Duane Retraction Syndrome (DRS) is a congenital eye movement disorder, characterized by limited abduction (lateral movement away from the nose) of the affected eye, and on attempted adduction (movement towards the nose), the eye retracts into the orbit and the lid narrows. It is often accompanied by other eye alignment or vision anomalies. The exact cause is not known, but it is believed to be a result of abnormal development of the cranial nerves that control eye movement during fetal development. DRS is usually idiopathic, but it can also be associated with other congenital anomalies. It is typically diagnosed in early childhood and managed with a combination of observation, prism glasses, and/or surgery, depending on the severity and impact on vision.

Chimerin 1 is a protein that in humans is encoded by the CHN1 gene. It belongs to a family of proteins known as Rac GTPase-activating proteins (RacGAPs), which are involved in regulating various cellular processes such as cell growth, division, and movement. Chimerin 1 specifically inhibits the activity of Rac GTPases, which are important regulators of the actin cytoskeleton and play a role in various signaling pathways.

Chimerin 1 contains several functional domains, including a CH domain, a RhoGAP domain, and a coiled-coil domain. The CH domain binds to calcium/calmodulin, allowing Chimerin 1 to be activated by calcium signaling. The RhoGAP domain is responsible for the GTPase-activating activity of Chimerin 1, which promotes the hydrolysis of GTP to GDP and inactivates Rac GTPases. The coiled-coil domain mediates protein-protein interactions and may be involved in targeting Chimerin 1 to specific cellular locations.

Mutations in the CHN1 gene have been associated with certain neurological disorders, including spinocerebellar ataxia type 36 (SCA36) and hereditary spastic paraplegia type 58 (SPG58). These mutations may affect the function of Chimerin 1 and lead to abnormalities in neuronal development and maintenance.

The oculomotor muscles are a group of extraocular muscles that control the movements of the eye. They include:

1. Superior rectus: This muscle is responsible for elevating the eye and helping with inward rotation (intorsion) when looking downwards.
2. Inferior rectus: It depresses the eye and helps with outward rotation (extorsion) when looking upwards.
3. Medial rectus: This muscle adducts, or moves, the eye towards the midline of the face.
4. Inferior oblique: The inferior oblique muscle intorts and elevates the eye.
5. Superior oblique: It extorts and depresses the eye.

These muscles work together to allow for smooth and precise movements of the eyes, enabling tasks such as tracking moving objects, reading, and maintaining visual fixation on a single point in space.