Chimenes ND, et al. A complex CLCN1 variant associated with hereditary myotonia in a mixed-breed dog. JVDI 2023;35:414–417. https://journals.sagepub.com/doi/full/10.1177/10406387231176736
The positions of the identified variants were checked, and an inconsistency was observed with the cited reference sequence (NC_051820.1). The errors are highlighted in red within the complete paragraphs of the published version, while in the new version, the corrected text is in blue. The error in the numbering of the sequence does not alter any of the study’s conclusions, but its correction is essential for those who may rely on the sequence to design diagnostic tests.
Abstract.
Published version:
Hereditary myotonia (HM) is characterized by delayed muscle relaxation after contraction as a result of a mutation in the CLCN1 gene. We describe here a complex CLCN1 variant in a mixed-breed dog with clinical and electromyographic signs of HM. Blood samples from the myotonic dog, as well as from his male littermate and parents, were analyzed via amplification of the 23 exons encoding CLCN1. After sequencing the CLCN1 gene, a complex variant was found in exon 6 c.[705T>G; 708del; 712_732del], resulting in a premature stop codon in exon 7 and a protein that was 717 amino acids shorter than the normal CLC protein. The myotonic dog was identified as homozygous recessive for the complex CLCN1 variant; its parents were heterozygous, and its male littermate was homozygous wild-type. Knowledge of the CLCN1 mutations responsible for the development of hereditary myotonia allows greater clarification of this condition.
New version with corrections:
Hereditary myotonia (HM) is characterized by delayed muscle relaxation after contraction as a result of a mutation in the CLCN1 gene. We describe here a complex CLCN1 variant in a mixed-breed dog with clinical and electromyographic signs of HM. Blood samples from the myotonic dog, as well as from his male littermate and parents, were analyzed via amplification of the 23 exons encoding CLCN1. After sequencing the CLCN1 gene, a complex variant was found in exon 6 c.[703T>G; 706delG; 710_730del], resulting in a premature stop codon in exon 7 and a protein that was 717 amino acids shorter than the normal CLC protein. The myotonic dog was identified as homozygous recessive for the complex CLCN1 variant; its parents were heterozygous, and its male littermate was homozygous wild-type. Knowledge of the CLCN1 mutations responsible for the development of hereditary myotonia allows greater clarification of this condition.
Page 415, sixth paragraph.
Published version:
Alignments of the sequences obtained for the affected dog, dog 3 (dam), the unaffected nonrelated dog (Fig. 1B), and the reference GenBank sequence revealed a complex variant c.[705T>G; 708del; 712_732del] in exon 6 (i.e., a nonsynonymous variant at the seventh nucleotide of exon 6 [c.705T>G] that resulted in the change of a phenylalanine to a valine [p. Phe234Val], Fig. 1C); 3 bases downstream, there was a deletion of a guanine (c.708del); and further down-stream, 21 bases were deleted from positions 712–732 (c.712_732del). The first deletion caused a premature stop codon in exon 7 (c.800–802 positions), which led to the production of a truncated protein product of 259 amino acids, which was 717 amino acids shorter than the normal CLC protein (NP_001003124.1).
New version with corrections:
Alignments of the sequences obtained for the affected dog, dog 3 (dam), the unaffected nonrelated dog (Fig. 1B), and the reference GenBank sequence revealed a complex variant c.[703T>G; 706delG; 710_730del] in exon 6 (i.e., a nonsynonymous variant at the seventh nucleotide of exon 6 [c.705T>G] that resulted in the change of a phenylalanine to a valine [p. Phe235Val], Fig. 1C); 3 bases downstream, there was a deletion of a guanine (c.708del); and further down-stream, 21 bases were deleted from positions 712–732 (c.710_730del). The first deletion caused a premature stop codon in exon 7 (c.800–802 positions), which led to the production of a truncated protein product of 259 amino acids, which was 717 amino acids shorter than the normal CLC protein (NP_001003124.1).
Page 415, ninth paragraph.
Published version:
All genomic variants in our patient occurred in exon 6, namely, a nonsynonymous variant (c.705T>G), causing a substitution from a phenylalanine to a valine (p. Phe234Val); deletion of a guanine (c.708del); and 21-bp deletion (c.712_732del). The final result was a deletion of 717 amino acids from the normal CLC protein. The nonsynonymous variant (c.705T>G), with a change from a phenylalanine to a valine (p. Phe234Val) sequence, was compared to that of variants in a cat (NC_058369.1), dog (NC_051820.1), pig (NC_010460.4), horse (NC_009147.3), sheep (NC_056057.1), water buffalo (NC_059164. 1), goat (NC_030811.1), mouse (NC_000072.7), mouse (NM_013147.1), and human (NG_009815.2). The modification was not observed in these species.
New version with corrections:
All genomic variants in our patient occurred in exon 6, namely, a nonsynonymous variant (c.703T>G), causing a substitution from a phenylalanine to a valine (p. Phe235Val); deletion of a guanine (c.706delG); and 21-bp deletion (c.710_730del). The final result was a deletion of 717 amino acids from the normal CLC protein. The nonsynonymous variant (c.703T>G), with a change from a phenylalanine to a valine (p. Phe235Val) sequence, was compared to that of variants in a cat (NC_058369.1), dog (NC_051820.1), pig (NC_010460.4), horse (NC_009147.3), sheep (NC_056057.1), water buffalo (NC_059164. 1), goat (NC_030811.1), mouse (NC_000072.7), mouse (NM_013147.1), and human (NG_009815.2). The modification was not observed in these species.
Figure 1 legend.
Published version:
Figure 1. Hereditary myotonia (HM) in a 6-mo-old male mixed-breed dog. A. Electromyography tracing obtained from the semitendinosus muscle. Note the high-frequency discharges characteristic of HM. Sustained runs of positive waves with initial sharp positivity followed by a slow negative component are also present. Vertical divisions represent 150 μV; horizontal divisions represent 40 ms. B. Partial capillary sequencing chromatogram for CLCN1 exon 6 in mutated homozygous myotonic dog 1, wild-type homozygous dog 5, and heterozygous dam (dog 3). The complex CLCN1 variant is a nonsynonymous single-nucleotide variation (SNV) at nucleotide 7 of exon 6 (c.705T>G; arrow) that resulted in the change of a phenylalanine to a valine (p.Phe234Val); the deletion of a guanine (c.708del; arrowhead); and the deletion of 21 bases (c.712_732del; Geneious 10.0 software, Biomatters). C. Schematic of the coding gene and amino acid sequences in the myotonic dog (above; sequence NC_0518520.1) and a normal dog (below). The c.705T>G SNV is represented in green, the c.708del and c.712_732del variants in red, and the new stop codon (TGA) in blue.
New version with corrections:
Figure 1. Hereditary myotonia (HM) in a 6-mo-old male mixed-breed dog. A. Electromyography tracing obtained from the semitendinosus muscle. Note the high-frequency discharges characteristic of HM. Sustained runs of positive waves with initial sharp positivity followed by a slow negative component are also present. Vertical divisions represent 150 μV; horizontal divisions represent 40 ms. B. Partial capillary sequencing chromatogram for CLCN1 exon 6 in mutated homozygous myotonic dog 1, wild-type homozygous dog 5, and heterozygous dam (dog 3). The complex CLCN1 variant is a nonsynonymous single-nucleotide variation (SNV) at nucleotide 7 of exon 6 (c.703T>G; arrow) that resulted in the change of a phenylalanine to a valine (p.Phe235Val); the deletion of a guanine (c.706delG; arrowhead); and the deletion of 21 bases (c.710_730del; Geneious 10.0 software, Biomatters). C. Schematic of the coding gene and amino acid sequences in the myotonic dog (above; sequence NC_051820.1) and a normal dog (below). The c.703T>G SNV is represented in green, the c.706delG and c.710_730del variants in red, and the new stop codon (TGA) in blue.
Mariana I. P. Palumbo and authors
