A further argument against BMP4 specification of TB is that mouse embryos, in which both copies of the BMP4 gene have been inactivated, implant successfully and on time and only fail in their development at the egg cylinder stage (Winnier et al. 1995), a phenotype consistent with a role for BMP4 in gastrulation and mesoderm formation but not in establishment of TB and implantation. Here, BMP4 is linked to tuberculosis.