Lanosterol 14alpha-demethylase (CYP51), NADPH-cytochrome P450 reductase and squalene synthase in spermatogenesis: late spermatids of the rat express proteins needed to synthesize follicular fluid meiosis activating sterol

Potential anti-acanthamoebic effects through inhibition of CYP51 by novel quinazolinones

Acanthamoeba spp. are free living amoebae which can give rise to Acanthamoeba keratitis and granulomatous amoebic encephalitis. The surface of Acanthamoeba contains ergosterol which is an important target for drug development against eukaryotic microorganisms. A library of ten functionally diverse quinazolinone derivatives (Q1-Q10) were synthesised to assess their activity against Acanthamoeba castellanii T4. The in-vitro effectiveness of these quinazolinones were investigated against Acanthamoeba castellanii by amoebicidal, excystation, host cell cytopathogenicity, and NADPH-cytochrome c reductase assays. Furthermore, wound healing capability was assessed at different time durations. Maximum inhibition at 50 μg/mL was recorded for compounds Q5, Q6 and Q8, while the compound Q3 did not exhibit amoebicidal effects at tested concentrations. Moreover, LDH assay was conducted to assess the cytotoxicity of quinazolinones against HaCaT cell line. The results of wound healing assay revealed that all compounds are not cytotoxic and are likely to promote wound healing at 10 μg/mL. The excystation assays revealed that these compounds significantly inhibit the morphological transformation of A. castellanii. Compound Q3, Q7 and Q8 elevated the level of NADPH-cytochrome c reductase up to five folds. Sterol 14alpha-demethylase (CYP51) a reference enzyme in ergosterol pathway was used as a potential target for anti-amoebic drugs. In this study using i-Tasser, the protein structure of Acanthamoeba castellanii (AcCYP51) was developed in comparison with Naegleria fowleri protein (NfCYP51) structure. The sequence alignment of both proteins has shown 42.72% identity. Compounds Q1-Q10 were then molecularly docked with the predicted AcCYP51. Out of ten quinazolinones, three compounds (Q3, Q7 and Q8) showed good binding activity within 3 Å of TYR 114. The in-silico study confirmed that these compounds are the inhibitor of CYP51 target site. This report presents several potential lead compounds belonging to quinazolinone derivatives for drug discovery against Acanthamoeba infections.

Cytochrome P450 metabolism of the post-lanosterol intermediates explains enigmas of cholesterol synthesis

Cholesterol synthesis is among the oldest metabolic pathways, consisting of the Bloch and Kandutch-Russell branches. Following lanosterol, sterols of both branches are proposed to be dedicated to cholesterol. We challenge this dogma by mathematical modeling and with experimental evidence. It was not possible to explain the sterol profile of testis in cAMP responsive element modulator tau (Crem τ) knockout mice with mathematical models based on textbook pathways of cholesterol synthesis. Our model differs in the inclusion of virtual sterol metabolizing enzymes branching from the pathway. We tested the hypothesis that enzymes from the cytochrome P450 (CYP) superfamily can participate in the catalysis of non-classical reactions. We show that CYP enzymes can metabolize multiple sterols in vitro, establishing novel branching points of cholesterol synthesis. In conclusion, sterols of cholesterol synthesis can be oxidized further to metabolites not dedicated to production of cholesterol. Additionally, CYP7A1, CYP11A1, CYP27A1, and CYP46A1 are parts of a broader cholesterol synthesis network.

Organization of Membrane Rafts in Chicken Sperm

Being transcriptionally and translationally inactive, sperm must utilize preassembled pathways into specific compartments in which they function to fertilize ovum. Membrane rafts are specific membrane regions enriched in sterols and glycosphingolipids such as ganglioside G_M1 (G_M1) and play an important role in a variety of cellular functions. Recent findings have demonstrated that membrane rafts are present in mammalian sperm and are involved in regulating the induction of acrosome exocytosis. However, no information is available on whether avian sperm possess membrane rafts. Thus, we investigated the organization of membrane rafts in chicken sperm. Our localization experiments for G_M1 and sterols showed that the plasma membrane overlaying the sperm head possesses specific membrane domains enriched in both aforementioned lipids. Caveolin-1, which localizes into membrane rafts in other systems, was localized only to the sperm tail. Based on the biochemical definition that membrane rafts are insoluble membranes when subjected to a Triton X-100 treatment, we isolated detergent-insoluble membranes from chicken sperm and quantified the G_M1 content, which showed an enrichment of G_M1 in the membrane fraction relative to the detergent-soluble fraction. Together with the results of localization and biochemical experiments, we demonstrate for the first time that membrane rafts exist in chicken sperm. Thus, our results provide a foundation for investigating a novel cellular pathway inherent in avian sperm membranes that might be involved in functions necessary to achieve fertilization.

Male germ cell-specific knockout of cholesterogenic cytochrome P450 lanosterol 14α-demethylase (Cyp51)

Cytochrome P450 lanosterol 14α-demethylase (CYP51) and its products, meiosis-activating sterols (MASs), were hypothesized by previous in vitro studies to have an important role in regulating meiosis and reproduction. To test this in vivo, we generated a conditional male germ cell-specific knockout of the gene Cyp51 in the mouse. High excision efficiency of Cyp51 allele in germ cells resulted in 85-89% downregulation of Cyp51 mRNA and protein levels in germ cells. Quantitative metabolic profiling revealed significantly higher levels of CYP51 substrates lanosterol and 24,25-dihydrolanosterol and substantially diminished levels of MAS, the immediate products of CYP51. However, germ cell-specific ablation of Cyp51, leading to lack of MAS, did not affect testicular morphology, daily sperm production, or reproductive performance in males. It is plausible that due to the similar structures of cholesterol intermediates, previously proposed biological function of MAS in meiosis progression can be replaced by some other yet-unidentified functionally redundant lipid molecule(s). Our results using the germ cell-specific knockout model provide first in vivo evidence that the de novo synthesis of MAS and cholesterol in male germ cells is most likely not essential for spermatogenesis and reproduction and that MASs, originating from germ cells, do not cell-autonomously regulate spermatogenesis and fertility.

Sterols in spermatogenesis and sperm maturation

Mammalian spermatogenesis is a complex developmental program in which a diploid progenitor germ cell transforms into highly specialized spermatozoa. One intriguing aspect of sperm production is the dynamic change in membrane lipid composition that occurs throughout spermatogenesis. Cholesterol content, as well as its intermediates, differs vastly between the male reproductive system and nongonadal tissues. Accumulation of cholesterol precursors such as testis meiosis-activating sterol and desmosterol is observed in testes and spermatozoa from several mammalian species. Moreover, cholesterogenic genes, especially meiosis-activating sterol-producing enzyme cytochrome P450 lanosterol 14α-demethylase, display stage-specific expression patterns during spermatogenesis. Discrepancies in gene expression patterns suggest a complex temporal and cell-type specific regulation of sterol compounds during spermatogenesis, which also involves dynamic interactions between germ and Sertoli cells. The functional importance of sterol compounds in sperm production is further supported by the modulation of sterol composition in spermatozoal membranes during epididymal transit and in the female reproductive tract, which is a prerequisite for successful fertilization. However, the exact role of sterols in male reproduction is unknown. This review discusses sterol dynamics in sperm maturation and describes recent methodological advances that will help to illuminate the complexity of sperm formation and function.

Indispensable function for embryogenesis, expression and regulation of the nonspecific form of the 5-aminolevulinate synthase gene in mouse

The first step of heme biosynthesis in animals is catalyzed by 5-aminolevulinate synthase (ALAS), which controls heme supply in various tissues. To clarify the roles that the nonspecific isoform of ALAS (ALAS-N) plays in vivo, we prepared a green fluorescent protein (GFP) knock-in mouse line in which the Alas1 gene (encoding ALAS-N) is replaced with a gfp gene. We found that mice bearing a homozygous knock-in allele (Alas1(GFP/GFP)) were lethal by embryonic day 8.5, demonstrating that ALAS-N is essential for early embryogenesis. Fluorescence microscopic and flow cytometric analyses of heterozygous mouse (Alas1(+/GFP)) tissues showed that the Alas1 expression level differs substantially in tissues; Alas1 is highly expressed in testis Leydig cells, exocrine glands (including submandibular and parotid glands), endocrine glands (such as adrenal and thyroid glands) and hematopoietic lineage cells (including neutrophils and eosinophils). Quantitative analyses of GFP mRNA and ALAS-N mRNA in various tissues of Alas1(+/GFP) mice suggested that the destabilization of ALAS-N mRNA was not uniform in the various tissues. These results thus lay bare that elaborate control of the endogenous heme supply operates in various mouse tissues through regulation of the ALAS-N expression level and that this control is essential for heme homeostasis in animals.

TNF-alpha interferes with lipid homeostasis and activates acute and proatherogenic processes

The interaction between disrupted lipid homeostasis and immune response is implicated in the pathogenesis of several diseases, but the molecular bridges between the major players are still a matter of controversy. Our systemic study of the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in the livers of mice exposed to 20-h cytokine/fasting for the first time shows that TNF-alpha interferes with adaptation to fasting and activates harmful proatherogenic pathways, partially through interaction with the insulin-Insig-sterol regulatory element binding protein (Srebp) signaling pathway. In addition to the increased expression of acute-phase inflammatory genes, the most prominent alterations represent modified lipid homeostasis observed on the gene expression and metabolite levels. These include reduction of HDL-cholesterol, increase of LDL-cholesterol, and elevated expression of cholesterogenic genes, accompanied by increase of potentially harmful precholesterol metabolites and suppression of cholesterol elimination through bile acids, likely by farnesoid X receptor-independent mechanisms. On the transcriptional level, a shift from fatty oxidation toward fatty acid synthesis is observed. The concept of the influence of TNF-alpha on the Srebp regulatory network, followed by downstream effects on sterol metabolism, is novel. Observed acute alterations in lipid metabolism are in agreement with chronic disturbances found in patients.

Cloning of chicken lanosterol 14alpha-demethylase (CYP51) cDNA: discovery of a testis-specific CYP51 transcript

A lanosterol 14alpha-demethylase (CYP51) cDNA, which consisted of a 1419 bp open reading frame encoding 472 amino acids and a 918 bp 3'-untranslated region, was isolated from the chicken testis. The sequence corresponding to exon 1 of this cDNA was completely different from those of CYP51 cDNAs in other tissues, including the liver. The expression level of the CYP51 gene with the testis-specific exon 1 was much higher in mature (2-year-old) male chickens than in immature (5-week-old) chickens. In addition, a CYP51 transcript common to several tissues, including the liver, adrenal gland, cerebellum, cerebrum, lobus opticus, kidney, lung, heart, muscle, spleen, small intestine and ovary, was also detected in the testis by RT-PCR. Furthermore, testis-specific shorter transcripts, which have been observed in mammals such as humans, rats and pigs, were not detected in the chicken testis. The results of this study demonstrate for the first time the presence of a chicken testis-specific CYP51 transcript and its sexual maturation-related expression, although its biological significance remains unclear.

cDNA Cloning, Genomic Structure and Expression Analysis of the Bovine Lanosterol 14.ALPHA.-Demethylase (CYP51) in Gonads

Meiosis activating sterol (MAS), the intermediate of cholesterol biosynthesis, is an important substance to stimulate oocytes maturation in FSH-induced signal transduction pathway. Lanosterol 14alpha-demethylase (CYP51) converts lanosterol to MAS. Although MAS is firstly isolated from bovine testis, the information about bovine CYP51 gene and its expression is little. In present studies, the cDNA cloning, genomic structure, chromosomal mapping, and expression patterns of bovine CYP51 were demonstrated. The cDNA coding bovine CYP51 contains a 1509 bp open reading frame and a 1119 bp 3' untranslated region. And the bovine CYP51 gene includes 10 exons and spans about 17 kb. Screening the cattle RH5000 panel bovine CYP51 is mapped to chromosome 4 (0cR). The sequenced promoter region is TATA-less and contains several highly conserved regulatory elements, such as GC-box, cAMP-responsive elements (CRE), sterol regulatory element (SRE) which is important fragment for its transcription. No evidence of processed pseudogenes is found using long PCR and Southern blot. Northern blot analysis reveals that an approximately 2.7 kb mRNA is expressed in all the examined bovine tissues, while a 1.8 kb mRNA is found only in the mature bovine testis where the MAS is accumulated. Immunochemistry analysis shows that leydig cells express the highest level of the CYP51 protein in testis. Among different stages follicles it is localized primarily to the oocytes with the level varying slightly. Granulosa cells of primordial, primary and secondary follicles show background staining. While granulosa cells facing the antrum and cumulus granulosa cells of antral follicles show considerably heavier staining. The highest level is expressed in corpus lutea. These data indicate a stage- and cell type-specific expression of CYP51 protein in bovine oogenesis.

Resumption of oocyte meiosis in mammals: on models, meiosis activating sterols, steroids and EGF-like factors

De novo synthesis of meiosis activating sterols (MAS) was stimulated by LH- and AY-9944 in rat cultured follicles and cumulus oocyte complexes (COCs), but could not be measured in denuded oocytes. Thus, MAS synthesized by the somatic compartment of the follicle could serve as a signal for the resumption of meiosis. Nevertheless, the delay in germinal vesicle breakdown (GVB) after MAS or AY-9944 stimulation as compared with gonadotropins, obtained by several groups, remains the strongest evidence against the suggested role of MAS as an essential mediator of LH in meiosis resumption. Recently several studies using mammalian COCs in culture have implied that steroids, like in fish and amphibians, serve as signals in mediating the LH/hCG stimulation of meiosis. However, in these studies there was no clear distinction between the requirement for steroids for the acquisition of meiotic competence, oocyte and follicle wellbeing or as a signal for meiotic resumption. Further, some of the authors overlooked earlier studies showing that blocking ovarian or follicular steroidogenesis does not affect GVB, the first step of meiosis resumption. Finally, in vivo and in vitro studies in the rat confirm and extend recent studies showing that locally produced and released EGF-like factors, such as epiregulin, seem to mediate at least part of the LH/hCG actions on oocyte maturation and release of ova at ovulation.

Dual-action hypoglycemic and hypocholesterolemic agents that inhibit glycogen phosphorylase and lanosterol demethylase

Diabetic dyslipidemia requires simultaneous treatment with hypoglycemic agents and lipid-modulating drugs. We recently described glycogen phosphorylase inhibitors that reduce glycogenolysis in cells and lower plasma glucose in ob/ob mice (J. Med. Chem., 41: 2934, 1998). In evaluating the series prototype, CP-320626, in dogs, up to 90% reduction in plasma cholesterol was noted after 2 week treatment. Cholesterol reductions were also noted in ob/ob mice and in rats. In HepG2 cells, CP-320626 acutely and dose-dependently inhibited cholesterolgenesis without affecting fatty acid synthesis. Inhibition occurred together with a dose-dependent increase in the cholesterol precursor, lanosterol, suggesting that cholesterolgenesis inhibition was due to lanosterol 14alpha-demethylase (CYP51) inhibition. In ob/ob mice, acute treatment with CP-320626 resulted in a decrease in hepatic cholesterolgenesis with concomitant lanosterol accumulation, further implicating CYP51 inhibition as the mechanism of cholesterol lowering in these animals. CP-320626 and analogs directly inhibited rhCYP51, and this inhibition was highly correlated with HepG2 cell cholesterolgenesis inhibition (R2 = 0.77). These observations indicate that CP-320626 inhibits cholesterolgenesis via direct inhibition of CYP51, and that this is the mechanism whereby CP-320626 lowers plasma cholesterol in experimental animals. Dual-action glycogenolysis and cholesterolgenesis inhibitors therefore have the potential to favorably affect both the hyperglycemia and the dyslipidemia of type 2 diabetes.

Biochemical diagnosis of Antley-Bixler syndrome by steroid analysis

Antley-Bixler syndrome (ABS, MIM 207410) is a skeletal abnormality syndrome primarily affecting head and limbs. Little is known of the origin of the condition but inactivating mutations in the fibroblast growth factor receptor (FGFR2) has been found in some patients. Genital ambiguity is seen occasionally in this condition, suggesting possible disordered steroidogenesis in early pregnancy. We report the steroid excretion of eight patients diagnosed with the syndrome and one with a related condition, a mild phenotype of the disorder since skeletal and genital abnormalities were not evident. The steroid excretion pattern was consistent and very distinctive in all nine patients. Metabolites of the two primary precursors of steroid hormones, pregnenolone and progesterone, were elevated as were the classical diagnostic metabolites for 17- and 21-hydroxylase deficiencies. Cortisol production was typically within the normal range but generally had blunted response to ACTH. Androgen metabolite excretion tends to be low in patients over 2 months of age, but may be elevated in the newborn period. The metabolome suggested attenuated steroid hydroxylation (including 17,20-lyase activity) although underlying cause is yet to be established. Mutations in CYP17 and CYP21 have not been found and currently the prime suspect is an abnormality in an essential redox partner (P450 oxidoreductase). This paper proposes use of the distinctive steroid metabolome as the primary biochemical parameter for diagnosis of ABS, at least the form not associated with FGFR2 mutations.

Expression of the putative sterol binding protein Stard6 gene is male germ cell specific

Mammalian spermatogenesis is orchestrated by many specific molecular and cellular events. To understand the detailed mechanism by which spermatogenesis is controlled, the specific genes involved in this process must be identified and studied. From the subtracted cDNA library of rat testis prepared using the representational difference analysis (RDA) method, we isolated the cDNA clone of steroidogenic acute regulatory (StAR) protein-related lipid transfer (START) protein 6 (Stard6). Stard6 cDNA consists of 1146 base pairs of nucleotides and has the longest open reading frame, of 227 amino acids. Northern blot analysis revealed Stard6 mRNA to be testis-specific. The mRNA transcript appeared from the third week of postnatal development, and the expression level increased up to adulthood. Moreover, in situ hybridization showed Stard6 mRNA expression to be germ cell-specific and expressed only during the maturation stages of round and elongated spermatids of adult rat testis. Western blot analysis with Stard6 antibody revealed a 28-kDa Stard6 protein only in testis. Immunohistochemistry further confirmed localization of Stard6 protein expressed in mature germ cells, in concert with the in situ hybridization result. Taken together, these results suggest that Stard6, a member of the START protein family, may play a role during germ cell maturation in adult rat testis.

Fluconazole binding and sterol demethylation in three CYP51 isoforms indicate differences in active site topology

14alpha-Demethylase (CYP51) is a key enzyme in all sterol biosynthetic pathways (animals, fungi, plants, protists, and some bacteria), catalyzing the removal of the C-14 methyl group following cyclization of squalene. Based on mutations found in CYP51 genes from Candida albicans azole-resistant isolates obtained after fluconazole treatment of fungal infections, and using site-directed mutagenesis, we have found that fluconazole binding and substrate metabolism vary among three different CYP51 isoforms: human, fungal, and mycobacterial. In C. albicans, the Y132H mutant from isolates shows no effect on fluconazole binding, whereas the F145L mutant results in a 5-fold increase in its IC(50) for fluconazole, suggesting that F145 (conserved only in fungal 14alpha-demethylases) interacts with this azole. In C. albicans, F145L accounts, in part, for the difference in fluconazole sensitivity reported between mammals and fungi, providing a basis for treatment of fungal infections. The C. albicans Y132H and human Y145H CYP51 mutants show essentially no effect on substrate metabolism, but the Mycobacterium tuberculosis F89H CYP51 mutant loses both its substrate binding and metabolism. Because these three residues align in the three isoforms, the results indicate that their active sites contain important structural differences, and further emphasize that fluconazole and substrate binding are uncoupled properties.

Quantitation of lanosterol and its major metabolite FF-MAS in an inhibition assay of CYP51 by azoles with atmospheric pressure photoionization based LC-MS/MS

Azoles affect the steroid balance in all biological systems and may therefore be called endocrine disrupters. Lanosterol 14alpha-demethylase (CYP51) is an enzyme inhibited by azoles. Only few data have been reported showing their inhibitory potency since an assay in an in vitro system is not available so far. In the present work an inhibition assay using human recombinant CYP51, coexpressed with human P450 oxido-reductase by the baculovirus/insect cell expression system, and LC-MS/MS as analytical method is described. Atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI) sources were used with a triple quadrupole mass spectrometer to compare quantitation of lanosterol (substrate) and 4,4-dimethyl-5alpha-cholesta-8,14,24-triene-3beta-ol (FF-MAS) (product of CYP51) with d(6)-2,2,3,4,4,6-cholesterol (d(6)-cholesterol) as internal standard. Optimization of analytical parameters resulted in a LC-APPI-MS/MS method with a LOQ of 10 pg on column for FF-MAS. The sensitivity of the method (LOD 0.5 ng/ml) makes it possible to analyze supernatants of inhibition experiments after precipitation of proteins by isopropanol without any sample enrichment. The coefficient of variation of the analytical method was <20% (n = 5) for FF-MAS, lanosterol and d(6)-cholesterol. The external calibration curve was linear from 1 to 10,000 ng/ml with R(2) >/= 0.999 and an accuracy of 94-115%. Compared with APCI, APPI provides a ten- to 500-fold increase in sensitivity for the analytes in this study. IC(50) values of epoxiconazole and miconazole-two widely used azole fungicides used in agriculture and in human medicine, respectively-were 1.95 microM and 0.057 microM.

Many facets of mammalian lanosterol 14alpha-demethylase from the evolutionarily conserved cytochrome P450 family CYP51

Lanosterol 14alpha-demethylase is a cytochrome P450 enzyme of the cholesterol biosynthetic pathway belonging to the CYP51 gene family which is the most evolutionarily conserved member of the CYP superfamily. Mammalian (human, mouse, rat, pig) CYP51 genes are unique in sharing several common characteristics: highly conserved exon/intron borders and proximal promoter structures, ubiquitous expression at the highest level in the testis, and appearance of testis-specific transcripts that arise from differential polyadenylation site usage. CYP51 protein demethylates lanosterol to form follicular fluid meiosis-activating sterol, FF-MAS, which is, besides being an intermediate of cholesterol biosynthesis, also a signaling sterol that accumulates in ovaries. CYP51 protein resides in the endoplasmatic reticulum of most cells and also in acrosomal membranes of spermatids where transport through the Golgi apparatus is suggested. While sterol regulatory element binding protein (SREBP)-dependent transcriptional regulation of CYP51 contributes to synthesis of cholesterol, the germ-cell-specific cAMP/CREMtau-dependent upregulation might contribute to increased production of MAS.

Is meiosis activating sterol (MAS) an obligatory mediator of meiotic resumption in mammals

In-vitro studies of mouse oocytes have provided evidence that two closely related sterols, subsequently named meiosis-activating sterols (MAS), can overcome the inhibitory effect of hypoxanthine on resumption of meiosis. These sterols are synthesized by cytochrome P450 (CYP) lanosterol 14alpha-demethylase (LDM), a key enzyme in cholesterol biosynthesis. Our studies in the rat with specific inhibitors and molecular approaches did not support the hypothesis that MAS is an obligatory step in the stimulation of the resumption of meiosis. (i) Specific inhibitors of MAS synthesizing enzymes did not prevent spontaneous or LH-stimulated meiosis at doses that have previously been shown to effectively suppress LDM activity. At higher doses, they caused degeneration of oocytes. (ii) The timing of LDM expression in the ovary was incompatible with a role for MAS in meiosis. (iii) The preferential localization of LDM protein in the oocytes suggests MAS production in oocytes, rather than its transport from the somatic compartment as expected by the suggested role of MAS in the regulation of meiosis as a putative cumulus-oocyte signal molecule. (iv) AY-9944, which supposedly increases MAS levels by inhibiting its metabolism, induced the maturation of follicle-enclosed oocytes that was much delayed as compared with gonadotropic stimulation. Thus, the resumption of meiosis induced by added MAS [Biol. Reprod. 61 (1999) 1362, Biol. Reprod. 64 (2001) 418] or presumed endogenous MAS accumulation by AY-9944, resulted in oocyte maturation with remarkably slower kinetics than observed with LH stimulation. This delay in meiosis after MAS stimulation, the studies with LDM inhibitors and its spatial and temporal expression, cast serious doubts whether MAS is indeed mediating the meiosis inducing action of the gonadotropins, as suggested.

Lanosterol 14alpha-demethylase and MAS sterols in mammalian gametogenesis

The lanosterol 14alpha-demethylase protein complex is composed of a cytochrome P450 enzyme CYP51 and its redox partner NADPH cytochrome P450 reductase. The complex participates in cholesterol biosynthesis and produces folicular fluid meiosis activating sterol (FF-MAS) from lanosterol. FF-MAS is metabolized further by sterol Delta14-reductase to testis-meiosis activating sterol (T-MAS). Additional enzymatic steps are needed before cholesterol is produced. Using the anti-human CYP51 antibody we have studied CYP51 protein expression by confocal microscopy in male and female mouse gonads. Leydig cells and acrosomes of spermatids express the highest levels of the CYP51 protein. CYP51 protein is also detected in primary mouse oocytes of non-treated mice and in some granulosa cells. While regulatory mechanisms responsible for FF-MAS accumulation in the ovary are not yet established, two mechanisms contributing to production the of T-MAS in the testis have been found. Potential in vivo roles of FF-MAS and T-MAS in fertilization are discussed.

cAMP response element modulator (CREM): an essential factor for spermatogenesis in primates?

CREM is a cAMP-related transcription factor and alternate promotor usage and splicing generate repressor and activator transcripts of CREM within the testis. CREM activators are highly expressed in post-meiotic haploid germ cells and are essential for spermatid maturation in the mouse model as revealed by gene-targeting studies. Analysis of testicular CREM expression in rodent and monkey species, and in men yielded a highly comparable pattern thus suggesting that CREM is of general importance for spermatid development in the mammalian testis. Also, many CREM target genes have been identified in haploid germ cells. Studies in men with spermatogenic disturbance and spermatid maturation arrest demonstrated abnormal CREM expression and altered splicing events. Collectively, the data strongly argue for an essential role of CREM during spermatid maturation in primates.