Beyond Acephalic Spermatozoa: The Complexity of Intracytoplasmic Sperm Injection Outcomes

Table 1

The classification of AS defects based on ultrastructural observations, broken points of the neck region of sperm, and AS target genes. AS: acephalic spermatozoa.

Subtypes	Separation point	Phenotype	Candidate gene	References
I	Between the two centrioles	The tailless head contains the complete proximal centriole with intact implantation fossa and basal body		Holstein et al. [20]
II	Between the nucleus and proximal centriole	The sperm head contains the intact nucleus and acrosome with absent basal body and/or aplasia of the implantation fossa	HOOK1,	Chemes and Rawe [8]
			SUN5,	Zhu et al. [10]
			PMFBP1	Chen et al. [12]
III	Between the distal centriole and mitochondrial sheath	The sperm tail can be observed with/without the incomplete mitochondrial sheath	TSGA10	Toyama et al. [7]
			BRDT,	Li et al. [26]
				Sha et al. [11]