TM4SF1 and subarachnoid hemorrhage: We anticipate, based on our occasional observations of the end-stage necrosis of Tm4sf1-heterozygous embryos as early as E14.5 (Figure 4A), that some Tm4sf1-heterozygous embryos may experience lethality before they have developed the apparent intraventricular and subarachnoid hemorrhage seen near birth (Figure 4B).