Activation of Six1 Expression in Vertebrate Sensory Neurons
Fig 5
mSix1-8-NLSCre induces sensory neuron-specific recombination in mouse embryos.
(A-I) Immunofluorescence analysis of Cre-mediated recombination in mSix1-8-NLSCre/R26R-LacZ double transgenic embryos. Distribution of ß-Gal was examined at E10.5 (A-D, H), E11.5 (E) and E12.5 (F, G). At E10.5, ß-Gal (Aa) co-localized with a neuron marker ISL1/2 (Aa') in the trigeminal ganglion (yellow signals in Aa''), geniculate-vestibuloacoustic ganglion complex (Ba, Ba', Ba''), petrosal ganglion (Ca, Ca', Ca'') and nodose ganglion (Da, Da', Da'') in transverse sections through the cervical area. In contrast, the same sections stained for a glial marker SOX10 showed no overlap of ß-Gal (green)-positive cells with SOX10 (red)-positive cells in all cranial sensory ganglia (Ab, Bb, Cb, Db). At E11.5, ß-Gal (Ea) also co-localized with ISL1/2 (Ea') in the DRG (yellow signals in Ea'') in a transverse section through the trunk region but not with SOX10 on the same section (Eb). In the frontal sections through the OE at E12.5 (F, G), ß-Gal (green)-positive cells were detected not only in the OE (F, G) but also in the vomeronasal organ (G) and in the surrounding mesenchyme along the TUBB3 (red)-positive axons of the olfactory and vomeronasal sensory neurons (white arrowheads). Many ß-Gal-positive cells were also found in the "migratory mass (white square bracket)" comprising placode-derived migratory cells and axons of olfactory sensory neurons located ventral to the forebrain (F). (H) At E10.5, ß-Gal (green)-positive cells were found in the OE (demarcated by white dotted line) and in an aggregate of TUBB3-positive cells (white arrowheads) located next to the OE. (I) Immunofluorescence analysis of Six1-8 enhancer activity in chick. Frontal section through the olfactory pit of a representative chick embryo at 48 h.p.e. EGFP (green) derived from pT2A-BB-mSix1-8-EGFP was detected in the OE and in an aggregate of TUBB3 (red)-positive cells (yellow arrow) located subjacent to the OE, a likely avian homolog of the rodent migratory mass. DAPI was used for nuclear staining (blue, Aa'', Ab, Ba'', Bb, Ca'', Cb, Da'', Db, Ea'', Eb, F-I). In all panels, dorsal is to the top and midline is to the left (A-E, H) or right (F, G, P). drg: dorsal root ganglia, fb: forebrain, mm: migratory mass, oe: olfactory epithelium, ov: otic vesicle, vno: vomeronasal organ, V: trigeminal ganglia, VII: geniculate ganglia, VIII: vestibuloacoustic ganglion, IX: petrosal ganglion, X: nodose ganglion. Scale bars: 0.1 mm (A-I).