Dendrites with specialized glial attachments develop by retrograde extension using SAX-7 and GRDN-1

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• Dendrite development is coordinated with surrounding glial cells, but the underlying molecular mechanisms are largely unknown.
• The nematode *C. elegans* provides a model system to study neuron-glia interactions.
• Previous studies focused on epithelial contexts, while this work examines non-epithelial neuron-glia interactions.

Purpose of the Study:

• To identify molecular factors coordinating dendrite and glial cell morphogenesis in non-epithelial contexts.
• To elucidate the mechanism of dendrite development for the BAG and URX neurons in *C. elegans*.
• To investigate the roles of SAX-7 and GRDN-1 in dendrite extension.

Main Methods:

• Forward genetic screens in *C. elegans*.
• Analysis of neuronal and glial cell development using microscopy.
• Molecular genetics to study protein function in neurons and glia.

Main Results:

• Dendrites of BAG and URX neurons extend via retrograde extension, anchoring to the nose and stretching during embryogenesis.
• The adhesion protein SAX-7 (L1CAM) and cytoplasmic protein GRDN-1 (CCDC88C) are essential for anchoring dendrite endings.
• SAX-7 functions in both neurons and glia, while GRDN-1 acts non-autonomously in glia to promote dendrite extension.

Conclusions:

• Glial factors play a crucial role in shaping neuronal dendrites.
• A novel molecular mechanism involving retrograde extension, mediated by SAX-7 and GRDN-1, facilitates dendrite growth.
• This study provides insights into conserved mechanisms of dendrite-glia interactions relevant to the mammalian brain.