A zebrafish model for FHL1-opathy reveals loss-of-function effects of human FHL1 mutations

Abstract

Missense mutations in the four and a half LIM domain 1 (FHL1) gene were found to cause X-linked inherited myopathies of both skeletal and heart muscles. However, the mechanisms by which FHL1 mutations impact on FHL1 function and lead to alteration of muscle structure and function have not been deciphered yet. We generated here by Morpholino-modified antisense oligonucleotide-mediated gene knockdown fHL1-deficient zebrafish embryos. Similar to the human situation, fhl1a-morphants zebrafish displayed severe skeletal and heart muscle myopathy. Whereas ectopic expression of wild-type FHL1 (FHL1 wt) suppressed both skeletal and heart muscle myopathy in fhl1a-morphants zebrafish, overexpression of the FHL1-opathy associated human mutations FHL1-H123Y, FHL1-C132F or FHL1-C224W did not rescue skeletal and heart muscle myopathy in fhl1a-morphants. Overexpression of FHL1-H123Y, FHL1-C132F or FHL1-C224W in wild-type zebrafish did not induce myopathy in a dominant-negative mode. Altogether these results indicate that FHL1 mutations found to cause X-linked FHL1-opathies in humans consistently lead to severely impaired FHL1 function.

FHL1 regulates myoblast differentiation and autophagy through its interaction with LC3

“…Previous studies have reported defects in muscle fiber structure and mass due to the absence of FHL1. Keßler et al () found that FHL1 knockout caused skeletal muscle structural defects accompanied by muscle fiber disorders in zebrafish. Domenighetti et al () found that the deletion of FHL1 leads to age‐dependent skeletal muscle myopathies associated with myofibrillar and intermyofibrillar disorganization in mice.…”

“…The FHL1 gene encodes a 280‐amino‐acid protein containing a zinc finger and four LIM domains that mediate protein–protein interactions in the cytoplasm and nucleus (Dawid, Breen, & Toyama, ). FHL1 is predominantly expressed in skeletal and cardiac muscles where it regulates growth and development through its action as a scaffolding protein during sarcomere assembly (Keßler et al, ). FHL1 mutations cause a series of muscular disorders, including postural muscle atrophy (Keßler et al, ), reduced body myopathy (Selcen, Bromberg, Chin, & Engel, ), X‐linked dominant scapuloperoneal myopathy (Chen et al, ), rigid spine syndrome (Shalaby et al, ), hypertrophic cardiomyopathy (Friedrich et al, ), and Emery–Dreifuss muscular dystrophy (Knoblauch et al, ).…”

“…FHL1 is predominantly expressed in skeletal and cardiac muscles where it regulates growth and development through its action as a scaffolding protein during sarcomere assembly (Keßler et al, 2018). FHL1 mutations cause a series of muscular disorders, including postural muscle atrophy (Keßler et al, 2018), reduced body myopathy (Selcen, Bromberg, Chin, & Engel, 2011), X-linked dominant scapuloperoneal myopathy (Chen et al, 2010), rigid spine syndrome (Shalaby et al, 2008), hypertrophic cardiomyopathy (Friedrich et al, 2012), and Emery-Dreifuss muscular dystrophy (Knoblauch et al, 2010). Previous studies have shown that autophagy influences the pathophysiological mechanisms of muscle pathology, particularly mutations (p.C150R) in the second LIM domain of FHL1 gene (Sabatelli et al, 2014).…”

Streamlining drug discovery assays for cardiovascular disease using zebrafish

“…Whereas in the beginnings of zebrafish research, developmental biology studies had priority [40,[56][57][58][59][60], more and more, the ability to model essential features of human cardiac disorders moved into the center of attraction [51,[61][62][63][64][65]. Since early development of zebrafish embryos does not require proper blood circulation, this model organism is amenable to a broad range of functional genomic approaches including forward genetics by e.g.…”

“…Based on zebrafish transparency during embryogenesis functional impact on zebrafish cardiovascular system after genome/gene editing can be easily evaluated via simple light microscopy. Using innovative functional genomic approaches several important key molecules regulating cardiac pump function and rhythm were identified leading to a more in-depth understanding of important human cardiac disorders such as cardiomyopathies, arrhythmias or heart failure [38,51,63,64,70] Large forward genetic screens led to the identification of numerous zebrafish mutants with heart defects resembling severe human cardiac pathologies such as cardiomyopathies, valvular defects, arrhythmias and heart failure [57]. Genetic analyses by positional cloning of these mutants identified known and novel genes and molecular pathways of cardiovascular disease and demonstrated the validity of the zebrafish to simulate and model human cardiovascular diseases as well as to dissect the molecular pathomechanisms of human CVD (selected zebrafish mutants see Table 2).…”