Cataracts and NrCAM

The Ig superfamily member NrCAM is believed to help orchestrate neuronal development, so Moré et al. (page 187) were surprised at the phenotype of their recently generated NrCAM −/− mice; the animals appear to have nearly normal nervous systems, but develop cataracts.

The mice are slightly smaller than their heterozygous littermates and show a slight motor defect, but are viable and fertile, and lack any histological abnormalities in any neural tissues. Their commissural axons cross the spinal cord midline normally, an unexpected result because previous work had suggested a requirement for NrCAM in directing commissural axon growth.

While the absence of NrCAM does not appear to cause serious problems in neuronal tissue, NrCAM -/- mice develop cataracts because of a failure in establishing contact between lens fiber cells, and thus presumably a failure in forming normal water channels. Flow...