1999 Nature America Inc.• http://genetics. nature. com correspondence nature genetics• volume 21• march 1999 263 insulin resistance is also supported by reported associations of the INS VNTR class III allele with a number of conditions in which insulin resistance is a major feature2, 3, such as polycystic ovary syndrome and central obesity. Thus, selective peripheral insulin resistance could explain the III/III genotype associations with both larger size at birth and insulin resistance or type 2 diabetes risk. Similarly, in conditions of fetal growth restraint, such as poor nutrition in pregnancy, peripheral insulin resistance may also represent a fetal metabolic adaptation that diverts nutrients to protect brain and skeletal growth in utero12, but may lead to disease in adulthood.

Hereditary hearing impairment shows extreme genetic heterogeneity and more than 40 different loci have been reported. One of these, DFNA2, was localized to chromosome 1p34 on the basis of linkage analysis in two large families with autosomal dominant nonsyndromic hearing loss originating from Indonesia and the United States1. Subsequently, hearing loss in three additional large families from Belgium and the Netherlands was found to map to the same region2. Two different genes are now reported to be the ‘DFNA2’gene. In December’s issue of Nature Genetics, Jia-Hui Xia and colleagues described two small Chinese families with nonsyndromic autosomal dominant hearing loss in which they found a missense and a nonsense mutation in GJB3, which encodes connexin 31 (ref. 3). As GJB3 is located on chromosome 1p34, it was proposed, in an accompanying News & Views that GJB3 is a good candidate for involvement in DFNA2 families4. Extensive sequence analysis of the coding region and the 5 UTR of GJB3 in