Fig 2: BCMA mediates APRIL-promoted axonal outgrowth. (A) Representative E18 hippocampal pyramidal neurons that were transfected after 2 days in vitro with plasmids expressing either GFP alone or GFP together with either wild-type BCMA or truncated BCMA (BCMA ΔC86). After transfection, the neurons were cultured for a further 18 h with and without APRIL (100 ng/ml) before GFP immunostaining. Scale bar = 100 μm. (B) Bar chart of axonal length under the experimental conditions illustrated in A. (C) Bar chart of axonal length of neurons cultured in the presence or absence of 3 μg/ml of anti-BCMA or 1.5 μg/ml of anti-APRIL with or without APRIL (100 ng/ml). The mean ± s.e.m. of data obtained from > 150 neurons per condition compiled from at least three separate experiments are shown (*** indicates P < 0.0001, statistical comparison with control, Mann–Whitney U test).

Fig 3: Localization of APRIL and BCMA in the developing hippocampus. Frozen sections of P10 hippocampus triple labeled with TO-PRO®-3 Iodide, anti-MAP-2 or anti-200 kD neurofilament and either (A) anti-APRIL (B) or anti-BCMA. For each set, the upper panels show a higher power image of CA1 (scale bars = 25 μm), the middle panels show lower power images of the CA regions (scale bars = 200 μm) and the lower panel show a higher power image of the fimbria (scale bars = 25 μm). Abbreviations: rad, stratum radiatum; py, stratum pyramidale; fim, fimbria; alv, alveus; ori, stratum oriens.

Fig 4: Developmental changes in the expression of April and Bcma mRNA in the midbrain and striatum. (A) April mRNA in the midbrain, (B) April mRNA in the striatum and (C) Bcma mRNA in the midbrain relative to the geometric mean of reference mRNAs. The mean S.E.M. of data from between three and six separate sets of tissues at each age are plotted.

Fig 5: Expression of APRIL and BCMA in the developing hippocampus. Graphs of the levels of APRIL mRNA (A) and BCMA mRNA (B) relative to reference mRNAs for GAPDH and SDHA in total RNA extracted from E18, P0, P5 and P10 hippocampi (mean ± s.e.m., n = 4 separate sets of hippocampal tissue at each age). Representative Western blots of lysates of E18, P0, P5, and P10 hippocampi probed for GAPDH together with either APRIL (C) or BCMA (D). Lysates from spleen tissue were probed as positive control.