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The mutated gene responsible for the tubby obesity phenotype has been identified by positional cloning. A single base change within a splice donor site results in the incorrect retention of a single intron in the mature tub mRNA transcript. The consequence of this mutation is the substitution of the carboxy-terminal 44 amino acids with 24 intron-encoded amino acids. The normal transcript appears to be abundantly expressed in the hypothalamus, a region of the brain involved in body weight regulation. Variation in the relative abundance of alternative splice products is observed between inbred mouse strains and appears to correlate with an intron length polymorphism. This allele of tub is a candidate for a previously reported diet-induced obesity quantitative trait locus on mouse chromosome 7.

The complete sequence of the polycystic kidney disease gene (PKD1) and its transcript have been described. The predicted protein is not a member of a previously described gene family, but contains several structural motifs that are present in proteins of known function. Most of these domains are present in the extracellular parts of proteins involved in interactions with other proteins and carbohydrates. The PKD1 gene product also contains potential transmembrane sequences. The molecule is likely to be involved in cell-cell or cell-matrix interactions, which is consistent with the different manifestations of polycystic kidney disease.