Mitral and tufted cell-specific expression of Tbx21 protein. (A) A parasagittal section of adult mouse brain labelled with anti-Tbx21 antibody. Strong fluorescent signals are specifically observed in the olfactory bulb (OB). (B) A higher magnification of the OB. (C) No immunoreactivity in the OB section from Tbx21-deficient mouse. (D-F) Double immunofluorescence labelling of OB section with anti-Tbx21 (D, F (magenta)) and anti-Arx (E and F (green)) antibodies. Tbx21 protein is expressed in the mitral and tufted cells but not in Arx-positive interneurons. (G-J) Triple immunofluorescence labelling of OB section with anti-Tbx21 (G and J (red)), anti-Tbr1 (H and J (green)) and anti-Tbr2 (I and J (blue)) antibodies. The three T-box family transcription factors are expressed in mostly overlapping, but some differential, subpopulations of mitral and tufted cells. (K-N) Triple immunofluorescence labelling of the OB section with anti-Tbx21 (K and N (red)), anti-PGP9.5 (L and N (green)) and anti-protocadherin 21 (Pcdh21) (M and N (blue)) antibodies. All three molecules are expressed in the mitral and tufted cells but localized to different subcellular compartments (Tbx21 in nuclei; PGP9.5 in cell bodies and proximal dendrites; Pcdh21 in cell bodies and glomeruli). (O-R) Developmental expression of Tbx21 protein in OB coronal sections from E14.5 (O), E16.5 (P), P0 (Q) and P7 (R) mice. EPL, external plexiform layer; GCL, granule cell layer; GL, glomerular layer; IPL, internal plexiform layer; MCL, mitral cell layer.