# The GgcxK325Q Mutation Does Not Affect the Calcium Homeostasis of the Epididymis and Male Fertility in Mice

## TL;DR

This study finds that a specific mutation in the GGCX gene does not affect mouse fertility or epididymal calcium levels.

## Contribution

The novel contribution is the discovery that the GgcxK325Q mutation has no impact on mouse male fertility or epididymal calcium homeostasis.

## Key findings

- GGCX and MGP are enriched in mouse epididymis, especially in the initial segment.
- GgcxK325Q−/− mice showed normal epididymal calcium levels, sperm function, and fertility.
- The GgcxK325Q mutation does not impair male fertility in mice.

## Abstract

A low-calcium microenvironment is imperative for spermatozoa maturation within the epididymis. Our previous work has shown that γ-glutamyl carboxylase (GGCX), the carboxylation enzyme of the matrix Gla protein (MGP), plays an essential role in epididymal calcium homeostasis and sperm maturation in rats and that the GGCX SNP mutation rs699664 was associated with asthenozoospermia (AZS) in humans. Here, we investigated the expression patterns of GGCX and MGP in the mouse epididymis and generated GgcxK325Q knock-in (KI) mice. We also tested the effects of this mutation on epididymal calcium homeostasis, sperm function, and male fertility in GgcxK325Q−/− mice. The results showed that both GGCX and MGP were enriched in all regions of the mouse epididymis, especially in the initial segment of the epididymis. Double immunofluorescence staining revealed that GGCX colocalized with MGP in the epithelial cells of the initial segment and caput regions as well as in the lumen of the corpus and cauda regions of the mouse epididymis. However, the GgcxK325Q−/− mice were fertile with normal epididymal morphology, sperm functions, and epididymal calcium concentration. Overall, our findings revealed that the GgcxK325Q mutation does not exert any discernible effect on male fertility in mice.