High-throughput detection of mutations responsible for childhood hearing loss using resequencing microarrays

Background  

Despite current knowledge of mutations in 45 genes that can cause nonsyndromic sensorineural hearing loss (SNHL), no unified clinical test has been developed that can comprehensively detect mutations in multiple genes. We therefore designed Affymetrix resequencing microarrays capable of resequencing 13 genes mutated in SNHL (GJB2, GJB6, CDH23, KCNE1, KCNQ1, MYO7A, OTOF, PDS, MYO6, SLC26A5, TMIE, TMPRSS3, USH1C). We present results from hearing loss arrays developed in two different research facilities and highlight some of the approaches we adopted to enhance the applicability of resequencing arrays in a clinical setting.     

GJB2 mutations and degree of hearing loss: a multicenter study

Hearing impairment (HI) affects 1 in 650 newborns, which makes it the most common congenital sensory impairment. Despite extraordinary genetic heterogeneity, mutations in one gene, GJB2, which encodes the connexin 26 protein and is involved in inner ear homeostasis, are found in up to 50% of patients with autosomal recessive nonsyndromic hearing loss. Because of the high frequency of GJB2 mutations, mutation analysis of this gene is widely available as a diagnostic test. In this study, we assessed the association between genotype and degree of hearing loss in persons with HI and biallelic GJB2 mutations. We performed cross-sectional analyses of GJB2 genotype and audiometric data from 1,531 persons, from 16 different countries, with autosomal recessive, mild-to-profound nonsyndromic HI. The median age of all participants was 8 years; 90% of persons were within the age range of 0-26 years. Of the 83 different mutations identified, 47 were classified as nontruncating, and 36 as truncating. A total of 153 different genotypes were found, of which 56 were homozygous truncating (T/T), 30 were homozygous nontruncating (NT/NT), and 67 were compound heterozygous truncating/nontruncating (T/NT). The degree of HI associated with biallelic truncating mutations was significantly more severe than the HI associated with biallelic nontruncating mutations (P<.0001). The HI of 48 different genotypes was less severe than that of 35delG homozygotes. Several common mutations (M34T, V37I, and L90P) were associated with mild-to-moderate HI (median 25-40 dB). Two genotypes--35delG/R143W (median 105 dB) and 35delG/dela(GJB6-D13S1830) (median 108 dB)--had significantly more-severe HI than that of 35delG homozygotes.     

Screening for diabetes in general practice: cross sectional population study

ObjectiveTo assess the policy proposed by the American Diabetes Association of universal screening in general practice of all patients aged over 45 years for diabetes.Design Cross sectional population study.Setting Local general practice in the United Kingdom.Participants All patients aged over 45 not known to have diabetes.Results Of 2481 patients aged over 45 and not known to have diabetes, 876 attended for screening. There were no significant demographic differences between the screened and unscreened patients. Prevalence of diabetes in patients with age as a sole risk factor was 0.2% (95% confidence interval 0% to 1.4%). Prevalence of diabetes in patients with age and one or more other risk factors (hypertension, obesity, or a family history of diabetes) was 2.8% (1.6% to 4.7%). Four hours a week for a year would be needed to screen all people over 45 in the practice''s population; about half this time would be needed to screen patients with risk factors other than age. More than 80% of patients newly diagnosed as having diabetes had a 10 year risk of coronary heart disease >15%, 73% (45% to 92%) were hypertensive, and 73% (45% to 92%) had a cholesterol concentration >5 mmol/l.Conclusions Screening for diabetes in general practice by measuring fasting blood glucose is feasible but has a very low yield in patients whose sole risk factor for diabetes is age over 45. Screening in a low risk population would best be targeted at patients with multiple risk factors.

What is already known on this topic

Between a third and a half of cases of diabetes are undiagnosed at any one timeNew cases can be identified by screening groups of patients at riskThe American Diabetes Association has proposed the screening of all patients aged over 45 every three years

What this study adds

Screening for diabetes in general practice by measuring fasting blood glucose is feasible but requires much staff timeScreening solely on the basis of age has a very low yield and screening would best be targeted at patients with multiple risk factors for diabetes     

Linkage study of DFNB3 responsible for hearing loss in human

BACKGROUND:

Hearing disorders represent a significant health problem worldwide. Recessive inherited cases of the deafness are more prevalent in Pakistan due to consanguineous marriages. Deafness caused by DFNB3 is due to mutation in the gene MYO XVA and its prevalence among Pakistani population is about 5%.

MATERIALS AND METHODS:

Families with at least two or more individual affected with deafness were selected from different areas of District Okara of Pakistan. Six consanguineous families of different ethnic groups having deaf individuals were studied. All these families had three or more deaf individuals in either two or more sib ships. Family history was taken to minimize the chances of other abnormalities. Pedigrees drawn by using Cyrillic software (version 2.1) showed that all the marriages were consanguineous and the families have recessive mode of inheritance. Three STR markers were selected and amplified on all the samples of six families through PCR. The PCR products were then genotyped on non denaturing polyacrylamide gel electrophoresis (PAGE). Haplotypes were constructed to determine the pattern of inheritance and also to determine whether a family was linked or unlinked with known DFNB3 locus.

RESULTS:

One out of six families showed linkage to the DFNB3 while rest of the families remained unlinked. Carriers of deafness genes were identified and information was provided to the families on request.

CONCLUSION:

Knowledge about the genetic causes of deafness provide insight into the variable expression of genes involved in this hereditary problem and may allow the prediction and prevention of associated health problems.     

Identification of impaired hearing in early childhood.

Although the incidence of congenital deafness is high, routine neonatal screening for this problem is not practised, and early identification of congenital or early acquired deafness is relatively rare. Delaying therapy until a child is 3 or more years old severely limits speech development, language acquisition and learning. The commonest causes of delay in diagnosis are the refusal of physicians to listen to the parents'' observations, their failure to screen children for hearing and speech problems, and their reluctance to arrange prompt referral for audiologic assessment. Diagnostic delay occurs even though half the children who have impaired hearing are known to be at increased risk. A plea is made for the setting up of a register of infants known to be at risk for impaired hearing. First-contact physicians should be alert to the possibility of hearing problems, particularly in children at high risk. Screening methods for use by nonspecialist practitioners are outlined.     

Prognosis in adult asthma: a national study.

Although one million people consult their general practitioners for asthma each year, data on the prognosis of this disease are scarce, particularly in adults. Mortality was studied among 2547 adult asthmatics attending a national sample of 60 general practices between 1970 and 1976; they were compared with a matched group of non-asthmatic patients. Mortality from all causes was significantly raised in the asthmatic cohort (189 deaths v 112 among controls; relative risk 1.61, 95% confidence interval 1.3 to 2.0), especially in women (92 v 42 deaths; relative risk 2.2 (1.5 to 3.1)), and in the oldest age group (55-59 years). In both sexes the predominant cause of excess mortality was respiratory disease, particularly asthma (25 v 0 deaths) and chronic obstructive airways disease (37 v 4 deaths; relative risk 8.8 (2.8 to 23)). Overall, 94% of the asthmatic cohort survived the mean follow up period of eight years compared with 96% of the controls. In contrast to previous findings, the risk of death due to malignant neoplasms was not significantly reduced overall (34 v 36 deaths), though the risk was significantly reduced among those aged under 45 years (2 v 10 deaths; relative risk 0.2 (0.02 to 0.9)) and there was a significant trend of lowering of relative risk with younger age (p less than 0.01).     

Measles immunisation: profit and loss in a general practice.

A survey in one general practice of the occurrence of measles and of immunisation in patients who were born between 1963 and 1982 showed that immunisation not only brought some financial reward to the practice, but by preventing measles reduced the number of consultations related to measles by 40%. Although practice policy often entailed a home visit to immunise a patient, measles disease was three times more likely to require a visit. It is surprising that, considering the efficacy and safety of measles immunisation, in Britain measles has not become the rarity it now is in the United States.     

干细胞治疗感音神经性耳聋

治疗内耳疾病的主要困难之一是找到耳蜗毛细胞或者螺旋神经元丢失所导致的听力损失的治疗方法。本文讨论使用干细胞替代感觉细胞丢失为目的的几个治疗策略。作者最近在成年内耳中发现了可以分化为毛细胞的干细胞,发现了胚胎干细胞可在体外转化为毛细胞并表达毛细胞标记物。在动物模型中,成年内耳干细胞、神经干细胞和胚胎干细胞来源的前体细胞可分化成为毛细胞和神经细胞。本文将讨论使用干细胞再生损伤毛细胞的不同方法,介绍几种可行的动物模型,并讨论发展基于干细胞的细胞替代疗法治疗内耳损伤中存在的困难。     

Restaurant noise,hearing loss,and hearing aids.

Our multidisciplinary team obtained noise data in 27 San Francisco Bay Area restaurants. These data included typical minimum, peak, and average sound pressure levels; digital tape recordings; subjective noise ratings; and on-site unaided and aided speech discrimination tests. We report the details and implications of these noise measurements and provide basic information on selecting hearing aids and suggestions for coping with restaurant noise.