MBTPS1 and neoplasm: In light of the requirement of Matriptase-dependent S1P signalling to promote tumour-suppressive ACE in both the hypomorphic hai1ahi2217 [29] and the amorphic hai1afr26 (Fig. 3e) allele, and in light of its known effect promoting cell survival in multiple other contexts [21, 25], we tested whether S1P might also be involved in regulating the observed caspase-dependent epidermal cell death.