The sequence and gene characterization of a 400-kb candidate region for IDDM4 on chromosome 11q13.

Type 1 diabetes is a complex disorder with interaction of both genetic and environmental factors. One of the loci, IDDM4, has been mapped to chromosome 11q13, with evidence of association to two markers, D11S1917 and H0570polyA. To identify putative candidate genes for IDDM4, we have constructed a 400-kb clone contig in this region and sequenced the clones. We have also sequenced the orthologous DNA from mouse. Previously, we identified a cDNA for the low-density lipoprotein receptor-related protein 5 gene (LRP5) 3 kb distal to H0570polyA. We have now determined the exon-intron structure of this gene. Detailed sequence analysis has identified a further three genes in this region: the CGI-85 gene (previously identified by W.-C. Lin) and two novel genes, C11orf24 and C11orf23. The C11orf24 gene has no known similarity to other genes, and its function is unknown. C11orf23 has similarity to the SIT4 (sporulation-induced transcript 4)-associated protein (SAP) family of yeast proteins, which are involved in regulation of the cell cycle. The full-length C11orf23 cDNA is the first mammalian orthologue of the yeast SAP family to be identified. Identification of these four genes in a 400-kb region of the IDDM4 region underpins our strategy to identify the IDDM4 locus.