RESUMO
BACKGROUND: Autosomal recessive ataxias represent a group of clinically overlapping disorders. These include ataxia with oculomotor apraxia type1 (AOA1), ataxia with oculomotor apraxia type 2 (AOA2) and ataxia-telangiectasia-like disease (ATLD). Patients are mainly characterized by cerebellar ataxia and oculomotor apraxia. Although these forms are not quite distinctive phenotypically, different genes have been linked to these disorders. Mutations in the APTX gene were reported in AOA1 patients, mutations in SETX gene were reported in patients with AOA2 and mutations in MRE11 were identified in ATLD patients. In the present study we describe in detail the clinical features and results of genetic analysis of 9 patients from 4 Saudi families with ataxia and oculomotor apraxia. METHODS: This study was conducted in the period between 2005-2010 to clinically and molecularly characterize patients with AOA phenotype. Comprehensive sequencing of all coding exons of previously reported genes related to this disorder (APTX, SETX and MRE11). RESULTS: A novel nonsense truncating mutation c.6859 C > T, R2287X in SETX gene was identified in patients from one family with AOA2. The previously reported missense mutation W210C in MRE11 gene was identified in two families with autosomal recessive ataxia and oculomotor apraxia. CONCLUSION: Mutations in APTX , SETX and MRE11 are common in patients with autosomal recessive ataxia and oculomotor apraxia. The results of the comprehensive screening of these genes in 4 Saudi families identified mutations in SETX and MRE11 genes but failed to identify mutations in APTX gene.
Assuntos
Proteínas de Ligação a DNA/genética , Mutação , RNA Helicases/genética , Adolescente , Adulto , Sequência de Aminoácidos , Substituição de Aminoácidos , Apraxias/genética , Ataxia Telangiectasia/genética , Sequência de Bases , Ataxia Cerebelar/congênito , Mapeamento Cromossômico , Códon sem Sentido , DNA/genética , DNA Helicases , Análise Mutacional de DNA , Feminino , Variação Genética , Humanos , Hipoalbuminemia/genética , Proteína Homóloga a MRE11 , Masculino , Enzimas Multifuncionais , Mutação de Sentido Incorreto , Proteínas Nucleares/genética , Linhagem , Arábia Saudita , Ataxias Espinocerebelares/congênito , Degenerações Espinocerebelares/genética , Adulto JovemRESUMO
OBJECTIVE: To document the genotype for familial congenital fibrosis of the extraocular muscles (CFEOM) with apparent autosomal recessive inheritance. DESIGN: Interventional family study. PARTICIPANTS: Two affected siblings, 3 asymptomatic siblings, and their 2 asymptomatic parents. METHODS: Ophthalmologic examination and candidate gene analysis (KIF21A and PHOX2A from venous blood samples) of the 2 affected siblings and their parents; confirmatory testing for 3 available asymptomatic siblings. MAIN OUTCOME MEASURES: Significant clinical observations and results of gene testing. RESULTS: The 2 affected siblings had large-angle exotropia, moderate bilateral hypotropia, moderate bilateral ptosis, sluggish pupils, and almost complete ophthalmoloplegia with some abnormal synkinesis. The asymptomatic parents were not related and had unremarkable ophthalmic examinations. Four other siblings were normal by history; 3 underwent venous blood sampling for confirmatory testing. Candidate gene testing of PHOX2A, the gene for recessive CFEOM (CFEOM2), did not reveal mutation in the 2 patients or their parents. Sequencing of KIF21A, the gene for dominant CFEOM (CFEOM1), revealed heterozygous p.R954L in both affected individuals but in not in their parents or 3 asymptomatic siblings, consistent with parental germline mosaicism. Haplotype analysis suggested paternal inheritance but was not conclusive. CONCLUSIONS: Parental germline mosaicism can mimic recessive inheritance in CFEOM and likely is underrecognized. Ophthalmologists should be aware of this phenomenon when counseling parents of children with apparent recessive (or de novo) hereditary eye disease. Unlike other reported KIF21A mutations that cause CFEOM1, the p.R954L variant seems to be associated with abnormal pupils. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
