During the late 1970s, Axel, along with
microbiologist Saul J. Silverstein and geneticist
Michael H. Wigler, discovered a technique of
cotransformation via
transfection, a process which allows foreign DNA to be inserted into a host cell to produce certain proteins. A family of
patents, now colloquially referred to as the "Axel patents", covering this technique were filed for February 1980 and were issued in August 1983. As a fundamental process in recombinant DNA research as performed at
pharmaceutical and
biotech companies, this patent proved quite lucrative for Columbia University, earning it almost $100 million a year at one time, and a top spot on the list of top universities by licensing revenue. Buck and Axel
cloned olfactory receptors, showing that they belong to the family of
G protein coupled receptors. By analyzing rat
DNA, they estimated that there were approximately one thousand different
genes for olfactory receptors in the
mammalian
genome. This research opened the door to the
genetic and
molecular analysis of the mechanisms of
olfaction. In their later work, Buck and Axel have shown that each
olfactory receptor neuron remarkably only expresses one kind of olfactory receptor protein and that the input from all neurons expressing the same receptor is collected by a single dedicated
glomerulus of the
olfactory bulb. Axel's primary research interest is on how the brain interprets the sense of smell, specifically mapping the parts of the brain that are sensitive to specific olfactory receptors. He holds the titles of
University Professor at
Columbia University, Professor of
Biochemistry and Molecular
Biophysics and of
Pathology at Columbia University's College of Physicians and Surgeons, and Investigator of the
Howard Hughes Medical Institute. In addition to contributions to neurobiology, Axel has also made seminal discoveries in immunology, and his lab was one of the first to identify the link between
HIV infection and immunoreceptor
CD4. In addition to making contributions as a scientist, Axel has also mentored many leading scientists in the field of neurobiology. Seven of his trainees have become members of the National Academy of Sciences, and currently six of his trainees are affiliated with the Howard Hughes Medical Institute's investigator and early scientist award programs. ==Awards and honors==