Genetic background-dependent role of <i>Egr1</i> for eyelid development.

Abstract

EGR1 is an early growth response zinc finger transcription factor with broad actions, including in differentiation, mitogenesis, tumor suppression, and neuronal plasticity. Here we demonstrate that <i>Egr1</i>^-/- mice on the C57BL/6 background have normal eyelid development, but back-crossing to BALB/c background for four or five generations resulted in defective eyelid development by day E15.5, at which time EGR1 was expressed in eyelids of WT mice. Defective eyelid formation correlated with profound ocular anomalies evident by postnatal days 1-4, including severe cryptophthalmos, microphthalmia or anophthalmia, retinal dysplasia, keratitis, corneal neovascularization, cataracts, and calcification. The BALB/c albino phenotype-associated <i>Tyr</i>^<i>c</i> tyrosinase mutation appeared to contribute to the phenotype, because crossing the independent <i>Tyr</i>^<i>c-2J</i> allele to <i>Egr1</i>^<i>-/-</i> C57BL/6 mice also produced ocular abnormalities, albeit less severe than those in <i>Egr1</i>^-/- BALB/c mice. Thus EGR1, in a genetic background-dependent manner, plays a critical role in mammalian eyelid development and closure, with subsequent impact on ocular integrity.