RESUMO
The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue-nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.
Assuntos
Células-Tronco Embrionárias/citologia , Regulação da Expressão Gênica no Desenvolvimento , Fosfatase Alcalina/metabolismo , Antígenos CD/biossíntese , Biotecnologia/métodos , Diferenciação Celular , Linhagem da Célula , Membrana Celular/metabolismo , Células Cultivadas , Análise por Conglomerados , Feminino , Perfilação da Expressão Gênica , Genótipo , Glicolipídeos/química , Humanos , Glicoproteínas de Membrana/biossíntese , Tetraspanina 29RESUMO
Quantitative polymerase chain reaction (Q-PCR) is now considered the "technique of choice" for validating gene expression changes identified with ribonucleic acid-based expression profiling technologies (especially micro- and macroarray techniques). The identification of altered gene expression profiles with microarrays is best viewed as the first step in the determination of potential disease-associated genes; however, the false-positive rate can be high, particularly with small sample sets and in view of the typically small differences observed in brain expression studies. Quantitative PCR is a rapid and highly sensitive technique for accurate quantification of microarray results; however, careful consideration of experimental design, quality of primer/probe design, internal standards, and normalization procedures are pivotal, particularly when the work involves postmortem tissue.