Deletion of the RMGA and CHD2 genes in a child with epilepsy and mental deficiency.

We describe a novel chromosome microdeletion at 15q26.1 detected by oligo-array-CGH in a 6-year-old girl presenting with global development delay, epilepsy, autistic behavior and facial dysmorphisms. Although these features are often present in Angelman syndrome, no alterations were present in the methylation pattern of the Prader-Willi-Angelman critical region. The deletion encompasses only 2 genes: CHD2, which is part of a gene family already involved in CHARGE syndrome, and RGMA which exerts a negative control on axon growth. Deletion of either or both genes could cause the phenotype of this patient. These results provide a further chromosome region requiring evaluation in patients presenting Angelman features.

Next generation sequencing of pooled samples reveals new SNRNP200 mutations associated with retinitis pigmentosa.

The gene SNRNP200 is composed of 45 exons and encodes a protein essential for pre-mRNA splicing, the 200 kDa helicase hBrr2. Two mutations in SNRNP200 have recently been associated with autosomal dominant retinitis pigmentosa (adRP), a retinal degenerative disease, in two families from China. In this work we analyzed the entire 35-Kb SNRNP200 genomic region in a cohort of 96 unrelated North American patients with adRP. To complete this large-scale sequencing project, we performed ultra high-throughput sequencing of pooled, untagged PCR products. We then validated the detected DNA changes by Sanger sequencing of individual samples from this cohort and from an additional one of 95 patients. One of the two previously known mutations (p.S1087L) was identified in 3 patients, while 4 new missense changes (p.R681C, p.R681H, p.V683L, p.Y689C) affecting highly conserved codons were identified in 6 unrelated individuals, indicating that the prevalence of SNRNP200-associated adRP is relatively high. We also took advantage of this research to evaluate the pool-and-sequence method, especially with respect to the generation of false positive and negative results. We conclude that, although this strategy can be adopted for rapid discovery of new disease-associated variants, it still requires extensive validation to be used in routine DNA screenings.

Dementia in Fragile X-associated Tremor/Ataxia Syndrome / Demência na síndrome de tremor-ataxia associada ao X-Frágil

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a cause of movement disorders and cognitive decline which has probably been underdiagnosed, especially if its prevalence proves similar to those of progressive supranuclear palsy and amyotrophic lateral sclerosis. We report a case of a 74-year-old man who presented with action tremor, gait ataxia and forgetfulness. There was a family history of tremor and dementia, and one of the patient?s grandsons was mentally deficient. Neuropsychological evaluation disclosed a frontal network syndrome. MRI showed hyperintensity of both middle cerebellar peduncles, a major diagnostic hallmark of FXTAS. Genetic testing revealed premutation of the FMR1 gene with an expanded (CGG)90 repeat. The diagnosis of FXTAS is important for genetic counseling because the daughters of the affected individuals are at high risk of having offspring with fragile X syndrome. Tremors and cognitive decline should raise the diagnostic hypothesis of FXTAS, which MRI may subsequently reinforce, while the detection of the FMR1 premutation can confirm the condition.

A síndrome de tremor-ataxia associada ao X-frágil (FXTAS) é uma causa de distúrbios do movimento e de declínio cognitivo que provavelmente tem sido subdiagnosticada, especialmente se a sua prevalência for realmente similar às da paralisia supranuclear progressiva e esclerose lateral amiotrófica. Relatamos um caso de um homem de 74 anos que se apresentou com tremor de ação, ataxia de marcha e esquecimento. Havia história familiar de tremor e de demência e um de seus netos era mentalmente deficiente. A avaliação neuropsicológica demonstrou uma síndrome frontal. A ressonância magnética (RM) revelou hiperintensidade de ambos os pedúnculos cerebelares médios, um critério maior para o diagnóstico de FXTAS. Os testes genéticos confirmaram a presença da pré-mutação do gene FMR1, com uma repetição (CGG)90. O diagnóstico de FXTAS é importante para o aconselhamento genético porque as filhas dos indivíduos afetados tem alto risco de ter uma criança com síndrome do X-frágil. A presença de tremores e declínio cognitivo deve levantar a hipótese diagnóstica de FXTAS, que poderá ser reforçada pela RM e confirmada pela presença da pré-mutação do gene FMR1.

Dementia in Fragile X-associated Tremor/Ataxia Syndrome.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a cause of movement disorders and cognitive decline which has probably been underdiagnosed, especially if its prevalence proves similar to those of progressive supranuclear palsy and amyotrophic lateral sclerosis. We report a case of a 74-year-old man who presented with action tremor, gait ataxia and forgetfulness. There was a family history of tremor and dementia, and one of the patient's grandsons was mentally deficient. Neuropsychological evaluation disclosed a frontal network syndrome. MRI showed hyperintensity of both middle cerebellar peduncles, a major diagnostic hallmark of FXTAS. Genetic testing revealed premutation of the FMR1 gene with an expanded (CGG)90 repeat. The diagnosis of FXTAS is important for genetic counseling because the daughters of the affected individuals are at high risk of having offspring with fragile X syndrome. Tremors and cognitive decline should raise the diagnostic hypothesis of FXTAS, which MRI may subsequently reinforce, while the detection of the FMR1 premutation can confirm the condition.

A síndrome de tremor-ataxia associada ao X-frágil (FXTAS) é uma causa de distúrbios do movimento e de declínio cognitivo que provavelmente tem sido subdiagnosticada, especialmente se a sua prevalência for realmente similar às da paralisia supranuclear progressiva e esclerose lateral amiotrófica. Relatamos um caso de um homem de 74 anos que se apresentou com tremor de ação, ataxia de marcha e esquecimento. Havia história familiar de tremor e de demência e um de seus netos era mentalmente deficiente. A avaliação neuropsicológica demonstrou uma síndrome frontal. A ressonância magnética (RM) revelou hiperintensidade de ambos os pedúnculos cerebelares médios, um critério maior para o diagnóstico de FXTAS. Os testes genéticos confirmaram a presença da pré-mutação do gene FMR1, com uma repetição (CGG)90. O diagnóstico de FXTAS é importante para o aconselhamento genético porque as filhas dos indivíduos afetados tem alto risco de ter uma criança com síndrome do X-frágil. A presença de tremores e declínio cognitivo deve levantar a hipótese diagnóstica de FXTAS, que poderá ser reforçada pela RM e confirmada pela presença da pré-mutação do gene FMR1.

Fragile X-associated tremor/ataxia syndrome: intrafamilial variability and the size of the FMR1 premutation CGG repeat.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurological progressive disorder associated with the FMR1 gene premutation. We report on variable presentation of findings associated with FXTAS in 3 brothers aged 68, 74, and 73 years, carrying premutation alleles of (CGG)(123,) (CGG)(109), and (CGG)(91) triplets, respectively. Based on previously proposed diagnostic criteria for the syndrome, clinical and radiological data allowed establishing a "definite" diagnosis of FXTAS in the two carriers of the longest (CGG)(n). The carrier of the (CGG)(91) allele, although presenting a major radiological sign of the syndrome (symmetrical white-matter lesions in the middle cerebellar peduncles), did not have any significant neurological manifestation at 73 years of age.

Structure and stability upon maternal transmission of common and intermediate FMR1 (Fragile X Mental Retardation 1) alleles in a sample of the Brazilian population

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 percent of the alleles with (CGG)29, (CGG)30 or (CGG)31, 7.5 percent with (CGG)20, and 5.7 percent with (CGG)23. Regarding the AGG interspersion pattern, 69.8 percent had two AGG repeats, 20.8 percent had one, 5.7 percent had three and 3.8 percent had none. The most common patterns were 10+9+9 (30.2 percent), 9+9+9 (18.9 percent), 10+9 (7.5 percent), and 10+9+10 (7.5 percent). About 70 percent 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.