Avaliação de perdas e ganhos de DNA na região 7q11.23 em indivíduos com diagnóstico clínico de síndrome de Williams-Beuren e FISH negativo.
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Data
2019-09-24
Autores
Batista, Letícia Cassimiro
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Universidade Estadual Paulista (Unesp)
Resumo
A síndrome de Williams-Beuren (SWB) é uma doença genética caracterizada por dismorfismos faciais, anomalias cardiovasculares, deficiência intelectual e perfil cognitivo típico. A SWB é causada por uma microdeleção hemizigótica da região cromossômica 7q11.23, de ~1,5Mb a 1,8Mb de genes de copias únicas e deleções maiores ou menores que esses limites são considerados deleções atípicas. O objetivo do trabalho foi detectar perdas ou ganhos de DNA por meio da técnica de MLPA na região crítica da SWB em pacientes com diagnóstico clínico estabelecido pela pontuação de escore da AAP, (2001) e com exame de FISH (-) realizado anteriormente pelo nosso grupo de pesquisa, e assim correlacionar os achados de perdas ou ganhos de DNA com os já descritos na literatura e correlaciona-los aos fenótipos/genótipo descritos em bancos de dados público como DVG, DECIPHER, UCSC Genome Browser dentre outros. Foram selecionados 30 indivíduos com hipótese diagnóstica de SWB e análise citogenética negativa para SWB estabelecida pela técnica da FISH. O diagnóstico clínico de SWB “clássica” foi estabelecido pelo escore da Academia Americana de Pediatria (2001). Foi realizada a extração de DNA das amostras e foi aplicada a técnica de MLPA com o kit SALSA P029 (MRC-Holland, Amsterdam, The Netherlands) com sondas específicas para os principais genes encontrados na região crítica da SWB. Nesta amostra predominou o sexo masculino (2M:1F) e a idade do 1° atendimento foi tardia (mediana 9,5 anos). A casuística apresentou as características faciais que determinam a face considerada como típica na SWB. Apenas 11/30 pacientes apresentavam cardiopatia, e desses apenas 2/11 apresentavam a estenose aórtica supravalvar. Das alterações gastrointestinais as mais frequentes foram as dificuldades alimentares e constipação. As características que compõem o perfil cognitivo típico da SWB as mais frequentes foram: hiperatividade, loquacidade, sociabilidade excessiva e deficiência intelectual. Apesar da casuística apresentar características típicas da SWB a análise molecular pela técnica de MLPA não detectou nenhuma perda ou ganho de DNA na região crítica da SWB. A técnica pode não ter detectado nenhuma perda ou ganho de DNA, porque as alterações podem estar presentes em regiões que não são cobertas pelas sondas presentes no kit comercial P029-C1. Assim, para os casos com diagnóstico clínico de SWB e FISH (-), sugerimos o uso de outras técnicas como o array-CGH ou NGS. Foi realizado o Aconselhamento genético dos familiares, informando esses resultados e comunicando-lhes que o estudo prosseguirá com aplicações de outras metodologias laboratoriais subsidiárias ao diagnóstico clínico do paciente.
Williams-Beuren Syndrome (WBS) is a genetic disorder characterized by facial dysmorphisms, cardiovascular anomalies, intellectual disability and typical cognitive profile. WBS is caused by a hemizygous microdeletion of the 7q11.23 chromosomal region, ~ 1.5Mb to 1.8Mb of single copy genes, and deletions larger or smaller than those limits are considered atypical deletions. The objective of this study was to detect DNA loss or gain by MLPA technique in the critical region of SWB in patients with clinical diagnosis established by AAP score (2001) and with FISH (-) examination previously performed by our search group, and thus correlate the findings of DNA loss or gain with those already described in the literature and correlate them with the phenotypes / genotype described in public databases such as DVG, DECIPHER, UCSC Genome Browser and others. Thirty individuals with diagnostic hypothesis of WBS and negative cytogenetic analysis for WBS established by the FISH technique were selected. The clinical diagnosis of “classic” WBS was established by the American Academy of Pediatrics score (2001). DNA extraction from the samples was performed and the MLPA technique was applied with the SALSA P029 kit (MRC-Holland, Amsterdam, The Netherlands) with probes specific for the major genes found in the critical region of the SWB. In this sample, the male gender predominated (2M: 1F) and the age of the first attendance was late (median 9.5 years). The sample presented the facial characteristics that determine the face considered as typical in WBS. Only 11/30 patients had heart disease, and of these only 2/11 had supravalvular aortic stenosis. The most frequent gastrointestinal alterations were eating difficulties and constipation. The most frequent characteristics that make up the typical SWB cognitive profile were: hyperactivity, loquacity, excessive sociability and intellectual disability. Although the sample presents typical WBS characteristics, molecular analysis by MLPA technique did not detect any DNA loss or gain in the critical WBS region. The technique may not have detected any DNA loss or gain because the changes may be present in regions that are not covered by the probes in the commercial kit P029-C1. Thus, for cases with clinical diagnosis of WBS and FISH (-), we suggest the use of other techniques such as array-CGH or NGS. Genetic counseling of the relatives was carried out, informing these results and informing them that the study will continue with the application of other subsidiary laboratory methodologies to the clinical diagnosis of the patient.
Williams-Beuren Syndrome (WBS) is a genetic disorder characterized by facial dysmorphisms, cardiovascular anomalies, intellectual disability and typical cognitive profile. WBS is caused by a hemizygous microdeletion of the 7q11.23 chromosomal region, ~ 1.5Mb to 1.8Mb of single copy genes, and deletions larger or smaller than those limits are considered atypical deletions. The objective of this study was to detect DNA loss or gain by MLPA technique in the critical region of SWB in patients with clinical diagnosis established by AAP score (2001) and with FISH (-) examination previously performed by our search group, and thus correlate the findings of DNA loss or gain with those already described in the literature and correlate them with the phenotypes / genotype described in public databases such as DVG, DECIPHER, UCSC Genome Browser and others. Thirty individuals with diagnostic hypothesis of WBS and negative cytogenetic analysis for WBS established by the FISH technique were selected. The clinical diagnosis of “classic” WBS was established by the American Academy of Pediatrics score (2001). DNA extraction from the samples was performed and the MLPA technique was applied with the SALSA P029 kit (MRC-Holland, Amsterdam, The Netherlands) with probes specific for the major genes found in the critical region of the SWB. In this sample, the male gender predominated (2M: 1F) and the age of the first attendance was late (median 9.5 years). The sample presented the facial characteristics that determine the face considered as typical in WBS. Only 11/30 patients had heart disease, and of these only 2/11 had supravalvular aortic stenosis. The most frequent gastrointestinal alterations were eating difficulties and constipation. The most frequent characteristics that make up the typical SWB cognitive profile were: hyperactivity, loquacity, excessive sociability and intellectual disability. Although the sample presents typical WBS characteristics, molecular analysis by MLPA technique did not detect any DNA loss or gain in the critical WBS region. The technique may not have detected any DNA loss or gain because the changes may be present in regions that are not covered by the probes in the commercial kit P029-C1. Thus, for cases with clinical diagnosis of WBS and FISH (-), we suggest the use of other techniques such as array-CGH or NGS. Genetic counseling of the relatives was carried out, informing these results and informing them that the study will continue with the application of other subsidiary laboratory methodologies to the clinical diagnosis of the patient.
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Palavras-chave
Deleção 7q11.23, Fish (-), Síndrome de Williams-Beuren