A defect in the mitochondrial protein Mpv17 underlies the transparent casper zebrafish

Abstract

The casper strain of zebrafish is widely used in studies ranging from cancer to neuroscience. casper offers the advantage of relative transparency throughout adulthood, making it particularly useful for in vivo imaging by epifluorescence, confocal, and light sheet microscopy. casper was developed by selective breeding of two previously described recessive pigment mutants: 1) nacre, which harbors an inactivating mutation of the mitfa gene, rendering the fish devoid of pigmented melanocytes; and 2) roy orbison, a mutant with so-far unidentified genetic cause that lacks reflective iridophores. To clarify the molecular nature of the roy orbison mutation, such that it can inform studies using casper, we undertook an effort to positionally clone the roy orbison mutation. We find that roy orbison is caused by an intronic defect in the gene mpv17, encoding an inner mitochondrial membrane protein that has been implicated in human mitochondrial DNA depletion syndrome. The roy orbison mutation is phenotypically and molecularly remarkably similar to another zebrafish iridophore mutant called transparent. Using Cas9-induced crispants and germline mutants with disrupted mpv17 open reading frame, we show in trans-heterozygote embryos that new frameshift alleles of mpv17, roy orbison, and transparent fail to complement each other. Our work provides genetic evidence that both roy orbison and transparent affect the mpv17 locus by a similar if not identical genetic lesion. Identification of mpv17 mutants will allow for further work probing the relationship between mitochondrial function and pigmentation, which has to date received little attention.

GABA‐A receptor and mitochondrial TSPO signaling act in parallel to regulate melanocyte stem cell quiescence in larval zebrafish

“…This metabolic fasting also activated transcriptional changes beyond gluconeogenesis genes and modulated other fasting adaptation pathways, such as β‐oxidation and cellular respiration, which drive ATP production in the mitochondria during low‐energy states (Houten, Violante, Ventura, & Wanders, ). A role for TSPO in regulating pigment patterning has not been uncovered, although changes in mitochondrial function and metabolic regulation have been noted to disrupt pigmentation in vertebrates (D'Agati et al, ).…”

Cancer modeling by Transgene Electroporation in Adult Zebrafish (TEAZ)

“…Transgenic lines used in these studies included wild-type ( AB ), casper (D'Agati et al, 2017;White et al, 2008) , and the triple line (Ceol et al, 2011) ( mitfa :BRAF V600E ; p53 -/-; mitfa -/-) (provided by the Houvras lab at Weill Cornell).…”

Genome and Transcriptome Sequencing of casper and roy Zebrafish Mutants Provides Novel Genetic Clues for Iridophore Loss

“…The roy mutant shows a recessive phenotype with complete loss of iridophores and partial reduction of melanophores. Recent studies using cDNA cloning reported that mpv17 (a gene encoding a mitochondrial inner membrane protein) in casper and roy mutants had a 19-bp deletion in its mRNA (between exons 2 and 3), which is possibly responsible for the iridophore loss [7,8]. A mpv17-knockdown zebrafish exhibited a moderate loss of iridophores along the body axis [8].…”