Abstract
Purpose: :
Muscleblind (Mbl) –1, –2 and –3 are zinc finger transcription factors discovered in Drosophila, in which they control muscle development and photoreceptor differentiation. Mbl genes were subsequently identified in vertebrates, but their role in vertebrate retinal development remains unknown. As an initial approach to their investigation, we report here their expression patterns in the developing chick embryo retina.
Methods: :
Expression of Mbl –1, –2 and –3 was investigated by RT–PCR and QPCR (real–time PCR) in RNA from retinas isolated at different stages between embryonic day (ED) 6–18. Spatial patterns of expression were investigated by in situ hybridization (ISH) in retinal sections from the same stages, using probes against non–conserved regions of the genes. Expression in individual rod and cone photoreceptors was investigated by PCR in cDNA samples synthesized from individual photoreceptors isolated from ED 20 chicken embryo retina cell suspensions as described by Huang and Adler (ARVO abstracts, 2005).
Results: :
Mbl –1,–2 and –3 were detected at all the stages analyzed, but QPCR showed gene–specific temporal changes in their expression patterns; Mbl–1 levels remained essentially unchanged, but Mbl –2 and –3 showed 2.1–fold and 9.7–fold increases, respectively, between ED 6–18. By ISH at ED 8, 15 and 18, Mbl–3 was detectable in all 3 retinal layers, whereas Mbl–2 predominated in the ONL and the outer part of the INL; Mbl–1 is currently under investigation. PCR analysis of single cell cDNA detected Mbl–1 in red and green cones, but not in rods; Mbl–3 was detected in red cones and rods, but not in green cones, whereas Mbl–2 was detected in all of these photoreceptor types.
Conclusions: :
Three Mbl genes are expressed in the developing chick embryo retina, but their temporal and spatial patterns of expression are different. The possibility that they may influence photoreceptor development in the chick as they do in Drosophila is suggested by their expression patterns in photoreceptor subtypes, and is currently under investigation.
Keywords: retinal development • gene/expression • transcription factors