Refik Caylan

Mutations of ESRRB Encoding Estrogen-Related Receptor Beta Cause Autosomal-Recessive Nonsyndromic Hearing Impairment DFNB35

In a large consanguineous family of Turkish origin, genome-wide homozygosity mapping revealed a locus for recessive nonsyndromic hearing impairment on chromosome 14q24.3-q34.12. Fine mapping with microsatellite markers defined the critical linkage interval to a 18.7 cM region flanked by markers D14S53 and D14S1015. This region partially overlapped with the DFNB35 locus. Mutation analysis of ESRRB, a candidate gene in the overlapping region, revealed a homozygous 7 bp duplication in exon 8 in all affected individuals. This duplication results in a frame shift and premature stop codon. Sequence analysis of the ESRRB gene in the affected individuals of the original DFNB35 family and in three other DFNB35-linked consanguineous families from Pakistan revealed four missense mutations. ESRRB encodes the estrogen-related receptor beta protein, and one of the substitutions (p.A110V) is located in the DNA-binding domain of ESRRB, whereas the other three are substitutions (p.L320P, p.V342L, and p.L347P) located within the ligand-binding domain. Molecular modeling of this nuclear receptor showed that the missense mutations are likely to affect the structure and stability of these domains. RNA in situ hybridization in mice revealed that Esrrb is expressed during inner-ear development, whereas immunohistochemical analysis showed that ESRRB is present postnatally in the cochlea. Our data indicate that ESRRB is essential for inner-ear development and function. To our knowledge, this is the first report of pathogenic mutations of an estrogen-related receptor gene.

Mutations of LRTOMT, a fusion gene with alternative reading frames, cause nonsyndromic deafness in humans

Many proteins necessary for sound transduction have been identified through positional cloning of genes that cause deafness. We report here that mutations of LRTOMT are associated with profound nonsyndromic hearing loss at the DFNB63 locus on human chromosome 11q13.3–q13.4. LRTOMT has two alternative reading frames and encodes two different proteins, LRTOMT1 and LRTOMT2, detected by protein blot analyses. LRTOMT2 is a putative methyltransferase. During evolution, new transcripts can arise through partial or complete coalescence of genes. We provide evidence that in the primate lineage LRTOMT evolved from the fusion of two neighboring ancestral genes, which exist as separate genes (Lrrc51 and Tomt) in rodents.

Effect of Education on the Rate of and the Understanding of Risk Factors for Intravascular Catheter–Related Infections

OBJECTIVE Intravascular catheters are indispensable tools in modern medical therapy. In spite of their great benefits, however, the widespread use of catheters leads to several complications, including infections that cause significant morbidity, mortality, and economic losses for hospitalized patients. DESIGN This study was conducted at Farabi Hospital, a 495-bed facility at Karadeniz Technical University Medical School in Trabzon, Turkey, and involved 3 separate periods: preeducation, education, and posteducation. Patients with intravascular catheters were monitored daily, as were the results of their physical examinations. The information acquired was recorded in a questionnaire. RESULTS During the preeducation period (October 2003 through March 2004), 405 intravascular catheters inserted into 241 patients were observed for 5,445 catheter-days. Seventy-one cases of intravascular catheter-related infection (CRI) were identified, giving a CRI rate of 13.04 infections per 1,000 catheter-days. The catheter-related bloodstream infection (CRBSI) rate was 8.3 infections per 1,000 catheter-days, and the exit-site infection (ESI) rate was 3.5 infections per 1,000 catheter-days. During the posteducation period (June through November 2004), 365 intravascular catheters inserted into 193 patients were observed for 5,940 catheter-days. Forty-five cases of CRI were identified, giving a rate of 7.6 infections per 1,000 catheter-days. The CRBSI rate was 4.7 infections per 1,000 catheter-days, and the ESI rate was 2.2 infections per 1,000 catheter-days. When findings from the 2 periods were compared, it was determined that education reduced CRI incidence by 41.7%. CONCLUSION CRI can be prevented when hospital personnel are well informed about these infections. We compared the knowledge levels of the relevant personnel in our hospital before and after theoretical and practical training and identified a significant increase in knowledge after training (P<.0001). Parallel to this, although still below ideal levels, we identified a significant improvement in the incidence of CRI during the posteducation period (P=.004). The rate was low for the first 3 months of this period but increased 2.08 times after the third month. In conclusion, regular training for the residents in charge of inserting intravascular catheters and the nurses and interns who maintain the catheters is highly effective in reducing the rate of CRI in large teaching hospitals.

GJB2 mutations in Turkish patients with ARNSHL: prevalence and two novel mutations.

Mutations in the connexin 26 gene (GJB2) cause a significant proportion of prelingual non-syndromic autosomal recessive deafness in all populations studied so far. To determine the percentage of hearing loss attributed to GJB2 in northeast Turkey, 93 unrelated patients with autosomal recessive non-syndromic hearing loss (ARNSHL) were screened. Seven different mutations were found in 29 of the patients with severe to profound hearing loss. The 35delG mutation was the most common mutation, accounting for 76% of all mutant GJB2 alleles. Four already described mutations, W24X, 310del14, delE120 and R184P and two novel mutations, Q80K and P173S, were identified. The allelic Delta(GJB6-D13S1830), which can cause hearing loss in combination with GJB2 mutations, was not present in our patients. Our results are comparable to those reported in other regions in Turkey and indicate that GJB2 mutations account for about 30% of Turkish patients with ARNSHL. Besides 35delG, W24X and delE120 occur more than once in the Turkish ARNSHL population with a frequency of about 5%.

A novel TMPRSS3 missense mutation in a DFNB8/10 family prevents proteolytic activation of the protein

Pathogenic mutations in TMPRSS3, which encodes a transmembrane serine protease, cause non-syndromic deafness DFNB8/10. Missense mutations map in the low density-lipoprotein receptor A (LDLRA), scavenger-receptor cysteine-rich (SRCR), and protease domains of the protein, indicating that all domains are important for its function. TMPRSS3 undergoes proteolytic cleavage and activates the ENaC sodium channel in a Xenopus oocyte model system. To assess the importance of this gene in non-syndromic childhood or congenital deafness in Turkey, we screened for mutations affected members of 25 unrelated Turkish families. The three families with the highest LOD score for linkage to chromosome 21q22.3 were shown to harbor P404L, R216L, or Q398X mutations, suggesting that mutations in TMPRSS3 are a considerable contributor to non-syndromic deafness in the Turkish population. The mutant TMPRSS3 harboring the novel R216L missense mutation within the predicted cleavage site of the protein fails to undergo proteolytic cleavage and is unable to activate ENaC, thus providing evidence that pre-cleavage of TMPRSS3 is mandatory for normal function.

A novel D458V mutation in the SANS PDZ binding motif causes atypical Usher syndrome

Homozygosity mapping and linkage analysis in a Turkish family with autosomal recessive prelingual sensorineural hearing loss revealed a 15-cM critical region at 17q25.1–25.3 flanked by the polymorphic markers D17S1807 and D17S1806. The maximum two-point lod score was 4.07 at θ=0.0 for the marker D17S801. The linkage interval contains the Usher syndrome 1G gene (USH1G) that is mutated in patients with Usher syndrome (USH) type 1g and encodes the SANS protein. Mutation analysis of USH1G led to the identification of a homozygous missense mutation D458V at the −3 position of the PDZ binding motif of SANS. This mutation was also present homozygously in one out of 64 additional families from Turkey with autosomal recessive nonsyndromic hearing loss and heterozygously in one out of 498 control chromosomes. By molecular modeling, we provide evidence that this mutation impairs the interaction of SANS with harmonin. Ophthalmologic examination and vestibular evaluation of patients from both families revealed mild retinitis pigmentosa and normal vestibular function. These results suggest that these patients suffer from atypical USH.

MYO15A (DFNB3) mutations in Turkish hearing loss families and functional modeling of a novel motor domain mutation.

Myosin XVA is an unconventional myosin which has been implicated in autosomal recessive nonsyndromic hearing impairment (ARNSHI) in humans. In Myo15A mouse models, vestibular dysfunction accompanies the autosomal recessive hearing loss. Genomewide homozygosity mapping and subsequent fine mapping in two Turkish families with ARNSHI revealed significant linkage to a critical interval harboring a known deafness gene MYO15A on chromosome 17p13.1‐17q11.2. Subsequent sequencing of the MYO15A gene led to the identification of a novel missense mutation, c.5492G → T (p.Gly1831Val) and a novel splice site mutation, c.8968 − 1G → C. These mutations were not detected in additional 64 unrelated ARNSHI index patients and in 230 Turkish control chromosomes. Gly1831 is a conserved residue located in the motor domains of the different classes of myosins of different species. Molecular modeling of the motor head domain of the human myosin XVa protein suggests that the Gly1831Val mutation inhibits the powerstroke by reducing backbone flexibility and weakening the hydrophobic interactions necessary for signal transmission to the converter domain.

The effect on the middle-ear cavity of an absorbable gelatine sponge alone and with corticosteroids

Abstract. The objectives of this study were to establish whether there is an obvious difference between intact mucosa and abraded mucosa of the middle-ear cavity in respect to the potential side effects from the application of absorbable gelatine sponge (Gelfoam) and to investigate if Gelfoam combined with corticosteroid ointment (cortimycine, sterile 1% hydrocortisone acetate) can reduce the occurrence of these effects. Twenty Albino rats were used in the study. These animals were divided into four groups, with ten ears in each group. In group A, the middle-ear mucosa was kept intact, and Gelfoam was inserted into the middle-ear cavity. In group B, the middle-ear mucosa was abraded, and Gelfoam was inserted. In group C, Gelfoam with corticosteroid was implanted over the intact mucosa, and in group D, the mucosa was abraded prior to the insertion of Gelfoam with corticosteroid. The changes were evaluated 8 weeks postoperatively. In group A, there was a minimal increase in fibroblastic activity, vascular proliferation with mild to moderate fibrosis and all but two tympanic membranes were perfectly normal. However, in group B, we encountered a significant increase in fibroblastic activity, vascular proliferation and fibrosis, and we observed that all tympanic membranes were moderately to severely thickened. These histopathologic changes related to Gelfoam were noted to be decreased in group C and especially in group D. As previously reported in the literature, Gelfoam was found to promote the formation of connective tissue in the middle-ear cavity regardless of the status of the mucosa. The unwanted effects of this material may be decreased if it is combined with corticosteroids in the middle-ear cavity.

Otolaryngologic aspects of tetanus

Abstract. Tetanus is considered a major health problem in the developing and under-developed countries, with approximately 1 million new cases occurring each year. We have evaluated the tetanus patients and their presenting complaints, the clinical findings and their relations to the head and neck region along with the frequency of otolaryngological findings and their correlation to the prognosis of this highly mortal disease. There were a total of 37 patients with generalized tetanus diagnosed and treated between 1991 and 2001. There were 25 women and 12 men with a mean age of 55±15.6 years. The most common presenting symptom was trismus, followed by neck pain, dysphagia, generalized pain and facial muscular contractions. Wound evaluation revealed that 72.9% of the patients had tetanus-prone wounds, and 27% had either no obvious wounds or a wound considered to be trivial by the patient. Only 62% percent of the patients had sought medical attention immediately after being injured. Three patients in our series were admitted to the otolaryngology clinic with upper aerodigestive tract symptoms. A comparison of complaints with clinical findings revealed a significant lack of correlation, emphasizing that complete physical examination must be performed when evaluating patients with trismus, dysphagia and neck pain. Tracheotomy was performed in 21 cases. There was a direct correlation between the clinical stage and the requirement of tracheotomy. Wound debridment was performed, and antibiotherapy, tetanus toxoid vaccine and immunoglobulin were administered. The mortality rate was 59.4% (22/37). Shorter incubation periods and periods of onset and a higher grade of disease were significantly related to high mortality rates (P=0.001). It is important to realize the fact that instead of looking for tetanus-prone wounds, one should be on the lookout for tetanus-prone patients. Consequently, on the part of the otolaryngologist, there should always be a high index of suspicion, and concerning patients with trismus or subacute progressive dysphagia, the possibility of tetanus must be borne in mind.

VEMP responses are not affected in non-insulin-dependent diabetes mellitus patients with or without polyneuropathy

Conclusion. Vestibular evoked myogenic responses (VEMPs) are not affected in non-insulin-dependent diabetes mellitus (NIDDM) patients with or without polyneuropathy. Objective. To compare VEMP responses of NIDDM patients and healthy subjects. Subjects and methods. VEMP responses were collected from 25 NIDDM patients with polyneuropathy (PNP), 13 NIDDM patients without PNP and 21 healthy subjects using click stimulation. After excluding ears with hearing loss (HL) (worse than 25 dB) the VEMP responses (p13 and n21 latencies and amplitude) recorded in 105 dB stimulus intensity were compared. Results. There was no statistically significant difference between groups. VEMP responses were found to be normal in NIDDM patients with or without PNP.