Characterization of terminally differentiated cell state by categorizing cDNA clones derived from chicken lens fibers

To characterize a terminally differentiated state of cells at the gene expression level, a cDNA library of chicken lens fibers was analyzed. The major population of the library consisted of cDNAs encoding delta-crystallin (about 35% of the recombinants) and other crystallins (alpha A-, alpha B-, beta A3/A1-, beta B1-, beta B2-), as well as cytoskeletal proteins (CP49, CP95), and membrane protein (MP28). These cDNA clones representing lens structural proteins known, accounted for about 60% of the library. When 96 clones were randomly selected from this library, 55 clones corresponded to the above-mentioned major class proteins. Analyses of the remaining clones indicated that many of them were expressed in a lens-specific manner at very low levels. The partial nucleotide sequence analysis of these clones revealed that two cDNAs corresponded to the genes encoding lens-type connexin, three cDNAs to the genes encoding housekeeping proteins, and some cDNAs to the genes encoding regulatory proteins. The mRNA composition in the chicken lens fiber cells indicated rather simple organization of mRNA species of this cell type, and gave scope to the possibility of full description of differentiated lens fiber cells at gene activity level.