1d), calyx terminals were counted only if they completely surrounded individual hair cells with a continuous band of -III tubulin/neurofilament immunoreactivity that extended though the level of the cell nucleus. were immature and not classifiable by type. At P30, tdTomato-positive hair cells improved 1.8-fold compared to P9, and 91% of tdTomato-labeled hair cells were type II. Our findings show that most neonatally-derived hair cells become type II, and many type I hair cells (created before P2) downregulate Sox2 and acquire calyces between P0 and P14. (Shailam et al., 1999; McInturff et al., 2018), Liquidambaric lactone and cells with hair cell morphology emerge around E13 (Anniko et al., 1979, 1983; Mbiene et al., 1988). Hair cells continue to be produced over the next 7C8 days of development and into the first two weeks of postnatal existence (Ruben, 1967; Sans and Chat, 1982; Rsch et al., 1998; Denman-Johnson and Forge, 1999; Kirkegaard and Nyengaard, 2005; Hume et al., 2007; Raft et al., 2007; Burns up et al., 2012). In fact, approximately half of the hair cells in the mouse utricle emerge between postnatal day time (P0) and P12 (Burns up et al., 2012). Of these, about one third are derived from cell divisions that happen between P0 and P2, while the remaining hair cells presumably differentiate from hair cell precursors that exited the cell cycle prior to P0. Postnatally, hair cells are most frequently added to the lateral region of the macula or near the striola (Burns up et al., 2012; Bucks et al., 2017). While there is evidence of sporadic synaptic boutons of vestibular afferent nerves at E15 and partial calyces at E18 in mice, most hair cells do not look like innervated by vestibular afferents until birth or a few days later on (Anniko et al., 1983; Nordemar, 1983; Anniko, 1985; Mbiene et al., 1988; Rsch et al., 1998). No detailed analysis of calyx development has been carried out in mouse utricles. The present study characterized the development of type I and II hair cells and calyceal afferent terminals in utricles of postnatal mice. Using a combination of immunofluorescence and transmission electron microscopy (TEM), we examined the spatial and temporal patterns of Sox2 down-regulation and calyx formation in type I hair cells. Between P0-P14, we observed a ~25-collapse increase in the denseness of well-formed calyces throughout the utricle, and a Rabbit Polyclonal to CPZ related increase in Sox2-bad (presumptive type I) Liquidambaric lactone hair cells. During early postnatal phases, calyces enclosed either Sox2-positive or Sox2-bad hair cells. By P14, however, calyces enclosed only Sox2-bad hair cells. Next, we fate-mapped (stock #5975; (Doerflinger et al., 2003) and (mice were injected with tamoxifen [3 mg/40 g, intraperitoneal injection (IP); Sigma-Aldrich (St. Louis, MO)] at P2 and P3 (~20C24hr apart). Samples were collected one week post-tamoxifen injection (at P9) or one month post-tamoxifen (at P30). Settings were age-matched mice that did not receive tamoxifen injection and were housed separately from your tamoxifen-treated experimental mice. Immunofluorescent staining The development of hair cell phenotype and the formation of calyx nerve terminals were examined in utricles of neonatal C57Bl/6J mice. Temporal bones were harvested at P0, P3, P5, P7, P14, and P17 and placed in chilled HEPES-buffered tradition medium (Medium-199, Thermo Fisher, Waltham, MA). Small openings were made in Liquidambaric lactone the cochlear apex and along an revealed semicircular canal, and temporal bones were fixed for 60 min by immersion in 4% paraformaldehyde (PFA). Following Liquidambaric lactone thorough rinsing in PBS, the temporal bones were decalcified immediately in 0.1M EDTA at Liquidambaric lactone 4 C. Utricles were then isolated and processed for immunofluorescent staining, either as whole mounts or as 20 m freezing sections. Hair cells and/or neurons were labeled with the following antibodies (details provided in Table 1): anti-?III-tubulin (RRID Abdominal_2721321), anti-myosin VIIa (RRID Abdominal_10015251), anti-neurofilament (160 kD, RRID Abdominal_531793, or 200 kD, RRID Abdominal_177520), and anti-Sox2 (RRID Abdominal_2286684). Specimens were incubated in main antibodies over night at space heat. The next day, they were rinsed 5x in PBS and incubated for 2 hours in secondary antibodies (anti-mouse,-rabbit, -chick, and -goat IgG, conjugated with Alexa488, 555 or 647; Thermo Fisher, Waltham, MA). Utricles were then stained for 30 minutes with DAPI; 1 g/ml in 1X PBS; Sigma-Aldrich, St. Louis MO). Both whole mounts and labeled frozen sections were coverslipped in glycerol:PBS (9:1). Table 1. Antibodies used in the study mice, temporal bones were eliminated and post-fixed in electron microscopy grade 4% PFA (Polysciences, Inc., Warrington, PA) immediately at room heat. After fixation, temporal bones were.