• concomitant with a bent sperm head and bent midpiece phenotype, the sperm cytoplasmic droplet (CD) is greatly reduced in size and devoid of saccular elements in epididymal sperm
• both caput and cauda epididymal sperm lack the typically large, dilated CD regions seen in control littermates by phase contrast microscopy; no sperm bearing typical saccular elements in the CD region are detected by TEM
• further TEM analysis showed very few saccules, if any, in the CD region of step16 spermatids and epididymal sperm
• although reduced in size, the integrity of the CD region remains intact and an electron dense finely granular background is observed along with occasional small round vesicles
• key glycolytic enzymes HK1 (hexokinase 1) and PGK2 (phosphoglycerate kinase 2) are expressed at normal levels but fail to accumulate in the forming CD region of step 16 spermatids and epididymal sperm; both HK1 and PGK2 are absent in putative CD regions but are detectable in the cytoplasm along the flagellar midpiece and residual bodies, indicating that enrichment of protein components selectively to the CD is disrupted