Abstract
Mammalian spermatogenesis is a highly coordinated process that requires cooperation between specific proteins to coordinate diverse biological functions. For example, mouse Parkin coregulated gene (PACRG) recruits meiosis-expressed gene 1 (MEIG1) to the manchette during normal spermiogenesis. Here we mutated Y68 of MEIG1 using the CRISPR/cas9 system and examined the biological and physiological consequences in mice. All homozygous mutant males examined were completely infertile, and sperm count was dramatically reduced. The few developed sperm were immotile and displayed multiple abnormalities. Histological staining showed impaired spermiogenesis in these mutant mice. Immunofluorescent staining further revealed that this mutant MEIG1 was still present in the cell body of spermatocytes, but also that more MEIG1 accumulated in the acrosome region of round spermatids. The mutant MEIG1 and a cargo protein of the MEIG1/PACRG complex, sperm-associated antigen 16L (SPAG16L), were no longer found to be present in the manchette; however, localization of the PACRG component was not changed in the mutants. These findings demonstrate that Y68 of MEIG1 is a key amino acid required for PACRG to recruit MEIG1 to the manchette to transport cargo proteins during sperm flagella formation. Given that MEIG1 and PACRG are conserved in humans, small molecules that block MEIG1/PACRG interaction are likely ideal targets for the development of male contraconception drugs.
Highlights
Mouse Meig1 was originally cloned in a screen for genes essential for meiosis [1]
We previously discovered that four amino acids, W50, K57, F66, and Y68, mediate interactions between meiosis-expressed gene 1 (MEIG1) and Parkin co-regulated gene (PACRG) in vitro [47]
We further examined the role of the 12 amino acids on MEIG1’s surface in MEIG1/PACRG interaction and discovered that the four amino acids located on the same surface, W50, K57, F66, and especially Y68, are involved in interaction with PACRG [47]
Summary
Mouse Meig was originally cloned in a screen for genes essential for meiosis [1]. Multiple Meig transcripts are present in different tissues encoding the same protein but differing in their 5’- or 3’-UTRs [1,2]. Two major functions of the manchette have been proposed: shaping spermatid heads and sorting structural proteins to the centrosome and the developing sperm tail through intra-manchette transport (IMT) [13,14]. These proposed functions are supported by the characteristics of its structural proteins and mutant mouse models. The single amino acid mutant MEIG1 was still present in the cell bodies of spermatocytes and round spermatids, but was no longer present in the manchette of the remaining elongating spermatids. The study demonstrates that Y68 is a key amino acid for PACRG to recruit MEIG1 to the manchette to form the MEIG1/PACRG complex which is essential for transporting cargo proteins for sperm formation
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