Abstract
Abstract: :
Purpose: Crim1 (cysteine-rich motor neuron 1), a transmembrane protein thought to antagonise members of the TGFß superfamily of growth factors (Kolle et al., 1999: MOD), has been shown by us to be prominently expressed during ocular development, in particular during lens morphogenesis (Lovicu et al., 2000: MOD). The aim of this study was to identify the putative role(s) of Crim1 in normal lens and ocular development. Methods: The presence of Crim1 protein within ocular fluids was determined using Western blotting. Lens explants and transgenic mice overexpressing Crim1 specifically to the lens were used to examine the influence of Crim1 on lens cells. Furthermore, lens and ocular development was examined in KST264 gene trap lacZ knockin mice (http://socrates.berkeley.edu/~skarnes/resource.html) deficient for Crim1. Results: Using polyclonal antibodies to Crim1 protein, we have determined that Crim1 is present in both aqueous and vitreous, suggesting that it can be cleaved and released from its membrane-bound state. Lens epithelial explants cultured with recombinant Crim1 extracellular domain did not demonstrate any prominent change in lens cell behaviour. This was consistent with our in vivo data using transgenic mice that showed that overexpression of Crim1 in the eye does not influence lens development or growth. In contrast to this, our in vivo studies using Crim1 null mice clearly demonstrate an important role for Crim1 in lens and/or ocular morphogenesis. Mice deficient for Crim1 display perinatal lethality and microphthalmia. At embryonic day 13.5, lenses and eyes appear relatively normal, however, by E16.5, they are smaller in size, with prominent disruptions to the lens and differentiating optic cup. In many cases the developing lens and optic cup appear attached to each other, and this appears to be associated with a disruption in the formation of the hyaloid vasculature and vitreous. Conclusions: Consistent with the specificity and strength of Crim1 expression throughout lens/ocular development, our in vivo studies support an important role for Crim1 in the normal development of the lens and/or eye. The nature and degree to which this molecule plays a role is yet to be elucidated.
Keywords: growth factors/growth factor receptors • vitreous • transgenics/knock-outs