Reduced CD5(+) CD24(hi) CD38(hi) and interleukin-10(+) regulatory B cells in active anti-neutrophil cytoplasmic autoantibody-associated vasculitis permit increased circulating autoantibodies.

Pathogenesis of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis is B cell-dependent, although how particular B cell subsets modulate immunopathogenesis remains unknown. Although their phenotype remains controversial, regulatory B cells (Bregs ), play a role in immunological tolerance via interleukin (IL)-10. Putative CD19(+) CD24(hi) CD38(hi) and CD19(+) CD24(hi) CD27(+) Bregs were evaluated in addition to their CD5(+) subsets in 69 patients with ANCA-associated vasculitis (AAV). B cell IL-10 was verified by flow cytometry following culture with CD40 ligand and cytosine-phosphate-guanosine (CpG) DNA. Patients with active disease had decreased levels of CD5(+) CD24(hi) CD38(hi) B cells and IL-10(+) B cells compared to patients in remission and healthy controls (HCs). As IL-10(+) and CD5(+) CD24(hi) CD38(hi) B cells normalized in remission within an individual, ANCA titres decreased. The CD5(+) subset of CD24(hi) CD38(hi) B cells decreases in active disease and rebounds during remission similarly to IL-10-producing B cells. Moreover, CD5(+) B cells are enriched in the ability to produce IL-10 compared to CD5(neg) B cells. Together these results suggest that CD5 may identify functional IL-10-producing Bregs . The malfunction of Bregs during active disease due to reduced IL-10 expression may thus permit ANCA production.

Fertilization defects in sperm from mice lacking fertilin beta.

Fertilin, a member of the ADAM family, is found on the plasma membrane of mammalian sperm. Sperm from mice lacking fertilin beta were shown to be deficient in sperm-egg membrane adhesion, sperm-egg fusion, migration from the uterus into the oviduct, and binding to the egg zona pellucida. Egg activation was unaffected. The results are consistent with a direct role of fertilin in sperm-egg plasma membrane interaction. Fertilin could also have a direct role in sperm-zona binding or oviduct migration; alternatively, the effects on these functions could result from the absence of fertilin activity during spermatogenesis.

Postnatal sex reversal of the ovaries in mice lacking estrogen receptors alpha and beta.

Mice lacking estrogen receptors alpha and beta were generated to clarify the roles of each receptor in the physiology of estrogen target tissues. Both sexes of alphabeta estrogen receptor knockout (alphabetaERKO) mutants exhibit normal reproductive tract development but are infertile. Ovaries of adult alphabetaERKO females exhibit follicle transdifferentiation to structures resembling seminiferous tubules of the testis, including Sertoli-like cells and expression of Müllerian inhibiting substance, sulfated glycoprotein-2, and Sox9. Therefore, loss of both receptors leads to an ovarian phenotype that is distinct from that of the individual ERKO mutants, which indicates that both receptors are required for the maintenance of germ and somatic cells in the postnatal ovary.

Brca1 and Brca2 expression patterns in mitotic and meiotic cells of mice.

The mouse homologues of the breast cancer susceptibility genes, Brca1 and Brca2, are expressed in a cell cycle-dependent fashion in vitro and appear to be regulated by similar or overlapping pathways. Therefore, we compared the non isotopic in situ hybridization expression patterns of Brca1 and Brca2 mRNA in vivo in mitotic and meiotic cells during mouse embryogenesis, mammary gland development, and in adult tissues including testes, ovaries, and hormonally altered ovaries. Brca1 and Brca2 are expressed concordantly in proliferating cells of embryos, and the mammary gland undergoing morphogenesis and in most adult tissues. The expression pattern of Brca1 and Brca2 correlates with the localization of proliferating cell nuclear antigen, an indicator of proliferative activity. In the ovary, Brca1 and Brca2 exhibited a comparable hormone-independent pattern of expression in oocytes, granulosa cells and thecal cells of developing follicles. In the testes, Brca1 and Brca2 were expressed in mitotic spermatogonia and early meiotic prophase spermatocytes. Northern analyses of prepubertal mouse testes revealed that the time course of Brca2 expression was delayed in spermatogonia relative to Brca1. Thus, while Brca1 and Brca2 share concordant cell-specific patterns of expression in most proliferating tissues, these observations suggest that they may have distinct roles during meiosis.

Prevention of the polycystic ovarian phenotype and characterization of ovulatory capacity in the estrogen receptor-alpha knockout mouse.

Ovarian-derived estradiol plays a critical endocrine role in the regulation of gonadotropin synthesis and secretion from the hypothalamic-pituitary axis. In turn, several para/autocrine effects of estrogen within the ovary are known, including increased ovarian weight, stimulation of granulosa cell growth, augmentation of FSH action, and attenuation of apoptosis. The estrogen receptor-alpha (ERalpha) is present in all three components of the hypothalamic-pituitary-ovarian axis of the mouse. In contrast, estrogen receptor-beta (ERbeta) is easily detectable in ovarian granulosa cells but is low to absent in the pituitary of the adult mouse. This distinct expression pattern for the two ERs suggests the presence of separate roles for each in the regulation of ovarian function. Herein, we definitively show that a lack of ERalpha in the hypothalamic-pituitary axis of the ERalpha-knockout (alphaERKO) mouse results in chronic elevation of serum LH and is the primary cause of the ovarian phenotype of polycystic follicles and anovulation. Prolonged treatment with a GnRH antagonist reduced serum LH levels and prevented the alphaERKO cystic ovarian phenotype. To investigate a direct role for ERalpha within the ovary, immature alphaERKO females were stimulated to ovulate with exogenous gonadotropins. Ovulatory capacity in the immature alphaERKO female was reduced compared with age-matched wild-type (14.5+/-2.9 vs. 40.6+/-2.6 oocytes/animal, respectively); however, oocytes collected from the alphaERKO were able to undergo successful in vitro fertilization. A similar discrepancy in oocyte yield was observed after superovulation of peripubertal (42 days) wild-type and alphaERKO females. In addition, ovaries from immature superovulated alphaERKO females possessed several ovulatory but unruptured follicles. Investigations of the possible reasons for the reduced number of ovulations in the alphaERKO included ribonuclease protection assays to assess the mRNA levels of several markers of follicular maturation and ovulation, including ERbeta, LH-receptor, cyclin-D2, P450-side chain cleavage enzyme, prostaglandin synthase-2, and progesterone receptor. No marked differences in the expression pattern for these mRNAs during the superovulation regimen were observed in the immature alphaERKO ovary compared with that of the wild-type. Serum progesterone levels just before ovulation were slightly lower in the alphaERKO compared with wild-type. These studies indicate that treatment of alphaERKO females with a GnRH antagonist decreased the serum LH levels to within the wild-type range and concurrently prevented development of the characteristic ovarian phenotype of cystic and hemorrhagic follicles. Furthermore, a lack of functional ERalpha within the ovary had no effect on the regulation of several genes required for follicular maturation and ovulation. However, the reduced numbers of ovulations following the administration of exogenous gonadotropins in the alphaERKO suggests an intraovarian role for ERalpha in follicular development and ovulation.

Targeted disruption of the estrogen receptor gene in male mice causes alteration of spermatogenesis and infertility.

The reproductive system of male mice homozygous for a mutation in the estrogen receptor (ER) gene (ER knock-out; ERKO) appears normal at the anatomical level. However, these males are infertile, indicating an essential role for ER-mediated processes in the regulation of male reproduction. Adult ERKO male mice have significantly fewer epididymal sperm than heterozygous or wild-type males. Although spermatogenesis is occurring in some seminiferous tubules of 3- to 5-month-old ERKO males, other tubules either have a dilated lumen and a disorganized seminiferous epithelium with few spermatogenic cells or lack a lumen and contain mainly Sertoli cells. There are no obvious differences in seminiferous tubules at 10 days of age between wild-type and ERKO mice, but the lumen in ERKO males is dilated in all seminiferous tubules by 20 days. However, spermatogenesis progresses and similar numbers of sperm are present in the cauda epididymis of ERKO and wild-type males until 10 weeks of age. Disruption of spermatogenesis and degeneration of the seminiferous tubules become apparent after 10 weeks in the caudal pole of the testis and progresses in a wave to the cranial pole by 6 months. However, the seminal vesicles, coagulating glands, prostate, and epididymis do not appear to be altered morphologically in ERKO mice. Serum testosterone levels are somewhat elevated, but LH and FSH levels are not significantly different from those in wild-type males. Sperm from 8- to 16-week-old mice have reduced motility and are ineffective at fertilizing eggs in vitro. In addition, ERKO males housed overnight with hormone-primed wild-type females produce significantly fewer copulatory plugs than do heterozygous or wild-type males. These results suggest that estrogen action is required for fertility in male mice and that the mutation of the ER in ERKO males leads to reduced mating frequency, low sperm numbers, and defective sperm function.

Human glyceraldehyde 3-phosphate dehydrogenase-2 gene is expressed specifically in spermatogenic cells.

Although the process of glycolysis is highly conserved in eukaryotes, several glycolytic enzymes have unique structural or functional features in spermatogenic cells. We previously identified and characterized the mouse complementary DNA (cDNA) and a gene for 1 of these enzymes, glyceraldehyde 3-phosphate dehydrogenase-s (Gapds). This gene is expressed only in spermatids. The enzyme appears to have an essential role in energy production required for fertilization, and it is reported to be susceptible to inhibition by certain environmental chemicals. We have now cloned and sequenced the cDNA for the human homologue of glyceraldehyde 3-phosphate dehydrogenase (GAPD2) and determined the structure of the gene. The messenger RNA (mRNA) was detected in testis, but not in 15 other human tissues analyzed by Northern blot technique. The deduced GAPD2 protein contains 408 amino acids and is 68% identical with somatic cell GAPD. GAPD2 has a 72-amino acid segment at the amino terminal end that is not present in somatic cell GAPD. This segment is proline-rich but contains smaller stretches of polyproline and is 30 amino acids shorter than the comparable segment of mouse GAPDS. The structure of the human GAPD2 gene was determined by polymerase chain reaction (PCR) to identify exon-intron junctions in a genomic clone and in total genomic DNA. The locations of these junctions in the GAPD2 gene corresponded precisely to those of the 11 exon-intron junctions in the mouse Gapds gene. Immunohistochemical studies found that GAPD2 is located in the principal piece of the flagellum of human spermatozoa, as are GAPDS in mouse and rat spermatozoa. GAPD2 extracted from human spermatozoa and analyzed by Western blot technique migrated with an apparent molecular weight of approximately 56,000, although the calculated molecular weight is 44 501. The conserved nature of the mouse, rat, and human enzymes suggests that they serve similar roles in these and other mammalian species.

Mapping of myeloperoxidase epitopes recognized by MPO-ANCA using human-mouse MPO chimers.

Myeloperoxidase (MPO) is one of the major target antigens of antineutrophil cytoplasmic autoantibodies (ANCA) found in patients with small-vessel vasculitis and pauci-immune necrotizing glomerulonephritis. To date, the target epitopes of MPO-ANCA remain poorly defined. Human MPO-ANCA do not typically bind mouse MPO. We utilized the differences between human and mouse MPO to identify the target regions of MPO-ANCA. We generated five chimeric MPO molecules in which we replaced different segments of the human or mouse molecules with their homologous counterpart from the other species. Of serum samples from 28 patients screened for this study, 43 samples from 14 patients with MPO-ANCA-associated vasculitis were tested against recombinant human and mouse MPO and the panel of chimeric molecules. Sera from 64 and 71% of patients bound to the carboxy-terminus of the heavy chain, in the regions of amino acids 517-667 or 668-745, respectively. No patient serum bound the MPO light chain or the amino-terminus of the heavy chain. All sera bound to only one or two regions of MPO. Although the pattern of MPO-ANCA binding changed over time (4-27 months) in 6 of 10 patients with several serum samples, such changes were infrequent. Other target regions of MPO-ANCA may not have been detected due to conformational differences between the native and recombinant forms of MPO. MPO-ANCA do not target a single epitope, but rather a small number of regions of MPO, primarily in the carboxy-terminus of the heavy chain.

Generation of a mouse sperm membrane fraction with zona receptor activity.

To identify mouse sperm components involved in primary sperm binding to zonae pellucidae, a mouse sperm plasma membrane-enriched fraction was generated using a vortex method. The crude membrane fraction recovered after vortexing was resolved into three bands and a pellet by centrifugation on a discontinuous sucrose gradient. Ultrastructural analysis indicated that Bands 2 and 3 were composed predominantly of membranes, although Band 3 was contaminated with mitochondria; Band 1 and the gradient pellet contained insufficient material and were unsuitable for ultrastructural analysis. To determine where plasma membranes migrate in the gradient, sperm were labeled vectorially with 125I; subsequently, membrane fractions were analyzed by SDS-PAGE and autoradiography. Band 2 was enriched threefold in radiolabel when compared with Band 3. Examination of intact and vortexed sperm stained with regionally distributed anti-mouse sperm monoclonal antibodies revealed that vortexing removed anterior head plasma membrane preferentially. Bioactivity, defined as the ability to inhibit primary sperm binding to the zona pellucida in a concentration-dependent manner, was contained in the crude membrane fraction and Band 2 exclusively, with inhibition of 53% and 44%, respectively, at the maximum concentration tested. Band 3 exhibited no significant bioactivity. We conclude from these results that a plasma membrane-enriched fraction, Band 2, isolated from mouse cauda epididymal sperm, exhibits zona pellucida receptor activity.

Glyceraldehyde 3-phosphate dehydrogenase-S protein distribution during mouse spermatogenesis.

The spermatogenic cell-specific isoform of glyceraldehyde 3-phosphate dehydrogenase (GAPD-S) may regulate glycolysis and energy production required for sperm motility. Although the steady-state level of Gapd-s mRNA is maximal at step 9 of mouse spermatogenesis, GAPD-S protein was not detected by immunohistochemistry until steps 12-13. This result suggests that Gapd-s is translationally regulated. Western blot analysis of isolated germ cells confirmed that GAPD-S is not detected in pachytene spermatocytes or round spermatids. A major immunoreactive protein migrating with a molecular weight (M(r)) of 69,200 was observed in condensing spermatids and cauda sperm. Additional minor proteins that migrated at M(r) 55,200, 32,500, and 27,500 were detected in sperm. The molecular weight of GAPD-S is higher than the predicted molecular weight of 47,445, apparently due to a proline-rich 105-amino acid domain at the N-terminus. Recombinant GAPD-S protein lacking the proline-rich region migrated at M(r) 38,250, comparably to somatic GAPD, which also lacks the proline-rich domain. Indirect immunofluorescence demonstrated that GAPD-S is restricted to the principal piece in the sperm flagellum. Western blot analysis indicated that GAPD-S is tightly associated with the fibrous sheath of the flagellum, consistent with a potential role in regulating sperm motility.

BRCA2-null embryonic survival is prolonged on the BALB/c genetic background.

Women who inherit mutations in the BRCA2 cancer susceptibility gene have an 85% chance of developing breast cancer. The function of the BRCA2 gene remains elusive, but there is evidence to support its role in transcriptional transactivation, tumor suppression, and the maintenance of genomic integrity. Individuals with identical BRCA2 mutations display a different distribution of cancers, suggesting that there are low-penetrance genes that can modify disease outcome. We hypothesized that genetic background could influence embryonic survival of a Brca2 mutation in mice. Brca2-null embryos with a 129/SvEv genetic background (129(B2-/-)) died before embryonic day 8. 5. Transfer of this Brca2 mutation onto the BALB/cJ genetic background (BALB/c(B2-/-)) extended survival to embryonic day 10.5. These results indicate that the BALB/c background harbors genetic modifiers that can prolong Brca2-null embryonic survival. The extended survival of BALB/c(B2-/-) embryos enabled us to ask whether transcriptional regulation of the Brca1 and Brca2 genes is interdependent. The interdependence of Brca1 and Brca2 was evaluated by studying Brca2 gene expression in BALB/c(B1-/-) embryos and Brca1 gene expression in BALB/c(B2-/-) embryos. Nonisotopic in situ hybridization demonstrated that Brca2 transcript levels were comparable in BALB/c(B1-/-) embryos and wild-type littermates. Likewise, reverse transcriptase-polymerase chain reactions confirmed Brca1 mRNA expression in embryonic day 8.5 BALB/c(B2-/-) embryos that was comparable to Brca2-heterozygous littermates. Thus, the Brca1 and Brca2 transcripts are expressed independently of one another in Brca1- and Brca2-null embryos. Mol. Carcinog. 28:174-183, 2000.