What is in this article?:
- The division of labor among honey bees coincides with the presence in their brains of tiny snippets of noncoding RNA, called micro-RNAs, or miRNAs, that suppress the expression of genes.
Ben-Shahar was curious about the role newly discovered molecules called miRNAs might play in the control of behavior.
Francis Crick, the co-discoverer of the structure of DNA, said in 1956 that the central dogma of biology is that DNA makes RNA makes protein — and protein then does the cell’s work, including activating other genes.
The central dogma still holds, but in the past 50 years it has been enormously complicated by the discovery of many mechanisms for regulating gene expression, including a proliferation of regulatory RNAs.
Among these are miRNAS, tiny snippets of noncoding RNA typically only 22 nucleotide units long that bind to RNA transcripts of a gene, reducing protein production and, in effect, silencing the gene.
Micro-RNAs are known to regulate development and disease processes such as cancer, Ben-Shahar says.
“We wondered if they weren’t playing a role in regulating social behaviors,” he says, “because recent studies have implicated them in complex nervous-system functions such as neurodevelopment, psychiatric disease, and circadian clocks.”
A library of possibilities
Because nobody knew much about the miRNAs in bees, Ben-Shahar and the paper’s first author, undergraduate student Jacob Greenberg (now a medical student at WUSTL’s School of Medicine), decided to make a grand survey of the miRNA “library” in a bee’s head.
They ground up heads, extracted the RNA from the tissue, sorted out the small RNA fragments, and sent those to a company that sequences DNA (or RNA, which is a similar molecule).
Because the entire honey bee genome has been sequenced, the short sequences the company supplied could be compared with the bee genome and non-matching sequences discarded as junk.
Various criteria were applied to the remaining sequences to whittle the candidates down to true miRNAs.
All of this sorting and sifting was done in collaboration with Weixiong Zhang, PhD, professor of computer science and engineering in the School of Engineering & Applied Science, who is an expert in computational biology.
“Zhang’s lab has a lot of experience doing the bioinformatics part, which is important because not every little snippet of RNA is a miRNA; there are certain criteria they use to prove it’s an miRNA,” says Ben-Shahar.
At the end of this monumental cataloguing effort, the scientists had a list of 97 miRNAs that are expressed in the heads of honey bees, including 17 that had never been identified before, and many others that had been found in flies and mammals but not in bees.