Impaired Extraocular Muscle Innervation Is Present Before Eye Opening in a Mouse Model of Infantile Nystagmus Syndrome.

Purpose: To determine if extraocular muscles (EOMs) from mice with nystagmus show abnormalities in myofiber composition and innervation, as seen in EOMs from human nystagmus patients, and to determine when in development those changes occur.

Methods: Balb/c albino mice were crossed to pigmented mice to generate heterozygous mice, which were mated to create experimental litters containing albinos and wild-type controls. Orbits were harvested from adult animals (12 weeks old); on postnatal day (P)0, P10, P14, and P21; and from 6-week-old animals.

TWIST1, a gene associated with Saethre-Chotzen syndrome, regulates extraocular muscle organization in mouse.

Heterozygous loss of function mutations in TWIST1 cause Saethre-Chotzen syndrome, which is characterized by craniosynostosis, facial asymmetry, ptosis, strabismus, and distinctive ear appearance. Individuals with syndromic craniosynostosis have high rates of strabismus and ptosis, but the underlying pathology is unknown. Some individuals with syndromic craniosynostosis have been noted to have absence of individual extraocular muscles or abnormal insertions of the extraocular muscles on the globe.