Tohoku J. Exp. Med., 2019 October, 249(2)

A Nonsense Mutation in HOXD13 Gene from A Chinese Family with Non-Syndromic Synpolydactyly

XIAOYAN GUO,¹ TENGFEI SHI,¹ MINGRUI LIN² and YIYUAN ZHANG³

¹Department of Laboratory Medicine, Fuzhou Second Hospital Affiliated to Xiamen University, Fuzhou, Fujian, China
²Intensive Care Unit, The Affiliated People's Hospital of Fujian Traditional Medical University, Fuzhou, Fujian, China
³Department of Orthopedics, Fuzhou Second Hospital Affiliated to Xiamen University, Fuzhou, Fujian, China

Synpolydactyly is a congenital limb malformation characterized by incomplete separation and duplication in fingers and/or toes, which is mainly caused by mutations in the homeobox D13 (HOXD13) gene. Here, a four-generation family with variant phenotypes of synpolydactyly was analyzed, in which the proband had bilateral preaxial synpolydactyly in toes with normal fingers, the father had clinodactyly in the fifth fingers, while the mother and grandma was normal. Trio whole-exome sequencing (trio-WES) is a high throughput sequencing targeting whole genome for detecting exonic variants from the proband and the parents in a family. Through trio-WES followed by Sanger sequencing and enzyme digestion, a heterozygous nonsense mutation (c.859 C>T/p.Gln287Ter) was newly identified in the homeodomain of the HOXD13 gene from the proband and the affected father, but not from the unaffected mother, the unaffected grandma, or the normal control. Mutation Taster, Human Splicing Finder and EX-SKIP predicted that the heterozygous mutation (c.859 C>T) would result in haploinsufficiency of HOXD13 protein through nonsense-mediated mRNA decay (NMD) and splicing abnormality, which might disrupt the integrity and reduce the expression level of the HOXD13 protein (loss-of-function). In short, a heterozygous nonsense mutation in the HOXD13 gene was newly identified in two patients with mild phenotypes of synpolydactyly, which extends the mutation spectrum in HOXD13 gene. Moreover, the findings we presented here deepen our understanding of the clinical consequences of non-syndromic synpolydactyly and may provide a new clue for further studies of the pathogenic mechanism of the mutation that causes aberrant splicing of HOXD13 gene.

Keywords —— exome sequencing; exonic splicing regulatory mutation; HOXD13 gene; nonsense-mediated mRNA decay; synpolydactyly

© 2019 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2019, 249, 93-100

Correspondence: Yiyuan Zhang, Department of Orthopedics, Fuzhou Second Hospital Affiliated to Xiamen University, No.47 Shangteng Road, Fuzhou, Fujian 350007, China.

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