Primordial germ cells and gastrointestinal stromal tumors respond distinctly to a cKit overactivating allele

Abstract

KitL, via its receptor cKit, supports primordial germ cell (PGC) growth, survival, migration and reprogramming to pluripotent embryonic germ cells (EGCs). However, the signaling downstream of KitL and its regulation in PGCs remain unclear. A constitutively activating mutation, cKitV558D, causes gain-of-function phenotypes in mast cells and intestines, and gastrointestinal stromal tumors (GISTs) when heterozygous. Unexpectedly, we find that PGC growth is not significantly affected in cKitV558D heterozygotes, whereas in homozygotes, increased apoptosis and inefficient migration lead to the depletion of PGCs. Through genetic studies, we reveal that this oncogenic cKit allele exhibits loss-of-function behavior in PGCs distinct from that in GIST development. Examination of downstream signaling in GISTs from cKitV558D/+ mice confirmed hyperphosphorylation of AKT and ERK, but both remain unperturbed in cKitV558D/+ PGCs and EGCs. In contrast, we find reduced activation of ERK1/2 and JNK1 in cKitV558D homozygous PGCs and EGCs. Inhibiting JNK, though not ERK1/2, increased apoptosis of wild-type PGCs, but did not further affect the already elevated apoptosis of cKitV558D/V558D PGCs. These results demonstrate a cell-context-dependent response to the cKitV558D mutation. We propose that AKT overload protection and JNK-mediated survival comprise PGC-specific mechanisms for regulating cKit signaling. © The Author 2012. Published by Oxford University Press. All rights reserved.