COLCHICINE EFFECTS ON MEIOSIS IN THE MALE-MOUSE .1. MEIOTIC PROPHASE - SYNAPTIC ARREST, UNIVALENTS, LOSS OF DAMAGED SPERMATOCYTES AND A POSSIBLE CHECKPOINT AT PACHYTENE
Jh. Tepperberg et al., COLCHICINE EFFECTS ON MEIOSIS IN THE MALE-MOUSE .1. MEIOTIC PROPHASE - SYNAPTIC ARREST, UNIVALENTS, LOSS OF DAMAGED SPERMATOCYTES AND A POSSIBLE CHECKPOINT AT PACHYTENE, Chromosoma, 106(3), 1997, pp. 183-192
Antimitotic agents administered at the time of synapsis (leptotene/zyg
otene) have been shown to induce synaptic abnormalities visible during
pachytene in the male mouse. The object of this study was to test the
hypothesis that cells with relatively large amounts of colchicine-ind
uced damage to the synaptonemal complex (SC) are eliminated from proph
ase whereas cells with relatively small amounts of SC damage proceed t
hrough to the end of prophase. Male mice were injected with tritiated
thymidine to mark a cohort of spermatocytes at premeiotic S-phase for
tracking through pachytene. Forty-eight hours later, when those cells
were at leptotene/zygotene, colchicine was administered intratesticula
rly. Whole-mount SC spreads were made from animals sacrificed at vario
us times following colchicine administration, and prepared for autorad
iography. The marked cells were examined by light and electron microsc
opy and the kind and number of synaptic abnormalities were scored thro
ughout pachytene. Colchicine-induced SC damage included single axial e
lements (univalents), together with partially synapsed and nonhomologo
usly synapsed SCs. The amount of SC damage (amount and type per cell a
nd frequency of cells with damage) scored at early pachytene exceeded
by three-to fivefold the amount at late pachytene. This is consistent
with spermatogenic cell loss from the seminiferous tubule via colchici
ne-induced destruction of Sertoli cell microtubules. The presence of s
permatocytes with no more than four autosomal univalents at late pachy
tene indicates that some cells with low amounts of synaptic damage pro
gress to the end of pachytene. The loss of the most severely damaged c
ells may represent a meiotic checkpoint at early pachytene in the male
mouse.