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Background/Aims: Germline mutations of the rearranged during transfection (RET) gene cause multiple endocrine neoplasia type 2 (MEN2). About 85% of RET mutations in MEN2 occur in codon Cys634. The RET D631Y mutation has recently been discovered, and we have studied its molecular expression and clinical consequences.Methods: We analyzed the clinical characteristics of a total of 34 D631Y variant MEN2 individuals from seven families. We also constructed wild-type and mutant C630Y, D631Y, and C634R/W expression vectors and investigated their effects on signaling pathways and ability to correct the phenotypes of RET mutant cells.Results: The median ages at diagnosis of pheochromocytoma and medullary thyroid carcinoma (MTC) were higher in patients with RET D631Y variant MEN2 than in those with the C634R/W variant (49:53.5 years vs. 33.5:27 years, respectively), and the penetration of the D631Y mutation with respect to MTC was lower than that of the C634R/W mutation (32.3% vs. 90%). The effects of the mutant vectors on phosphorylation of RET signaling molecules and focus formation were significantly different from those of wild type, but there were no significant differences between the mutants. D631Y scored significantly higher for chemotaxis and wound healing than C630Y, but lower than C634R and C634W.Conclusions: We suggest that the tumorigenic potential conferred by the D631Y mutation is lower than that conferred by the C634R/W mutation, but higher than that conferred by C630Y. Thus, the risk level of the RET D631Y variant appears to be higher than that of C630Y and lower than that of C634R/W.

The CDC73/HRPT2 gene, a defect which causes hyperparathyroidism–jaw tumor (HPT-JT) syndrome, encodes CDC73/parafibromin. We aimed to investigate whether CDC73 would be a target for ubiquitin–proteasome degradation. We cloned full-length cDNAs encoding a family of 58 ubiquitin-specific deubiquitinating enzymes (DUBs), also known as ubiquitin-specific proteases (USPs). Use of the yeast two-hybrid system then enabled us to identify USP37 as interacting with CDC73. The biochemical interaction between the USP37 and CDC73 and their reciprocal binding domains were studied. Co-localization of CDC73 and USP37 was observed in cells. CDC73 was found to be polyubiquitinated, and polyubiquitination of CDC73 was prominent in mutants. CDC73 was deubiquitinated via K48-specific ubiquitin chains by USP37, but not by the catalytically inactive USP37C350S mutant. Observation of the binding between deletion mutants of CDC73 and USP37 revealed that the β-catenin binding site of CDC73 and the ubiquitin-interacting motifs 2 and 3 (UIM2 and 3) of USP37 were responsible for the interaction between the two proteins. Moreover, these two enzymes co-existed within the nucleus of COS7 cells. We conclude that USP37 is a DUB for CDC73 and that the two proteins interact through specific domains, suggesting that USP37 is responsible for the stability of CDC73 in HPT-JT syndrome.

A 52-year-old man was referred to our hospital due to fever and myalgia that occurred 2 weeks earlier. He showed a complete atrioventricular block on his electrocardiogram, and his vital signs were unstable. On his transthoracic echocardiograph, the 1.5 cm vegetation in the aortic valve with severe aortic regurgitation suggested infective endocarditis. His transesophageal enchocardiograph showed abscess in his mitral-aortic intervalvular fibrosa and vegetation was suspected on his anterior mitral valve leaflet. The patient underwent an emergent operation for valve replacement with temporary epicardial pacing. Intraoperatively, the septal leaflet of his tricuspid valve was injured during the debridement of the abscess pocket that was extended to the membranous septum. The aortic, mitral, and tricuspid mechanical valves were replaced with annular reconstruction without complications. After 14 days of intravenous antibiotics, we successfully changed the epicardial pacemaker into a transvenous DDD-type permanent pacemaker by placing a left ventricular lead via the coronary sinus and an atrial lead in the right atrium appendage. The patient was discharged in a tolerable state and was examined uneventfully in our hospital’s outpatient clinic for 8 months.

Correspondence to Sung-Ho Her, M.D. Department of Internal Medicine, Daejeon St. Mary’s Hospital, 64 Daeheung-ro, Jung-gu, Daejeon 301-723, Korea Tel: +82-42-220-9504, Fax: +82-42-253-9505, E-mail: hhhsungho@naver.com Copyrightc 2013 The Korean Association of Internal Medicine This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 단일관상동맥: 좌회선지 원위부에서 기원하는 우관상동맥