Number of chromocentres in the nuclei of mouse Sertoli cells in relation to the strain and age of males from puberty to senescence

Nuclei of mouse Sertoli cells were examined on air-dried toluidine blue-sta ined preparations to analyse factors influencing the aggregation of heteroc hromatin into chromocentres. For the CBA strain males tested at 1.3, 2, 3, 6, 9 and 12 months of age, mean numbers of heterochromatin bodies were 4.8, 2.4, 2.1, 1.8, 1.6 and 1.4, respectively; two chromocentres predominated f rom 2 to 9 months of age. In the KE strain, heterochromatin aggregation was significantly accelerated; nuclei containing only one chromocentre were pr edominant from 6 months. The number of chromocentres did not change with th e stages of the seminiferous cycle, and after 1 month of cryptorchid condit ion. Cryptorchidism resulted in disruption of spermatogenesis and Sertoli c ell dysfunction, as demonstrated by the lack of immunohistochemically detec table androgen receptors. The difference in the number of chromocentres bet ween KE and CBA Sertoli cells persisted after 3 days of in vitro culture, b ut unidentified cells with numerous chromatin bodies were also observed. Te sting recombinant inbred strains indicates that at least two genes are invo lved in the difference in the number of chromocentres between progenitor KE and CBA strains; however, no correlations were found with 15 marker loci o r with parameters linked to reproduction. Of the eight strains tested, AKR and C3H showed a 'CBA-like' chromocentre pattern; C57BL, B10.BR, B10.BR-Y-d el and KP were 'KE-like'; and BALB/c and DBA/2 were intermediate. The resul ts showed that centromere aggregation in the Sertoli cell progresses throug hout the life of a male in a strain specific manner; however, its functiona l significance remains unknown.