Strain-specific caspase-3-dependent programmed cell death in the early developing mouse forebrain

Caspase-3-deficient 129/Sv mice show hyperplasia of the forebrain at embryonic day (E) 10.5, which suggests that caspase-3-dependent programmed cell death (PCD) plays an essential role in brain morphogenesis prior to neurogenesis. However, little is known about region-specific caspase-3-dependent PCD in the developing forebrain. We examined the PCD region in the early developmental brain at E9.5 by whole mount terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL). In addition to hindbrain, TUNEL-reactivity was detected in the ventral forebrain and in the caudal portion of the front nasal region, just behind the regions expressing fgf-8 and otx-2. It has been shown recently that brain hyperplasia induced by caspase-3-deficiency is mouse strain-dependent; such that brain abnormalities were observed in caspase-3-deficient 129/Sv mice but not in caspase-3-deficient C57BL/6 mice. We examined the caspase-3-dependent PCD in the ventral forebrain of 129/Sv and C57BL/6 mouse embryos (E8.5-9 and E9.5) by double staining of TUNEL and antiserum against the active form of caspase-3 (anti-m3DI75). TUNEL/anti-m3DI75 reactivity in the ventral forebrain was mouse strain-dependent, such that many TUNEL/anti-m3DI75-positive cells were detected in the ventral forebrains of 129/Sv mice, but were not observed in C57BL/6 mice. Thus, it is likely that this region is the site of the strain-specific caspase-3-dependent PCD. A strain-dependent 'modulator' that regulates both caspase-3-dependent and -independent cell death pathways may control PCD in the ventral forebrain at E8.5-9.5.