CHICKEN EYES ABSENT 2 GENE - ISOLATION AND EXPRESSION PATTERN DURING DEVELOPMENT

In all vertebrates studied (human, mouse, chicken), there are at least three genes related to Drosophila eyes absent (eya) gene. The chicken Eyes absent 2 (Eya2) cDNA was isolated from 14 day embryonic chicken lenses, and a complete open reading frame encoding a 59 kDa protein wa s elucidated. The chicken Eya2 protein is moderately conserved and 78- 82% identical to the mouse and human Eya2, The Eya2 gene demonstrated a dynamic expression pattern in different tissues of diverse embryolog ical origin. Expression of Eya2 was first detected at Hamburger and Ha milton stage 9 in the foregut. At later stages of development, Eya2 mR NA was detected in neural crest derivatives (dorsal root ganglia, bran chial arches and cranial nerve ganglia), In the cranial placodes, expr ession of Eya2 was first detected in the nasal pit at stage 13, In the eye, expression of Eya2 was first convincingly detected in neural ret ina at stage 24 (day 4). The highest level of Eya2 mRNA in the lens wa s detected around day 9. Eya2 is also expressed in the cornea and iris . Therefore, chicken Eya2 as well as mouse Eya2 is expressed relativel y early in the nasal (but not in the lens) placode and may mediate ind uction of the nasal placode. Expression of Eya2 in the wing and limb b uds is consistent with its proposed role in the patterning of limb con nective tissues.