Fig. 1

Identification of a homozygous mutation c.456delT in MAP3K20. a A large consanguineous family with congenital myopathy. Filled symbols represent affected individuals; open symbols represent unaffected individuals; squares denote males and circles denote females; symbols with a diagonal line denote deceased individuals. The genotype of the MAP3K20 mutation is indicated below each examined member: TT (wildtype), T/– (heterozygous), and –/– (homozygous mutant). An asterisk (*) indicates the individual for whom exome sequencing was performed. A hash (#) designates individuals for whom genotyping was performed. The number indicates the current age of each living affected individual. b Recombination events in individuals V:I and IV:10 delimit the region of interest between flanking markers AX-11545873 (174.15 cM, 169757541 bp) and AX-11097507 (181.96 cM, 175417011 bp). Physical positions refer to human genome build GRCh37.p13 (hg19). The MAP3K20 location is boxed. c Representative sequence chromatograms showing the normal sequence, c.456delT, in heterozygous and homozygous individuals. The vertical arrow indicates the site of the mutation. d Quantitative real-time PCR of MAP3K20. Levels of functional MAP3K20 are reduced to 12–15% of the normal level in patients with the c.456delT mutation. RNA was extracted from the patients, heterozygous carriers, and a healthy control. qPCR reactions were run in triplicate in three independent experiments (n = 3). Data are expressed as the mean ± SEM (****P < 0.001, ***P < 0.001, and **P < 0.01; compared with MAP3K20 wildtype). All data were normally distributed (Shapiro–Wilk test). P values were calculated using an unpaired, parametric, one-tailed Student’s t-test, assuming unequal SDs. e Schematic representation for gene and protein domain structure of the human MAP3K20. The red arrow marks the region for primers in exons 4 and 7 for RT-PCR. Previously reported mutations ([c.280_281insT p.Asn95*]; [c.490_491delAT p.Met164fs*24 [c.515G>A; p.Trp172*]) associated with CNM6 are shown in black [1], whereas the novel mutation (c.456delT, p.Phe152Leufs*49) identified in this study is shown by a dotted line. Blue arrows indicate the positions of mutations associated with SHFM described by Spielmann et al. [6]. The MAP3K20 protein comprises a kinase domain (16–277 aa), a leucine-zipper (LZ; 287–308 aa), and a sterile-alpha motif (SAM) domain (336–410 aa) in isoform 1. Two isoforms (Iso 1 and Iso 2) are known, and these differ in their C terminus