Ann Lab Med 2018; 38(3): 242-248  https://doi.org/10.3343/alm.2018.38.3.242
Spectrum of MNX1 Pathogenic Variants and Associated Clinical Features in Korean Patients with Currarino Syndrome
Seungjun Lee, M.D.1,2, Eun Jin Kim, M.T.3, Sung Im Cho, M.T.3, Hyunwoong Park, M.D.4, Soo Hyun Seo, M.D.5, Moon-Woo Seong, M.D.3, Sung Sup Park, M.D.3, Sung-Eun Jung, M.D.6, Seong-Cheol Lee, M.D.6,*, Kwi-Won Park, M.D.6,*, and Hyun-Young Kim, M.D.6
Department of Laboratory Medicine1, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul; Department of Laboratory Medicine2, Seoul National University College of Medicine, Seoul; Department of Laboratory Medicine3, Seoul National University Hospital, Seoul National University College of Medicine, Seoul; Department of Laboratory Medicine4, Gyeongsang National University Changwon Hospital, Changwon; Department of Laboratory Medicine5, Seoul National University Bundang Hospital, Seongnam; Department of Pediatric Surgery6, Seoul National University College of Medicine, Seoul, Korea
Corresponding author: Hyun-Young Kim
Department of Pediatric Surgery, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 03080, Korea
Tel: +82-2-2072-2478
Fax: +82-2-747-5130
E-mail: spkhy02@snu.ac.kr
*Professor emeritus
Received: April 9, 2017; Revised: September 20, 2017; Accepted: December 11, 2017; Published online: May 1, 2018.
© Korean Society for Laboratory Medicine. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background: The major genetic cause of Currarino syndrome (CS), a congenital malformation syndrome typically characterized by sacral agenesis, anorectal malformation, and presence of a pre-sacral mass, is known to be pathogenic variants in motor neuron and pancreas homeobox 1 (MNX1), which exist in almost all familial cases and 30% of sporadic cases. Less commonly, a large deletion or a complex rearrangement involving the 7q36 region is associated with CS. We investigated the spectrum of MNX1 pathogenic variants and associated clinical features in the Korean patients with CS.
Methods: We enrolled 25 patients with CS, including 24 sporadic cases and one familial case. Direct sequencing of MNX1 and multiplex ligation-dependent probe amplification were performed. We also analyzed clinical phenotypes and evaluated genotype-phenotype correlations.
Results: We identified six novel variants amongst a total of six null variants, one missense variant, and one large deletion. The null variants included four frameshift variants (p.Gly98Alafs* 124, p.Gly145Alafs*77, p.Gly151Leufs*67, and p.Ala216Profs*5) and two nonsense variants (p.Tyr186* and p.Gln212*). The missense variant, p.Lys295Gln, was located in the highly-conserved homeobox domain and was predicted to be deleterious. A large deletion involving the 7q36 region was detected in one patient. Pathogenic variants in MNX1 were detected in 28% of all CS cases and 25% of sporadic cases. The clinical phenotype was variable in patients with and without pathogenic variants; no significant genotype-phenotype correlation was observed.
Conclusions: This study revealed the spectrum and phenotypic variability of MNX1 pathogenic variants in the Korean population.
Keywords: Currarino syndrome, MNX1, Pathogenic variant, Korean



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