GREM1 and colorectal carcinoma: If the downstream SMAD effectors that function within both the BMP and TGF-beta pathways are included, the components of BMP signalling involved in CRC risk might comprise up to 3 high-penetrance predisposition genes (SMAD4, BMPR1A, GREM1) and 8 low-penetrance variants at GREM1, BMP4, BMP2, SMAD7 and LAMA5 (tagged respectively by rs16969681 and rs11632715, rs4444235 and rs1957636, rs961253 and rs4813802, rs4939827, and rs4925386) [1], [2], [3], [5], [8], [9], [10], [11].