UCLA researchers examine human embryonic stem c...(s in the March 27 2008 express edition o...),Health

Differences between individual DNA sequences provide the basis for human genetic variability. Forms of variation include single DNA base pair alterations, duplications or deletions of genes or sets of genes, and translocations, a chromosomal rearrangement in which a segment of genetic material from one chromosome becomes heritably linked to another chromosome. These changes can be benign, but they can also promote diseases such as certain cancers, or confer increased risk to other diseases, such as HIV infection or certain types of kidney ailments.

In this study, Teitell and his team sought to determine copy number variants (CNVs), or differences in the numbers of certain genes, in two embryonic stem cell lines. The CNVs provide a unique genetic fingerprint for each line, which can also indicate relatedness between any two stem cell lines. Teitell used embryonic stem cell lines that made different types of neurons and studied them with array CGH for comparison. His team found CNV differences between the two lines in at least seven different chromosome locations below the level of detection using standard karyotype studies. Such differences could impact the therapeutic utility of the lines and could have implications in disease development. More studies will be required to determine the effect of specific CNVs in controlling stem cell function and disease susceptibility, he said.

In studying embryonic stem cell lines in the future, if we find differences in regions of the genome that we know are associated with certain undesirable traits or diseases, we would choose against using such stem cells, provided safer alternative lines are available, Teitell said.

Large genome-wide association studies are underway in a variety of diseases to determine what genetic abnormalities might be at play. When the genetic fingerprint or predisposing genes for a certain disease
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