SPATIAL REPOSITIONING OF CENTROMERIC DOMAINS DURING REGROWTH OF AXONSIN NUCLEI OF MURINE DORSAL-ROOT GANGLION NEURONS IN-VITRO

Specific chromatin domains within interphase nuclei are organized in c ell type specific distributions and are rearranged in association with changes in cell function. Axotomy leads to changes in gene expression . Dorsal root ganglion (DRG) neurons in vitro are a model for axotomy because they are detached from their axons in preparation for the cult uring procedure. In a test of the hypothesis that neurons regrowing in vitro undergo rearrangement of specific chromatin domains, changes in the distribution of centromere-associated kinetochores proteins withi n DRG neurons were assessed as a function of time in vitro, Comparison of the kinetochore distributions in neurons in situ to those 24 h aft er placement into culture showed that the mean proportion (+/-S.E.M.) of kinetochore signals in the karyoplasm decreased from 41.0+/-1.8% to 28.6+/-33%, while the proportion at the nucleolus increased from 35.2 +/-2.01 to 48.4+/-2.9%. This indicated redistribution of centromeric d omains to the nucleolus. Between 1 day and 16 days in vitro, signals w ere redistributed to the nuclear periphery, indicated by an increase i n the proportion of signals in this nuclear compartment from 23.0+/-4. 3% to 37.6+/-3.4% and a decrease in the proportion of signals from 48. 4+/-2.9% to 23.0+/-2.3% at the nucleolus. The results indicate that ne urite regrowth following axotomy is associated with changes in nuclear topology. The reorganization that occurs within 24 h is speculated to be associated with a recapitulation of a cytoskeletal development pro gram, while later changes in centromeric distributions may be related to cues elicited by in vitro conditions. (C) 1996 John Wiley & Sons, I nc.