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The paternal environment has been linked to infertility and negative outcomes. Such effects may be transmitted via sperm through histone modifications. To date, in-depth profiling of the sperm chromatin in men has been limited. Here, we use deep sequencing to characterize the sperm profiles of histone H3 lysine 4 tri-methylation (H3K4me3) and DNA methylation in a representative reference population of 37 men. Our analysis reveals that H3K4me3 is localized throughout the genome and at genes for fertility and development. Remarkably, enrichment is also found at regions that escape epigenetic reprogramming in primordial germ cells, embryonic enhancers, and short-interspersed nuclear elements (SINEs). There is significant overlap in H3K4me3 and DNA methylation throughout the genome, suggesting a potential interplay between these marks previously reported to be mutually exclusive in sperm. Comparisons made between H3K4me3 marked regions in sperm and the embryonic transcriptome suggest an influence of paternal chromatin on embryonic gene expression.

In clinical exome/genome sequencing, the American College of Medical Genetics and Genomics (ACMG) recommends reporting of secondary findings unrelated to a patient's phenotype when pathogenic single-nucleotide variants (SNVs) are observed in one of 59 genes associated with a life-threatening, medically actionable condition. Little is known about the incidence and sensitivity of chromosomal microarray analysis (CMA) for detection of pathogenic copy number variants (CNVs) comprising medically-actionable genes. Clinical CMA has been performed on 8865 individuals referred for molecular cytogenetic testing. We retrospectively reviewed the CMA results to identify patients with CNVs comprising genes included in the 59-ACMG list of secondary findings. We evaluated the clinical significance of these CNVs in respect to pathogenicity, phenotypic manifestations, and heritability. We identified 23 patients (0.26%) with relevant CNV either deletions comprising the entire gene or intragenic alterations involving one or more secondary findings genes. A number of patients and/or their family members with pathogenic CNVs manifest or expected to develop an anticipated clinical phenotype and would benefit from preventive management similar to the patients with pathogenic SNVs. To improve patients' care standardization should apply to reporting of both sequencing and CNVs obtained via clinical genome-wide analysis, including chromosomal microarray and exome/genome sequencing.

Whole exome sequencing (WES) is an emerging technique in prenatal diagnosis. In this retrospective study, we examined diagnostic utility and limitations of WES in prenatal cases with structural birth defects. DNA from 20 trios (fetal and parental), with normal karyotype and microarray findings, underwent WES and variant interpretation at a reference laboratory. The WES results were later re-evaluated in our academic center utilizing prenatal and postnatal phenotyping. Initial analysis using only prenatal ultrasound findings revealed no pathogenic or likely pathogenic variants in 20 pregnancies with structural birth defects. Re-analysis of WES variants and combination of prenatal and postnatal phenotyping yielded pathogenic variants in at least 20% of cases including PORCN gene in a fetus with split-hand/foot malformation, as well as variants of uncertain significance in NEB and NOTCH1 in fetuses with postnatal muscle weakness and Adams-Oliver syndrome, respectively. Furthermore, Sanger sequencing in a patient with holoprosencephaly, elucidated by postnatal MRI, revealed a pathogenic 47-base pairs deletion in ZIC2 which was missed by prenatal WES. This study suggests that incomplete prenatal phenotyping and lack of prenatal ultrasound-genotype databases are the limiting factors for current interpretation of WES data in prenatal diagnosis. Development of prenatal phenotype-genotype databases would significantly help WES interpretation in this setting. Patients who underwent prenatal clinical WES may benefit from the re-analysis based on detailed postnatal findings.

STUDY QUESTION Do paternal exposures to folic acid deficient (FD), and/or folic acid supplemented (FS) diets, throughout germ cell development adversely affect male germ cells and consequently offspring health outcomes? SUMMARY ANSWER Male mice exposed over their lifetimes to both FD and FS diets showed decreased sperm counts and altered imprinted gene methylation with evidence of transmission of adverse effects to the offspring, including increased postnatal-preweaning mortality and variability in imprinted gene methylation. WHAT IS KNOWN ALREADY There is increasing evidence that disruptions in male germ cell epigenetic reprogramming are associated with offspring abnormalities and intergenerational disease. The fetal period is the critical time of DNA methylation pattern acquisition for developing male germ cells and an adequate supply of methyl donors is required. In addition, DNA methylation patterns continue to be remodeled during postnatal spermatogenesis. Previous studies have shown that lifetime (prenatal and postnatal) folic acid deficiency can alter the sperm epigenome and increase the incidence of fetal morphological abnormalities. STUDY DESIGN, SIZE, DURATION Female BALB/c mice (F0) were placed on one of four amino-acid defined diets for 4 weeks before pregnancy and throughout pregnancy and lactation: folic acid control (Ctrl; 2 mg/kg), 7-fold folic acid deficient (7FD; 0.3 mg/kg), 10-fold high FS (10FS, 20 mg/kg) or 20-fold high FS (20FS, 40 mg/kg) diets. F1 males were weaned to their respective prenatal diets to allow for diet exposure during all windows of germline epigenetic reprogramming: the erasure, re-establishment and maintenance phases. PARTICIPANTS/MATERIALS, SETTINGS, METHODS F0 females were mated with chow-fed males to produce F1 litters whose germ cells were exposed to the diets throughout embryonic development. F1 males were subsequently mated with chow-fed female mice. Two F2 litters, unexposed to the experimental diets, were generated from each F1 male; one litter was collected at embryonic day (E)18.5 and one delivered and followed postnatally. DNA methylation at a global level and at the differentially methylated regions of imprinted genes (H19, Imprinted Maternally Expressed Transcript (Non-Protein Coding)-H19, Small Nuclear Ribonucleoprotein Polypeptide N-Snrpn, KCNQ1 Opposite Strand/Antisense Transcript 1 (Non-Protein Coding)-Kcnq1ot1, Paternally Expressed Gene 1-Peg1 and Paternally Expressed Gene 3-Peg3) was assessed by luminometric methylation analysis and bisulfite pyrosequencing, respectively, in F1 sperm, F2 E18.5 placenta and F2 E18.5 brain cortex. MAIN RESULTS AND THE ROLE OF CHANCE F1 males exhibited lower sperm counts following lifetime exposure to both folic acid deficiency and the highest dose of folic acid supplementation (20FS), (both P < 0.05). Post-implantation losses were increased amongst F2 E18.5 day litters from 20FS exposed F1 males (P < 0.05). F2 litters derived from both 7FD and 20FS exposed F1 males had significantly higher postnatal-preweaning pup death (both P < 0.05). Sperm from 10FS exposed males had increased variance in methylation across imprinted gene H19, P < 0.05; increased variance at a few sites within H19 was also found for the 7FD and 20FS groups (P < 0.05). While the 20FS diet resulted in inter-individual alterations in methylation across the imprinted genes Snrpn and Peg3 in F2 E18.5 placenta, ≥50% of individual sites tested in Peg1 and/or Peg3 were affected in the 7FD and 10FS groups. Inter-individual alterations in Peg1 methylation were found in F2 E18.5 day 10FS group brain cortex (P < 0.05). LARGE SCALE DATA Not applicable. LIMITATIONS REASONS FOR CAUTION The cause of the increase in postnatal-preweaning mortality was not investigated post-mortem. Further studies are required to understand the mechanisms underlying the adverse effects of folic acid deficiency and supplementation on developing male germ cells. Genome-wide DNA and histone methylome studies as well as gene expression studies are required to better understand the links between folic acid exposures, an altered germ cell epigenome and offspring outcomes. WIDER IMPLICATIONS OF THE FINDINGS The findings of this study provide further support for paternally transmitted environmental effects. The results indicate that both folic acid deficiency and high dose supplementation can be detrimental to germ cell development and reproductive fitness, in part by altering DNA methylation in sperm. STUDY FUNDING AND COMPETING INTERESTS This study was supported by a grant to J.M.T. from the Canadian Institutes of Health Research (CIHR #89944). The authors declare they have no conflicts of interest.

Background: The sperm DNA methylation landscape is unique and critical for offspring health. If gamete-derived DNA methylation escapes reprograming in early embryos, epigenetic defects in sperm may be transmitted to the next generation. Current techniques to assess sperm DNA methylation show bias toward CpG-dense regions and do not target areas of dynamic methylation, those predicted to be environmentally sensitive and tunable regulatory elements. Objectives: Our goal was to assess variation in human sperm DNA methylation and design a targeted capture panel to interrogate the human sperm methylome. Methods: To characterize variation in sperm DNA methylation, we performed whole genome bisulfite sequencing (WGBS) on an equimolar pool of sperm DNA from a wide cross section of 30 men varying in age, fertility status, methylenetetrahydrofolate reductase (MTHFR) genotype, and exposures. With our targeted capture panel, in individual samples, we examined the effect of MTHFR genotype (n=13 677CC, n=8 677TT), as well as high-dose folic acid supplementation (n=6, per genotype, before and after supplementation). Results: Through WGBS we discovered nearly 1 million CpGs possessing intermediate methylation levels (20–80%), termed dynamic sperm CpGs. These dynamic CpGs, along with 2 million commonly assessed CpGs, were used to customize a capture panel for targeted interrogation of the human sperm methylome and test its ability to detect effects of altered folate metabolism. As compared with MTHFR 677CC men, those with the 677TT genotype (50% decreased MTHFR activity) had both hyper- and hypomethylation in their sperm. High-dose folic acid supplement treatment exacerbated hypomethylation in MTHFR 677TT men compared with 677CC. In both cases, >80% of altered methylation was found in dynamic sperm CpGs, uniquely measured by our assay. Discussion: Our sperm panel allowed the discovery of differential methylation following conditions affecting folate metabolism in novel dynamic sperm CpGs. Improved ability to examine variation in sperm DNA methylation can facilitate comprehensive studies of environment–epigenome interactions. https://doi.org/10.1289/EHP4812

Supplementation with high doses of folic acid, an important mediator of one-carbon transfers for DNA methylation, is used clinically to improve sperm parameters in infertile men. We recently detected an unexpected loss of DNA methylation in the sperm of idiopathic infertile men after 6 months of daily supplementation with 5 mg folic acid (>10× the daily recommended intake—DRI), exacerbated in men homozygous for a common variant in the gene encoding an important enzyme in folate metabolism, methylenetetrahydrofolate reductase (MTHFR 677C>T). To investigate the epigenomic impact and mechanism underlying effects of folic acid on male germ cells, wild-type and heterozygote mice for a targeted inactivation of the Mthfr gene were fed high-dose folic acid (10× the DRI) or control diets (CDs) for 6 months. No changes were detected in general health, sperm counts or methylation of imprinted genes. Reduced representation bisulfite sequencing revealed sperm DNA hypomethylation in Mthfr(+/−) mice on the 10× diets. Wild-type mice demonstrated sperm hypomethylation only with a very high dose (20×) of folic acid for 12 months. Testicular MTHFR protein levels decreased significantly in wild-type mice on the 20× diet but not in those on the 10× diet, suggesting a possible role for MTHFR deficiency in sperm DNA hypomethylation. In-depth analysis of the folic acid-exposed sperm DNA methylome suggested mouse/human susceptibility of sequences with potential importance to germ cell and embryo development. Our data provide evidence for a similar cross-species response to high dose folic acid supplementation, of sperm DNA hypomethylation, and implicate MTHFR downregulation as a possible mechanism.

Postacrosomal sheath WW domain-binding protein (PAWP) is a novel sperm protein identified as a candidate sperm-borne, oocyte-activating factor (SOAF). However, regulation of PAWP gene expression is poorly understood. Therefore, we examined the PAWP gene expression across different stages of mouse embryonic stem cell (ESC)-based spermatogenesis in vitro and compared this expression at different stages of mouse testis development in vivo. Expression of PAWP was also examined in mouse embryonic fibroblasts (MEF), Sertoli cell, and the NIH3T3 cancerous cell line. We used a transgenic mouse ESC line C57BL/6J expressing Stra8-EGFP that was plated in murine ESC medium. To induce differentiation, cells were cultured on gelatin-coated medium with Retinoic Acid (RA) treatment. We applied reverse transcription-PCR and real-time PCR to analyze the differential expression of PAWP mRNA during different stages of mouse ESC differentiation in vitro parallel with mouse testis development in vivo and in cell lines. We found that expression of PAWP is increased during testis development in vivo with greatest expression at postmeiotic phase. It is also highly expressed in mouse ESC-derived germ-like cells after 30 d of RA induction in vitro. PAWP is remarkably expressed in mouse ESC and NIH3T3 cell line. These results indicate that PAWP plays a role in spermatogenesis and germ cell development. Moreover, we suggest PAWP as one of the markers that could be looked in ESC studies as a confirmed testis-specific gene. We also suggest an additional possible role for PAWP in proliferation of cancerous cell in general.

Background Cancer–testis genes are a group of genes expressed in testicular germinal cells and a range of human cancers. Testis-specific gene A10 (TSGA10) is expressed in testis and actively dividing and fetal differentiating tissues. Mouse homologue (Tsga10) mRNA is translated to a 65kDa protein and appears to be processed to a major fibrous sheath protein of sperm tail. SYCP3 gene is supposed to be a testis-specific gene and constitutes the core of the lateral elements of synaptonemal complex. It has role in regulating DNA binding to the chromatid axis, sister chromatid cohesion, synapsis, and recombination. Methods In this study expression of TSGA10 and SYCP3 were investigated in different cancers (156 tumor samples) using RT-PCR. Diagnosis of cancer was based on histopathological reports. The association with histopathological characteristics of tumors was analyzed using statistical programs. Results TSGA10 expression was observed in 83% of brain tumors, 66% of breast cancers, 58% of gastrointestinal tumors, 66% of skin tumors and 53% of soft tissue tumors. But, SYCP3 transcripts were found in four tumor samples (moderately differentiated gemistocytic astrocytoma, pituitary adenoma, glioma and an ovarian tumor). Conclusion These results may get further insight into TSGA10, but not SYCP3, potential role as a cancer marker and a cancer testis gene implicated in tumorogenesis of cancers.

Dietary folate is a major source of methyl groups required for DNA methylation, an epigenetic modification that is actively maintained and remodeled during spermatogenesis. While high-dose folic acid supplementation (up to 10 times the daily recommended dose) has been shown to improve sperm parameters in infertile men, the effects of supplementation on the sperm epigenome are unknown. To assess the impact of 6 months of high-dose folic acid supplementation on the sperm epigenome, we studied 30 men with idiopathic infertility. Blood folate concentrations increased significantly after supplementation with no significant improvements in sperm parameters. Methylation levels of the differentially methylated regions of several imprinted loci (H19, DLK1/GTL2, MEST, SNRPN, PLAGL1, KCNQ1OT1) were normal both before and after supplementation. Reduced representation bisulfite sequencing (RRBS) revealed a significant global loss of methylation across different regions of the sperm genome. The most marked loss of DNA methylation was found in sperm from patients homozygous for the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, a common polymorphism in a key enzyme required for folate metabolism. RRBS analysis also showed that most of the differentially methylated tiles were located in DNA repeats, low CpG-density and intergenic regions. Ingenuity Pathway Analysis revealed that methylation of promoter regions was altered in several genes involved in cancer and neurobehavioral disorders including CBFA2T3, PTPN6, COL18A1, ALDH2, UBE4B, ERBB2, GABRB3, CNTNAP4 and NIPA1. Our data reveal alterations of the human sperm epigenome associated with high-dose folic acid supplementation, effects that were exacerbated by a common polymorphism in MTHFR.

Objective To determine the expression of the synaptonemal complex protein-3 ( SYCP3 ) gene in men with nonobstructive azoospermia. Design Cross-sectional case study. Setting Avesina Infertility Clinic, Tehran, Iran. Patient(s) One hundred and ten consecutive infertile men presenting nonobstructive azoospermia. Intervention(s) Testicular biopsies for histopathological assessment and analyses of SYCP3 expression level by semiquantitative nested reverse transcription–polymerase chain reaction (RT-PCR). The SYCP3 levels were normalized to expression of the housekeeping phosphoglucomutase 1 gene. Main Outcome Measure(s) Expression of SYCP3 messenger ribonucleic acid (mRNA). Correlation of the histopathological findings with SYCP3 expression levels. Results(s) Testicular SYCP3 mRNA expression was observed in 67/110 (60.9%) patients. The expression level correlated with the degree of spermatogenic failure. Although it was expressed in patients with spermatogenesis and maturation arrest, a lack of expression was seen in all of those men with spermatogonial arrest, Sertoli cell-only syndrome, and testicular atrophy. Conclusion(s) These data indicate that SYCP3 is expressed in human testis and is restricted to germ cells. Our findings, in association with those obtained in experimental animals, shows that lack of SYCP3 expression in human testis may have a negative effect on spermatogenesis and male fertility.

Objective To determine the levels of postacrosomal WW binding protein (PAWP) in the spermatozoa of men that were used clinically for intracytoplasmic sperm injection (ICSI) and to correlate them with infertility treatment outcomes. Design Prospective clinical and laboratory study. Setting University-based laboratory and infertility clinic. Patient(s) Men undergoing ICSI for the treatment of couples' infertility (n = 110). Intervention(s) Quantitative analysis of sperm PAWP levels by flow cytometry and developmental analysis of PAWP expression by immunoblotting, immunofluorescence, and immunohistochemistry. Main Outcome Measure(s) PAWP flow-cytometric levels and immunolocalization in spermatozoa. Result(s) A strong positive correlation was found between PAWP expression levels and fertilization rates after ICSI, with high levels of PAWP being associated with higher fertilization rates; the positive correlation was independent of age, DNA fragmentation index, and other sperm parameters. PAWP expression levels were correlated with embryonic development, with high levels of PAWP being associated with a lower number of arrested embryos within 3–5 days post-ICSI. PAWP expression was detected during the late stages of human spermiogenesis in elongating spermatids, confirming previous findings in various animal models. Conclusion(s) Our clinical data from infertile couples demonstrate significant correlations between sperm PAWP levels and both fertilization rates and normal embryonic development after ICSI. Considering its proposed role in the initiation of oocyte activation, we suggest that PAWP could have potential applications in the diagnosis and treatment of infertility.

Phospholipase C zeta (PLCζ) is a candidate sperm-borne oocyte activating factor (SOAF) which has recently received attention as a potential biomarker of human male infertility. However, important SOAF attributes of PLCζ, including its developmental expression in mammalian spermiogenesis, its compartmentalization in sperm head perinuclear theca (PT) and its release into the ooplasm during fertilization have not been established and are addressed in this investigation. Different detergent extractions of sperm and head/tail fractions were compared for the presence of PLCζ by immunoblotting. In both human and mouse, the active isoform of PLCζ was detected in sperm fractions other than PT, where SOAF is expected to reside. Developmentally, PLCζ was incorporated as part of the acrosome during the Golgi phase of human and mouse spermiogenesis while diminishing gradually in the acrosome of elongated spermatids. Immunofluorescence localized PLCζ over the surface of the postacrosomal region of mouse and bull and head region of human spermatozoa leading us to examine its secretion in the epididymis. While previously thought to have strictly a testicular expression, PLCζ was found to be expressed and secreted by the epididymal epithelial cells explaining its presence on the sperm head surface. In vitro fertilization (IVF) revealed that PLCζ is no longer detectable after the acrosome reaction occurs on the surface of the zona pellucida and thus is not incorporated into the oocyte cytoplasm for activation. In summary, we show for the first time that PLCζ is compartmentalized as part of the acrosome early in human and mouse spermiogenesis and is secreted during sperm maturation in the epididymis. Most importantly, no evidence was found that PLCζ is incorporated into the detergent-resistant perinuclear theca fraction where SOAF resides.

Perinuclear antineutrophil cytoplasmic autoantibodies (pANCA) and anti-Saccharomyces Cerevisiae antibody (ASCA) are potential markers for diagnosis of inflammatory bowel disease (IBD). The aim of the present study was to evaluate the diagnostic value of pANCA and ASCA in Iranian patients with IBD.Serum samples were collected from 144 patients with IBD (113 ulcerative colitis and 31 Crohn's disease) and patients with non-IBD problems were assayed for ASCA by Enzyme-Linked Immunosorbent Assay (ELISA) and for pANCA by indirect immunofluorescence assay.Sensitivity and specificity of pANCA in UC were 39.8% and 82.1%, respectively. For CD, pASCA test provided the sensitivity of 58% and specificity of 70%. A combination of pANCA+/ASCA- for diagnosis of UC showed a sensitivity of 31.9% and specificity of 89.1%. In addition the combination of pANCA-/ASCA+ showed a sensitivity of 35.5% and specificity of 79.8% for diagnosis of CD.Due to low sensitivity of pANCA and ASCA alone or in combination, they are not valuable serological markers for diagnosis of UC or CD.

We previously reported postacrosomal sheath WW domain binding protein (PAWP) as a candidate sperm borne, oocyte-activating factor. PAWP enters the oocyte during fertilization and induces oocyte activation events including meiotic resumption, pronuclear formation, and egg cleavage. However, in order to provide proof that PAWP is a primary initiator of zygotic development it is imperative to show that PAWP initiates intracellular calcium signaling, which is considered essential for oocyte activation. Utilizing Xenopus laevis as our model, we injected recombinant PAWP or Xenopus sperm into metaphase II-arrested oocytes and observed a significant rise in intracellular calcium levels over controls. Concurring intensities and durations of PAWP and sperm-induced calcium waves, detected by infrared two-photon laser-scanning fluorescence microscopy, were prevented by coinjection of a competitive PPGY-containing peptide derived from PAWP but not by the point-mutated form of this peptide. This study also correlates PAWP and sperm-induced calcium release with meiotic resumption in Xenopus. The similar mode of oocyte activation, and the ability of the competitive peptide in blocking both sperm- and PAWP-induced calcium release, provide evidence for the first time that sperm-anchored PAWP is a primary initiator of zygotic development.

HOX genes are well-known to encode transcriptional regulatory proteins that play essential roles in directing embryonic development. TGIFLX/Y contains two genes, TGIFLX (X-linked) and TGIFLY (Y-linked), which are specifically expressed in human adult testes. The function(s) of these genes in normal and abnormal development are unknown. To investigate the potential role(s) of the TGIFLX/Y gene in infertile males, a nested reverse transcriptase polymerase chain reaction (RT-PCR) was performed on testicular samples from 110 patients with nonobstructive azoospermia. Although the only 51 (46.4%) of the 110 patients had detectable levels of TGIFLY expression, none of the patients with various spermatogenesis defects showed any of the TGIFLX gene expression found in normal testes. These results suggest that the function of TGIFLX may be required for the regulation of spermatogonial stem cell specification and proliferation. While functional similarity has been demonstrated among some homeobox genes, these results may refute the suggestion of redundancy between TGIFLX and TGIFLY. Furthermore, TGIFLX might be a potential biomarker candidate for male infertility assessment.

Biomarker-based sperm analysis elevates the treatment of human infertility and ameliorates reproductive performance in livestock. The negative biomarker-based approach focuses on proteins and ligands unique to defective spermatozoa, regardless of their morphological phenotype, lending itself to analysis by flow cytometry (FC). A prime example is the spermatid specific thioredoxin SPTRX3/TXNDC8, retained in the nuclear vacuoles and superfluous cytoplasm of defective human spermatozoa. Infertile couples with high semen SPTRX3 are less likely to conceive by assisted reproductive therapies (ART) and more prone to recurrent miscarriage while low SPTRX3 has been associated with multiple ART births. Ubiquitin, a small, proteolysis-promoting covalent posttranslational protein modifier is found on the surface of defective posttesticular spermatozoa and in the damaged protein aggregates, the aggresomes of spermiogenic origin. Semen ubiquitin content correlates negatively with fertility and conventional semen parameters, and with sperm binding of lectins LCA (Lens culinaris agglutinin; reveals altered sperm surface) and PNA (Arachis hypogaea/peanut agglutinin; reveals acrosomal malformation or damage). The Postacrosomal Sheath WWI Domain Binding Protein (PAWP), implicated in oocyte activation during fertilization, is ectopic or absent from defective human and animal spermatozoa. Consequently, FC-parameters of PAWP correlate with ART outcomes in infertile couples and with fertility in bulls. Assays based on the above biomarkers have been combined into multiplex FC semen screening protocols, and the surface expression of lectins and ubiquitin has been utilized to develop nanoparticle-based bull semen purification method validated by field artificial insemination trials. These advances go hand-in-hand with the innovation of FC-technology and genomics/proteomics-based biomarker discovery., Work summarized in this review was supported by grants 2013-67015-20961 and 2011-67015-20025 from USDA-NIFA, award #1R21HD066333-01 from NIH-NICHD and award #13324-2007 from Missouri Life Science Research Board, and by seed funding from the F21C Program, University of Missouri to PS. AMV was supported by the Instituto de Salud Carlos III [Projects PI050065 and PI080557, co-financed by the Fondo Social Europeo, FEDER] and Junta de Andalucía [Projects P07-CVI-02697 and P08-CVI-03629}, Spain. This study was also supported by a Canadian Institutes of Health Research grant (MOP-84440 to R.O.).