title: Impairment of the tRNA-splicing endonuclease subunit 54 (tsen54) gene causes neurological abnormalities and larval death in zebrafish models of pontocerebellar hypoplasia.
abstract: Pontocerebellar hypoplasia (PCH) represents a group (PCH1-6) of neurodegenerative autosomal recessive disorders characterized by hypoplasia and/or atrophy of the cerebellum, hypoplasia of the ventral pons, progressive microcephaly and variable neocortical atrophy. The majority of PCH2 and PCH4 cases are caused by mutations in the TSEN54 gene; one of the four subunits comprising the tRNA-splicing endonuclease (TSEN) complex. We hypothesized that TSEN54 mutations act through a loss of function mechanism. At 8 weeks of gestation, human TSEN54 is expressed ubiquitously in the brain, yet strong expression is seen within the telencephalon and metencephalon. Comparable expression patterns for tsen54 are observed in zebrafish embryos. Morpholino (MO) knockdown of tsen54 in zebrafish embryos results in loss of structural definition in the brain. This phenotype was partially rescued by co-injecting the MO with human TSEN54 mRNA. A developmental patterning defect was not associated with tsen54 knockdown; however, an increase in cell death within the brain was observed, thus bearing resemblance to PCH pathophysiology. Additionally, N-methyl-N-nitrosourea mutant zebrafish homozygous for a tsen54 premature stop-codon mutation die within 9 days post-fertilization. To determine whether a common disease pathway exists between TSEN54 and other PCH-related genes, we also monitored the effects of mitochondrial arginyl-tRNA synthetase (rars2; PCH1 and PCH6) knockdown in zebrafish. Comparable brain phenotypes were observed following the inhibition of both genes. These data strongly support the hypothesis that TSEN54 mutations cause PCH through a loss of function mechanism. Also we suggest that a common disease pathway may exist between TSEN54- and RARS2-related PCH, which may involve a tRNA processing-related mechanism.
authors.affiliation: Department of Genome Analysis, Academic Medical Center, Meibergdreef 9, 1105AZ Amsterdam, The Netherlands.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Kasher
authors.forename: Yasmin
authors.initials: Y
authors.lastname: Namavar
authors.forename: Paula
authors.initials: P
authors.lastname: van Tijn
authors.forename: Kees
authors.initials: K
authors.lastname: Fluiter
authors.forename: Aleksander
authors.initials: A
authors.lastname: Sizarov
authors.forename: Maarten
authors.initials: M
authors.lastname: Kamermans
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Grierson
authors.forename: Danica
authors.initials: D
authors.lastname: Zivkovic
authors.forename: Frank
authors.initials: F
authors.lastname: Baas
mesh_terms: D000818:Animals; D001126:Arginine-tRNA Ligase / Q000235:genetics; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D001921:Brain / Q000002:abnormalities / Q000196:embryology / Q000378:metabolism; D016923:Cell Death / Q000235:genetics; D004722:Endoribonucleases / Q000235:genetics* / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000235:genetics; D020868:Gene Silencing; D006801:Humans; D017403:In Situ Hybridization; D007814:Larva / Q000254:growth & development; D009849:Olivopontocerebellar Atrophies / Q000235:genetics*; D051857:Otx Transcription Factors / Q000235:genetics; D010641:Phenotype; D014158:Transcription, Genetic; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000254:growth & development*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D051857:Otx Transcription Factors; D029961:Zebrafish Proteins; C517774:fgf8a protein, zebrafish; C497662:otx2b protein, zebrafish; D005346:Fibroblast Growth Factors; D004722:Endoribonucleases; C559616:TSEN54 protein, human; C559617:TSEN54 protein, zebrafish; D001126:Arginine-tRNA Ligase