REX1BD and proximal spinal muscular atrophy: As an example, we found that MRLP41, encoding for the protein BMRP with pro-apoptotic activity (by binding Bcl-2) (Malladi et al. 2011), was related to 9 others (TICAM2, ATP5F1D, TRAPPC5, SCAND1, ALKBH7, TMEM160, TMED7-TICAM2, REX1BD, RPL17-C18orf32) with a high bottleneck coefficient suggesting a fundamental role of this gene in the SMA molecular network.