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A Nose for Science

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Mouse Nasal Cavity
Credit: Lu Yang, David Ornitz, and Sung-Ho Huh, Washington University School of Medicine, St. Louis; University of Nebraska Medical Center, Omaha

Our nose does a lot more than take in oxygen, smell, and sometimes sniffle. This complex organ also helps us taste and, as many of us notice during spring allergy season when our noses get stuffy, it even provides some important anatomic features to enable us to speak clearly.

This colorful, almost psychedelic image shows the entire olfactory epithelium, or “smell center,” (green) inside the nasal cavity of a newborn mouse. The olfactory epithelium drapes over the interior walls of the nasal cavity and its curvy bony parts (red). Every cell in the nose contains DNA (blue).

The olfactory epithelium detects odorant molecules in the air, providing a sense of smell. In humans, the nose has about 400 types of scent receptors, and they can detect at least 1 trillion different odors [1].

But this is more than just a cool image captured by graduate student Lu Yang, who works with David Ornitz at Washington University School of Medicine, St. Louis. The two discovered a new type of progenitor cell, called a FEP cell, that has the capacity to generate the entire smell center [2]. Progenitor cells are made by stem cells. But they are capable of multiplying and producing various cells of a particular lineage that serve as the workforce for specialized tissues, such as the olfactory epithelium.

Yang and Ornitz also discovered that the FEP cells crank out a molecule, called FGF20, that controls the growth of the bony parts in the nasal cavity. This seems to regulate the size of the olfactory system, which has fascinating implications for understanding how many mammals possess a keener sense of smell than humans.

But it turns out that FGF20 does a lot more than control smell. While working in Ornitz’s lab as a postdoc, Sung-Ho Huh, now an assistant professor at the University of Nebraska Medical Center, Omaha, discovered that FGF20 helps form the cochlea [3]. This inner-ear region allows us to hear, and mice born without FGF20 are deaf. Other studies show that FGF20 is important for development of the kidney, teeth, mammary gland, and of specific types of hair [4-7]. Clearly, this indicates multi-tasking can be a key feature of a protein, not a trivial glitch.

The image was one of the winners in the 2018 BioArt Scientific Image & Video Competition, sponsored by the Federation of American Societies for Experimental Biology (FASEB). Its vibrant colors help to show the basics of smell, and remind us that every scientific picture tells a story.

References:

[1] Humans can discriminate more than 1 trillion olfactory stimuli. Bushdid C1, Magnasco MO, Vosshall LB, Keller A. Science. 2014 Mar 21;343(6177):1370-1372.

[2] FGF20-Expressing, Wnt-Responsive Olfactory Epithelial Progenitors Regulate Underlying Turbinate Growth to Optimize Surface Area. Yang LM, Huh SH, Ornitz DM. Dev Cell. 2018;46(5):564-580.

[3] Differentiation of the lateral compartment of the cochlea requires a temporally restricted FGF20 signal. Huh SH, Jones J, Warchol ME, Ornitz DM. PLoS Biol. 2012;10(1):e1001231.

[4] FGF9 and FGF20 maintain the stemness of nephron progenitors in mice and man. Barak H, Huh SH, Chen S, Jeanpierre C, Martinovic J, Parisot M, Bole-Feysot C, Nitschke P, Salomon R, Antignac C, Ornitz DM, Kopan R. Dev. Cell. 2012;22(6):1191-1207

[5] Ectodysplasin target gene Fgf20 regulates mammary bud growth and ductal invasion and branching during puberty. Elo T, Lindfors PH, Lan Q, Voutilainen M, Trela E, Ohlsson C, Huh SH, Ornitz DM, Poutanen M, Howard BA, Mikkola ML. Sci Rep. 2017;7(1):5049

[6] Ectodysplasin regulates activator-inhibitor balance in murine tooth development through Fgf20 signaling. D Haara O, Harjunmaa E, Lindfors PH, Huh SH, Fliniaux I, Aberg T, Jernvall J, Ornitz DM, Mikkola ML, Thesleff I. Development. 2012;139(17):3189-3199.

[7] Fgf20 governs formation of primary and secondary dermal condensations in developing hair follicles. Huh SH, Närhi K, Lindfors PH, Häärä O, Yang L, Ornitz DM, Mikkola ML. Genes Dev. 2013;27(4):450-458.

Links:

Taste and Smell (National Institute on Deafness and Other Communication Disorders/NIH)

Ornitz Lab, (Washington University, St. Louis)

Huh Lab, (University of Nebraska Medical Center, Omaha)

BioArt Scientific Image & Video Competition, (Federation of American Societies for Experimental Biology, Bethesda, MD)

NIH Support: National Heart, Lung, and Blood Institute; National Institute of Neurological Disorders and Stroke; National Institute on Deafness and Other Communication Disorders

2 Comments

  • Mike Hasan says:

    Superb

  • Jennifer Boyer says:

    As a congenital anosmic (born without a sense of smell), the discovery of the FEP cell is especially exciting, as I wonder if it could eventually help to generate a functioning olfactory system in those of us with anosmia!

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