Differential localization by in situ hybridization of specific crystallin transcripts during mouse lens development

The embryonic development of the mammalian lens is well known at the biochemical and histologi-cal level. However few data are available at the molecular level concerning gene expression during the continuous differentiation of the lens. In the present study, we have investigated by in situ hybridization the changes in the distribution of mouse crystallin mRNA as a marker of differentiated lens cells, during development of the lens primordium, when tissue interactions are known to be essential. The transcripts of α and β crystal-lins are first detected at the early elongation stage of primary fibres; γ-crystallin-transcripts do not appear until the late elongation phase. All areas of the lenses exhibited crystallin mRNA until the beginning of secondary fiber formation at 18 days of development. Hybridization for α and β crystallin is confined at that time to the equatorial part of the lens. The γ crystallin transcripts are no longer found in the equatorial region after 1 post-natal day, but remain in the lens core, decreasing gradually. A possible mechanism is discussed.