Multiple endocrine neoplasia-type 1 (MEN1) is an autosomal dominant familial cancer syndrome characterized by tumors in parathyroids, enteropancreatic endocrine tissues, and the anterior pituitary. DNA sequencing from a previously identified minimal interval on chromosome 11q13 identified several candidate genes, one of which contained 12 different frameshift, nonsense, missense, and in-frame deletion mutations in 14 probands from 15 families. The MEN1 gene contains 10 exons and encodes a ubiquitously expressed 2.8-kilobase transcript. The predicted 610-amino acid protein product, termed menin, exhibits no apparent similarities to any previously known proteins. The identification of MEN1 will enable improved understanding of the mechanism of endocrine tumorigenesis and should facilitate early diagnosis.

We report here the identification of a gene associated with the hyperparathyroidism-jaw tumor (HPT-JT) syndrome. A single locus associated with HPT-JT (HRPT2) was previously mapped to chromosomal region 1q25-q32. We refined this region to a critical interval of 12 cM by genotyping in 26 affected kindreds. Using a positional candidate approach, we identified thirteen different heterozygous, germline, inactivating mutations in a single gene in fourteen families with HPT-JT. The proposed role of HRPT2 as a tumor suppressor was supported by mutation screening in 48 parathyroid adenomas with cystic features, which identified three somatic inactivating mutations, all located in exon 1. None of these mutations were detected in normal controls, and all were predicted to cause deficient or impaired protein function. HRPT2 is a ubiquitously expressed, evolutionarily conserved gene encoding a predicted protein of 531 amino acids, for which we propose the name parafibromin. Our findings suggest that HRPT2 is a tumor-suppressor gene, the inactivation of which is directly involved in predisposition to HPT-JT and in development of some sporadic parathyroid tumors.

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MEN1 is a tumor suppressor gene that encodes a 610 amino acid nuclear protein (menin) of previously unknown function. Using a yeast two-hybrid screen with menin as the bait, we have identified the transcription factor JunD as a direct menin-interacting partner. Menin did not interact directly with other Jun and Fos family members. The menin-JunD interaction was confirmed in vitro and in vivo. Menin repressed transcriptional activation mediated by JunD fused to the Gal4 DNA-binding domain from a Gal4 responsive reporter, or by JunD from an AP1-responsive reporter. Several naturally occurring and clustered MEN1 missense mutations disrupted menin interaction with JunD. These observations suggest that menin's tumor suppressor function involves direct binding to JunD and inhibition of JunD activated transcription.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant cancer syndrome, characterized primarily by multiple tumors in the parathyroid glands, endocrine pancreas, and anterior pituitary. Other tumors, including gastrinoma, carcinoid, adrenal cortical tumors, angiofibroma, collagenoma, and lipoma, also occur in some patients. Individuals with MEN1 almost always have loss-of-function mutations in the MEN1 gene on chromosome 11, and endocrine tumors arising in these patients usually show somatic loss of the remaining wild-type allele. To examine the role of MEN1 in tumor formation, a mouse model was generated through homologous recombination of the mouse homolog Men1. Homozygous mice die in utero at embryonic days 11.5-12.5, whereas heterozygous mice develop features remarkably similar to those of the human disorder. As early as 9 months, pancreatic islets show a range of lesions from hyperplasia to insulin-producing islet cell tumors, and parathyroid adenomas are also frequently observed. Larger, more numerous tumors involving pancreatic islets, parathyroids, thyroid, adrenal cortex, and pituitary are seen by 16 months. All of the tumors tested to date show loss of the wild-type Men1 allele, further supporting its role as a tumor suppressor gene.M ultiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant cancer syndrome characterized by multiple tumors of the parathyroid, endocrine pancreas, and the anterior pituitary. Additional tumors have been associated with MEN1, including foregut carcinoid, adrenal cortical tumors, angiofibroma, collagenoma, and lipoma (1, 2). Linkage studies in affected families mapped the MEN1 locus to chromosome 11q13 (3), and the responsible gene, MEN1, was identified by positional cloning in 1997 (4). Germline mutations in MEN1 have been identified in almost all MEN1 kindreds (5-7), and somatic mutations in MEN1 have been reported in sporadic parathyroid adenomas, pituitary tumors, insulinomas, gastrinomas, and lung carcinoids (8 -12). Over 70% of germline mutations are nonsense and frameshifts, predicting truncation or absence of the resulting protein.Missense mutations and in-frame deletions account for the remaining 30% of the almost 250 unique mutations identified to date. Hence, MEN1 appears to be a classic tumor suppressor gene with tumors in affected patients showing somatic loss of the wild-type allele.The MEN1 gene consists of 10 exons (the first of which is untranslated), spanning 7.2 kb of genomic sequence and encoding a protein of 610 amino acids. The protein product, menin, does not reveal homologies to any other known proteins or possess notable motifs from which the putative function of the protein could be deduced. Menin RNA and protein apparently are expressed in all tissues (13), leaving unexplained the basis for endocrine predominance of neoplasia. Menin is found in the nucleus (14) and binds to the AP1 transcription factor JunD (15). This finding suggests a role in transcriptional regulation, although a detailed model for menin tumor suppression ...

Multiple endocrine neoplasia type 1 (MEN1) consists of benign, and sometimes malignant, tumors (often multiple in a tissue) of the parathyroids, enteropancreatic neuroendocrine system, anterior pituitary, and other tissues. Skin angiofibromas and skin collagenomas are common. Typically, MEN1 tumors begin two decades earlier than sporadic tumors. Because of tumor multiplicity and the tendency for postoperative tumor recurrence, specialized methods have been developed for preoperative and intraoperative localization of many MEN1-associated tumors. The MEN1 gene was recently isolated by positional cloning. This strategy progressively narrows the size of the candidate MEN1 gene interval on the chromosome and then finds and tests many or, if needed, all genes within that interval. The MEN1 gene was finally identified because it was the one gene that contained mutations in most DNAs from a test panel of MEN1 cases. It has been suggested that MEN1, like many hereditary cancer syndromes, is caused by mutation in a tumor suppressor gene that contributes to neoplasia when both gene copies in a tumor precursor cell have been sequentially inactivated ("two-hit" oncogenesis mechanism). Germline MEN1 mutations were found in most families with MEN1 and in most cases of sporadic MEN1. In addition, the MEN1 gene was the gene most likely to show acquired mutation in several sporadic or nonhereditary tumors-parathyroid adenomas, gastrinomas, insulinomas, and bronchial carcinoids. Most germline or acquired MEN1 mutations predicted truncation (and thus likely inactivation) of the encoded protein, supporting expectations for the "first hit" to a tumor suppressor gene. Testing for MEN1 germline mutation is possible in a research setting. Candidates for MEN1 mutation testing include patients with MEN1 or its phenocopies and first-degree relatives of persons with MEN1.

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