Roundabout (gene)
Encyclopedia
Roundabout is the gene
for the Roundabout (Robo) receptor
. There is a family of Robo transmembrane receptors and they are the canonical receptors for the signaling molecule
Slit
, although there may be more Slit receptors besides Robo. Slit is a midline repellent molecule and Robo proteins are expressed on axons that avoid the midline, such as ipsilateral longitudinal axons in flies and post-crossing axons in flies and rodents. This Slit/Robo signaling is important in determining the trajectory of pioneer axon
s in the central nervous system
. Together, they prevent longitudinal axons from crossing the midline of the brain
and spinal cord
. They also prevent commissural axons from recrossing the midline. It is present in many animal species, including C. elegans
nematode worms, Drosophila
flies, chicken
s, rodent
s (including mice
) and probably humans. There are several versions of this gene and they are referred to as Robo 1 and Robo 2 in the literature. They are thought to be largely genetically redundant but axon trajectories can be strongly disrupted when both are mutated. In Drosophila, loss of multiple Robo proteins results in the collapse of longitudinal axons onto the midline. This is similar to Slit mutants.
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
for the Roundabout (Robo) receptor
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...
. There is a family of Robo transmembrane receptors and they are the canonical receptors for the signaling molecule
Signaling molecule
A signaling molecule is a chemical involved in transmitting information between cells. Such molecules are released from the cell sending the signal, cross over the gap between cells by diffusion, and interact with specific receptors in another cell, triggering a response in that cell by activating...
Slit
Slit (gene)
Slit refers collectively to a family of related genes which encode a corresponding set of secreted proteins, also collectively referred to as Slit...
, although there may be more Slit receptors besides Robo. Slit is a midline repellent molecule and Robo proteins are expressed on axons that avoid the midline, such as ipsilateral longitudinal axons in flies and post-crossing axons in flies and rodents. This Slit/Robo signaling is important in determining the trajectory of pioneer axon
Pioneer axon
Pioneer axon is an axon that lays down initial growing path for the axons of other neurons to follow.-References:; covered in...
s in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. Together, they prevent longitudinal axons from crossing the midline of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
and spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. They also prevent commissural axons from recrossing the midline. It is present in many animal species, including C. elegans
Caenorhabditis elegans
Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
nematode worms, Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...
flies, chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
s, rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s (including mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
) and probably humans. There are several versions of this gene and they are referred to as Robo 1 and Robo 2 in the literature. They are thought to be largely genetically redundant but axon trajectories can be strongly disrupted when both are mutated. In Drosophila, loss of multiple Robo proteins results in the collapse of longitudinal axons onto the midline. This is similar to Slit mutants.