Two structurally related, G-protein-coupled receptors were identified as receptors for the neuropeptide, neuromedin U. This peptide is found in highest levels in the gut and genitourinary system where it potently contracts smooth muscle but is also expressed in the spinal cord and discrete regions of the brain. Binding sites for neuromedin U have been characterized in rat uterus, however, little is known about the activity of this peptide in the regions of the central nervous system where it is expressed. The receptors characterized in this report are activated by neuromedin U at nanomolar potency in heterologous expression systems and bind radiolabeled neuromedin U with high affinity. Localization of the receptor RNA by quantitative reverse transcription-polymerase chain reaction in a variety of human tissues shows distinct expression patterns for the two receptors. NMU1 is expressed predominantly in peripheral tissues, whereas NMU2 is more highly expressed in the central nervous system. Identification of neuromedin U receptor subtypes will greatly aid in the determination of the physiological roles of this peptide.

Germline mutations in MSH6 can cause HNPCC, which is associated with a tumor phenotype featuring MSI. However, tumors arising in persons with disease-causing mutations of MSH6 may or may not exhibit MSI. We used D-HPLC to screen for germline mutations in the promoter region, the coding region and the 3-UTR of MSH6. Eighty-four families, enrolled on the basis of Amsterdam I and II criteria (HNPCC families) and less stringent criteria (HNPCC-like families), were tested for MMR gene mutations; 27 families had a disease-causing mutation in MLH1 or MSH2, and the remaining 57 families were tested for mutations in MSH6. Two protein-truncating mutations were identified in each of 2 families fulfilling the Amsterdam I criteria, being present in persons affected with early-onset colorectal cancers exhibiting MSI. Immunohistochemical analysis showed that expression of both MSH2 and MSH6 proteins was lost in the cancer cells of the 2 mutation carriers but only MSH6 protein expression was lost in 2 adenomatous polyps. A third possibly disease-causing mutation was found in a person affected with a tumor that did not exhibit MSI. In addition, we found 4 new polymorphisms and determined that neither of the 2 studied by association analysis conferred susceptibility to colorectal or endometrial cancer. HNPCC is an autosomal dominant syndrome characterized by susceptibility to CRC with a mean age at diagnosis of approximately 45 years. 1 In HNPCC patients, the risk of developing cancers of the endometrium, ovary, stomach, small intestine, hepatobiliary tract, renal pelvis and brain is increased. 2,3 Germline mutation in one of the genes of the DNA MMR system is most often responsible for the syndrome. DNA-based genetic testing usually is offered to persons who satisfy certain family history criteria. The Amsterdam I criteria select families that have (i) 3 or more relatives affected with CRC in at least 2 consecutive generations, one person being a first-degree relative of the other 2; (ii) at least one CRC diagnosed before age 50; and (iii) absence of gastrointestinal polyposis. 4 Because these criteria did not include the noncolonic cancers that are associated with MMR gene mutations, the Amsterdam I criteria were modified to include cancers of the endometrium, small bowel and renal pelvis (Amsterdam II). 5 HNPCC is caused primarily by inactivating mutations in one of the genes that constitute the MMR system, most commonly MLH1 or MSH2. 6,7 Mutations in these 2 genes are associated with a tumor phenotype featuring accumulation of mutations at microsatellite repeat sequences, which is referred to as MSI. 8 -10 MSI results from failure of the MMR system to repair deletions or insertions of repeat units of microsatellite loci that spontaneously occur during DNA replication. A tumor is classified as MSI-high when a fraction greater than one-third of the microsatellite loci tested display novel locus-specific fragments; a tumor is classified as non-MSIhigh when a fraction Ͻ0.3 of the microsatellite loci tested exhibit novel fragments...

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