ABSTRACT
The round spermatids are transformed into spermatozoa by a series of progressive changes collectively known as spermiogenesis. The changes include condensation of nuclear chromatin, formation of the sperm tail or flagellum apparatus, and development of the acrosomal cap. The various developmental stages of spermatic transformation are divided into
Table 2.1 Genetic control of testis determination
Gene Role during testis development
Tdy (testis determining factor in mice) Act on supporting cell lineage and induce differentiation of supporting cells to Sertoli cells
Sry (a Y chromosome-specific gene) Different homologs of Sry have a common open reading frame which has 41% homology to a DNA-binding motif HMG box; Sry encoded protein might have DNA-binding activity
Sox6 (Sry-related gene), Sox5 Overlapping functions in the adult mouse
Sox9 A critical Sertoli cell differentiation factor
TAZ83 Coding at early to mid-pachytene germ-cell stage
TAZ4 Testis-specific gene located on chromosome 11
TNZ1 Expressed in neonatal Leydig cells
four phases: Golgi body formation, cap formation, acrosomal and maturation phases. The reshaping of the nucleus and acrosome of each spermatid, initiated during the previous phase, produces the spermatozoon. Within the nucleus, the chromatin granules undergo progressive condensation as the transitional proteins are replaced by protamines which form a fine homogeneous material that uniformly fills the entire sperm nucleus.
