Using a bioinformatic approach, we have identified a new transcript, SLC7AS, mapping to 14q11.2, within the lysinuric protein intolerance (LPI) critical region. This gene is highly expressed in skeletal muscle, intestine, kidney, and placenta and encodes a predicted protein of 535 amino acids, homologous to the amino acid permease CD98 light chain and cationic amino acid transporters. RNA in situ hybridization data on mouse embryos confirm the expression in kidney and intestine and, interestingly, reveal that SLC7A8 is also highly expressed in eye, in retinal pigmented epithelium, and in tooth buds at day 16.5 of gestation. Mutational analysis excluded any direct involvement of the SLC7A8 gene product in LPI disease. The homology data and the expression pattern are in agreement with the hypothesis that SLC7A8 represents a novel light chain interacting with the 4F2 heavy chain in the multimeric complex mediating neutral and/or cationic amino acid transport and cystine/glutamate exchange.
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