Shaping the sperm head: an ER enzyme leaves its mark

Phase 1 Healthy Volunteer Study of AL01211, an Oral, Non-brain Penetrant Glucosylceramide Synthase Inhibitor, to Treat Fabry Disease and Type 1 Gaucher Disease

Glycosphingolipid (GSL) storage diseases are caused by deficiencies in the enzymes that metabolize different GSLs in the lysosome. Glucosylceramide synthase (GCS) inhibitors reduce GSL production and have potential to treat multiple GSL storage diseases. AL01211 is a potent, oral GCS inhibitor being developed for the treatment of Type 1 Gaucher disease and Fabry disease. AL01211 has minimal central nervous system penetration, allowing for treatment of peripheral organs without risking CNS-associated adverse effects. AL01211 was evaluated in a Phase 1 healthy volunteer study with single ascending dose (SAD) and multiple ascending dose (MAD) arms, to determine safety, pharmacokinetics including food effect, and pharmacodynamic effects on associated GSLs. In the SAD arm, AL01211 showed a Tmax of approximately 3.5 hours, mean clearance (CL/F) of 130.1 L/h, and t1/2 of 39.3 hours. Consuming a high-fat meal prior to dose administration reduced exposures 3.5-5.5-fold, indicating a food effect. In the MAD arm, AL01211 had an approximately 2-fold accumulation, reaching steady-state levels by 10 days. Increasing exposure inversely correlated with a decrease in GSL with plasma glucosylceramide and globotriacylceramide reduction from baseline levels, reaching 78% and 52% by day 14, respectively. AL01211 was generally well-tolerated with no AL01211 associated serious adverse events, thus supporting its further clinical development.

Molecular genetic mechanisms of teratozoospermia

In recent years, the incidence of teratospermia has been increasing, and it has become a very important factor leading to male infertility. The research on the molecular mechanism of teratospermia is also progressing rapidly. This article briefly summarizes the clinical incidence of teratozoospermia, and makes a retrospective summary of related studies reported in recent years. Specifically discussing the relationship between gene status and spermatozoa, the review aims to provide the basis for the genetic diagnosis and gene therapy of teratozoospermia.

The molecular mechanisms underlying acrosome biogenesis elucidated by gene-manipulated mice

Sexual reproduction requires the fusion of two gametes in a multistep and multifactorial process termed fertilization. One of the main steps that ensures successful fertilization is acrosome reaction. The acrosome, a special kind of organelle with a cap-like structure that covers the anterior portion of sperm head, plays a key role in the process. Acrosome biogenesis begins with the initial stage of spermatid development, and it is typically divided into four successive phases: the Golgi phase, cap phase, acrosome phase, and maturation phase. The run smoothly of above processes needs an active and specific coordination between the all kinds of organelles (endoplasmic reticulum, trans-golgi network and nucleus) and cytoplasmic structures (acroplaxome and manchette). During the past two decades, an increasingly genes have been discovered to be involved in modulating acrosome formation. Most of these proteins interact with each other and show a complicated molecular regulatory mechanism to facilitate the occurrence of this event. This Review focuses on the progresses of studying acrosome biogenesis using gene-manipulated mice and highlights an emerging molecular basis of mammalian acrosome formation.

Increase of germ cell nuclear factor expression in globozoospermic Gopc-/- knockout mice

BACKGROUND

Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC) is a Golgi protein that plays a role in vesicular transport and intracellular protein trafficking and degradation. Mice deficient in GOPC protein have globozoospermia and are infertile. The germ cell nuclear factor (GCNF) is a member of the nuclear receptor superfamily which is expressed in male germ cells, from spermatocytes and spermatids, both in the nucleus and the acrosomal region. It is not known if its expression could be altered in Gopc^-/- mice with defective acrosomes.

OBJECTIVES

The aim of the present work was to analyze the distribution of GCNF protein in spermatids of Gopc^-/- knockout mice.

MATERIALS AND METHODS

We have analyzed the expression and distribution during spermatogenesis of GCNF and its deregulation in Gopc^-/- mutant mice by RT-qPCR, Western blot, immunohistochemistry and immunogold.

RESULTS

Germ cell nuclear factor was localized in the nucleus of all the cell types in the seminiferous tubules. Despite being a nuclear protein, it was also located in the acrosome and in the manchette of elongating spermatids. We have found that in the absence of GOPC, the expression of GCNF was increased in the nucleus of spermatocytes, mainly in leptotene, and in the nucleus and the manchette during the spermatid elongation.

DISCUSSION AND CONCLUSION

Gopc^-/- mice have defective acrosome and manchette. The manchette is involved in the transport of proteins through the cytoplasm and the nucleus. Considering that the GCNF protein is normally transported to the acrosome and the nucleus, it can be thought that transport deficiencies in Gopc^-/- mice are responsible for the increased expression of this protein.

Analysis of male reproductive parameters in a murine model of mucopolysaccharidosis type I (MPS I)

Mucopolysaccharidosis (MPS) I is a lysosomal storage disorder (LSD) that is characterised by alpha-L-iduronidase (Idua) deficiency and continuous deposition of glycosaminoglycans (GAGs), which consequently interferes with cell signalling mechanisms and results in multisystemic and progressive symptoms. The animal model of MPS I (Idua-/-) has been widely studied to elucidate the consequences and progression of the disorder; however, studies specifically assessing the male reproductive tract are lacking. The aim of this study was to evaluate some of the reproductive characteristics of male MPS I mice in two phases of life. Reproductive organ biometry, sperm counts, sperm morphological evaluation, plasma testosterone measurements and histopathological, histomorphometrical and immunohistochemical analysis were performed in 3- and 6-month-old C57BL/6 Idua+/+ and Idua-/- mice. Seminal vesicle weights were decreased in both the 3- and 6-month-old Idua-/- mice. Decrease in sperm counts and the majority of the histopathological signs were observed in the 6-month-old Idua-/- mice. No differences were detected in the sperm morphological analysis. Immunohistochemistry revealed that seminiferous tubules from 3-month-old Idua-/- mice were more intensely stained with anti-caspase-3 than 3-month-old Idua+/+ mice, but no difference was found at 6 months. These results suggest that MPS I interferes with male reproductive parameters both in 3 and 6-month-old animals and histopathological signs are more pronounced in 6-month-old mice, indicating that the effects of the disorder may intensify with the disease progression.

Phenotyping male infertility in the mouse: how to get the most out of a 'non-performer'

BACKGROUND

Functional male gametes are produced through complex processes that take place within the testis, epididymis and female reproductive tract. A breakdown at any of these phases can result in male infertility. The production of mutant mouse models often yields an unexpected male infertility phenotype. It is with this in mind that the current review has been written. The review aims to act as a guide to the ‘non-reproductive biologist’ to facilitate a systematic analysis of sterile or subfertile mice and to assist in extracting the maximum amount of information from each model.

METHODS

This is a review of the original literature on defects in the processes that take a mouse spermatogonial stem cell through to a fully functional spermatozoon, which result in male infertility. Based on literature searches and personal experience, we have outlined a step-by-step strategy for the analysis of an infertile male mouse line.

RESULTS

A wide range of methods can be used to define the phenotype of an infertile male mouse. These methods range from histological methods such as electron microscopy and immunohistochemistry, to hormone analyses and methods to assess sperm maturation status and functional competence.

CONCLUSION

With the increased rate of genetically modified mouse production, the generation of mouse models with unexpected male infertility is increasing. This manuscript will help to ensure that the maximum amount of information is obtained from each mouse model and, by extension, will facilitate the knowledge of both normal fertility processes and the causes of human infertility.

Male infertility caused by spermiogenic defects: lessons from gene knockouts

Spermiogenesis refers to the process by which postmeiotic spermatids differentiate into elongated spermatids and eventually spermatozoa. During spermiogenesis, round spermatids undergo dynamic morphologic changes, which include nuclear condensation and elongation, formation of flagella and acrosome, reorganization of organelles and elimination of cytoplasm upon spermiation. This cellular differentiation process is unique to male haploid germ cells, which may explain why approximately half of the testis-specific genes are exclusively expressed in spermiogenesis. The spermiogenesis-specific expression implies that these genes contribute to either structural or functional aspects of future sperm. Many such genes have been inactivated in mice and some of these gene knockout mice display male infertility due to nonfunctional sperm which display no or various degrees of structural abnormalities. Since the majority of these spermiogenesis-specific genes are highly conserved between mice and humans, findings from knockout mouse studies may be applicable to human infertility. Here, I briefly review some of these spermatid-specific gene knockouts. The mouse studies strongly suggest that sperm quality rather than quantity is a better indicator of male fertility and novel assays should be developed to determine sperm functionality.

Accumulation of Glucosylceramide in Murine Testis, Caused by Inhibition of β-Glucosidase 2

One of the hallmarks of male germ cell development is the formation of a specialized secretory organelle, the acrosome. This process can be pharmacologically disturbed in C57BL/6 mice, and thus infertility can be induced, by small molecular sugar-like compounds (alkylated imino sugars). Here the biochemical basis of this effect has been investigated. Our findings suggest that in vivo alkylated imino sugars primarily interact with the non-lysosomal glucosylceramidase. This enzyme cleaves glucosylceramide into glucose and ceramide, is sensitive to imino sugars in vitro, and has been characterized as beta-glucosidase 2 (GBA2). Imino sugars raised the level of glucosylceramide in brain, spleen, and testis, in a dose-dependent fashion. In testis, multiple species of glucosylceramide were similarly elevated, those having long acyl chains (C16-24), as well as those with very long polyunsaturated acyl chains (C28-30:5). Both of these GlcCer species were also increased in the testes from GBA2-deficient mice. When considering that the very long polyunsaturated sphingolipids are restricted to germ cells, these results indicate that in the testis GBA2 is present in both somatic and germ cells. Furthermore, in all mouse strains tested imino sugar treatment caused a rise in testicular glucosylceramide, even in a number of strains, of which the males remain fertile after drug administration. Therefore, it appears that acrosome formation can be derailed by accumulation of glucosylceramide in an extralysosomal localization, and that the sensitivity of male germ cells to glucosylceramide is genetically determined.

The sensitivity of murine spermiogenesis to miglustat is a quantitative trait: a pharmacogenetic study

BACKGROUND

A major event in the post-meiotic development of male germ cells is the formation of the acrosome. This process can be perturbed in C57BL/6 mice by administration of the small molecule miglustat (N-butyldeoxynojirimycin, NB-DNJ). The miglustat-treated mice produce morphologically abnormal spermatozoa that lack acrosomes and are poorly motile. In C57BL/6 mice, miglustat can be used to maintain long-term reversible infertility. In contrast, when miglustat was evaluated in normal men, it did not affect spermatogenesis. To gain more insight into this species difference we have now evaluated the reproductive effects of miglustat in rabbits, in multiple mouse strains and in interstrain hybrid mice.

METHODS

Male mice of 18 inbred strains were administered miglustat orally or via miniosmotic pumps. Rabbits were given the compound in their food. Fourth-generation interstrain hybrid mice, bred from C57BL/6 and FVB/N mice (which differ in their response to miglustat), also received the drug. Data on fertility (natural mating), sperm motility and morphology, acrosome status, and serum drug levels were collected.

RESULTS

In rabbits the drug did not induce aberrations of sperm shape or motility, although the serum level of miglustat in rabbits far exceeded the level in C57BL/6 mice (8.4 microM and 0.5 microM, respectively). In some strains of the Swiss and Castle lineages of inbred mice miglustat did not cause infertility, severe morphological sperm aberrations or reduced sperm motility. In these strains miglustat only had milder effects. However, miglustat strongly disturbed acrosome and sperm nucleus development in AKR/J and BALB/c mice and in a number of C57BL/6-related strains. The consequences of drug administration in the interstrain hybrid mice were highly variable. Judging by the number of grossly abnormal spermatozoa, these genetically heterogeneous mice displayed a continuous range of intermediate responses, distinct from either of their parental strains.

CONCLUSION

The effects of miglustat on spermatogenesis in mice are strain-dependent, while in rabbits the drug is ineffective. Evaluation of interstrain hybrid mice indicated that the sensitivity of spermatogenesis to miglustat is a quantitative trait. These studies pave the way for identifying the genetic factors underlying the strain/species differences in the effect of miglustat.