Diagnóstico citogenético de pacientes com retardo mental idiopático / Cytogenetic diagnosis of patients with idiopathic mental retardation

O retardo mental é uma condição presente em 2 por cento a 3 por cento da população e mais da metade dos casos ainda são considerados idiopáticos. Sua etiologia é heterogênea e as anomalias cromossômicas têm importante contribuição. A aplicação de técnicas de citogenética clássica e de citogenética molecular tem permitido o diagnóstico preciso em muitos casos, proporcionando melhor acompanhamento clínico e aconselhamento genético. Este trabalho tem como objetivo informar sobre os principais exames atualmente disponíveis para a investigação de rearranjos cromossômicos em pacientes com retardo mental idiopático, incluindo cariótipo com bandeamento G, hibridação in situ fluorescente (FISH), cariotipagem espectral (SKY), amplificação de múltiplas sondas dependente de ligação (MLPA) e hibridação genômica comparativa em array (array-CGH).

Mental retardation is a condition that affects 2 percent-3 percent of the population and more than half of the cases are still deemed idiopathic. Its etiology is heterogeneous and chromosome abnormalities play a significant role. The application of classical cytogenetic and molecular cytogenetic techniques has enabled accurate diagnosis in several cases, which allows better clinical monitoring and genetic counseling. This paper aims at informing about the major tests currently available to investigate chromosome abnormalities in patients with idiopathic mental retardation, including GTG-banded karyotyping, fluorescence in situ hybridization (FISH), spectral karyotyping (SKY), multiplex ligation-dependent probe amplification (MLPA) and array-comparative genomic hybridization (array-CGH).

American marsupials chromosomes: why study them?

Marsupials, one of the three main groups of mammals, are only found in Australia and in the American continent. Studies performed in Australian marsupials have demonstrated the great potential provided by the group for the understanding of basic genetic mechanisms and chromosome evolution in mammals. Genetic studies in American marsupials are relatively scarce and cytogenetic data of most species are restricted to karyotype descriptions, usually without banding patterns. Nevertheless, the first marsupial genome sequenced was that of Monodelphis domestica, a South American species. The knowledge about mammalian genome evolution and function that resulted from studies on M. domestica is in sharp contrast with the lack of genetic data on most American marsupial species. Here, we present an overview of the chromosome studies performed in marsupials with emphasis on the South American species.