AAAS President Gerald Fink at the 2015 AAAS Annual Meeting | Atlantic Photography Boston
SAN JOSE, California — In the 1920s, biologists counted the number of human chromosomes by cutting up blurry microscopic images and pasting together potential chromosome pairs by size. The scientists came up with the wrong number — 48 instead of 46 — until 30 years later when a revolution in imaging allowed them to paint each chromosome in dazzling and detailed fluorescent colors.
"In this instance, as in all of our science, whether through a microscope or a telescope, we saw something that we had never witnessed before, something that lets us visualize a world we never knew existed," said AAAS President Gerald Fink at the start of the association's 2015 Annual Meeting. "That vision changes the basis of our science, and changes the textbooks, and changes our view of the universe."
In his presidential address, Fink showed how the 2015 meeting theme of "Innovation, Information, and Imaging" has impacted his own field of genetics in the era of genome sequencing. Fink, the Margaret and Herman Sokol Professor of Biology at the Whitehead Institute at MIT, pioneered a technique to insert DNA into yeast that has been fundamental to genetic engineering and drug development.
When chromosomes first leapt into living color, scientists were able to identify the causes of diseases such as Down syndrome — which previously had been attributed to "the erratic emotional state" of expecting mothers, Fink recalled.
"A new picture can destroy our past understanding of our universe, a universe we thought we understood only yesterday."
Gerald Fink, AAAS President
Now, the resolution of chromosomal images is such "that even a small flaw in chromosome structure can be revealed by imaging the genome, and computer-generated pattern recognition has shown such aberrations to be the cause of diverse childhood leukemias, many of which are now treatable," he noted.
Before the human genome was sequenced, Fink said, biologists had a "stable definition" of a gene. Genes were pieces of DNA that could be transcribed into RNA and then translated into proteins. When researchers were finally able to see the complete human sequence, however, they soon realized that only 2% of the human genome counted as "genes" under this definition. The other 98% was dubbed "junk DNA" while the scientists pondered this new vision of the genome.
"That new vision is exciting because it reveals an unknown world that stimulates our curiosity and spawns new fields," Fink said. "But it's also threatening, because a new picture can destroy our past understanding of our universe, a universe we thought we understood only yesterday."
"In genetics, we lost the definition of a gene," he added, "but loss of the definition spawned whole new fields trying to find the information in junk DNA."
In some of those new fields, geneticists have uncovered a menagerie of RNA molecules that silence, regulate, and alter traditional genes in ways that were previously invisible to science. Fink described one long non-coding RNA or lincRNA that silences all the genes on one X chromosome in females, with fascinating results.
New studies in female mice, for instance, show that this silencing can produce a "mosaic" of gene expression in individual cells, with some cells carrying an X chromosome from the mother and others carrying the father's version. Using fluorescent probes and confocal microscopy, scientists have produced images of female brains filled with a kaleidoscope-like spread of neurons that is not seen in male brains.
There are hints of a similar mosaic in human female brains, and Fink said researchers are eager to learn more about when this pattern might develop and whether it has an impact on function and behavior.
Fink said these new discoveries produce "intense moments of exhilaration" for scientists that can't often be described in words — so he played the opening strains of the Star Trek theme to illustrate his own feelings on the matter.
"To go where no one has gone before, to see what no one has seen before, the lure of these unexpected voyages is what draws all to science in the first place," he concluded.