Presence of hybridizing DNA sequences homologous to bovine acidic and basic beta-crystallins in all classes of vertebrates.

The eye lens beta-crystallins in cow and chicken are encoded by a family of at least six genes. In order to assess the distribution of the corresponding genes among other vertebrates we hybridized beta-crystallin sequences (beta A2, beta A3/A1, beta A4, beta B1, beta B2, beta B3), isolated from a bovine lens cDNA library, to Southern blots on which EcoR1-digested chromosomal DNA was blotted from different vertebrate species. These included human, chimpanzee, calf, rat, pigeon, duck, monitor lizard, toad, trout, and lamprey. Positive hybridization signals were found in the representatives of virtually all classes of vertebrates. The basic beta B-crystallins gave hybridization signals in more species than the acidic beta A ones. In monitor lizard and toad the weakest hybridization signals for basic crystallin probes were found. For acidic crystallin probes the distribution pattern was more simple; among cold-blooded vertebrates a signal for beta A2 was found in trout and lamprey, for beta A4 in trout, and for beta A3/A1 only in toad. The results demonstrate that the duplications leading to the beta-crystallin gene family occurred before or during the earliest stages of vertebrate evolution.