ZFIN ID: ZDB-PUB-170607-6
A genetic model to study increased hexosamine biosynthetic flux
Hugo, S.E., Schlegel, A.
Date: 2017
Source: Endocrinology   158(8): 2420-2426 (Journal)
Registered Authors: Hugo, Sarah, Schlegel, Amnon
Keywords: none
MeSH Terms:
  • Amino Acid Sequence
  • Animals
  • Carbohydrate Conformation
  • DNA, Complementary
  • Female
  • Gene Expression Regulation/physiology*
  • Glycosylation
  • Hexosamines/biosynthesis*
  • Larva
  • Male
  • Microsatellite Repeats
  • Mutagenesis
  • Protein Conformation
  • Zebrafish
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
PubMed: 28582574 Full text @ Endocrinology
Recently, we identified harvest moon (hmn), a fully penetrant and expressive recessive zebrafish mutant with hepatic steatosis. Larvae showed increased triacylglycerol in the absence of other obvious defects. When we attempted to raise these otherwise normal appearing mutants to adulthood, we observed a developmental arrest and death in the early juvenile period. Here we report the positional cloning of the hmn locus and characterization of the defects caused by the mutation. Using bulk segregant analysis, fine mapping, and immunoblot assays we find that hmn mutants harbor a point mutation in an invariant residue within the sugar isomerase 1 domain of the gene encoding the rate-limiting enzyme of the hexosamine biosynthetic pathway (HBP) Glutamine-fructose-6-phosphate transamidase (Gfpt1). The HBP generates β-N-acetyl-glucosamine (GlcNAc) as a spill-over pathway from glucose. GlcNAc can be O-linked to seryl and threonyl residues of diverse cellular proteins (O-GlcNAc modification). While some of these O-GlcNAc modifications serve an essential structural role, many others are dynamically generated on signaling molecules, including several impacting insulin signaling. We find that gfpt1 mutants show global increase in O-GlcNAc modification, and, surprisingly, lower fasting blood glucose in males. Taken together with our previously reported work, gfpt1 mutant demonstrates that global increase in O-GlcNAc modification causes some severe insulin resistance phenotypes (hepatic steatosis and runting), but do not have hyperglycemia. This animal model will provide a platform for dissecting how O-GlcNAc modification alters insulin responsiveness in multiple tissues.