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.

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.

We describe two different novel mutations in the PAX3 gene, detected in two families with cases of Waardenburg syndrome type I (WSI). The missense mutation detected in one family involved a single substitution in exon 2 (c.142 G > T) and was present both in the affected individual and in his clinically normal father. The mutation found in the second family consisted of a deletion of 13 bases, c.764-776del(TTACCCTGACATT), in exon 5.

In order to investigate the stability of the FMR1 (Fragile X Mental Retardation 1) alleles from the normal population, when maternally inherited, we analyzed 75 mother-to-son transmissions. Sixty-eight alleles fell within the common range with 20-40 CGG repeats, and seven alleles were intermediate, with 41-48 repeats. No change was observed either in the length or in the structure of these repeats upon transmission. Fifty-three alleles were ascertained in different families, and their size distribution was similar to those described for European and European-derived populations, with three peaks of frequency: 66% of the alleles with (CGG)29, (CGG)30 or (CGG)31, 7.5% with (CGG)20, and 5.7% with (CGG)23. Regarding the AGG interspersion pattern, 69.8% had two AGG repeats, 20.8% had one, 5.7% had three and 3.8% had none. The most common patterns were 10+9+9 (30.2%), 9+9+9 (18.9%), 10+9 (7.5%), and 10+9+10 (7.5%). About 70% of the alleles with up to 40 repeats were linked to the DXS548/FRAXAC1 haplotype 7-3, the most commonly reported in normal populations. Four out of five intermediate alleles were in linkage with the two haplotypes most frequently associated to the FMR1 full mutation, 2-1 and 6-4. These four alleles showed long uninterrupted CGG repeats at the 3' end. The 9+9+22, 9+9+23 and 9+9+28 alleles were linked to the haplotype 2-1, and the 9+37 allele, to the haplotype 6-4. The pattern of AGG interspersion of these alleles and the associated haplotypes were in accordance with the two main pathways toward mutation previously proposed.

Entrevistamos 193 mulheres de famílias com afetados pela síndrome do cromossomo X frágil, quanto a sua história ginecológica e reprodutiva. Entre as 101 portadoras da pré-mutação, 14 tiveram menopausa precoce, mas nenhuma das 37 portadoras da mutação completa ou das 55 não portadoras apresentaram esta anomalia. Observamos uma tendência para a concentração da menopausa precoce em certas famílias, o que poderia significar uma peculiariedade de certas pré-mutações. Entretanto, o fato de as mulheres pré-mutadas tenderem a entrar em menopausa mais cedo do que as não portadoras sugere que a menopausa precoce seja o extremo do espectro de efeitos ovarianos da pré-mutação.

The gynecological and reproductive histories of 193 women from fragile X families were surveyed. Among the 101 carriers of the premutation, 14 experienced premature menopause, contrarily to their 37 fully mutated and 55 noncarrier female relatives. Although premature menopause showed a tendency to cluster in certain fragile X families, as a group, the premutated women experienced menopause earlier than noncarriers. This suggests that premature menopause may be the extreme effect of a spectrum of ovarian anomalies associated with the fragile X premutation.

Realizamos análises citogenéticas e moleculares em 55 famílias com a mutação da síndrome do cromossomo X frágil, loco FMR-1 (318 indivíduos e 15 amostras de vilosidade coriônica). Foram estudados 129 indivíduos do sexo masculino, 75 com retardo mental e 54 normais. Entre os 54 normais, 11 eram portadores da pré-mutação e nenhum apresentou o sítio frágil. Foram detectados 73 portadores da mutação completa e 18% eram mosaicos, ou seja, apresentavam também a pré-mutação. Todos expressaram o sítio frágil em pelo menos um dos sistemas de indução utilizados. O tamanho da expansão de trinucleotídeos CGG (<FONT FACE="Symbol">D</FONT>) e a freqüência de manifestação do sítio frágil apresentaram correlação positiva. Entre as 153 mulheres normais, 85 eram portadoras da pré-mutação e 15 da mutação completa. A freqüência de expressão do fra(X) foi zero ou extremamente baixa entre as pré-mutadas e essa freqüência não diferiu da expressão das não portadoras da mutação. Portanto, a análise citogenética é ineficaz na detecção de indivíduos pré-mutados, homens ou mulheres. Entre as 51 mulheres com a mutação completa, 70% manifestaram algum grau de comprometimento mental. Encontramos também correlação entre o <FONT FACE="Symbol">D</FONT> e a freqüência de expressão do fra(X) nessas mulheres. Contudo, a detecção citogenética das mulheres com mutação completa foi menos eficiente do que no caso dos homens, pois 14% de falsos negativos foram observados. A análise de segregação confirmou que o risco de prole afeta- da aumenta com o <FONT FACE="Symbol">D</FONT>, e o risco médio de prole afetada para todas as heterozigotas foi de 30%. Não houve indicação de desvio de segregação nas famílias estudadas, pois o número de indivíduos que herdaram a mutação não diferiu do número daqueles que herdaram os alelos normais. Não foi detectada nenhuma mutação nova nas 55 genealogias investigadas

We report on the cytogenetic and DNA analysis of 55 families with the fragile X (FMR-1 locus) mutation (318 individuals and 15 chorionic villi samples). A total of 129 males were investigated, 54 mentally normal and 75 presenting mental retardation. Among the 54 normal males, 11 had the premutation, and none expressed the fragile site. The full mutation was detected in 73 retarded males, and 14 (18%) presented a premutation along with the full mutation (mosaics). All of them manifested the fragile site. The frequencies of fragile site expression correlated positively with the sizes of the expansion of the CGG repeats (<FONT FACE="Symbol">D</FONT>). Among 153 normal females, 85 were found to be heterozygous for the premutation and 15 had the full mutation. In the premutated females the fragile site was not observed or it occurred at frequencies that did not differ from those observed in 53 noncarriers. Cytogenetic analysis was thus ineffective for the diagnosis of premutated males or females. Among the 51 heterozygotes for the full mutation, 36 (70%) had some degree of mental impairment. As in males, a positive correlation was detected between the frequencies of fragile site manifestation and the size of the expansion. However, the cytogenetic test was less effective for the detection of fully mutated females, than in the case of males, since 14% false negative results were found among females. Segregation analysis confirmed that the risk of mental retardation in the offspring of heterozygotes increases with the length of <FONT FACE="Symbol">D</FONT>. The average observed frequency of mental retardation in the offspring of all heterozygotes was 30%. There was no indication of meiotic drive occurring in female carriers, since the number of individuals who inherited the mutation did not differ from the number of those inheriting the normal allele. No new mutations were detected in the 55 genealogies studied here.