Sequential Maturation of Olfactory Sensory Neurons in the Mature Olfactory Epithelium

Abstract

The formation of the olfactory nerve and olfactory bulb (OB) glomeruli begins embryonically in mice. However, the development of the olfactory system continues throughout life with the addition of new olfactory sensory neurons (OSNs) in the olfactory epithelium (OE). Much attention has been given to the perinatal innervation of the OB by OSN axons, but in the young adult the process of OSN maturation and axon targeting to the OB remains controversial. To address this gap in understanding, we used BrdU to label late-born OSNs in young adult mice at postnatal day 25 (P25-born OSNs) and timed their molecular maturation following basal cell division. We show that OSNs in young adults undergo a sequential molecular development with the expression of GAP 43 (growth-associated protein 43) > AC3 (adenylyl cyclase 3) > OMP (olfactory marker protein), consecutively, in a time frame of ∼8 d. To assess OSN axon development, we implemented an in vivo fate-mapping strategy to label P25-born OSNs with ZsGreen. Using sampling intervals of 24 h, we demonstrate the progressive extension of OSN axons in the OE, through the foramen of the cribriform plate, and onto the surface of the OB. OSN axons reached the OB and began to target and robustly innervate specific glomeruli ∼10 d following basal cell division, a time point at which OMP expression becomes evident. Our data demonstrate a sequential process of correlated axon extension and molecular maturation that is similar to that seen in the neonate, but on a slightly longer timescale and with regional differences in the OE.

The micro RNA / TET 3/ REST axis is required for olfactory globose basal cell proliferation and male behavior

“…The costaining results showed that the BrdU + /GAP43 + cells accounted for 18.30 AE 0.7709% of the total GAP43 + cells in the NC mice ( Fig 4D and E). The results were consistent with previous studies (Coleman et al, 2017;Liberia et al, 2019). However, in the MOE of the miR-200b/a KD mice, the number of BrdU + /GAP43 + cells was only 1.007 AE 0.1217% of the GAP43 + cells (Fig 4D and E).…”

“…For analysis of differentiation of GBCs, male mice (NC and miR-200 KD, n = 3 mice each group, 12-14 weeks old) were injected with BrdU twice (with intervals of 2 h). Tissues were collected 3 days after BrdU injection (Liberia et al, 2019).…”

“…The time between BrdU injection and perfusion can be used to map the fate of recently generated OSNs, as identified by their incorporation of BrdU. It has been revealed that a newborn OSN requires 24 h to differentiate into an iOSN, and until 3 days after BrdU injection, a corresponding fraction of BrdU + cells is GAP43 positive (Liberia et al, 2019). Therefore, we perfused the mice at 3 days after BrdU injection for analysis of GBC differentiation.…”

A Comparison of the Primary Sensory Neurons Used in Olfaction and Vision

“…Two groups of stem cells exist in the OE, the quiescent horizontal basal cells which serve as a reserve stem cell population that activates following severe OE injury, and the actively cycling globose basal cells which are the primary progenitor for OSN renewal and recovery following minor injury (Schwob et al, 2017). The development of new OSN takes roughly 10 days as marked by both expressions of mature OSN markers and glomeruli innervation (Liberia et al, 2019). One challenge inherent in this process is the need to constantly rewire the OE to the OB.…”

Inhibition of focal adhesion kinase increases adult olfactory stem cell self-renewal and neuroregeneration through ciliary neurotrophic factor

“…To determine whether FAK inhibition-induced CNTF affects neuronal differentiation, the FAK14 and BrdU treatments were followed (pulse-chase method) by 9 and 20 days before analyses. This extended period allows for basal stem cells to proliferate and differentiate into mature OSNs, a process that takes 10–20 days ( Schwob et al, 1995 ; Jia et al, 2009 ; Liberia et al, 2019 ). To analyze the fate of FAK14-induced GBC proliferation, BrdU-positive nuclei in the total olfactory epithelium, middle OSN layer and basal stem cell layer were counted.…”