MEN1
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 3U84, 3U85, 3U86, 3U88, 4GPQ, 4GQ3, 4GQ4, 4I80, 4OG3, 4OG4, 4OG5, 4OG6, 4OG7, 4OG8, 4X5Y, 4X5Z, 5DDF, 5DD9, 5DDA, 5DDE, 5DDB, 5DDD, 5DDC, 5DB0, 5DB3, 5DB1, 5DB2
Identifiers
Aliases	MEN1, MEAI, SCG2, menin 1
External IDs	OMIM: 613733 MGI: 1316736 HomoloGene: 7418 GeneCards: MEN1
Gene location (Human) Chr. Chromosome 11 (human)[1] Band 11q13.1 Start 64,803,510 bp[1] End 64,811,294 bp[1]
Gene location (Mouse) Chr. Chromosome 19 (mouse)[2] Band 19|19 A Start 6,385,009 bp[2] End 6,390,921 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right adrenal gland ganglionic eminence right lobe of liver right lobe of thyroid gland left adrenal gland stromal cell of endometrium left lobe of thyroid gland anterior pituitary body of stomach skin of abdomen Top expressed in ganglionic eminence yolk sac adrenal gland mesencephalon neural tube rhombencephalon thymus cerebellum secondary oocyte proximal tubule More reference expression data BioGPS More reference expression data
Gene ontology Molecular function DNA binding protein-macromolecule adaptor activity R-SMAD binding protein N-terminus binding chromatin binding histone-lysine N-methyltransferase activity protein binding four-way junction DNA binding Y-form DNA binding double-stranded DNA binding Cellular component cytoplasm cytosol nuclear matrix nucleoplasm chromatin cleavage furrow nucleus histone methyltransferase complex endoplasmic reticulum lumen protein-containing complex Biological process negative regulation of cell-substrate adhesion negative regulation of protein phosphorylation positive regulation of transforming growth factor beta receptor signaling pathway regulation of transcription, DNA-templated negative regulation of cyclin-dependent protein serine/threonine kinase activity negative regulation of telomerase activity negative regulation of cell cycle regulation of activin receptor signaling pathway negative regulation of transcription by RNA polymerase II negative regulation of DNA-binding transcription factor activity negative regulation of osteoblast differentiation negative regulation of cell cycle G1/S phase transition MAPK cascade cellular response to DNA damage stimulus negative regulation of JNK cascade brain development cellular response to peptide hormone stimulus decidualization negative regulation of epithelial cell proliferation mitotic cell cycle osteoblast development positive regulation of protein binding negative regulation of transcription, DNA-templated response to gamma radiation response to UV type B pancreatic cell differentiation DNA repair regulation of type B pancreatic cell proliferation cellular response to glucose stimulus positive regulation of transcription by RNA polymerase II negative regulation of cell population proliferation response to transforming growth factor beta histone lysine methylation beta-catenin-TCF complex assembly transcription, DNA-templated post-translational protein modification chromatin organization Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 4221 17283 Ensembl ENSG00000133895 ENSMUSG00000024947 UniProt O00255 O88559 RefSeq (mRNA) NM_000244 NM_130799 NM_130800 NM_130801 NM_130802 NM_130803 NM_130804 NM_001370251 NM_001370259 NM_001370260 NM_001370261 NM_001370262 NM_001370263 NM_001168488 NM_001168489 NM_001168490 NM_008583 RefSeq (protein) NP_000235 NP_570711 NP_570712 NP_570713 NP_570714 NP_570715 NP_570716 NP_001357180 NP_001357188 NP_001357189 NP_001357190 NP_001357191 NP_001357192 NP_001161960 NP_001161961 NP_001161962 NP_032609 Location (UCSC) Chr 11: 64.8 – 64.81 Mb Chr 19: 6.39 – 6.39 Mb PubMed search [3] [4]
Wikidata
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Menin is a protein that in humans is encoded by the MEN1 gene.^[5] Menin is a putative tumor suppressor associated with multiple endocrine neoplasia type 1 (MEN-1 syndrome) and has autosomal dominant inheritance.^[6] Variations in the MEN1 gene can cause pituitary adenomas, hyperparathyroidism, pancreatic neuroendocrine tumors, gastrinoma, and adrenocortical cancers.

In vitro studies have shown that menin is localized to the nucleus, possesses two functional nuclear localization signals, and inhibits transcriptional activation by JunD. However, the function of this protein is not known. Two messages have been detected on northern blots but the larger message has not been characterized. Two variants of the shorter transcript have been identified where alternative splicing affects the coding sequence. Five variants where alternative splicing takes place in the 5' UTR have also been identified.^[5]

History

In 1988, researchers at Uppsala University Hospital and the Karolinska Institute in Stockholm mapped the MEN1 gene to the long arm of chromosome 11.^[7] The gene was finally cloned in 1997.^[8]

Genomics

The gene is located on long arm of chromosome 11 (11q13) between base pairs 64,570,985 and 64,578,765. It has 10 exons and encodes a 610-amino acid protein.

Over 1300 mutations have been reported to date (2010). The majority (>70%) of these are predicted to lead to truncated forms are scattered throughout the gene. Four - c.249_252delGTCT (deletion at codons 83-84), c.1546_1547insC (insertion at codon 516), c.1378C>T (Arg460Ter) and c.628_631delACAG (deletion at codons 210-211) have been reported to occur in 4.5%, 2.7%, 2.6% and 2.5% of families.^[6]

Clinical implications

The MEN1 phenotype is inherited via an autosomal-dominant pattern and is associated with neoplasms of the pituitary gland, the parathyroid gland, and the pancreas (the 3 "P"s). While these neoplasias are often benign (in contrast to tumours occurring in MEN2A), they are adenomas and, therefore, produce endocrine phenotypes. Pancreatic presentations of the MEN1 phenotype may manifest as Zollinger-Ellison syndrome.

MEN1 pituitary tumours are adenomas of anterior cells, typically prolactinomas or growth hormone-secreting. Pancreatic tumours involve the islet cells, giving rise to gastrinomas or insulinomas. In rare cases, adrenal cortex tumours are also seen.

Role in cancer

Most germline or somatic mutations in the MEN1 gene predict truncation or absence of encoded menin resulting in the inability of MEN1 to act as a tumor suppressor gene.^[9] Such mutations in MEN1 have been associated with defective binding of encoded menin to proteins implicated in genetic and epigenetic mechanisms.^[10] Menin is a 621 amino acid protein associated with insulinomas^[11] which acts as an adapter while also interacting with partner proteins involved in vital cell activities such as transcriptional regulation, cell division, cell proliferation, and genome stability. Insulinomas are neuroendocrine tumors of the pancreas with an incidence of 0.4 % which usually are benign solitary tumors but 5-12 % of cases have distant metastasis at diagnosis.^[12] These familial MEN-1 and sporadic tumors may arise either due to loss of heterozygosity or the chromosome region 11q13 where MEN1 is located, or due to presence of mutations in the gene.^[13][14]

MEN1 mutations comprise mostly frameshift deletions or insertions, followed by nonsense, missense, splice-site mutations and either part or complete gene deletions resulting in disease pathology.^[15] Frameshift and nonsense mutations result in a supposed inactive and truncated menin protein while splice-site mutations result in incorrectly spliced mRNA. Missense mutations of MEN1 are especially important as they result in a change to crucial amino acids needed in order to bind and interact with other proteins and molecules. As menin is located predominantly in the nucleus,^[16] these mutations can impact the stability of the cell and may further affect functional activity or expression levels of the protein. Studies have also shown that single amino acid changes in genes involved in oncogenic disorders may result in proteolytic degradation leading to loss of function and reduced stability of the mutant protein; a common mechanism for inactivating tumor suppressor gene products.^[17][18] MEN1 gene mutations and deletions also play a role in the development of hereditary and a subgroup of sporadic pituitary adenomas and were detected in approximately 5% of sporadic pituitary adenomas.^[19] Consequently, alterations of the gene represent a candidate pathogenetic mechanism of pituitary tumorigenesis especially when considered in terms of interactions with other proteins, growth factors, oncogenes play a rule in tumorigenesis.

Although the exact function of MEN1 is not known, the Knudson "two-hit" hypothesis provides strong evidence that it is a tumor suppressor gene. Familial loss of one copy of MEN1 is seen in association with MEN-1 syndrome. Tumor suppressor carcinogenesis follows Knudson's "two-hit" model.^[20] The first hit is a heterozygous MEN1 germline mutation either developed in an early embryonic stage and consequently present in all cells at birth for the sporadic cases, or inherited from one parent in a familial case. The second hit is a MEN1 somatic mutation, oftentimes a large deletion occurring in the predisposed endocrine cell and providing cells with the survival advantaged needed for tumor development.^[21] The MEN-1 syndrome often exhibits tumors of parathyroid glands, anterior pituitary, endocrine pancreas, and endocrine duodenum. Less frequently, neuroendocrine tumors of lung, thymus, and stomach or non-endocrine tumors such as lipomas, angiofibromas, and ependymomas are observed neoplasms.^[22]

In a study of 12 sporadic carcinoid tumors of the lung, five cases involved inactivation of both copies of the MEN1 gene. Of the five carcinoids, three were atypical and two were typical. The two typical carcinoids were characterized by a rapid proliferative rate with a higher mitotic index and stronger Ki67 positivity than the other typical carcinoids in the study. Consequently, the carcinoid tumors with MEN1 gene inactivation in the study were considered to be characterized by more aggressive molecular and histopathological features than those without MEN1 gene alterations.^[23]

Interactions

MEN1 has been shown to interact with:

• FANCD2,^[24]
• GFAP,^[25]
• JunD,^[26]
• NFKB1,^[25]
• MLL,^[27]
• RPA2,^[28] and
• VIM.^[29]

References

Further reading

External links

• GeneReviews/NIH/NCBI/UW entry on Multiple Endocrine Neoplasia Type 1
• MEN1 gene variant database
• MEN1+protein,+human at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
• Overview of all the structural information available in the PDB for UniProt: O00255 (Menin) at the PDBe-KB.