Genetic etiological spectrum of sperm morphological abnormalities

Abstract

Purpose: Male infertility manifests in the form of a reduction in sperm count, sperm motility, or the loss of fertilizing ability. While the loss of sperm production can have mixed reasons, sperm structural defects, cumulatively known as teratozoospermia, have predominantly genetic bases. The aim of the present review is to undertake a comprehensive analysis of the genetic mutations leading to sperm morphological deformities/teratozoospermia.

Methods: We undertook literature review for genes involved in sperm morphological abnormalities. The genes were classified according to the type of sperm defects they cause and on the basis of the level of evidence determined by the number of human studies and the availability of a mouse knockout.

Results: Mutations in the SUN5, CEP112, BRDT, DNAH6, PMFBP1, TSGA10, and SPATA20 genes result in acephalic sperm; mutations in the DPY19L2, SPATA16, PICK1, CCNB3, CHPT1, PIWIL4, and TDRD9 genes cause globozoospermia; mutations in the AURKC gene cause macrozoospermia; mutations in the WDR12 gene cause tapered sperm head; mutations in the RNF220 and ADCY10 genes result in small sperm head; mutations in the AMZ2 gene lead to vacuolated head formation; mutations in the CC2D1B and KIAA1210 genes lead to pyriform head formation; mutations in the SEPT14, ZPBP1, FBXO43, ZCWPW1, KATNAL2, PNLDC1, and CCIN genes cause amorphous head; mutations in the SEPT12, RBMX, and ACTL7A genes cause deformed acrosome formation; mutations in the DNAH1, DNAH2, DNAH6, DNAH17, FSIP2, CFAP43, AK7, CHAP251, CFAP65, ARMC2 and several other genes result in multiple morphological abnormalities of sperm flagella (MMAF).

Conclusions: Altogether, mutations in 31 genes have been reported to cause head defects and mutations in 62 genes are known to cause sperm tail defects.

Keywords: Asthenozoospermia; Globozoospermia; Infertility genetics; Male infertility; Multiple morphological abnormalities of sperm flagella (MMAF); Sperm head defects; Teratozoospermia.

Fig. 1

Flow chart detailing the classification scheme for categorizing genes based on the level of evidence

Fig. 2

Normal morphology and dimensions of human sperm head (upper) and sperm head defects (lower). Genes associated with a particular head defect are listed in the corresponding position

Fig. 3

Normal morphology and dimensions of midpiece (upper) and sperm midpiece defects (lower)

Fig. 4

Normal dimensions of human sperm tail (upper) and sperm tail defects (lower). The names of genes causing different types of defects are listed below, and the length of the bar corresponds to the kinds of defects caused