Abstract
Purpose: :
LIM homeodomain (Lhx) family of transcription factors plays a crucial role in neuronal patterning and tissue differentiation. However, their role in retinal neurogenesis is not fully understood. Our initial set of experiments aims to elucidate expression patterns of the Lhx family of genes, during the different stages of development of different retinal cells and cell subtypes in mice.
Methods: :
Retinas were collected from C57BL/6J mice at progressive embryonic and postnatal time points. The eyes were fixed and cryoprotected and subsequently embedded prior to sectioning. Immunohistochemistry and in situ hybridization assays were employed to visualize expression patterns of individual Lhx genes.
Results: :
Immunofluorescence imaging showed an early expression of Lhx2 in retinal progenitor cells followed by expression in Müller glial cells in the inner nuclear layer (INL) postnatally. Lhx3 similarly was expressed in bipolar cells in the INL starting at postnatal day (P) 7. In situ hybridization images showed an expression of Lhx4 in the INL starting at P7. Lhx6 was expressed during later development stages of retinal ganglion cells at P0. Lhx7 expression was consistent in both the ganglion cell layer (GCL) and the INL starting at P7. The expression of Lhx9 began early at embryonic stage (E) 15.5 in the GCL and continued through birth. In addition, Lhx9 also showed expression postnatally in the INL along with the GCL.
Conclusions: :
With the exception of Lhx5, our results along with previously published work have shown that Lhx family of genes display unique spatiotemporal expression patterns during development of different retinal cell types in mammalian retina. Furthermore, phylogenetically related Lhx3 and Lhx4 display overlapping expression in the INL starting at approximately same time points, suggesting their potential functional redundancy in retinogenesis. Future functional experiments will help determine their role in retinal cell-fate determination.
Keywords: retinal development • transcription factors • gene/expression