The mutation is a nonsense mutation at base 4645 in exon 30, a sequence that encodes a portion of the chondroitin sulfate proteoglycan (neuron-glial antigen-2) repeat domain of FRAS1. This cytosine to thymine mutation at base 4645 (C4645T) resulted in a change at amino acid 1263 of the encoded protein, changing a glutamine codon to a stop codon. Transcript level was reduced in RNA derived from mutant limb buds. (c.3787C>T, p.Q1263* (NM_175473.3) )