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Functional characterization of zebrafish orthologs of the human Beta 3-Glucosyltransferase B3GLCT gene mutated in Peters Plus Syndrome. PLoS One 2017;12(9):e0184903

Date

09/20/2017

Pubmed ID

28926587

Pubmed Central ID

PMC5604996

DOI

10.1371/journal.pone.0184903

Scopus ID

2-s2.0-85029781984 (requires institutional sign-in at Scopus site)   14 Citations

Abstract

Peters Plus Syndrome (PPS) is a rare autosomal recessive disease characterized by ocular defects, short stature, brachydactyly, characteristic facial features, developmental delay and other highly variable systemic defects. Classic PPS is caused by loss-of-function mutations in the B3GLCT gene encoding for a β3-glucosyltransferase that catalyzes the attachment of glucose via a β1-3 glycosidic linkage to O-linked fucose on thrombospondin type 1 repeats (TSRs). B3GLCT was shown to participate in a non-canonical ER quality control mechanism; however, the exact molecular processes affected in PPS are not well understood. Here we report the identification and characterization of two zebrafish orthologs of the human B3GLCT gene, b3glcta and b3glctb. The b3glcta and b3glctb genes encode for 496-aa and 493-aa proteins with 65% and 57% identity to human B3GLCT, respectively. Expression studies demonstrate that both orthologs are widely expressed with strong presence in embryonic tissues affected in PPS. In vitro glucosylation assays demonstrated that extracts from wildtype embryos contain active b3glct enzyme capable of transferring glucose from UDP-glucose to an O-fucosylated TSR, indicating functional conservation with human B3GLCT. To determine the developmental role of the zebrafish genes, single and double b3glct knockouts were generated using TALEN-induced genome editing. Extracts from double homozygous b3glct-/- embryos demonstrated complete loss of in vitro b3glct activity. Surprisingly, b3glct-/- homozygous fish developed normally. Transcriptome analyses of head and trunk tissues of b3glct-/- 24-hpf embryos identified 483 shared differentially regulated transcripts that may be involved in compensation for b3glct function in these embryos. The presented data show that both sequence and function of B3GLCT/b3glct genes is conserved in vertebrates. At the same time, complete b3glct deficiency in zebrafish appears to be inconsequential and possibly compensated for by a yet unknown mechanism.

Author List

Weh E, Takeuchi H, Muheisen S, Haltiwanger RS, Semina EV

Author

Elena V. Semina PhD Chief, Professor in the Ophthalmology and Visual Sciences department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Animals
Cleft Lip
Cornea
Embryo, Nonmammalian
Gene Editing
Gene Expression Profiling
Gene Knockout Techniques
Glucosyltransferases
Growth Disorders
Humans
In Situ Hybridization
Limb Deformities, Congenital
Molecular Sequence Data
Mutation
Sequence Alignment
Transcription Activator-Like Effector Nucleases
Zebrafish
Zebrafish Proteins