Conservation of anatomically restricted glycosaminoglycan structures in divergent nematode species.

Heparan sulfates (HS) are glycosaminoglycans of the extracellular matrices and characterized by complex modification patterns owing to sulfations, epimerization, and acetylation. Distinct HS modification patterns have been shown to modulate protein-protein interactions during development in general and of the nervous system in particular. This has led to the heparan sulfate code hypothesis, which posits that specifically modified HS epitopes are distributed in a tissue and cell-specific fashion to orchestrate neural circuit formation.

A transgenic approach to live imaging of heparan sulfate modification patterns.

Heparan sulfate (HS) glycosaminoglycan chains contain highly modified HS domains that are separated by sections of sparse or no modification. HS domains are central to the role of HS in protein binding and mediating protein-protein interactions in the extracellular matrix. Since HS domains are not genetically encoded, they are impossible to visualize and study with conventional methods in vivo.

Skin-derived cues control arborization of sensory dendrites in Caenorhabditis elegans.

Sensory dendrites depend on cues from their environment to pattern their growth and direct them toward their correct target tissues. Yet, little is known about dendrite-substrate interactions during dendrite morphogenesis. Here, we describe MNR-1/menorin, which is part of the conserved Fam151 family of proteins and is expressed in the skin to control the elaboration of "menorah"-like dendrites of mechanosensory neurons in Caenorhabditis elegans.

Direct visualization of specifically modified extracellular glycans in living animals.

Modification patterns of heparan sulfate coordinate protein function in metazoans, yet in vivo imaging of such non-genetically encoded structures has been impossible. Here we report a transgenic method in Caenorhabditis elegans that allows direct live imaging of specific heparan sulfate modification patterns. This experimental approach reveals a dynamic and cell-specific heparan sulfate landscape and could in principle be adapted to visualize and analyze any extracellular molecule in vivo.

LINE-1 activity in facultative heterochromatin formation during X chromosome inactivation.

During X chromosome inactivation (XCI), Xist RNA coats and silences one of the two X chromosomes in female cells. Little is known about how XCI spreads across the chromosome, although LINE-1 elements have been proposed to play a role. Here we show that LINEs participate in creating a silent nuclear compartment into which genes become recruited.