Alport syndrome (AS) is an hereditary disease of basement membranes characterized by progressive renal failure and deafness. Changes in the glomerular basement membrane (GBM) in AS suggest that the type IV collagen matrix, the major structural component of GBM, is disrupted. We recently isolated the genes for two type IV collagens, alpha 3(IV) and alpha 4(IV), that are encoded head-to-head on human chromosome 2. These chains are abundant in normal GBM but are sometimes absent in AS. We screened for mutations in families in which consanguinity suggested autosomal recessive inheritance. Homozygous mutations were found in alpha 3(IV) in two families and in alpha 4(IV) in two others, demonstrating that these chains are important in the structural integrity of the GBM and that there is an autosomal form of AS in addition to the previously-defined X-linked form.
Point mutations at the 12th codon of c‐Ki‐ras in pancreatic cancer from Japanese patients were examined using the polymerase chain reaction, followed by cloning of the amplified gene fragments in pTZ phagemid and nucleotide sequence determination. The frequency of the point mutations found in the tumors was quite high (75%). The mutation most frequently detected was a G→A transition at the second position of codon 12 (GGT→GAT), but other types of mutations such as GGT→GTT and GGT→CGT were also found. In one case, silent mutation of GGT to GGC was detected in addition to the frequent mutation of GGT to GAT, These observations suggest that the 12th codon of pancreatic c‐Ki‐ras is highly mutatable.
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