ELAC2/RNaseZ-linked cardiac hypertrophy in Drosophila melanogaster

Abstract

A severe form of infantile cardiomyopathy (CM) has been linked to ELAC2 gene mutations. ELAC2 is a highly conserved human gene. It encodes RNaseZL endoribonuclease that plays an essential role in the production of mature tRNAs. To establish a causal connection between ELAC2 variants and CM, here we use a model organism Drosophila melanogaster, which carries ELAC2 homolog - dRNaseZ. Even though dRNaseZ and ELAC2 have diverged in some of their biological functions, our study demonstrates the utility of the fly model to study the mechanism of ELAC2 related pathology. We established transgenic lines harboring dRNaseZ with CM-linked mutations in the background of endogenous dRNaseZ knockout. Importantly, we found that the phenotype of these flies is consistent with pathological features in human patients. Specifically, expression of CM-linked variants in flies causes heart hypertrophy and leads to reduction in cardiac contractility associated with a rare form of CM. This study provides first experimental evidence for the pathogenicity of CM-causing mutations in the ELAC2 protein and lay the foundation to improve our understanding and diagnosis of this rare infantile disease.

Novel ELAC2 Mutations in Individuals Presenting with Variably Severe Neurological Disease in the Presence or Absence of Cardiomyopathy

“…However, direct correlation between these data and the disease severity observed in patients expressing the variants in question cannot be inferred due to the in vitro nature of these studies. Interestingly, modeling of the p.Phe154Leu and p.Thr520Leu variants in Drosophila showed that, like in humans, expression of the Drosophila orthologs p.Phe155Leu and p.Thre494Ile results in cardiomyopathy [ 31 ]. It remains to be seen, however, if mutagenesis of any of the other amino acids in DmELAC2, which are orthologous to amino acids affected by disease-causing variants in humans, can likewise lead to cardiomyopathy or other pathology in Drosophila.…”

The opportunities and challenges of using Drosophila to model human cardiac diseases

“…Multiple structural and functional readouts that have been established for the fly heart can capture these phenotypes. Brightfield microscopy of histological sections or micro computerized tomography, a 3D X-ray imaging technique, can be used to determine the thickness of the heart muscle wall ( Migunova et al, 2021 ; Petersen et al, 2022 ). Whereas high-speed movies of semi intact Drosophila heart preparations ( Ocorr et al, 2007 ), in vivo imaging of the heart in intact flies using high resolution optical coherence microscopy which yields imaging similar to ultrasound ( Migunova et al, 2021 ), or optical coherence tomography which is similar to echocardiography in humans ( Wolf et al, 2006 ), can be used to quantify muscle wall thickness and function, including diastolic diameter, end systolic diameter, and fractional shortening.…”

“…Brightfield microscopy of histological sections or micro computerized tomography, a 3D X-ray imaging technique, can be used to determine the thickness of the heart muscle wall ( Migunova et al, 2021 ; Petersen et al, 2022 ). Whereas high-speed movies of semi intact Drosophila heart preparations ( Ocorr et al, 2007 ), in vivo imaging of the heart in intact flies using high resolution optical coherence microscopy which yields imaging similar to ultrasound ( Migunova et al, 2021 ), or optical coherence tomography which is similar to echocardiography in humans ( Wolf et al, 2006 ), can be used to quantify muscle wall thickness and function, including diastolic diameter, end systolic diameter, and fractional shortening. Finally, the cardiac flow, a measure of contractile force, can be measured by a dye injection assay that times the flow from injection site to target site ( Zhu et al, 2017a ; 2017b ), or with intravital imaging which enables life tracking of the heart wall, quantitation of the chamber diameter during contraction (systole) and relaxation (diastole), and fractional shortening, as well as estimates of cardiac output and stroke volume using segmentation algorithms ( Klassen et al, 2017 ).…”

Inter-Species Rescue of Mutant Phenotype—The Standard for Genetic Analysis of Human Genetic Disorders in Drosophila melanogaster Model

“…Other cardiac disorders have been modelled in D. melanogaster , such as channelopathies [ 163 , 164 , 165 , 166 , 167 ] and different syndromic [ 168 , 169 , 170 ] or nonsyndromic cardiomyopathies [ 171 , 172 , 173 , 174 , 175 , 176 , 177 ]. To our knowledge, currently, none of these diseases benefit from effective human allele-based functional complementation studies, although some groups successfully tackled the heterologous rescuing of fly cardiac phenotype, the alleles of choice being of animal origin, mainly from mice [ 173 , 178 , 179 ].…”