Priscila Zonzini Ramos

Molecular analysis of SLC26A4 gene in patients with nonsyndromic hearing loss and EVA: Identification of two novel mutations in Brazilian patients

UNLABELLED The SLC26A4 gene has been described as the second gene involved in most cases of sensorineural non-syndromic hearing loss, since the first is the GJB2 gene. Recessive mutations in the SLC26A4 gene encoding pendrin, an anion transporter, are responsible for non-syndromic hearing loss associated with an enlarged vestibular aqueduct (EVA) and Pendred syndrome, which causes early hearing loss and affects the thyroid gland. Typically, the hearing loss is profound and prelingual. However, in some individuals, hearing impairment may develop later in childhood and then progress. Over 200 different SLC26A4 mutations have been reported, with each ethnic population having its own distinctive mutant allele series including a few prevalent founder mutations. OBJECTIVE Perform the screening of the 20 coding exons of SLC26A4 gene in Brazilian deaf individuals with EVA. PATIENTS AND METHODS Among the 23 unrelated non-syndromic hearing loss Brazilian patients with EVA, in whom no deafness-causing mutations of the GJB2 gene, the direct sequencing was performed to screen the 20 exons and their flanking regions of the SLC26A4 gene. RESULTS The sequencing results revealed 9 cases (39%) carrying 13 different SLC26A4 mutations, including 11 known mutations (279delT, V138F, T193I, IVS8+1G>A, T410M, Q413R, R409H, L445W, IVS15+5G>A, V609G, and R776C) and 2 novel mutation (G149R and P142L). CONCLUSION The SLC26A4 mutations have a high carrying rate in non-syndromic hearing loss Brazilian patients. The identification of a disease-causing mutation can be used to establish a genotypic diagnosis and provide important information to the patients and their families.

Etiologic and diagnostic evaluation: algorithm for severe to profound sensorineural hearing loss in Brazil.

Abstract Objective: Evaluation of the effectiveness of imaging and genetic testing, and establishment of a cost-effective diagnostic protocol for the etiologic diagnosis of sensorineural hearing loss (SNHL) in Brazil. Design: Prospective cohort study. Study sample: Analysis of 100 unrelated Brazilian patients with severe to profound bilateral SNHL submitted to cochlear implant (CI) between 2002 and 2010 at the University of Campinas hospital. The study was based upon three groups: individuals with congenital, progressive, and sudden SNHL. Results: After the diagnostic investigation, the number of cases with unknown etiology was reduced from 72 to 42 (a 42% reduction); 25% of cases were due to environmental factors, 19% to genetic causes, and 14% to inner-ear abnormalities or other clinical features. The genetic and imaging findings contributed to the diagnosis of SNHL in 19% and 20% of the cases analysed, respectively. Molecular testing mainly contributed to the diagnosis of patients with congenital SNHL, while the contribution of radiologic examination was higher for individuals with progressive or sudden SNHL. A sequential diagnostic protocol was proposed based on these data. Conclusions: The proposed diagnostic workup algorithm could provide better optimization of etiologic diagnosis, as well as reduced costs, compared to a simultaneous testing approach.

Genetic Diagnosis of Deafness

Genetic testing can provide an accurate diagnosis, contributing to appropriate treatment, prognosis and precise genetic counseling for patients with hearing loss. It is estimated that approximately 300 genes could be involved in determining syndromic and nonsyndromic hearing loss, making the diagnosis of hearing loss highly challenging. Conventional methodologies have been used for the screening of the most frequent mutations and genes according to ethnic background, but they are impractical for the screening of all genes associated with the complex auditory system. The Human Genome Project has directly or indirectly stimulated the development of many technologies and platforms for molecular diagnostics of genetic diseases, including hereditary hearing loss. All these tools are not only applicable to molecular diagnostics, but also enable the identification of new genes, providing new insights into the mechanisms of hearing loss.

Structural Analysis of Inhibitor Binding to CAMKK1 Identifies Features Necessary for Design of Specific Inhibitors

The calcium/calmodulin-dependent protein kinases (CAMKKs) are upstream activators of CAMK1 and CAMK4 signalling and have important functions in neural development, maintenance and signalling, as well as in other aspects of biology such as Ca2+ signalling in the cardiovascular system. To support the development of specific inhibitors of CAMKKs we have determined the crystal structure of CAMKK1 with two ATP-competitive inhibitors. The structures reveal small but exploitable differences between CAMKK1 and CAMKK2, despite the high sequence identity, which could be used in the generation of specific inhibitors. Screening of a kinase inhibitor library revealed molecules that bind potently to CAMKK1. Isothermal titration calorimetry revealed that the most potent inhibitors had binding energies largely dependent on favourable enthalpy. Together, the data provide a foundation for future inhibitor development activities.

Relationship Between Patients with Clinical Auditory Neuropathy Spectrum Disorder and Mutations in Gjb2 Gene.

The auditory neuropathy is a condition which there is a dyssynchrony in the nerve conduction of the auditory nerve fibers. There is no evidence about the relationship between patients with clinical auditory neuropathy spectrum disorder and mutations in GJB2 gene. There are only two studies about this topic in the medical literature. Connexin 26 (GJB2 gene) mutations are common causes of genetic deafness in many populations and we also being reported in subjects with auditory neuropathy. Objective: To analyze the pattern of clinical relationship between patients with clinical diagnosis with auditory neuropathy spectrum disorder and GJB2 gene. Patients and Methods: Study Design - Retrospective analysis and genetic evaluation. Setting - Tertiary referral center. Subjects - 40 patients with Auditory Neuropathy Spectrum Disorder. Intervention - Clinical information and genetic evaluation (GJB2 gene) were analyzed. Results: Biallelic mutations that accounted for hearing loss (HL) were found in three patients, both with c.35delG mutation in homozygous state. The splice site mutation IVS1+1G>A was detected in heterozygous state in one individual. However, since the second mutant allele was not identified, it was not possible to establish its correlation with the phenotype. Conclusion: Mutations in GJB2 gene mutations were found in 7.5% of the patients with ANSD. We found no relationship between patients with clinical auditory neuropathy spectrum disorder and mutations in GJB2 gene ( p>0.05).The auditory neuropathy is a condition which there is a dyssynchrony in the nerve conduction of the auditory nerve fibers. There is no evidence about the relationship between patients with clinical auditory neuropathy spectrum disorder and mutations in GJB2 gene. There are only two studies about this topic in the medical literature. Connexin 26 (GJB2 gene) mutations are common causes of genetic deafness in many populations and we also being reported in subjects with auditory neuropathy. Objective: To analyze the pattern of clinical relationship between patients with clinical diagnosis with auditory neuropathy spectrum disorder and GJB2 gene. Patients and Methods: Study Design - Retrospective analysis and genetic evaluation. Setting - Tertiary referral center. Subjects - 40 patients with Auditory Neuropathy Spectrum Disorder. Intervention - Clinical information and genetic evaluation (GJB2 gene) were analyzed. Results: Biallelic mutations that accounted for hearing loss (HL) were found in three patients, both with c.35delG mutation in homozygous state. The splice site mutation IVS1+1G>A was detected in heterozygous state in one individual. However, since the second mutant allele was not identified, it was not possible to establish its correlation with the phenotype. Conclusion: Mutations in GJB2 gene mutations were found in 7.5% of the patients with ANSD. We found no relationship between patients with clinical auditory neuropathy spectrum disorder and mutations in GJB2 gene (p>0.05).

Satisfaction of Children with Auditory Neuropathy and Cochlear Implant.

OBJECTIVE In auditory neuropathy (AN) a dyssynchrony in the nerve conduction of the auditory nerve fibers is observed. Typically, patients with AN exhibit moderate to profound sensorineural hearing loss, and treatment using cochlear implants (CIs) or hearing aids should be performed as early as possible for a better hearing rehabilitation. The aim of this study is to evaluate the satisfaction level of patients with AN spectrum disorder treated using CIs. The Satisfaction with Amplification in Daily Life questionnaire was selected to evaluate 10 patients with AN treated using CIs. MATERIALS AND METHODS Clinical study of patients with AN spectrum disorder submitted to CI. A retrospective data analysis, genetic and clinical evaluation in a tertiary referral center was done. RESULTS The means of the subscales for positive effects, services and costs, negative factors, and personal image were 6.15, 4.6, 3.26, and 3.33, respectively. CONCLUSIONS Patients with AN treated using CIs consider themselves satisfied.