I believe our paper is viewed as being the first to have established the abundance of human microRNAs: our results nearly doubled the number of human microRNAs sequenced until then, and provided the first solid evidence that there are many hundreds of microRNAs, several-fold higher than previously believed.

“The paper describes a novel methodology for detection of microRNAs, and the discovery of hundreds of novel microRNAs, 89 of which we have validated (i.e. sequenced) using this methodology.”

The paper describes a novel methodology for detection of microRNAs, and the discovery of hundreds of novel microRNAs, 89 of which we have validated (i.e., sequenced) using this methodology. The methodology integrates a computational approach, which for the first time scanned the entire human genome for possible microRNAs sequences, followed by high-throughput screening of these sequences using a microarray methodology we have developed, and validation of select sequences using a novel sequencing technique.

This methodology succeeded in identifying hundreds of microRNAs, which went undetected by the traditional biological approach for microRNAs discovery using random cloning and sequencing. Another significant advantage of the methodology we describe is that it does not rely on inter-species homology, and hence has identified hundreds of non-conserved microRNAs that were ignored by previous approaches.

MicroRNAs are a recently discovered group of "control" genes that regulate expression of proteins in our body. Our paper was the first to demonstrate that, contrary to previous estimates, there are in fact many hundreds of human microRNAs, a great many of which remain to be discovered.

Our results have nearly doubled the number of human microRNAs validated until then, and have shown that many of these "elusive" microRNAs go undetected by traditional microRNAs detection approaches, and that many are unique to humans and other primates. These findings are significant in that they helped establish microRNAs as a pervasive novel layer of gene regulation, a notion which has since been supported by hundreds of studies published over the last 12 months.

In this podcast audio commentary, Isaac Bentwich, founder of Rosetta Genomics, Ltd., discusses the therapeutic potential of human microRNAs. Podcast formats: mp3 (19.1 MB) wma (14.4 MB)

I started out back in 1999 from a biological theory I had formulated, which predicted the presence of many hundreds, possibly thousands, of short RNA regulatory genes that I predicted play an important role in cellular differentiation (Bentwich, The FASEB Journal, 2004). This led me to assemble and lead an inter-disciplinary team of talented researchers that dedicated the next several years to developing computational tools that could effectively scan the entire human genome for these "hidden" genes (if indeed they existed!), and microarray and other biological techniques that could validate these predictions.

These tasks were overwhelmingly challenging. No one at the time shared our views that there are many hundreds of microRNAs to be found, or that they can be found computationally. Scanning the entire human genome for these genes presented a daunting task, which no academic institute had undertaken, let alone a young, relatively inexperienced group with limited resources, working outside academia.

Another tough challenge was the lack of adequate "negative controls": whenever we failed to biologically validate one of our computer-predicted microRNAs, it was always difficult to tell whether the computer prediction was wrong, or the biological validation was not sensitive enough to pick it up, or perhaps both were fine and we were merely looking in the wrong tissue or clinical condition. Our advantage, of having focused on broad-scale computer-assisted microRNAs detection several years before others have, and having continued to work at it until we got it right, eventually led to overcoming these obstacles.