Candidate gene linkage analysis indicates genetic heterogeneity in Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant disease of the connective tissue that affects the ocular, skeletal and cardiovascular systems, with a wide clinical variability. Although mutations in the FBN1 gene have been recognized as the cause of the disease, more recently other loci have been associated with MFS, indicating the genetic heterogeneity of this disease. We addressed the issue of genetic heterogeneity in MFS by performing linkage analysis of the FBN1 and TGFBR2 genes in 34 families (345 subjects) who met the clinical diagnostic criteria for the disease according to Ghent. Using a total of six microsatellite markers, we found that linkage with the FBN1 gene was observed or not excluded in 70.6% (24/34) of the families, and in 1 family the MFS phenotype segregated with the TGFBR2 gene. Moreover, in 4 families linkage with the FBN1 and TGFBR2 genes was excluded, and no mutations were identified in the coding region of TGFBR1, indicating the existence of other genes involved in MFS. Our results suggest that the genetic heterogeneity of MFS may be greater that previously reported.Universidade de São Paulo Hospital das Clínicas, Faculdade de Medicina Instituto de BiociênciaUniversidade de São Paulo Hospital das Clínicas, Faculdade de Medicina Laboratório de Otorrinolaringologia/LIM32Universidade Federal de São Paulo (UNIFESP) Departamento de Morfologia e Genética Centro de Genética MédicaUNIFESP, Depto. de Morfologia e Genética Centro de Genética MédicaSciEL

Evidence of progenitor cells in the adult human cochlea: sphere formation and identification of ABCG2

OBJECTIVES: The aim of this study was to search for evidence of stem or progenitor cells in the adult human cochlea by testing for sphere formation capacity and the presence of the stem cell marker ABCG2. METHODS: Cochleas removed from patients undergoing vestibular schwannoma resection (n=2) and from brain-dead organ donors (n=4) were dissociated for either flow cytometry analysis for the stem cell marker ABCG2 or a sphere formation assay that is widely used to test the sphere-forming capacity of cells from mouse inner ear tissue. RESULTS: Spheres were identified after 2-5 days in vitro, and the stem cell marker ABCG2 was detected using flow cytometric analysis after cochlear dissociation. CONCLUSIONS: Evidence suggests that there may be progenitor cells in the adult human cochlea, although further studies are required

Study of a Brazilian family presenting non-syndromic hearing loss with mitochondrial inheritance

O presente estudo teve como objetivo descrever os achados audiológicos e genéticos de nove membros de uma família brasileira que apresenta a mutação no DNA mitocondrial. Todos os nove membros realizaram estudo genético, avaliação foniátrica e audiológica (audiometria tonal e logoaudiometria). O estudo genético revelou a presença de mutação mitocondrial A1555G no gene 12S rRNA (MT-RNR-1) do DNA mitocondrial em todos os sujeitos. Oito sujeitos apresentaram deficiência auditiva e somente um apresentou limiares auditivos normais até o término da realização do estudo. Os resultados audiológicos apontaram para perdas auditivas bilaterais, com prevalência das simétricas, de configurações e graus variados (de moderado a profundo) e pós-linguais. Progressão da perda auditiva foi observada em dois irmãos afetados. Não foi possível afirmar a época do início da perda auditiva por falta de informação dos sujeitos, no entanto, observou-se manifestação da perda em crianças e adultos. As mutações no DNA mitocondrial representam uma causa importante de perda auditiva, sendo imprescindível a realização do diagnóstico etiopatológico, a fim de retardar o início ou evitar a progressão da surdez.We hereby report on the audiological and genetic findings in individuals from a Brazilian family, with the following mitochondrial mutation A1555G in the 12SrRNA gene (MT-RNR-1). Nine individuals underwent speech, audiologic (tonal audiometry and logoaudiometry) and genetic evaluations. Eight individuals among the A1555G carriers were affected by hearing impairment and one person had normal hearing thresholds till the end of the present study. The audiologic evaluation results indicated normal hearing thresholds all the way to bilateral profound hearing loss with post-lingual onset and variable configuration. Two affected siblings presented progressive hearing loss. It was impossible to precise the time of hearing loss onset; however, the impairment was present in both children and adults. The genetic study revealed the A1555G mitochondrial mutation in the 12SrRNA gene. Given the prevalence of mitochondrial mutations as a cause of hearing loss, it is fundamental to perform the etiopathologic diagnosis in order to postpone the onset or avoid hearing impairment progression. This kind of hearing impairment represents a challenge to the professionals since there are no physical traits that indicate genetic transmission

c.G2114A MYH9 mutation (DFNA17) causes non-syndromic autosomal dominant hearing loss in a Brazilian family

We studied a family presenting 10 individuals affected by autosomal dominant deafness in all frequencies and three individuals affected by high frequency hearing loss. Genomic scanning using the 50k Affymetrix microarray technology yielded a Lod Score of 2.1 in chromosome 14 and a Lod Score of 1.9 in chromosome 22. Mapping refinement using microsatellites placed the chromosome 14 candidate region between markers D14S288 and D14S276 (8.85 cM) and the chromosome 22 near marker D22S283. Exome sequencing identified two candidate variants to explain hearing loss in chromosome 14 [PTGDR - c.G894A:p.R298R and PTGER2 - c.T247G:p.C83G], and one in chromosome 22 [MYH9, c.G2114A:p.R705H]. Pedigree segregation analysis allowed exclusion of the PTGDR and PTGER2 variants as the cause of deafness. However, the MYH9 variant segregated with the phenotype in all affected members, except the three individuals with different phenotype. This gene has been previously described as mutated in autosomal dominant hereditary hearing loss and corresponds to DFNA17. The mutation identified in our study is the same described in the prior report. Thus, although linkage studies suggested a candidate gene in chromosome 14, we concluded that the mutation in chromosome 22 better explains the hearing loss phenotype in the Brazilian family.We thank Dr. Erika Freitas and Dr. Carla Rosenberg for performing the array-CGH studies. We also thank Maria Teresa Balester de Mello Auricchio for technical assistance. We thank the Laboratório Multiusuários Centralizado de Genômica Funcional Aplicada à Agropecuária e Agroenergia - EASALQ-USP Piracicaba-SP-Brasil for providing the sequencing facilities. We thank CEPID - FAPESP and CAPES for financial support

MSX2 copy number increase and craniosynostosis: copy number variation detected by array comparative genomic hybridization

Fleury GroupFleury Grou

Spastic Paraplegia, Optic Atrophy, and Neuropathy: New Observations, Locus Refinement, and Exclusion of Candidate Genes

Summary SPOAN is an autosomal recessive neurodegenerative disorder which was recently characterized by our group in a large inbred Brazilian family with 25 affected individuals. This condition is clinically defined by: 1. congenital optic atrophy; 2. progressive spastic paraplegia with onset in infancy; and 3. progressive motor and sensory axonal neuropathy. Overall, we are now aware of 68 SPOAN patients (45 females and 23 males, with age ranging from 5 to 72 years), 44 of which are presented here for the first time. They were all born in the same geographic micro region. Those 68 patients belong to 43 sibships, 40 of which exhibit parental consanguinity. Sixty-one patients were fully clinically evaluated and 64 were included in the genetic investigation. All molecularly studied patients are homozygotes for D11S1889 at 11q13. This enabled us to reduce the critical region for the SPOAN gene from 4.8 to 2.3 Mb, with a maximum two point lod score of 33.2 (with marker D11S987) and of 27.0 (with marker D11S1889). Three genes located in this newly defined critical region were sequenced, but no pathogenic mutation was detected. The gene responsible for SPOAN remains elusive

Retention of progenitor cell phenotype in otospheres from guinea pig and mouse cochlea

Abstract\ud \ud Background\ud Culturing otospheres from dissociated organ of Corti is an appropriate starting point aiming at the development of cell therapy for hair cell loss. Although guinea pigs have been widely used as an excellent experimental model for studying the biology of the inner ear, the mouse cochlea has been more suitable for yielding otospheres in vitro. The aim of this study was to compare conditions and outcomes of otosphere suspension cultures from dissociated organ of Corti of either mouse or guinea pig at postnatal day three (P3), and to evaluate the guinea pig as a potential cochlea donor for preclinical cell therapy.\ud \ud \ud Methods\ud Organs of Corti were surgically isolated from P3 guinea pig or mouse cochlea, dissociated and cultivated under non-adherent conditions. Cultures were maintained in serum-free DMEM:F12 medium, supplemented with epidermal growth factor (EGF) plus either basic fibroblast growth factor (bFGF) or transforming growth factor alpha (TGFα). Immunofluorescence assays were conducted for phenotype characterization.\ud \ud \ud Results\ud The TGFα group presented a number of spheres significantly higher than the bFGF group. Although mouse cultures yielded more cells per sphere than guinea pig cultures, sox2 and nestin distributed similarly in otosphere cells from both organisms. We present evidence that otospheres retain properties of inner ear progenitor cells such as self-renewal, proliferation, and differentiation into hair cells or supporting cells.\ud \ud \ud Conclusions\ud Dissociated guinea pig cochlea produced otospheres in vitro, expressing sox2 and nestin similarly to mouse otospheres. Our data is supporting evidence for the presence of inner ear progenitor cells in the postnatal guinea pig. However, there is limited viability for these cells in neonatal guinea pig cochlea when compared to the differentiation potential observed for the mouse organ of Corti at the same developmental stage

Evidence of progenitor cells in the adult human cochlea: sphere formation and identification of ABCG2

OBJECTIVES: The aim of this study was to search for evidence of stem or progenitor cells in the adult human cochlea by testing for sphere formation capacity and the presence of the stem cell marker ABCG2. METHODS: Cochleas removed from patients undergoing vestibular schwannoma resection (n=2) and from brain-dead organ donors (n=4) were dissociated for either flow cytometry analysis for the stem cell marker ABCG2 or a sphere formation assay that is widely used to test the sphere-forming capacity of cells from mouse inner ear tissue. RESULTS: Spheres were identified after 2-5 days in vitro, and the stem cell marker ABCG2 was detected using flow cytometric analysis after cochlear dissociation. CONCLUSIONS: Evidence suggests that there may be progenitor cells in the adult human cochlea, although further studies are required

7q36 deletion and 9p22 duplication: effects of a double imbalance

<p>Abstract</p> <p>The etiology of mental retardation/developmental delay (MRDD) remains a challenge to geneticists and clinicians and can be correlated to environmental and genetic factors. Chromosomal aberrations are common causes of moderate to severe mental retardation and may represent 10% of these occurrences. Here we report the case of a boy with development delay, hypoplasia of corpus callosum, microcephaly, muscular hypotonia, and facial dysmorphisms. A deletion of 7q36.1 → 36.3 and duplication of 9p22.3 → 23 was detected as a result of an unbalanced translocation of paternal origin. Breakpoint delimitation was achieved with array comparative genomic hybridization assay. Additional multiplex ligation dependent probe amplification (MLPA) analyzes confirmed one copy loss of 7q36.3 region and one copy gain of 9p24.3 region. Patient resultant phenotype is consistent with the already described findings for both 7q deletion and 9p duplication syndromes.</p

Atualização em genética da surdez não-sindrômica

A surdez não-sindrômica é uma condição altamente heterogênea, com inúmeros genes de locos diferentes interferindo no desenvolvimento e na fisiologia da audição. Apresentamos uma revisão sobre a genética e biologia molecular do defeito. Estão envolvidos na surdez hereditária não-sindrômica cerca de 30genes autossômicos recessivos e 40 dominantes, 8 genes ligados ao cromossomo X e 5 mutações no DNA mitocondrial. 80% dos casos hereditários de surdez são determinados por mecanismo autossômico recessivo, com predomínio de uma única mutação, 35delG, no gene da Conexina 26, a qual é tida como a principal responsável pela deficiência auditiva neurossensorial congênita. Nos últimos anos, têm sido detectados vários casos de deficiência auditiva associada a mutações do DNA mitocondrial; a principal delas é a mutação A1555G, muitas vezes associada a casos de deficiência auditiva secundária ao uso de antibióticos aminoglicosídeos. Os avanços recentes na biologia molecular da surdez indicam ser justificável a triagem de mutações frequentes na surdez.Nonsyndromic hereditary deafness is a highly heterogeneous condition. Many different genes from many loci have been shown to influence the development and function of hearing. Here we present a review on the genetics and molecular biology of hearing loss. There exist about 30 different autosomal locirelated to recessive hearing loss, 40 dominant loci, eight X-linked loci; five different mitochondrial mutations have been already described. 80% of hereditary nonsyndromic hearing loss is produced by recessive mechanismand one specific mutation, 35delG, in the Conexin 26 gene, is the most frequent cause of congenital neurosensorial hearing loss. An increasing number of publications report cases of inherited hearing loss due to mitochondrial mutations; the most frequent of which is known as A1555G. In many families, hearing loss is associated to the use of aminoglicosidic antibiotics. Recent advances in molecular biology of hearing loss suggest that the screening of the frequent mutations in deaf populations should be considered