While further studies continue, possible interpretations include involvement of a regulatory gene(s) for PAX 3 and other genes at the other breakpoints related causally to the spina bifida and mental retardation.
Crossing the Sp (Splotch) mutation in the Pax3 gene onto the FVB/N background for two generations indicated that this resistant strain also decreases the penetrance of spina bifida.
In brain tissue, levels of PAX3 were significantly reduced in both encephalocele and spina bifida subtypes; the expression levels of cleaved caspase 3(17 kD) of encephalocele cases and cleaved caspase 8(47/45 kD) in spina bifida cases were higher than in controls; no difference was found in the expression of p53 or caspase 9 between NTDs and controls.