Differential expression of crystallin genes during development of the rat eye lens

The concentrations of alpha A-, beta B1-, and total gamma-crystallin mRNAs were measured during development of the rat eye lens, using Northern blot and dot blot analysis. After 14 days of fetal growth a sharp increase in the concentration of all three mRNA species was observed. After birth, the concentration of alpha A-crystallin transcripts remains high until 6 months of age, the concentration of gamma-crystallin transcripts decreases gradually, while the concentration of beta B1-crystallin transcripts decreases sharply. The composition of the gamma-crystallin mRNA pool was determined by measuring the relative amount of the transcripts of each of the six gamma-crystallin genes using primer extension and S1-nuclease mapping. The transcripts of all six genes are found until the third month after birth. Thereafter the transcripts of the gamma 1-1, the gamma 3-1, and gamma 4-1 crystallin genes are no longer detectable. Later on the transcripts of the gamma 2-1 and gamma 2-2 genes also disappear leaving only the transcripts of the gamma 1-2 crystallin gene at the age of 8 months. The concentration of the six different gamma-crystallin mRNAs is thus regulated differentially.