No abstract

Mutations in the Drosophila gene greatwall cause improper chromosome condensation and delay cell cycle progression in larval neuroblasts. Chromosomes are highly undercondensed, particularly in the euchromatin, but nevertheless contain phosphorylated histone H3, condensin, and topoisomerase II. Cells take much longer to transit the period of chromosome condensation from late G2 through nuclear envelope breakdown. Mutant cells are also subsequently delayed at metaphase, due to spindle checkpoint activity. These mutant phenotypes are not caused by spindle aberrations, by global defects in chromosome replication, or by activation of a caffeine-sensitive checkpoint. The Greatwall proteins in insects and vertebrates are located in the nucleus and belong to the AGC family of serine/threonine protein kinases; the kinase domain of Greatwall is interrupted by a long stretch of unrelated amino acids.

Now in its third decade of mechanistic investigation, testicular injury caused by 2,5-hexanedione (2,5-HD) exposure is a well-studied model with a rich database. The development of this model reflects the larger changes that have moved biology from a branch of chemistry into the molecular age. Critically examined in this review is the proposed mechanism for 2,5-HD-induced testicular injury in which germ cell maturation is disrupted owing to alterations in Sertoli cell microtubule-mediated functions. The goal is to evaluate the technical and conceptual approaches used to assess 2,5-HD-induced testicular injury, to highlight unanswered questions, and to identify fruitful avenues of future research.