Neonatal cytokine profile in the airway mucosal lining fluid is skewed by maternal atopy.

RATIONALE: Heredity from mother or father may impact differently in complex diseases, such as atopy. Maternal atopy is a stronger risk factor than paternal atopy for the development of atopy in the offspring. We hypothesized that mother's and father's atopy would have a differential imprinting on the cytokines and chemokines in the upper airway mucosal lining fluid of healthy neonates. OBJECTIVES: To study parental atopic imprinting on the cytokines and chemokines in the upper airway mucosal lining fluid of healthy neonates. METHODS: Eighteen cytokines and chemokines were quantified in nasal mucosal lining fluid in 309 neonates from the novel unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC) birth cohort. MEASUREMENTS AND MAIN RESULTS: Maternal, but not paternal, atopic status (asthma, hay fever, or eczema with or without sensitization) was associated with general down-regulation of all 18 mediators assessed by principal component analysis (overall P = 0.015). CONCLUSIONS: Maternal atopy, but not paternal atopy, showed a strong linkage with a suppressed mucosal cytokine and chemokine signature in asymptomatic neonates, suggesting imprinting by the maternal milieu in utero or perinatal life.

Fiber optical imaging of astroglial calcium signaling in the respiratory network in the working heart brainstem preparation.

The neuronal activity in the respiratory network strongly depends on a variety of different neuromodulators. Given the essential role of astrocytes in stabilizing respiratory network activity generated by neurons in the preBötzinger complex (preBötC), our aim was to investigate astrocytic calcium signaling in the working heart brainstem preparation using fiber-optical imaging. By using transgenic mice that express GCaMP6s specifically in astrocytes, we successfully recorded astrocytic calcium signals in response to norepinephrine from individual astrocytes.

Angiotensin II increases respiratory rhythmic activity in the preBötzinger complex without inducing astroglial calcium signaling.

Angiotensin II (Ang II) is the primary modulator of the renin-angiotensin system and has been widely studied for its effect on the cardiovascular system. While a few studies have also indicated an involvement of Ang II in the regulation of breathing, very little is known in this regard and its effect on brainstem respiratory regions such as the preBötzinger complex (preBötC), the kernel for inspiratory rhythm generation, has not been investigated yet. This study reports that Ang II temporarily increases phrenic nerve activity in the working heart-brainstem preparation, indicating higher central respiratory drive. Previous studies have shown that the carotid body is involved in mediating this effect and we revealed that the preBötC also plays a part, using acute slices of the brainstem. It appears that Ang II is increasing the respiratory drive in an AT1R-dependent manner by optimizing the interaction of inhibitory and excitatory neurons of the preBötC. Thus, Ang II-mediated effects on the preBötC are potentially involved in dysregulating breathing in patients with acute lung injury.

Computational modelling of 5-HT receptor-mediated reorganization of the brainstem respiratory network.

Brainstem respiratory neurons express the glycine α(3) receptor (Glyα(3) R), which is a target of modulation by several serotonin (5-HT) receptor agonists. Application of the 5-HT(1A) receptor (5-HT(1A) R) agonist 8-OH-DPAT was shown (i) to depress cellular cAMP, leading to dephosphorylation of Glyα(3) R and augmentation of postsynaptic inhibition of neurons expressing Glyα(3) R (Manzke et al., 2010) and (ii) to hyperpolarize respiratory neurons through 5-HT-activated potassium channels. These processes counteract opioid-induced depression and restore breathing from apnoeas often accompanying pharmacotherapy of pain. The effect is postulated to rely on the enhanced Glyα(3) R-mediated inhibition of inhibitory neurons causing disinhibition of their target neurons. To evaluate this proposal and investigate the neural mechanisms involved, an established computational model of the brainstem respiratory network (Smith et al., 2007), was extended by (i) incorporating distinct subpopulations of inhibitory neurons (glycinergic and GABAergic) and their synaptic interconnections within the Bötzinger and pre-Bötzinger complexes and (ii) assigning the 5-HT(1A) R-Glyα(3) R complex to some of these inhibitory neuron types in the network. The modified model was used to simulate the effects of 8-OH-DPAT on the respiratory pattern and was able to realistically reproduce a number of experimentally observed responses, including the shift in the onset of post-inspiratory activity to inspiration and conversion of the eupnoeic three-phase rhythmic pattern into a two-phase pattern lacking the post-inspiratory phase. The model shows how 5-HT(1A) R activation can produce a disinhibition of inspiratory neurons, leading to the recovery of respiratory rhythm from opioid-induced apnoeas.

Elevated exhaled nitric oxide in high-risk neonates precedes transient early but not persistent wheeze.

RATIONALE: Elevated fractional exhaled nitric oxide (Fe(NO)) concentration has been suggested to predict early childhood wheeze and sensitization. OBJECTIVES: To investigate the association between Fe(NO) in asymptomatic neonates and the development of wheeze patterns and atopic intermediary phenotypes in the first 6 years of life. METHODS: We measured Fe(NO) in 253 healthy 1-month-old neonates from the Copenhagen Prospective Study on Asthma in Childhood birth cohort and monitored prospectively wheezy episodes by daily diary cards during the first 6 years of life. Total IgE, specific IgE, and blood eosinophil count were assessed at age 6 months, 4 years, and 6 years. Associations were studied by Cox regression, logistic regression, and generalized linear models. MEASUREMENTS AND MAIN RESULTS: Increased neonatal Fe(NO) level was significantly associated with the development of recurrent wheeze in the first year of life (hazard ratio, 2.63; 95% confidence interval, 1.1 to 6.2; P = 0.026) but not thereafter. The association was unaffected by environmental tobacco smoke exposure. Fe(NO) was not associated with elevated levels of total IgE, specific IgE, or blood eosinophil count at any age point and was unrelated to neonatal lung function. CONCLUSIONS: An elevated Fe(NO) level in asymptomatic neonates born to mothers with asthma preceded the development of transient early wheezing, but not persistent wheezing during preschool age, and was unrelated to atopy. This suggests an early disease process other than small airway caliber contributing to the transient wheezing phenotype.

Persistent Expression of Serotonin Receptor 5b Alters Breathing Behavior in Male MeCP2 Knockout Mice.

Mutations in the transcription factor methyl-CpG-binding protein 2 (MeCP2) cause the neurodevelopmental disorder Rett syndrome (RTT). Besides many other neurological problems, RTT patients show irregular breathing with recurrent apneas or breath-holdings. MeCP2-deficient mice, which recapitulate this breathing phenotype, show a dysregulated, persistent expression of G-protein-coupled serotonin receptor 5-ht5b (Htr5b) in the brainstem. To investigate whether the persistence of 5-ht5b expression is contributing to the respiratory phenotype, we crossbred MeCP2-deficient mice with 5-ht5b-deficient mice to generate double knockout mice (Mecp2-/y ;Htr5b-/-). To compare respiration between wild type (WT), Mecp2-/y and Mecp2-/y ;Htr5b-/- mice, we used unrestrained whole-body plethysmography. While the breathing of MeCP2-deficient male mice (Mecp2-/y ) at postnatal day 40 is characterized by a slow breathing rate and the occurrence of prolonged respiratory pauses, we found that in MeCP2-deficient mice, which also lacked the 5-ht5b receptor, the breathing rate and the number of pauses were indistinguishable from WT mice. To test for a potential mechanism, we also analyzed if the known coupling of 5-ht5b receptors to Gi proteins is altering second messenger signaling. Tissue cAMP levels in the medulla of Mecp2-/y mice were decreased as compared to WT mice. In contrast, cAMP levels in Mecp2-/y ;Htr5b-/- mice were indistinguishable from WT mice. Taken together, our data points towards a role of 5-ht5b receptors within the complex breathing phenotype of MeCP2-deficient mice.

A neuronal role of the Alanine-Serine-Cysteine-1 transporter (SLC7A10, Asc-1) for glycine inhibitory transmission and respiratory pattern.

The Alanine-Serine-Cysteine-1 transporter (SLC7A10, Asc-1) has been shown to play a role in synaptic availability of glycine although the exact mechanism remains unclear. We used electrophysiological recordings and biochemical experiments to investigate the role of Asc-1 transporter in glycinergic transmission in the brainstem respiratory network. Using both the Asc-1 substrate and transportable inhibitor D-isoleucine (D-Ile), and the non-transportable Asc-1 blocker Lu AE00527 (Lu), we found that D-Ile reduces glycinergic transmission and increases glycine release via hetero-exchange, whereas Lu has no acute effect on glycinergic synaptic transmission. Furthermore, D-Ile increases the frequency and reduces amplitude of the phrenic nerve activity in the arterially-perfused working heart brainstem preparation. These results suggest a role of Asc-1 in modulating presynaptic glycine levels that can impact on the respiratory network.

Vertical corneal striae in families with autosomal dominant hearing loss: DFNA9/COCH.

PURPOSE: Investigation of a possible association between vertical corneal striae and mutations in the COCH gene, observed in four DFNA9 families with autosomal dominant hearing loss and vestibular dysfunction. DESIGN: Prospective case series. METHODS: Ophthalmologic examinations with photography of the cornea after instillation of fluorescein were performed in 98 family members with 61 mutation carriers of four DFNA9 families at the Radboud University Nijmegen Medical Centre. Families 1 and 2 harbor the Pro51Ser mutation, and families 3 and 4 harbor the Gly88Glu and the Gly87Trp mutation, respectively. Statistical analysis was performed to find an association between the vertical corneal striae and the COCH mutation for each family and to test whether the four families were different in this respect. RESULTS: The vertical corneal striae were exclusively visible after instillation of fluorescein. They caused minor problems, as dry eye symptoms, and were not present in the general Dutch ophthalmologic population. The striae were present from an age of 47 years in 32 individuals, of whom 27 individuals had a COCH mutation. Statistical analysis on the striae and the COCH mutations showed a significant association in families 1, 2, and 3 (P = .0006), but not in family 4 (P = .63). CONCLUSIONS: Data analysis demonstrated a significant association between vertical corneal striae and the Pro51Ser and Gly88Glu mutations in the COCH gene in DFNA9 families 1, 2, and 3 with cochleovestibular dysfunction. Our findings suggest that the vertical corneal striae and cochleovestibular dysfunction may be caused by the same COCH mutations.

Cochleovestibular and ocular features in a Dutch DFNA11 family.

OBJECTIVES: To report hearing impairment and vestibular and ocular features in a Dutch DFNA11 family and to compare these results to reported data on three other DFNA11 families. STUDY DESIGN: Family study. METHODS: Regression analysis was performed in relation to age to outline the development of hearing thresholds and speech recognition scores. Vestibular and ocular functions were examined. RESULTS: First symptoms of hearing impairment started between the ages of 4 and 43 years. Most of the audiograms were symmetric and flat or downsloping. The annual threshold deterioration increased from 0.2 to 2.6 dB per year at 0.25 to 8 kHz in the longitudinal analyses and in the cross-sectional analysis from 0.3 to 0.9 dB per year. The speech recognition score was quite good, deteriorating by 0.9% per year from a 90% score at the age of 36 years onward. Remarkably, extensive ocular examination including corrected visual acuity and refraction measurements, slit-lamp examination, ophthalmoscopy, Goldmann perimetry, electroretinography and electro-oculography revealed signs of subclinical retinal dysfunction. None of the patients showed the classic triad of retinitis pigmentosa. Pure-tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers were fairly similar to previously described DFNA11 families. CONCLUSION: Even though the diverse mutations are located in different regions of the myosin VIIa gene, the cochleovestibular phenotype is fairly similar in all DFNA11 families. Surprisingly, only in this family was subclinical retinal dysfunction detected.

Vestibular deterioration precedes hearing deterioration in the P51S COCH mutation (DFNA9): an analysis in 74 mutation carriers.

OBJECTIVES: To analyze cochleovestibular impairment features in P51S COCH mutation carriers (n = 22) in a new, large Dutch family and to compare the results to those obtained in previously identified similar mutation carriers (n = 52). To evaluate age-related features between progressive hearing and vestibular impairment of all mutation carriers (n = 74). STUDY DESIGN: Family study. METHODS: Regression analysis was performed in relation to age to outline the development of hearing thresholds, speech recognition scores, and vestibulo-ocular reflex time constant as the key vestibular response parameter. RESULTS: Pure tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers in the new family were essentially similar to those previously established in all other mutation carriers. Hearing started to deteriorate in all mutation carriers from 43 years of age onwards, whereas deterioration of vestibular function started from age 34. CONCLUSION: Vestibular impairment starts earlier, progresses more rapidly, and, eventually, is more complete than hearing impairment in P51S COCH mutation carriers.

Airway mucosal immune-suppression in neonates of mothers receiving A(H1N1)pnd09 vaccination during pregnancy.

BACKGROUND: It is recommended to vaccinate pregnant women against influenza. A possible impact on the immune expression of the fetus has never been studied. We aim to study the immune signature in the upper airways and the incidence of infections in neonates born to mothers receiving Influenza A(H1N1)pnd09 vaccination during pregnancy. METHODS: One hundred and fifty-six women from the unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC2010) received Influenza A(H1N1)pnd09-vaccination during the 2009 pandemic. Fifty-one mothers received the vaccine during pregnancy and 105 after pregnancy; 332 neonates of nonvaccinated mothers were included as secondary controls. Nasal mucosal lining fluid was sampled in 488 neonates and assessed for interleukin (IL)-12p70, IP-10, interferon-gamma (IFN)-γ, tumor necrosis factor-alpha (TNF)-α, MIP-1ß, MCP-1, MCP-4, IL-4, IL-5, IL-13, eotaxin-1, eotaxin-3, TARC, MDC, IL-17, IL-1ß, IL-8, transforming growth factor beta (TGF)-ß1, IL-10 and IL-2. Infections were monitored the first year of life by daily diary cards and clinical controls. RESULTS: Neonates of mothers vaccinated during pregnancy had significant up-regulation of TGF-ß1 [ratio = 1.52 (1.22-1.90), P = 0.0002], and corresponding down-regulation (P < 0.05) of IL-12p70, IFN-γ, IL-5, eotaxin-1, TARC, MDC, IL-8 in comparison to those vaccinated after pregnancy. The lag-time from vaccination during pregnancy to assessment of the immune signature showed significant and positive association to up-regulation of TGF-ß1 levels (P = 0.0003) and significant negative association to other mediators. The study was not powered to study differences in the incidence of infections in early infancy which did not differ between the study groups. CONCLUSION: Influenza A(H1N1)pnd09 vaccination during pregnancy up-regulates TGF-ß1 and down-regulates key mediators of the protective immunity.

DENND1B gene variants associate with elevated exhaled nitric oxide in healthy high-risk neonates.

RATIONALE OF THE STUDY: Increased neonatal fraction of exhaled nitric oxide (FeNO) is associated with lung symptoms early in life, while predictors of neonatal FeNO levels are unknown. The objective of this study was to investigate perinatal and genetic predictors of FeNO in healthy at-risk neonates. METHODS: FeNO was measured during sedation by single-breath and tidal-breathing techniques in 253 one-month-old neonates from the Copenhagen Prospective Study on Asthma in Childhood (COPSAC2000 ) birth cohort. The risk factor analyses included genetic variants in DENND1B, Filaggrin, and ORMDL3; anthropometrics; demographics; socioeconomics; paternal atopy; maternal smoking, and mother's consumption of paracetamol and antibiotics during 3rd trimester; and neonatal bacterial airway colonization. RESULTS: FeNO values measured by the single-breath versus tidal-breathing technique yielded slightly higher values (median, 21.0 ppb; range, 2.0-74.0 ppb vs. 16.0 ppb; 1.0-67.0 ppb; P<0.0001) with increasing differences conditional on increasing FeNO values (P<0.0001). The multivariable analysis including all risk factors showed that the DENND1B rs2786098 C allele was associated with increasing levels of FeNO (additive model; +2.30 ppb per C allele; 95% CI, 0.10-5.00 ppb; P=0.04) and that children of atopic fathers had elevated FeNO (+2.90 ppb; 95% CI, 0.38-5.43 ppb; P=0.02). We did not detect association between the remaining risk factors and neonatal FeNO levels. CONCLUSION: Increased FeNO in healthy newborns seems strongly influenced by genetics including father's atopy and child's variants in the DENND1B locus at chromosome 1q31.3.

Effects of glycinergic inhibition failure on respiratory rhythm and pattern generation.

Inhibitory interactions between neurons of the respiratory network are involved in rhythm generation and pattern formation. Using a computational model of brainstem respiratory networks, we investigated the possible effects of suppressing glycinergic inhibition on the activity of different respiratory neuron types. Our study revealed that progressive suppression of glycinergic inhibition affected all neurons of the network and disturbed neural circuits involved in termination of inspiration. Causal was a dysfunction of postinspiratory inhibition targeting inspiratory neurons, which often led to irregular preterm reactivation of these neurons, producing double or multiple short-duration inspiratory bursts. An increasing blockade of glycinergic inhibition led to apneustic inspiratory activity. Similar disturbances of glycinergic inhibition also occur during hypoxia. A clear difference in prolonged hypoxia, however, is that the rhythm terminates in expiratory apnea. The critical function of glycinergic inhibition for normal respiratory rhythm generation and the consequences of its reduction, including in pathological conditions, are discussed.

Prevalence and predictors of antibiotic administration during pregnancy and birth.

BACKGROUND: Antibiotic treatment during pregnancy and birth is very common. In this study, we describe the estimated prevalence of antibiotic administration during pregnancy and birth in the COPSAC2010 pregnancy cohort, and analyze dependence on social and lifestyle-related factors. METHODS: 706 pregnant women from the novel unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC2010) pregnancy cohort participated in this analysis. Detailed information on oral antibiotic prescriptions during pregnancy filled at the pharmacy was obtained and verified longitudinally. Information on intrapartum antibiotics, social, and lifestyle-factors was obtained by personal interviews. RESULTS: The prevalence of antibiotic use was 37% during pregnancy and 33% intrapartum. Lower maternal age at birth; adjusted odds ratio (aOR) 0.94, 95% CI, [0.90-0.98], p = 0.003 and maternal smoking; aOR 1.97, 95% CI, [1.07-3.63], p = 0.030 were associated with use of antibiotics for urinary tract infection during pregnancy. Maternal educational level (low vs. high), aOR 2.32, 95% CI, [1.24-4.35], p = 0.011, maternal asthma; aOR 1.99, 95% CI, [1.33-2.98], p < 0.001 and previous childbirth; aOR 1.80, 95% CI, [1.21-2.66], p = 0.004 were associated with use of antibiotics for respiratory tract infection during pregnancy. Lower gestational age; aOR 0.72, 95% CI, [0.61-0.85], p < 0.001, maternal smoking; aOR 2.84, 95% CI, [1.33-6.06], p = 0.007, and nulliparity; aOR 1.79, 95% CI, [1.06-3.02], p = 0.030 were associated with administration of intrapartum antibiotics in women giving birth vaginally. CONCLUSION: Antibiotic administration during pregnancy and birth may be influenced by social and lifestyle-factors. Understanding such risk factors may guide preventive strategies in order to avoid unnecessary use of antibiotics.

Altered response to A(H1N1)pnd09 vaccination in pregnant women: a single blinded randomized controlled trial.

BACKGROUND: Pregnant women were suspected to be at particular risk when H1N1pnd09 influenza became pandemic in 2009. Our primary objective was to compare the immune responses conferred by MF59®-adjuvanted vaccine (Focetria®) in H1N1pnd09-naïve pregnant and non-pregnant women. The secondary aims were to compare influences of dose and adjuvant on the immune response. METHODS: The study was nested in the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC2010) pregnancy cohort in 2009-2010 and conducted as a single-blinded block-randomised [1∶1∶1] controlled clinical trial in pregnant women after gestational week 20: (1) 7.5 µg H1N1pnd09 antigen with MF59-adjuvant (Pa7.5 µg); (2) 3.75 µg antigen half MF59-adjuvanted (Pa3.75 µg); (3) 15 µg antigen unadjuvanted (P15 µg); and in non-pregnant women receiving (4) 7.5 µg antigen full adjuvanted (NPa7.5 µg). Blood samples were collected at baseline, 3 weeks, 3 and 10 months after vaccination, adverse events were recorded prospectively. RESULTS: 58 pregnant women were allocated to Pa7.5 µg and 149 non-pregnant women were recruited to NPa7.5 µg. The sero-conversion rate was significantly increased in non-pregnant (NPa7.5 µg) compared with pregnant (Pa7.5 µg) women (OR = 2.48 [1.03-5.95], p = 0.04) and geometric mean titers trended towards being higher, but this difference was not statistically significant (ratio 1.27 [0.85-1.93], p = 0.23). The significant titer increase rate showed no difference between pregnant (Pa7.5 µg) and non-pregnant (NPa7.5 µg) groups (OR = 0.49 [0.13-1.85], p = 0.29). CONCLUSION: Our study suggests the immune response to the 7.5 µg MF59-adjuvanted Focetria® H1N1pnd09 vaccine in pregnant women may be diminished compared with non-pregnant women. TRIAL REGISTRATION: ClinicalTrials.gov NCT01012557.

Living with cat and dog increases vaginal colonization with E. coli in pregnant women.

BACKGROUND: Furred pets in the household are known reservoirs for pathogenic bacteria, but it is not known if transmission of bacteria between pet and owner leads to significantly increased rate of infections. We studied whether cats and dogs living in the household of pregnant women affect the commensal vaginal flora, and furthermore the need for oral antibiotics and rate of urinary tract infections during pregnancy. METHODS: The novel unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC(2010)) pregnancy cohort of 709 women participated in this analysis. Detailed information on pet exposure, oral antibiotic prescriptions filled at pharmacy and urinary tract infection during pregnancy was obtained and verified prospectively during clinic visits. Vaginal cultures were obtained at pregnancy week 36. RESULTS: Women, who had cat or dog in the home during pregnancy, had a different vaginal flora, in particular with increased Escherichia coli (E. coli) colonization; odds ratio after adjustment for lifestyle confounders and antibiotics 2.20, 95% CI, [1.27-3.80], p=0.005. 43% of women living with cat and/or dog in the home used oral antibiotics compared to 33% of women with no cat or dog; adjusted odds ratio 1.51, 95% CI, [1.08-2.12], p=0.016. Women living with cat had increased frequency of self-reported urinary tract infection; adjusted odds ratio 1.57, 95% CI, [1.02-2.43], p=0.042. CONCLUSIONS: The increased vaginal E. coli colonization in women living with cat or dog suggests a clinically important transmission of pathogenic bacteria from pet to owner substantiated by increased rate of antibiotic use and urinary tract infections which, which is of particular concern during pregnancy.

Osteopathic treatment of patients with chronic non-specific neck pain: a randomised controlled trial of efficacy.

OBJECTIVE: Chronic non-specific neck pain (CNP) is a common, often disabling condition which still lacks a reliable therapeutic standard. Empiric evidence suggests that osteopathic interventions might be effective in alleviating CNP symptoms. A randomized controlled clinical trial of efficacy was performed to test this hypothesis. MATERIALS AND METHODS: 135 CNP sufferers were identified through advertisements, and 41 patients who met all relevant predefined criteria were recruited. All participants received a 12-min session of sham ultrasound once a week for an average of 10 weeks. In addition, a test-dependent osteopathic intervention of 45 min was given to 24 participants every other week. 40 participants could be followed up for 12 weeks after the end of therapy. The main outcome parameter was pain intensity measured on a numeric rating scale (NRS, range: 0-10). RESULTS: There were 2 dropouts in the intervention group and 2 in the control group. Average pain intensity decreased from 4.7 to 2.2 in the osteopathic group (p < 0.0005), and from 4.8 to 4.0 in the control group (p = 0.09). The intergroup difference of longitudinal changes was clearly significant, too (p = 0.02). Further slight but comparable reductions were observed at follow-up (0.3 and 0.4 NRS points, respectively). These changes seem to have a positive impact on quality of life, as assessed by generic and specific instruments such as the MOS SF-36 and the Northwick Park Pain Questionnaire. CONCLUSIONS: A series of test-dependent osteopathic interventions may be a promising therapeutic regimen for CNP sufferers. Further studies will have to demonstrate a) whether these findings are reproducible, and b) whether positive long-term outcomes can be achieved.

Identification and molecular modelling of a mutation in the motor head domain of myosin VIIA in a family with autosomal dominant hearing impairment (DFNA11).

Myosin VIIA is an unconventional myosin that has been implicated in Usher syndrome type 1B, atypical Usher syndrome, non-syndromic autosomal recessive hearing impairment (DFNB2) and autosomal dominant hearing impairment (DFNA11). Here, we present a family with non-syndromic autosomal dominant hearing impairment that clinically resembles the previously published DFNA11 family. The affected family members show a flat audiogram at young ages and only modest progression, most clearly at the high frequencies. In addition, they suffer from minor vestibular symptoms. Linkage analysis yielded a maximum two-point lodscore of 3.43 for marker D11S937 located within 1 cM of the myosin VIIA gene. The myosin VIIA gene was sequenced and 11 nucleotide variations were found. Ten nucleotide changes represent benign intronic variants, silent exon mutations or non-pathologic amino acid substitutions. One variant, a c.1373A-->T transversion that is heterozygously present in all affected family members and absent in 300 healthy individuals, is predicted to result in an Asn458Ile amino acid substitution. Asn458 is located in a region of the myosin VIIA motor domain that is highly conserved in different classes of myosins and in myosins of different species. To evaluate whether the Asn458Ile mutation was indeed responsible for the hearing impairment, a molecular model of myosin VIIA was built based on the known structure of the myosin II heavy chain from Dictyostelium discoideum. In this model, conformational changes in the protein caused by the amino acid substitution Asn458Ile are predicted to disrupt ATP/ADP binding and impair the myosin power-stroke, which would have a severe effect on the function of the myosin VIIA protein.

A novel mutation identified in the DFNA5 gene in a Dutch family: a clinical and genetic evaluation.

A novel DFNA5 mutation was found in a Dutch family, of which 37 members were examined. A nucleotide substitution was identified in the splice acceptor site of intron 7, leading to skipping of exon 8 in part of the transcripts. The mutation was found in 18 individuals. Sensorineural hearing impairment was non-syndromic and symmetric. In early life, presumably congenitally, hearing impairment amounted to 30 dB in the high frequencies. Progression was most pronounced at 1 kHz (1.8 dB/year). Speech recognition was relatively good with a phoneme score of about 50% at the age of 70. Onset age was 37 years, and recognition deteriorated by 1.3% per year. The recognition score deteriorated by 1.0% per decibel threshold increase from a mean pure-tone average (PTA at 1, 2 and 4 kHz) of 63 dB onwards. Vestibular function was generally normal. The second mutation identified in the DFNA5 gene results in hearing impairment, similar to that in the original DFNA5 family in terms of pure-tone thresholds, but with more favourable speech recognition.