Exencephaly in the syndrome of trisomy No. 12 of the foetal mouse

Abstract

EXPERIMENTAL¹ and morphological² evidence suggests that exencephaly and anencephaly represent different degrees of severity of cranioschisis. Their morphogenesis seems to involve a primary disturbance of the cephalic somites and notochord. Both conditions are experimentally inducible in several species by the action of different causal factors and teratogens^3–7. Moreover, exencephaly has been observed occasionally in gene mutants, for example in the mouse⁸, though rarely with complete penetrance in the affected strains⁹, and apparent autosomal recessive inheritance of neural tube defects has been suggested to occur at least in some instances in man^10,11. Therefore, it can be assumed that the aetiology of cranioschisis is at least complex and multifactorial involving environmental agents as well as genetic factors. But so far, defects belonging to this entity have not yet been observed in human or other mammalian chromosome mutation syndromes. In this respect it seems of interest to report the finding of exencephaly as constant and characteristic feature of trisomy of chromosome 12 in the mouse foetus.