Controlling cellular connections
The researchers enabled cells to react with other cells in a controlled way by coating the cell surfaces with DNA (not where DNA is normally found!). First they induced the cells to express artificial sugars bearing special chemical groups. Lengths of synthetic DNA, introduced into the cell-growth medium, were equipped to recognize these synthetic sugars on the cell surfaces and chemically bind to them.
The researchers coated cell surfaces from one group with strands of single-stranded DNA only 20 bases long, and the surfaces of another group with the complementary DNA strand. When a cell from one group meets its counterpart, the single strands recognize each other and form double-stranded DNA, which binds the cells together.
Bertozzi and Gartner discovered three variables that determine how cells from different groups react with one another. One is the ratio of the two kinds of cells: if both cell populations are equal, every cell finds a single partner and no complex assemblies form. But if there are, say, 50 times more cells from one group than from the other, numerous cells from the larger group will cluster around each cell from the smaller group.
Another variable is the complexity of the synthetic DNA sequence. The researchers can specify the complexity for example, from a simple repeat of two bases such as cytosine and adenine (CACACA...) on one strand, which binds to
|Contact: Paul Preuss|
DOE/Lawrence Berkeley National Laboratory