Mapping Novel Pancreatic Islet Genes to Human Chromosomes

A strategy was developed to generate expressed sequence tags (ESTs) from human pancreatic islet gene products using differential display of mRNA. Screening of over 2,000 cDNA amplification products identified 42 cDNAs that were preferentially expressed in pancreatic islets relative to exocrine tissue. Public database analysis showed that 29 (69%) corresponded to novel genes, in contrast with only 66 of 250 (26.4%) cDNA clones randomly selected from a human islet library. Reverse transcription–polymerase chain reaction (RTPCR) and/or Northern analysis of RNA from multiple tissues confirmed that expression was enhanced in human islet cell RNA for 11 of 15 tested cDNAs. Sequencetagged sites developed from 19 islet cDNAs were used to map these genes to human chromosomes using a combination of monochromosomal somatic-cell hybrids, genome-wide radiation hybrids, and mega–yeast artificial chromosome analysis. These results indicate that this PCR-based cDNA selection strategy yields information on a distinct subset of pancreatic islet transcribed sequences, which complements ongoing human EST identification efforts based on random cDNA selection. These mapped ESTs may be used to assist in the positional cloning of diabetes susceptibility genes.