A discordant sibship analysis between beta-NGF and neurofibromatosis.

A new restriction fragment length polymorphism 5' to the beta-nerve growth factor (beta-NGF) gene has been found in proximity to the BglII polymorphism, and both polymorphisms are detectable with an EcoRI 7-kilobase (kb) subclone. Absence of the TaqI recognition site lengthens the 4.3-kb and 1.7-kb hybridizing fragments to 6 kb, and the alleles are in Hardy-Weinberg equilibrium with frequencies of 83% and 17%, respectively. Previous research has suggested that NGF is involved in disseminated neurofibromatosis (NF). We found four informative disseminated NF families with the two beta-NGF polymorphisms and have provided clearcut evidence against beta-NGF gene alteration in these families. If disseminated NF is found to be heterogeneous at a molecular level, more families should be tested to further rule out any role for beta-NGF in this syndrome.