Inhibition of SULT4A1 Expression Induces Up-Regulation of Phototransduction Gene Expression in 72-Hour Postfertilization Zebrafish Larvae

Abstract

Sulfotransferase (SULT) 4A1 is an orphan enzyme that shares distinct structure and sequence similarities with other cytosolic SULTs. SULT4A1 is primarily expressed in neuronal tissue and is also the most conserved SULT, having been identified in every vertebrate investigated to date. Certain haplotypes of the SULT4A1 gene are correlated with higher baseline psychopathology in schizophrenic patients, but no substrate or function for SULT4A1 has yet been identified despite its high level of sequence conservation. In this study, deep RNA sequencing was used to search for alterations in gene expression in 72-hour postfertilization zebrafish larvae following transient SULT4A1 knockdown (KD) utilizing splice blocking morpholino oligonucleotides. This study demonstrates that transient inhibition of SULT4A1 expression in developing zebrafish larvae results in the up-regulation of several genes involved in phototransduction. SULT4A1 KD was verified by immunoblot analysis and quantitative real-time polymerase chain reaction (qPCR). Gene regulation changes identified by deep RNA sequencing were validated by qPCR. This study is the first identification of a cellular process whose regulation appears to be associated with SULT4A1 expression.

Structural plasticity in the human cytosolic sulfotransferase dimer and its role in substrate selectivity and catalysis

“…Overall, this results in a large pore-like substrate binding pocket and a very small "PAPS" binding pocket. This SULT's inability to bind the sulfonate donor is intriguing as the isoform is expressed in human brain and is the most conserved SULT between species [35,99]. The isoform may be involved in the sulfation of non-classical substrates or may simply be performing a divergent function within the cell; one not associated with the sulfation of small molecules [99].…”

Activity Suppression Behavior Phenotype in SULT4A1 Frameshift Mutant Zebrafish

“…In 2014, our laboratory reported an upregulation of several conespecific phototransduction genes in SULT4A1 knockdown zebrafish larvae (Crittenden et al, 2014). This dysregulation of cone genes was observed at 72 hours postfertilization and was not accompanied by any overt morphologic or developmental defects.…”

“…SULT4A1 is expressed throughout the central nervous system, with especially strong expression in the neurons of the choroid plexus, cerebral cortex, cerebellum, thalamus, pituitary, medial temporal lobe, and lentiform nucleus (Liyou et al, 2003). In zebrafish, SULT4A1 is also expressed in the retina (Crittenden et al, 2014). SULT4A1 shares several conserved sequence similarities with the other SULTs: the active site histidine, the KXXFTVXXXE dimerization domain common among SULTs, and the PAPS binding domain (Falany et al, 2000).…”

“…Our laboratory recently reported that morpholino knockdown of SULT4A1 expression in larval zebrafish leads to an upregulation of several genes known to be involved in phototransduction, specifically in cone photoreceptors (Crittenden et al, 2014). Zebrafish represent an excellent model organism for the investigation of SULT4A1, due to the highly conserved nature of human SULT4A1 and zebrafish SULT4A1, which suggests an equally conserved function.…”

“…SULT4A1 is the most conserved member of the SULT gene family, having been identified in every vertebrate species investigated to date. Humans and zebrafish, two species who share no other homologous SULT genes, have SULT4A1 genes that are 87% identical and 92% similar in amino acid sequence (Crittenden et al, 2014). SULT4A1's singular conservation of protein sequence across vertebrate species sets it apart from the other cytosolic SULTs.…”