Department of Neurophysiology and Cellular Biophysics

Functional and molecular characterization of cell turnover in the olfactory system

Olfactory epithelium

Olfactory receptor neurons are regenerating throughout life, making the OE an excellent model for studying stem cell dynamics and neurogenesis during development and regeneration. The basal (stem) cells that give rise to ORNs may also generate two glial cell types of the primary olfactory pathway, i.e., SCs, which lie within the OE and olfactory ensheathing cells, which ensheath bundles of axons in the ON. Unlike many parts of the nervous system, neurogenesis proceeds throughout life in the OE, allowing studies of stem cell behavior to be conducted in the regenerating adult nervous system, as well as during development. Another intriguing question is how the axons of newborn ORNs find their way to the glomeruli in the OB.

Recent work in our lab led us to hypothesize that individual developing ORNs of larval Xenopus laevis may transiently express multiple ORs and that they then gradually lose ORs, to perhaps the limit of one OR per cell, in mature ORNs functionally connected with their target glomerulus in the OB. Currently we continue our work in this project by analyzing the expression of ORs in developing ORNs in detail.

A variety of neurotrophic factors are known to control and/or modulate the proliferation or differentiation of stem cells. In other sensory systems, like the retina, nucleotides (e.g. ATP) are known to play a major modulatory role in developmental or proliferative events. Nucleotides seem to play a comparable role in the olfactory epithelium with its capability of constant neuronal renewal (for more information see Purinergic signaling). We recently identified that a disruption of purinergic signaling leads to a significant decrease in BrdU-labeling in the basal cell layer. This implicates that nucleotides modulate the proliferative activity of basal stem/progenitor cells in the OE (Hassenklöver et al., 2009).