Boar proacrosin expressed in spermatids of transgenic mice does not reach the acrosome and disrupts spermatogenesis

Abstract

Transgenic mice that express boar proacrosin were produced to examine mechanisms for targeting hydrolytic enzymes to the acrosome. A 2.3 kb transgene was constructed by ligating the cDNA for boar preproacrosin with the mouse protamine 2 promoter region. Six founder mice that incorporated the transgene were identified by polymerase chain reaction and Southern blot analysis. Northern blots indicated that the two male founders (Ac.2 and Ac.5) and male progeny from three female founders (Ac.3, Ac.4, Ac.6) expressed the transgene mRNA in testis, but not in somatic tissues. In these transgenic animals boar proacrosin was detected by immunohistochemistry in condensing spermatids, but was not localized in the acrosome. This acrosomal targeting defect of the transgene product may result from its delayed expression during the later steps of haploid differentiation. Furthermore, both male founders and all Ac.4 and Ac.6 males were infertile, as determined by multipe matings for at least 2 months. Ac.3 males were either infertile or rarely transmitted the transgene to their offspring The infertile males mated, produced copulatory plugs, and had seminal vesicle weights and testosterone levels within the normal range. However, they produced significantly fewer spermatozoa and had lower testis weights than controls. Although the mitotic and meiotic phases of spermatogenesis appeared normal by histological criteria, condensing spermatids were missing from most tubules, and multinucleated cells were present in the lumen of seminiferous tubules and in the epididymis. We hypothesize that boar proacrosin which fails to reach the acrosome is activated in these transgenic mice, and that its proteolytic activity disrupts spermatogenesis during spermatid formation. © 1996 Wiley‐Liss, Inc.

SPINK2 deficiency causes infertility by inducing sperm defects in heterozygotes and azoospermia in homozygotes

“…The absence of SPINK2 likely allows proacrosin autoactivation within the reticulum and the Golgi apparatus compartments, leading to the above-described subcellular defects. It was previously shown that transgenic expression of porcine proacrosin in mice led to post-meiotic cell death and oligozoospermia, supporting the hypothesis that unbalanced expression of acrosin/Spink2 is deleterious (O'Brien et al, 1996). Interestingly, we have demonstrated that the cell responds to this stress by activating a microautophagy-like pathway: First, we showed that larger vacuoles engulfed small vacuoles, likely leading to the observed heterogeneity in vacuole size in the vicinity of the Golgi apparatus; and secondly, multivesicular bodies, a hallmark of microautophagy (Li et al, 2012), were clearly observed within Spink2 À/À round spermatids, whereas they were never observed in WT.…”

Mice lacking cyclin‐dependent kinase inhibitor p19Ink4d show strain‐specific effects on male reproduction

“…Individual testosterone levels were quite variable (Fig. 6A), as expected for mice (O'Brien et al, 1996). Because of this variability, we also determined the combined wet weights of an androgen-dependent accessory gland, the seminal vesicles, as a fraction of body weight.…”