Functional Roles for β1,4-N-Acetlygalactosaminyltransferase-A in Drosophila Larval Neurons and Muscles

Abstract

Adult Drosophila mutant for the glycosyltransferase b1,4-N-acetlygalactosaminyltransferase-A (b4Gal-NAcTA) display an abnormal locomotion phenotype, indicating a role for this enzyme, and the glycan structures that it generates, in the neuromuscular system. To investigate the functional role of this enzyme in more detail, we turned to the accessible larval neuromuscular system and report here that larvae mutant for b4GalNAcTA display distinct nerve and muscle phenotypes. Mutant larvae exhibit abnormal backward crawling, reductions in nerve terminal bouton number, decreased spontaneous transmitterrelease frequency, and short, wide muscles. This muscle shape change appears to result from hypercontraction since the individual sarcomeres are shorter in mutant muscles. Analysis of muscle calcium signals showed altered calcium handling in the mutant, suggesting a mechanism by which hypercontraction could occur. All of these phenotypes can be rescued by a transgene carrying the b4GalNAcTA genomic region. Tissue-specific expression, using the Gal4-UAS system, reveals that neural expression rescues the mutant crawling phenotype, while muscle expression rescues the muscle defect. Tissuespecific expression did not appear to rescue the decrease in neuromuscular junction bouton number, suggesting that this defect arises from cooperation between nerve and muscle. Altogether, these results suggest that b4GalNAcTA has at least three distinct functional roles.

B4GALNT3 Expression Predicts a Favorable Prognosis and Suppresses Cell Migration and Invasion via β1 Integrin Signaling in Neuroblastoma

“…15 Drosophila mutants deficient in B4GALNTA have defects in behavior and in the neuromuscular system. 16 In the present study, we hypothesized that B4GALNT3 may be involved in the pathogenesis of NB development.…”

Presynaptic establishment of the synaptic cleft extracellular matrix is required for post-synaptic differentiation

“…GlcNAc-containing carbohydrate and GAG scaffolds (e.g., chitin, hyaluronic acid [HA], heparin) and PG (e.g., heparin sulfate, chondroitin sulfate) are components of neuronal and muscle ECM, and concentrated within the specialized synaptic cleft matrix at the NMJ and other synapses in multiple species (Martin 2003b;. It was recently shown that loss of GlcNAc transferase alters In Drosophila NMJ synaptic structure, function, and locomotory behavior (Haines and Stewart 2007), independently demonstrating GlcNAc-mediated interactions have roles in synaptic maturation.…”

Dystroglycan and ProteinO-Mannosyltransferases 1 and 2 Are Required to Maintain Integrity ofDrosophilaLarval Muscles

“…No more than two muscles were measured from a single larvae. Sarcomeres were measured from gray scale intensity plots across phalloidinstained sarcomeres (see Figures 2 and 3; Haines and Stewart, 2007), sarcomere size being the distance between adjacent peaks. In cases where the graph did not clearly show a single peak for a sarcomere, the center of the high-intensity region was selected by eye as the peak value.…”

“…The spacing of the F-actin bands can be analyzed by graphing gray scale intensity across phalloidin-stained sarcomeres, and Z-bands are represented as peaks. The distance between peaks can be used as a measure of sarcomere size, and the width of the curve can be used to assess the width of the F-actin band ( Figure 2; Haines and Stewart, 2007). We examined the spacing of the F-actin bands along muscle 6, segments 3 or 4; when the banding pattern across the entire length of the muscle was intact (yw, n ϭ 8; Dg 248 , n ϭ 8; Dg 323 /Dg 248 , n ϭ 8; Dg 323 , n ϭ 6).…”