501 and D7S525, separated by a genetic distance estimated to be 2.5 cM. As potential candidate genes have as yet not been mapped to this interval, these data will contribute to a positional cloning approach for the identification of the Pendred syndrome gene.
Hepcidin is the master regulator of iron homeostasis. In the liver, iron-dependent hepcidin activation is regulated through Bmp6 and its membrane receptor hemojuvelin (Hjv) whereas, in response to iron deficiency, hepcidin repression seems to be controlled by a pathway involving the serine protease matriptase-2 (encoded by Tmprss6). To determine the relationship between Bmp6 and matriptase-2 pathways, Tmprss6−/− mice (characterized by increased hepcidin levels and anemia) and Bmp6−/− mice (exhibiting severe iron overload due to hepcidin deficiency) were intercrossed. We showed that loss of Bmp6 decreased hepcidin levels, increased hepatic iron and, importantly, corrected hematological abnormalities in Tmprss6−/− mice. This suggests that elevated hepcidin levels in patients with familial iron-refractory iron deficiency anemia are due to excess signaling through the Bmp6/Hjv pathway.
Anemia, Iron-Deficiency; metabolism; Animals; Antimicrobial Cationic Peptides; metabolism; Bone Morphogenetic Protein 6; metabolism; Female; Iron; metabolism; Iron, Dietary; metabolism; Liver; metabolism; Membrane Proteins; metabolism; Mice; Mice, Knockout; Serine Endopeptidases; metabolism; Signal Transduction; physiology; hepcidin; hemojuvelin; bmp6; matriptase2; tmprss6
Non-syndromal, recessive deafness (NSRD) is the most common form of inherited deafness or hearing impairment in humans. NSRD is genetically heterogeneous and it has been estimated that as many as 35 different loci may be involved. We report the mapping of a novel locus for autosomal recessive, non-syndromal deafness (DFNB16) in three consanguineous families originating from Pakistan and the Middle East. Using multipoint analysis (HOMOZ/MAPMAKER) a maximum combined lod score of 6.5 was obtained for the interval D15S1039-D15S123. Recombination events and haplotype analysis define a 12-14 cM critical region between the markers D15S1039 and D15S155 on chromosome 15q15-q21.
It has been demonstrated that mutations in deafness, autosomal recessive 31 (DFNB31), the gene encoding whirlin, is responsible for nonsyndromic hearing loss (NSHL; DFNB31) and Usher syndrome type II (USH2D). We screened DFNB31 in a large cohort of patients with different clinical subtypes of Usher syndrome (USH) to determine the prevalence of DFNB31 mutations among USH patients.
DFNB31 was screened in 149 USH2, 29 USH1, six atypical USH, and 11 unclassified USH patients from diverse ethnic backgrounds. Mutation detection was performed by direct sequencing of all coding exons.
We identified 38 different variants among 195 patients. Most variants were clearly polymorphic, but at least two out of the 15 nonsynonymous variants (p.R350W and p.R882S) are predicted to impair whirlin structure and function, suggesting eventual pathogenicity. No putatively pathogenic mutation was found in the second allele of patients with these mutations.
DFNB31 is not a major cause of USH.
Mutations of GJB2 and GJB6 (connexin-26 and 30) at the DFNB1 locus are the most common cause of autosomal recessive, nonsyndromic deafness. Despite their widespread expression throughout the vestibular system, vestibular dysfunction has not been widely recognized as a commonly associated clinical feature. The observations of vertigo accompanying DFNB1 deafness in several large families prompted our hypothesis that vestibular dysfunction may be an integral, but often overlooked, component of DFNB1 deafness. Our aim was to define the prevalence of vestibular dysfunction in Cases of DFNB1 deafness and Controls with other forms of deafness. We developed and used a survey to assess symptoms of vestibular dysfunction, medical, and family history was distributed to Cases with deafness due to pathogenic GJB2 and/or GJB6 mutations and deaf Controls without DFNB1 deafness. Our results showed: Surveys were returned by 235/515 Cases (46%) with DFNB1 mutations and 121/ 321 Controls (38%) without these mutations. The mean age of Cases (41) was younger than Controls (51; p<0.001). Vestibular dysfunction was reported by 127 (54%) of Cases and was present at significantly higher rates in Cases than in deaf Controls without DFNB1 deafness (p< 0.03). Most (63%) had to lie down in order for vertigo to subside, and 48% reported that vertigo interfered with activities of daily living. Vertigo was reported by significantly more Cases with truncating than non-truncating mutations and was also associated with a family history of dizziness. We conclude that vestibular dysfunction appears to be more common in DFNB1 deafness than previously recognized and affects activities of daily living in many patients.
Vertigo; Vestibular Dysfunction; Connexin; DFNB1; Deafness
In the present study, genotype–phenotype correlations in eight Dutch DFNB8/10 families with compound heterozygous mutations in TMPRSS3 were addressed. We compared the phenotypes of the families by focusing on the mutation data. The compound heterozygous variants in the TMPRSS3 gene in the present families included one novel variant, p.Val199Met, and four previously described pathogenic variants, p.Ala306Thr, p.Thr70fs, p.Ala138Glu, and p.Cys107Xfs. In addition, the p.Ala426Thr variant, which had previously been reported as a possible polymorphism, was found in one family. All affected family members reported progressive bilateral hearing impairment, with variable onset ages and progression rates. In general, the hearing impairment affected the high frequencies first, and sooner or later, depending on the mutation, the low frequencies started to deteriorate, which eventually resulted in a flat audiogram configuration. The ski-slope audiogram configuration is suggestive for the involvement of TMPRSS3. Our data suggest that not only the protein truncating mutation p.T70fs has a severe effect but also the amino acid substitutions p.Ala306Thr and p.Val199Met. A combination of two of these three mutations causes prelingual profound hearing impairment. However, in combination with the p.Ala426Thr or p.Ala138Glu mutations, a milder phenotype with postlingual onset of the hearing impairment is seen. Therefore, the latter mutations are likely to be less detrimental for protein function. Further studies are needed to distinguish possible phenotypic differences between different TMPRSS3 mutations. Evaluation of performance of patients with a cochlear implant indicated that this is a good treatment option for patients with TMPRSS3 mutations as satisfactory speech reception was reached after implantation.
Electronic supplementary material
The online version of this article (doi:10.1007/s10162-011-0282-3) contains supplementary material, which is available to authorized users.
DFNB8/10; TMPRSS3 mutations; cochlear implantation; ski-slope audiogram; genotype–phenotype correlations