REGULATION OF HOMEOBOX-CONTAINING GENES DURING LENS REGENERATION

In this study, the expression of homeobox-containing genes was evaluat ed after lentectomy in the newt, which is competent for lens regenerat ion, and in the axolotl which is not. Such a comparison was designed t o offer insights about possible regulation due to regenerative abiliti es. Six homeobox-containing genes were examined: NvHox A4, NvHox B1, N vHox 7, NvHox, Nomsx-1 and Xbr1. For all genes examined, it was found that soon after lentectomy in the newt there was a general down-regula tion in the retina. This down-regulation varied among the Hox genes wi th NvHox 7 and NvHox B1 being virtually absent in the initial stages; their expression was re-established to the original levels after the r eappearance of lens. The expression patterns, for NvHox 7 and NvHox B1 were the same when the lens was removed and then displaced. However, in axolotl, down-regulation was not observed. These data suggest that the observed regulation is related to the process of lens regeneration and provide the first molecular evidence that lens regeneration could be dependent on retina and underline the importance of this tissue in lens regeneration. Such patterns link expression of homeobox-containi ng genes and lens regeneration and can be now used to understand the u nderlying mechanisms of lens regeneration and transdifferentiation. (C ) 1998 Academic Press Limited.