RESUMO
Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disorder caused by the unstable expansion of a cytosine-adenine-guanine (CAG)/cytosine-adenine-adenine (CAA) repeat in the ATXN2 gene, which normally encodes 22 glutamines (Q22). A large study was conducted to characterize the CAG/CAA repeat intergenerational instability in SCA2 families. Large normal alleles (Q24-31) were significantly more unstable upon maternal transmissions. In contrast, expanded alleles (Q32-750) were significantly more unstable during paternal transmissions, in correlation with repeat length. Significant correlations were found between the instability and the age at conception in paternal transmissions. In conclusion, intergenerational instability at ATXN2 locus is influenced by the sex, repeat length and age at conception of the transmitting parent. These results have profound implications for genetic counseling services.
Assuntos
Fatores Etários , Ataxina-2/genética , Impressão Genômica , Instabilidade Genômica , Ataxias Espinocerebelares/genética , Repetições de Trinucleotídeos , Adulto , Alelos , Feminino , Humanos , MasculinoRESUMO
Having reported the world's highest prevalence of spinocerebellar ataxia type 2 (SCA2), health professionals in Cuba developed a program for the predictive testing of this condition. Between February 2001 and December 2011, a total of 1050 individuals requested their inclusion in the presymptomatic testing (PST) program. Their medical records were retrospectively analyzed in the present descriptive study. A total of 768 participants completed the protocol, 204 withdrew and 78 were excluded. The PST uptake was 24.91%. Females predominated and 70.96% had negative test results. Their main motivations were risk assessment in their descendants, physical and psychological preparation to cope with the disease and planning for the future. The profile of Cuban participants in the predictive testing program is similar to the one reported for other programs all over the world, nevertheless the genetic counseling practice at the community level is a distinctive aspect, which is valuable in providing at-risk individuals with wide and proper knowledge before their testing inclusion request. The SCA2 predictive testing program has high uptake rates and is renowned in our population. Future research is needed to assess the long-term psychological impact in the participants, their partners and relatives.