Genes Regulating Spermatogenesis and Sperm Function Associated With Rare Disorders

Abstract

Spermatogenesis is a cell differentiation process that ensures the production of fertilizing sperm, which ultimately fuse with an egg to form a zygote. Normal spermatogenesis relies on Sertoli cells, which preserve cell junctions while providing nutrients for mitosis and meiosis of male germ cells. Several genes regulate normal spermatogenesis, some of which are not exclusively expressed in the testis and control multiple physiological processes in an organism. Loss-of-function mutations in some of these genes result in spermatogenesis and sperm functionality defects, potentially leading to the insurgence of rare genetic disorders. To identify genetic intersections between spermatogenesis and rare diseases, we screened public archives of human genetic conditions available on the Genetic and Rare Diseases Information Center (GARD), the Online Mendelian Inheritance in Man (OMIM), and the Clinical Variant (ClinVar), and after an extensive literature search, we identified 22 distinct genes associated with 21 rare genetic conditions and defective spermatogenesis or sperm function. These protein-coding genes regulate Sertoli cell development and function during spermatogenesis, checkpoint signaling pathways at meiosis, cellular organization and shape definition during spermiogenesis, sperm motility, and capacitation at fertilization. A number of these genes regulate folliculogenesis and oogenesis as well. For each gene, we review the genotype-phenotype association together with associative or causative polymorphisms in humans, and provide a description of the shared molecular mechanisms that regulate gametogenesis and fertilization obtained in transgenic animal models.

Keywords: Sertoli; acrosome; centrosome; genetic disease; infertility; sperm motility.

FIGURE 1

Schematic of spermatogenesis and spermiogenesis: (A) Left, proteins regulating spermatogenesis. Right inset, proteins mediating cellular remodeling at spermiogenesis. (B) Meiosis during spermatogenesis, with focus on Prophase and Metaphase II and proteins regulating chromosome migration, DNA double strand breaks repair, and spindle assembly checkpoint.

FIGURE 2

Motility and functionality of mouse and human sperm: schematic portraying the structure of mature mouse and human sperm. Proteins regulating sperm motility and ability to fertilize eggs are expressed in the mid-piece, or in the principal piece. Sperm heads present a nucleus and an acrosome.