slc7a6os Gene Plays a Critical Role in Defined Areas of the Developing CNS in Zebrafish

Abstract

The aim of this study is to shed light on the functional role of slc7a6os, a gene highly conserved in vertebrates. The Danio rerio slc7a6os gene encodes a protein of 326 amino acids with 46% identity to human SLC7A6OS and 14% to Saccharomyces cerevisiae polypeptide Iwr1. Yeast Iwr1 specifically binds RNA pol II, interacts with the basal transcription machinery and regulates the transcription of specific genes. In this study we investigated for the first time the biological role of SLC7A6OS in vertebrates. Zebrafish slc7a6os is a maternal gene that is expressed throughout development, with a prevalent localization in the developing central nervous system (CNS). The gene is also expressed, although at different levels, in various tissues of the adult fish. To determine the functional role of slc7a6os during zebrafish development, we knocked-down the gene by injecting a splice-blocking morpholino. At 24 hpf morphants show morphological defects in the CNS, particularly the interface between hindbrain and midbrain is not well-defined. At 28 hpf the morpholino injected embryos present an altered somite morphology and appear partially or completely immotile. At this stage the midbrain, hindbrain and cerebellum are compromised and not well defined compared with control embryos. The observed alterations persist at later developmental stages. Consistently, the expression pattern of two markers specifically expressed in the developing CNS, pax2a and neurod, is significantly altered in morphants. The co-injection of embryos with synthetic slc7a6os mRNA, rescues the morphant phenotype and restores the wild type expression pattern of pax2a and neurod. Our data suggest that slc7a6os might play a critical role in defined areas of the developing CNS in vertebrates, probably by regulating the expression of key genes.

Toxicity Evaluation and Biomarker Selection with Validated Reference Gene in Embryonic Zebrafish Exposed to Mitoxantrone

“…In zebrafish, eef1α1l1 , encoding eukaryotic translation elongation factor 1 alpha 1 for protein translation, was a relatively stable reference gene. The gene eef1α1l1 has been reported as a reference gene for ovarian follicles of adult zebrafish [ 29 ], embryos [ 30 ], and larvae exposed to BPA structural analogs [ 31 ]. Similarly, BestKeeper and NormFinder in the present study suggested eef1α1l1 as a reference gene for the 96 hpf zebrafish embryo mitoxantrone test.…”

Progressive Myoclonus Epilepsy Caused by a Homozygous Splicing Variant of SLC7A6OS

“…The similar phenotypic presentation of the 6 patients, combined with a likely founder effect origin of the variant, strongly suggests that it is the underlying cause of PME for these patients. Whereas the clinical and electrophysiological presentation was similar to ULD, 3,12 onset age was slightly later (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21), mean = 14 years) and progression with loss of ambulation and cognitive decline was faster than typical for ULD. The c.191A > G variant was predicted to disrupt an SLC7A6OS donor splice site and patient cDNA, and protein studies confirmed this.…”

“…13 In the zebrafish, slc7a6os is highly expressed in the central nervous system (CNS) during development. 14 Furthermore, functional knockdown of slc7a6os by splice-blocking morpholinos showed morphological defects in the CNS and reduced mobility. Interestingly, the morpholino used by Benini and colleagues 14 targets the slc7a6os exon1-intron1 boundary and is expected to cause the retention of intron 1 in the mature mRNA, thus mimicking the effect of the c.191A > G variant in our PME patients.…”

“…The exact function of SLC7A6OS remains unknown, although there is some evidence to support it playing a role in RNA polymerase II nuclear import 13 . In the zebrafish, slc7a6os is highly expressed in the central nervous system (CNS) during development 14 . Furthermore, functional knockdown of slc7a6os by splice‐blocking morpholinos showed morphological defects in the CNS and reduced mobility.…”