High level of ferritin light chain mRNA in lens

Ferritin is of particular interest with regard to cataract because (i) cataract occurs in individuals with hereditary hyperferritinemia cataract syndrome (HHCS), a condition in which ferritin light chain (L-ferritin) protein is overexpressed systemically, and (ii) ferritin is an important regulator of oxidative stress, a primary factor in the etiology of aging-related cataract. From gene array analysis two novel observations were made with respect to ferritin gene expression: first, lenses from guinea pigs and humans have disproportionately high levels of L-ferritin mRNA relative to the amounts of ferritin protein present, and second, L-ferritin message increased markedly in lenses from guinea pigs with hereditary nuclear cataract. The human lens L-ferritin sequence was identical to previous data from human liver; the guinea pig sequence was 86% identical to the human sequence at the amino acid level. Despite mRNA levels similar to those of major lens crystallins, lens ferritin was undetectable by Western blot techniques.