From each of the four cultures, single-cell derived clonal cell strains were established.

Expression levels varied significantly from clone to clone and between cell strains (Fig.

Hayflick produced the first oral polio vaccine made on a continuously propagated cell strain.

Cell strains are cells that have been adapted to culture but, unlike cell lines, have a finite division potential.

Our study design was intended to take advantage of the mosaic X chromosome inactivation in cell strains of Rett syndrome females.

In order to verify that Esp1 does play a role in regulating Scc1 chromosome association, cell strains were arrested in G1 with an alpha factor.

A cell strain is derived either from a primary culture or a cell line by the selection or cloning of cells having specific properties or characteristics which must be defined.

We used one-sample, two-sided t-tests on the reported GeneChip fold changes to assess whether the log fold changes of mutant cell strains differ from zero on average.

We performed paired t-tests on the RT-PCR values for the original set of fibroblast clones to test whether the average log change across cell strains differs from zero.

We hypothesized that the effects of MeCP2 dysfunction in the mutant clonal cell strain would be more pronounced than in the original cell strain with mosaic X chromosome inactivation.

One such cell strain, developed by Hayflick and his colleague Paul Moorehead at the Wistar Institute in Philadelphia, called WI-38, was the most widely used and highly characterized normal human cell population in the world.

Our interrogations identified a statistically significant number of genes with differential expression patterns between wild-type and mutant cell strains, however, the results across multiple clones from the same individual showed substantial variability, questioning the significance of some of the genes identified.

Baseline genetic expression profiles of one clonal wild-type MeCP2-expressing fibroblast strain were compared to the expression profile of the matched clonal mutant MeCP2-expressing cell strain, for each of four different MECP2 mutations.

Moreover, we were able to establish the ideal matched control for each clonal mutant cell strain, a clonal cell strain with the wild-type MECP2 allele on the active X chromosome from the same individual.

Real-time comparative quantitative PCR Total RNA from the four matched pairs of clonal fibroblast cell strains and ten lymphoblast cell lines used on the GeneChips was used as template for RT-PCR to independently assess the validity of Affymetrix GeneChip data.