Bi-allelic variants in DNA mismatch repair proteins MutS Homolog MSH4 and MSH5 cause infertility in both sexes.

STUDY QUESTION: Do bi-allelic variants in the genes encoding the MSH4/MSH5 heterodimer cause male infertility? SUMMARY ANSWER: We detected biallelic, (likely) pathogenic variants in MSH5 (4 men) and MSH4 (3 men) in six azoospermic men, demonstrating that genetic variants in these genes are a relevant cause of male infertility. WHAT IS KNOWN ALREADY: MSH4 and MSH5 form a heterodimer, which is required for prophase of meiosis I. One variant in MSH5 and two variants in MSH4 have been described as causal for premature ovarian insufficiency (POI) in a total of five women, resulting in infertility. Recently, pathogenic variants in MSH4 have been reported in infertile men. So far, no pathogenic variants in MSH5 had been described in males. STUDY DESIGN, SIZE, DURATION: We utilized exome data from 1305 men included in the Male Reproductive Genomics (MERGE) study, including 90 males with meiotic arrest (MeiA). Independently, exome sequencing was performed in a man with MeiA from a large consanguineous family. PARTICIPANTS/MATERIALS, SETTING, METHODS: Assuming an autosomal-recessive mode of inheritance, we screened the exome data for rare, biallelic coding variants in MSH4 and MSH5. If possible, segregation analysis in the patients' families was performed. The functional consequences of identified loss-of-function (LoF) variants in MSH5 were studied using heterologous expression of the MSH5 protein in HEK293T cells. The point of arrest during meiosis was determined by γH2AX staining. MAIN RESULTS AND THE ROLE OF CHANCE: We report for the first time (likely) pathogenic, homozygous variants in MSH5 causing infertility in 2 out of 90 men with MeiA and overall in 4 out of 902 azoospermic men. Additionally, we detected biallelic variants in MSH4 in two men with MeiA and in the sister of one proband with POI. γH2AX staining revealed an arrest in early prophase of meiosis I in individuals with pathogenic MSH4 or MSH5 variants. Heterologous in vitro expression of the detected LoF variants in MSH5 showed that the variant p.(Ala620GlnTer9) resulted in MSH5 protein truncation and the variant p.(Ser26GlnfsTer42) resulted in a complete loss of MSH5. LARGE SCALE DATA: All variants have been submitted to ClinVar (SCV001468891-SCV001468896 and SCV001591030) and can also be accessed in the Male Fertility Gene Atlas (MFGA). LIMITATIONS, REASONS FOR CAUTION: By selecting for variants in MSH4 and MSH5, we were able to determine the cause of infertility in six men and one woman, leaving most of the examined individuals without a causal diagnosis. WIDER IMPLICATIONS OF THE FINDINGS: Our findings have diagnostic value by increasing the number of genes associated with non-obstructive azoospermia with high clinical validity. The analysis of such genes has prognostic consequences for assessing whether men with azoospermia would benefit from a testicular biopsy. We also provide further evidence that MeiA in men and POI in women share the same genetic causes. STUDY FUNDING/COMPETING INTEREST(S): This study was carried out within the frame of the German Research Foundation sponsored Clinical Research Unit 'Male Germ Cells: from Genes to Function' (DFG, CRU326), and supported by institutional funding of the Research Institute Amsterdam Reproduction and Development and funds from the LucaBella Foundation. The authors declare no conflict of interest.

[Genetic testing to prevent sudden cardiac death]. / Genetische Diagnostik zur Vermeidung des plötzlichen Herztods.

Successfully incorporating genetic testing into clinical practice to prevent sudden cardiac death (SCD) requires (1) appropriate recognition of an inherited cardiovascular condition, (2) identification of appropriate family members at risk and for genetic testing, (3) selection of the appropriate genetic test and information about the expected diagnostic yield, (4) understanding the complexity of result interpretation and distinct handling of incidental findings and (5) providing effective communication and medical advice regarding the genetic and medical results and implications to the patient and his family. Molecular autopsy in SCD victims will be of future importance to determine the cause of death. Interdisciplinary patient care should be provided in specialized centers with a high level of cardiogenetic expertise and is recommended to provide precise and individualized patient management.

Molecular genetic diagnostics for ventricular arrhythmias and sudden cardiac death syndromes.

Inherited forms of ventricular arrhythmias are rare diseases, but a major cause for severe cardiac events, sudden unexplained death syndromes, and death in young adults, infants, and children. Each disorder is genetically heterogeneous (5-20 genes per disease) and molecular testing may include both core genes and less common disease genes as well. Owing to the rapid development and feasibility of sequencing technologies enabling a parallel analysis of several hundred genes up to a whole exome, disease mutations can be identified very efficiently, but have to be seen in the complexity and natural variance of the human genome. Precise phenotypic knowledge and advanced gene variant interpretation are important to ensure adequate patient diagnostics and management. This article focuses on the genetic causes of inherited arrhythmia forms predisposing patients to sudden cardiac death and discusses practical issues and skills for molecular testing.

Mutational spectrum in the cardiac transcription factor gene NKX2.5 (CSX) associated with congenital heart disease.

Heterozygous mutations in the human transcription factor gene NKX2.5 are associated with either isolated or combined congenital heart disease (CHD), primarily secundum atrial septal defect-II (ASD-II), ventricular septal defect (VSD) or tetralogy of Fallot (TOF). Thus, NKX2.5 has an important role at different stages of cardiac development. The frequency of NKX2.5 mutations in a broader phenotypic spectrum of CHD is not completely determined. Here, we report the identification of two novel mutations in the NKX2.5 gene in a screening of 121 patients with a broad spectrum of CHDs. However, mutations were only associated with familial ASD-II and in both, patients also showed atrioventricular (AV) block. We found one missense mutation (R190L) in two siblings with ASD-II and a frame-shift mutation (A255fsX38) at the C-terminus in a mother and daughter. In addition, a single patient with hypoplastic left heart syndrome (HLHS) had the reported sequence variant R25C. Importantly, sporadic cases of CHD that share phenotypic aspects of NKX2.5 mutation carriers were negative for genetic analysis. Thus, even important for cardiac development, germline mutations in NKX2.5 are rare in patients with sporadic CHD and genetic and/or pathophysiologic heterogeneity is likely for sporadic forms of CHD.

A novel keratinocyte mitogen: regulation of leptin and its functional receptor in skin repair.

Wound re-epithelialization represents a tissue movement that crucially participates in wound closure. Recently, we demonstrated that supplemented leptin improved re-epithelialization processes in leptin-deficient ob/ob mice. In this study we investigated regulation of the leptin system during normal repair in healthy animals. We found leptin to be present at the wound site during healing, although leptin levels were clearly reduced upon injury compared with uninvolved control skin. The functional leptin receptor subtype obRb was observed to be constitutively expressed in nonwounded skin. During early healing, the leptin receptor obRb was downregulated, but re-increased again from day 5 postwounding. Immunohistochemistry revealed that highly proliferative keratinocytes of the wound margin epithelia strongly expressed the functional leptin receptor subtype obRb. In vitro studies demonstrated that murine and human primary epidermal keratinocytes responded to exogenously added leptin with a proliferative response. Moreover, specificity of leptin-mediated mitogenic effects on primary keratinocytes could be shown by completely blocking leptin actions by a soluble, nonfunctional chimeric leptin receptor. Finally, we report that leptin, besides the recently described activation of the janus tyrosine kinase signal transducers, also activated extracellular signal-regulated kinase-controlled signaling pathways in primary keratinocytes.

Systemically and topically supplemented leptin fails to reconstitute a normal angiogenic response during skin repair in diabetic ob/ob mice.

AIMS/HYPOTHESIS: In diabetic patients impaired wound healing conditions are a therapeutic problem of clinical importance. Recently, we showed that supplemented leptin induced an acceleration of impaired wound closure in diabetic ob/ob mice by reversion of the delayed re-epithelialization process. Additionally, angiogenesis is central to a normal repair. As leptin has been reported to represent an angiogenic factor, we hypothesized that leptin-mediated angiogenic processes at the wound site might participate in leptin-mediated improvement of disturbed repair in ob/ob mice. METHODS: Using a model of excisional wounding, C57BL/6J-ob/ob mice were treated systemically and topically with recombinant murine leptin during the phase of repair. Changes in blood glucose concentrations and body weight were monitored. We measured expression of the vascular endothelial growth factor (VEGF) and the endothelial cell marker protein CD31 as a read-out for angiogenic processes at the wound site. RESULTS: Expression of VEGF protein upon injury was reduced (30 to 40%) in ob/ob mice compared with wild-type C57BL/6 animals. Systemic and topical administration of leptin reconstituted normal wound VEGF expressions but failed to reverse the strongly reduced angiogenic response in ob/ob mice. Immunohistochemistry confirmed that the epithelium and blood vessels located in the granulation tissue expressed the functional leptin receptor obRb isoform during skin repair. CONCLUSION/INTERPRETATION: These data suggest that leptin reconstituted epithelial expression of VEGF during skin repair in ob/ob mice but failed to improve wound angiogenesis in the granulation tissue. Thus, the accelerated wound closure observed in leptin-supplemented ob/ob mice is not coupled to an improved wound angiogenesis.

Large and sustained induction of chemokines during impaired wound healing in the genetically diabetic mouse: prolonged persistence of neutrophils and macrophages during the late phase of repair.

Chemokines are seen as the stimuli that largely control leukocyte migration. To assess whether the severely impaired process of cutaneous repair observed in genetically diabetic db/db mice is associated with a dysregulated infiltration of immune cells, we determined the expressional kinetics for the murine growth-regulated oncogene/melanoma growth stimulatory activity homolog macrophage inflammatory protein-2, and the macrophage chemoattractant protein-1, respectively. Wound repair in db/db mice was characterized by a sustained inflammatory response and a prolonged expression of macrophage inflammatory protein-2 and macrophage chemoattractant protein-1. Immuno-histochemistry revealed that keratinocytes at the wound margins expressed macrophage chemoattractant protein-1, whereas macrophage inflammatory protein-2 immunopositive signals were observed only in keratinocytes of hair follicles located adjacent to the wound site. Inactivation studies using neutralizing antibodies against macrophage chemoattractant protein-1 or macrophage inflammatory protein-2 indicated that sustained expression of these chemokines participated in a prolonged presence of neutrophils and macrophages at the wound site during diabetic repair. Furthermore, our data provide evidence that late infiltration (day 13 after injury) of neutrophils and macrophages into wounds in db/db mice was associated with a simultaneous downregulation of mRNA for receptors specific for macrophage inflammatory protein-2 and macrophage chemoattractant protein-1 in these animals.

Leptin enhances wound re-epithelialization and constitutes a direct function of leptin in skin repair.

Wound-healing disorders are a therapeutic problem of extensive clinical importance. Leptin-deficient ob/ob mice are characterized by a severely delayed wound healing that has been explained by the mild diabetic phenotype of these animals. Here we demonstrate that systemically and topically supplemented leptin improved re-epithelialization of wounds in ob/ob mice. Leptin completely reversed the atrophied morphology of the migrating epithelial tongue observed at the wound margins of leptin-deficient animals into a well-organized hyperproliferative epithelium. Moreover, topically supplemented leptin accelerated normal wound-healing conditions in wild-type mice. As assessed by immunohistochemistry, proliferating keratinocytes located at the wound margins specifically expressed the leptin-receptor subtype ObRb during repair. Additionally, leptin mediated a mitogenic stimulus to the human keratinocyte cell line HaCaT and human primary keratinocytes in vitro. Therefore, leptin might represent an effective novel therapeutic factor to improve impaired wound-healing conditions.

Large induction of the chemotactic cytokine RANTES during cutaneous wound repair: a regulatory role for nitric oxide in keratinocyte-derived RANTES expression.

We investigated the role of NO on expressional regulation of the chemotactic cytokine RANTES (regulated upon activation, normal T-cell expressed and secreted) during tissue regeneration using an excisional wound-healing model in mice. Wound repair was characterized by a large and sustained induction of RANTES expression, and inhibition of inducible nitric oxide synthase (iNOS) during repair only slightly decreased RANTES expression levels. Immunohistochemical analysis revealed keratinocytes of the wound margins and the hyperproliferative epithelium to be the main RANTES-expressing cell type within the wound. Therefore we analysed the regulation of RANTES expression in vitro in cultured human keratinocytes of the cell line HaCaT. Here we demonstrate that NO very efficiently suppressed interleukin-1beta- and tumour-necrosis-factor-alpha-induced RANTES expression in keratinocytes. Furthermore, down-regulation of cytokine-induced RANTES mRNA in keratinocytes was dependent on endogenously produced NO, as inhibition of the co-induced iNOS by L-N(G)-monomethyl-L-arginine increased cytokine-triggered RANTES expression in the cells. Moreover, we observed strongest RANTES-immunopositive labelling in epithelial areas which were characterized by a NO-mediated low cellularity. Thus our data implicate NO as a negative regulator of RANTES expression during wound repair in vivo, as decreased numbers of keratinocytes observed in the absence of wound-derived NO might compensate for the high levels of RANTES expression which are associated with normal repair.

The function of nitric oxide in wound repair: inhibition of inducible nitric oxide-synthase severely impairs wound reepithelialization.

Recently, we demonstrated a large induction of inducible nitric oxide synthase (iNOS) during cutaneous wound repair. In this study, we established an in vivo model in mice to investigate the role of NO during the wound healing process. During excisional repair, mice were treated with L-N6-(1-iminoethyl)lysine (L-NIL), a selective inhibitor of iNOS enzymatic activity. Compared with control mice, L-NIL-treated animals were characterized by a severely impaired reepithelialization process, as the hyperproliferative epithelia at the wound edges appeared to be delayed and characterized by an atrophied morphology. Immunohistochemical labeling for detection of proliferating cells (BrdU-, Ki67-staining) revealed a strong reduction in proliferating keratinocyte cell numbers during the process of re-epithelialization after inhibition of iNOS activity during repair. Western blot analysis of total wound lysates from PBS- and L-NIL-treated mice clearly demonstrated a reduction in proliferating cell nuclear antigen, representing a marker for cell proliferation, in lysates isolated from L-NIL-treated mice. The dependency between keratinocyte proliferation and NO availability observed during wound repair in vivo is further supported by the observation that proliferation of the keratinocyte cell line (HaCaT) is stimulated by low concentrations of NO-donors also in vitro. In summary, our data demonstrate that the presence of a functionally active iNOS is a crucial prerequisite for normal wound reepithelialization.

Nitric oxide triggers enhanced induction of vascular endothelial growth factor expression in cultured keratinocytes (HaCaT) and during cutaneous wound repair.

Recently, we demonstrated a large induction of inducible nitric oxide synthase (iNOS) during cutaneous wound repair. In this study, we investigated the role of nitric oxide (NO) for the expression of vascular endothelial growth factor (VEGF), which represents the most important angiogenic factor during the proliferative phase of skin repair. Since keratinocytes are the major source of VEGF production during this process, we used cultured keratinocytes (HaCaT cell line) as an in vitro model to investigate NO action on growth factor- and cytokine-stimulated VEGF expression. Exogenously added NO enhanced transforming growth factor-beta1-, keratinocyte growth factor-, interleukin-1beta-, tumor necrosis factor-alpha-, and interferon-gamma-induced VEGF mRNA and protein synthesis in keratinocytes. We could demonstrate that high-level expression of cytokine-induced VEGF mRNA in keratinocytes is dependent on endogenously produced NO, as inhibition of the coinduced iNOS by N(G)-monomethyl-L-arginine (L-NMMA) markedly decreased cytokine-triggered VEGF mRNA levels in the cells. We also established an in vivo model in mice to investigate the role of NO during wound healing. During excisional wound repair, mice were treated with L-N(6)-(1-iminoethyl)lysine (L-NIL), a selective inhibitor of iNOS enzymatic activity. Compared to control mice, L-NIL-treated animals were characterized by markedly reduced VEGF mRNA levels during the inflammatory phase of repair. Immunohistochemistry demonstrated reduced VEGF protein expression and a completely disorganized pattern of VEGF-expressing keratinocytes within the hyperproliferative epithelium at the wound edge in L-NIL-treated mice. We demonstrate that triggering of VEGF expression is a crucial molecular mechanism underlying NO function during wound healing.

Human molybdopterin synthase gene: genomic structure and mutations in molybdenum cofactor deficiency type B.

Biosynthesis of the molybdenum cofactor (MoCo) can be divided into (1) the formation of a precursor and (2) the latter's subsequent conversion, by molybdopterin synthase, into the organic moiety of MoCo. These two steps are reflected by the complementation groups A and B and the two formally distinguished types of MoCo deficiency that have an identical phenotype. Both types of MoCo deficiency result in a pleiotropic loss of all molybdoenzyme activities and cause severe neurological damage. MOCS1 is defective in patients with group A deficiency and has been shown to encode two enzymes for early synthesis via a bicistronic transcript with two consecutive open reading frames (ORFs). MOCS2 encodes the small and large subunits of molybdopterin synthase via a single transcript with two overlapping reading frames. This gene was mapped to 5q and comprises seven exons. The coding sequence and all splice site-junction sequences were screened for mutations, in MoCo-deficient patients in whom a previous search for MOCS1 mutations had been negative. In seven of the eight patients whom we investigated, we identified MOCS2 mutations that, by their nature, are most likely responsible for the deficiency. Three different frameshift mutations were observed, with one of them found on 7 of 14 identified alleles. Furthermore, a start-codon mutation and a missense mutation of a highly conserved amino acid residue were found. The locations of the mutations confirm the functional role of both ORFs. One of the patients with identified MOCS2 mutations had been classified as type B, in complementation studies. These findings support the hypothetical mechanism, for both forms of MoCo deficiency, that formerly had been established by cell-culture experiments.

Human molybdopterin synthase gene: identification of a bicistronic transcript with overlapping reading frames.

A universal molybdenum-containing cofactor (MoCo) is essential for the activity of all human molybdoenzymes, including sulphite oxidase. The free cofactor is highly unstable, and all organisms share a similar biosynthetic pathway. The involved enzymes exhibit homologies, even between bacteria and humans. We have exploited these homologies to isolate a cDNA for the heterodimeric molybdopterin (MPT)-synthase. This enzyme is necessary for the conversion of an unstable precursor into molybdopterin, the organic moiety of MoCo. The corresponding transcript shows a bicistronic structure, encoding the small and large subunits of the MPT-synthase in two different open reading frames (ORFs) that overlap by 77 nucleotides. In various human tissues, only one size of mRNA coinciding with the bicistronic transcript was detected. In vitro translation and mutagenesis experiments demonstrated that each ORF is translated independently, leading to the synthesis of a 10-kDa protein and a 21-kDa protein for the small and large subunits, respectively, and indicated that the 3'-proximal ORF of the bicistronic transcript is translated by leaky scanning.

The neurotransmitter receptor-anchoring protein gephyrin reconstitutes molybdenum cofactor biosynthesis in bacteria, plants, and mammalian cells.

The molybdenum cofactor (Moco), a highly conserved pterin compound complexing molybdenum, is required for the enzymatic activities of all molybdenum enzymes except nitrogenase. Moco is synthesized by a unique and evolutionarily old pathway that requires the activities of at least six gene products. Some of the proteins involved in bacterial, plant, and invertebrate Moco biosynthesis show striking homologies to the primary structure of gephyrin, a polypeptide required for the clustering of inhibitory glycine receptors in postsynaptic membranes in the rat central nervous system. Here, we show that gephyrin binds with high affinity to molybdopterin, the metabolic precursor of Moco. Furthermore, gephyrin expression can reconstitute Moco biosynthesis in Moco-deficient bacteria, a molybdenum-dependent mouse cell line, and a Moco-deficient plant mutant. Conversely, inhibition of gephyrin expression by antisense RNA expression in cultured murine cells reduces their Moco content significantly. These data indicate that in addition to clustering glycine receptors, gephyrin also is involved in Moco biosynthesis and illustrate the remarkable conservation of its function in Moco biosynthesis throughout phylogeny.

Differential regulation of vascular endothelial growth factor and its receptor fms-like-tyrosine kinase is mediated by nitric oxide in rat renal mesangial cells.

Under conditions associated with local and systemic inflammation, mesangial cells and invading immune cells are likely to be responsible for the release of large amounts of nitric oxide (NO) in the glomerulus. To further define the mechanisms of NO action in the glomerulus, we attempted to identify genes which are regulated by NO in rat glomerular mesangial cells. We identified vascular endothelial growth factor (VEGF) and its receptor fms-like tyrosine kinase (FLT-1) to be under the regulatory control of exogenously applied NO in these cells. Using S-nitroso-glutathione (GSNO) as an NO-donating agent, VEGF expression was strongly induced, whereas expression of its FLT-1 receptor simultaneously decreased. Expressional regulation of VEGF and FLT-1 mRNA was transient and occurred rapidly within 1-3 h after GSNO treatment. Expression of a second VEGF-specific receptor, fetal liver kinase-1 (FLK-1/KDR), could not be detected. The inflammatory cytokine interleukin-1beta mediated a moderate increase in VEGF expression after 24 h and had no influence on FLT-1 expression. In contrast, platelet-derived growth factor-BB and basic fibroblast growth factor had no effect on VEGF expression, but strongly induced FLT-1 mRNA levels. Obviously, there is a differential regulation of VEGF and its receptor FLT-1 by NO, cytokines and growth factors in rat mesangial cells.

Mutations in a polycistronic nuclear gene associated with molybdenum cofactor deficiency.

All molybdoenzymes other than nitrogenase require molybdopterin as a metal-binding cofactor. Several genes necessary for the synthesis of the molybdenum cofactor (MoCo) have been characterized in bacteria and plants. The proteins encoded by the Escherichia coli genes moaA and moaC catalyse the first steps in MoCo synthesis. The human homologues of these genes are therefore candidate genes for molybdenum cofactor deficiency, a rare and fatal disease. Using oligonucleotides complementary to a conserved region in the moaA gene, we have isolated a human cDNA derived from liver mRNA. This transcript contains an open reading frame (ORF) encoding the human moaA homologue and a second ORF encoding a human moaC homologue. Mutations can be found in the majority of MoCo-deficient patients that confirm the functional role of both ORFs in the corresponding gene MOCS1 (for 'molybdenum cofactor synthesis-step 1'). Northern-blot analysis detected only full-length transcripts containing both consecutive ORFs in various human tissues. The mRNA structure suggests a translation reinitiation mechanism for the second ORF. These data indicate the existence of a eukaryotic mRNA, which as a single and uniform transcript guides the synthesis of two different enzymatic polypeptides with disease-causing potential.

Molybdenum co-factor biosynthesis: the Arabidopsis thaliana cDNA cnx1 encodes a multifunctional two-domain protein homologous to a mammalian neuroprotein, the insect protein Cinnamon and three Escherichia coli proteins.

The molybdenum co-factor (Moco) is an essential part of all eukaryotic molybdoenzymes. It is a molybdopterin and reveals the same principal structure in eubacteria, archaebacteria and eukaryotes. This paper reports the isolation of cnx1, a cDNA clone of Arabidopsis thaliana which complements the Escherichia coli Moco mutant mogA. The mapping data of this cDNA correlate well with the mapping position of the A. thaliana molybdenum co-factor locus chl6. As mutants in chl6 are known to be repairable by high concentrations of molybdate, the defective gene is very likely to be involved in the last step of Moco biosynthesis, that is, the insertion of molybdenum into molybdopterin. The protein encoded by cnx1 shows a two-domain structure: the N-terminal domain is homologous to the E. coli Moco protein MoeA, the C-terminal domain is homologous to the E. coli Moco proteins MoaB and MogA, respectively. These homologies show that part of the prokaryotic Moco biosynthetic pathway accomplished by monofunctional proteins in E. coli, is performed by a single multifunctional protein in eukaryotes. In addition Cnx1 is homologous to the eukaryotic proteins Gephyrin, a rat neuroprotein, and Cinnamon, a Drosophila protein with a function in Moco biosynthesis. These proteins also show a two-domain structure but the order of the domains is inversed as compared with Cnx1. Southern analysis indicates the existence of at least one further member, in addition to the cnx1 gene, of this novel gene family in the Arabidopsis genome.