Skeletal malformations of Meox1‐deficient zebrafish resemble human Klippel–Feil syndrome

Abstract

Klippel–Feil syndrome is a congenital vertebral anomaly, which is characterised by the fusion of at least two cervical vertebrae and a clinically broad set of symptoms, including congenital scoliosis and elevated scapula (Sprengel's deformity). Klippel–Feil syndrome is associated with mutations in MEOX1. The zebrafish mutant choker (cho) carries a mutation in its orthologue, meox1. Although zebrafish is being increasingly employed as fidelitous models of human spinal disease, the vertebral column of Meox1‐deficient fish has not been assessed for defects. Here, we describe the skeletal defects of meox1cho mutant zebrafish utilising alizarin red to stain bones and chemical maceration of soft tissue to detect fusions in an unbiased manner. Obtained data reveal that meox1cho mutants feature aspects of a number of described symptoms of patients who suffer from Klippel–Feil syndrome and have mutations in MEOX1. These include vertebral fusion, congenital scoliosis and an asymmetry of the pectoral girdle, which resembles Sprengel's deformity. Thus, the meox1cho mutant zebrafish may serve as a useful tool to study the pathogenesis of the symptoms associated with Klippel–Feil syndrome.

The mutational burden and oligogenic inheritance in Klippel-Feil syndrome

“…Previous studies suggested that mutations in GDF6 [10,36] and GDF3 [13] were associated with autosomal dominant KFS. In addition, a truncating mutation in MEOX1 [11,12,37] and a homozygous nonsense mutation in MYO18B [14,38] were identified in autosomal recessive KFS families. Using WES, a homozygous frameshift mutation (c.299delT: p. L100fs) in RIPPLY2 was confirmed as a novel gene for autosomal recessive KFS in a consanguineous family [15,39].…”

Zebrafish Models for Human Skeletal Disorders

“…Mutant choker of zebrafish meox1 gene ( Dauer et al, 2018 ) has also been proposed as a Klippel–Feil syndrome model in group 35 ( Supplementary Table 1 ), a disease caused by mutations in human ortholog MEOX1 gene (see Mortier et al, 2019 ). The vertebral fusion, congenital scoliosis, and pectoral girdle asymmetry observed in this mutant almost exactly resembles the cervical vertebra fusions, congenital scoliosis, and skeletal alterations found in patients with this disease ( Dauer et al, 2018 ).…”

Identification of potential pathogenic genes causing occipitalization of the atlas

“…Recent studies have suggested that failed development of the craniocervical junction that underlies AO could be caused by defective somitogenesis in the cervical region resulting from gene mutations [5][6][7]. According to OMIM (Online Mendelian Inheritance in Man), Genecards, and MGI (mouse genome informatics)( MP:0010728), it has been reported that mutations in MEOX1(GCID:GC17M043640, MIM:600147), MYO18B(GCID:GC22P025742, MIM:607295), and the HOX family of genes are associated with AO [7][8][9]. A study by David (1999) of 30 cases of Klippel-Feil syndrome (KFS) found that a mutation in the Hox gene was the mechanism possibly responsible for atlas assimilation, while reduced or impaired Pax-1 gene expression may result in vertebral fusions [10].…”

“…The principal etiology of AO is the impaired development of the bone of the cranio-cervical junction, leading to improper segmentation of the vertebrae. Recent studies have suggested that failed development of the craniocervical junction that underlies AO could be caused by defective somitogenesis in the cervical region resulting from gene mutations [5][6][7]. According to OMIM (Online Mendelian Inheritance in Man), Genecards, and MGI (mouse genome informatics)( MP:0010728), it has been reported that mutations in MEOX1(GCID:GC17M043640, MIM:600147), MYO18B(GCID:GC22P025742, MIM:607295), and the HOX family of genes are associated with AO [7][8][9].…”