Methylmalonic acidemia (MMA) in pregnancy: a case series and literature review

IntroductionWomen with inherited metabolic disorders, including those with previously life‐limiting conditions such as MMA, are reaching child‐bearing age more often due to advances in early diagnosis and improved pediatric care. Information surrounding maternal and fetal complications associated with the underlying disorders remains largely unexplored.MethodsPregnancies affected by maternal MMA were ascertained through study 04‐HG‐0127 “Clinical and Basic Investigations of Methylmalonic Acidemia and Related Disorders” (clinicaltrials.gov identifier: NCT00078078) and via literature review. Prenatal and delivery records in study participants were reviewed.ResultsSeventeen pregnancies were identified in women with isolated MMA, including three abortions, one termination, and 13 completed pregnancies [three cases with cblA (four pregnancies), four cases of mut‐ (one cobalamin responsive, three non‐responsive), five cases with unknown type of MMA]. Seventeen percent (3/17) of the pregnancies resulted in a first trimester abortion, while 38.5 % (5/13) of the completed pregnancies resulted in preterm deliveries. A cesarean delivery rate of 53.8 % (7/13) was noted among the cohort. Fetal distress or nonreassuring fetal status was the indication for 57 % (4/7) cesarean deliveries. One patient was reported to have metabolic crisis as well as episodes of mild hyperammonemia. Malformations or adverse outcomes in the progeny were not observed.ConclusionAlthough there have been a small number of pregnancies identified in women with MMA, the cumulative results suggest that the majority of pregnancies can be complicated by cesarean delivery and increased risk of prematurity. A pregnancy registry could clarify perinatal complications and define management approaches needed to ensure optimal maternal and fetal outcomes in this growing patient population.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147009/1/jimd0839.pd

Intravenous immune globulin in hereditary inclusion body myopathy: a pilot study

BACKGROUND: Hereditary Inclusion Body Myopathy (HIBM) is an autosomal recessive, adult onset, non-inflammatory neuromuscular disorder with no effective treatment. The causative gene, GNE, codes for UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, which catalyzes the first two reactions in the synthesis of sialic acid. Reduced sialylation of muscle glycoproteins, such as α-dystroglycan and neural cell adhesion molecule (NCAM), has been reported in HIBM. METHODS: We treated 4 HIBM patients with intravenous immune globulin (IVIG), in order to provide sialic acid, because IgG contains 8 μmol of sialic acid/g. IVIG was infused as a loading dose of 1 g/kg on two consecutive days followed by 3 doses of 400 mg/kg at weekly intervals. RESULTS: For all four patients, mean quadriceps strength improved from 19.0 kg at baseline to 23.2 kg (+22%) directly after IVIG loading to 25.6 kg (+35%) at the end of the study. Mean shoulder strength improved from 4.1 kg at baseline to 5.9 kg (+44%) directly after IVIG loading to 6.0 kg (+46%) at the end of the study. The composite improvement for 8 other muscle groups was 5% after the initial loading and 19% by the end of the study. Esophageal motility and lingual strength improved in the patients with abnormal barium swallows. Objective measures of functional improvement gave variable results, but the patients experienced improvements in daily activities that they considered clinically significant. Immunohistochemical staining and immunoblotting of muscle biopsies for α-dystroglycan and NCAM did not provide consistent evidence for increased sialylation after IVIG treatment. Side effects were limited to transient headaches and vomiting. CONCLUSION: The mild benefits in muscle strength experienced by HIBM patients after IVIG treatment may be related to the provision of sialic acid supplied by IVIG. Other sources of sialic acid are being explored as treatment options for HIBM

The development of the method of nuclear and mitochondrial DNA microarray for research on mitochondrial disorders

The pivotal role of mitochondria in cell energy metabolism and the complex nature of their genetic regulation, by both the nuclear and the mitochondrial DNA, form the basis for the diverse clinical presentation and the unique genetics of mitochondrial diseases. Moreover, primary or secondary mitochondrial dysfunction has been associated with the pathogenesis of a variety of conditions, such as obesity, diabetes, cancer, neurodegeneration, cardiomyopathy, depression and aging. Despite their significance, diagnostic tools for assessing mitochondrial function remain limited and labor intensive, as they involve biochemical analyses on muscle biopsy specimens and molecular testing, available only at limited specialized centers world-wide. The present work describes the development and first application of the microarray technology in studying mitochondrial genomics. We developed a human mitochondria-focused microarray, with 501 nuclear encoded genes related to mitochondrial structure, biogenesis and function. For the validation of that method we studied gene expression profiles in dexamethasone-treated primary human skeletal myocytes, as an in vitro model of steroid-induced myopathy. Changes were observed in the expression of genes involved in protein synthesis, fatty acid metabolism, oxidative stress and apoptosis, while the most significant finding was the induction of the gene encoding for monoamine oxidase-A (MAO-A). MAO-A is the primary enzyme metabolizing catecholamines, other neurotransmitters and dietary amines, and its role in skeletal muscle remains largely unexplored. We report a significant induction of MAO-A gene transcription and protein synthesis, followed by increased enzymatic activity, leading to downstream hydrogen peroxide production. We suggest that MAO-A mediated oxidative stress can lead to skeletal muscle cell damage, representing a novel pathogenetic mechanism for glucocorticoid-induced myopathy and a potential target for therapeutic intervention. The experience from this first application of the mitochondrial microarray led to the design and development of a more advanced version, the hMitChip3, which contains 1135 genes related to mitochondria, including the newly cloned mtDNA-encoded genes. We believe that the mitochondrial microarray represents a novel and reliable tool for studying mitochondrial genomics.Ο στρατηγικός ρόλος του μιτοχονδρίου στο κύτταρο και η σύνθετη ρύθμιση της λειτουργίας του από γονίδια του μιτοχονδριακού αλλά και του πυρηνικού DNA, έχουν ως συνέπεια το τεράστιο εύρος κλινικών εκδηλώσεων και την ιδιαίτερη κληρονομικότητα, που χαρακτηρίζουν τα μιτοχονδριακά νοσήματα. Παράλληλα, μιτοχονδριακή δυσλειτουργία, πρωτοπαθούς ή δευτεροπαθούς χαρακτήρα, έχει συσχετισθεί με πλειάδα παθήσεων, όπως παχυσαρκία, διαβήτης, καρκίνος, νευροεκφυλιστικά νοσήματα, καρδιοπάθειες, κατάθλιψη καθώς και τη διαδικασία της γήρανσης. Παρά τη σημασία τους, οι διαθέσιμες τεχνικές για τη μελέτη των μιτοχονδριακών νοσημάτων είναι περιορισμένες και επίπονες, καθώς περιλαμβάνουν βιοχημικές εξετάσεις σε υλικό μυϊκής βιοψίας και μοριακό έλεγχο, που είναι εφικτός σε λίγα μόνον εξειδικευμένα κέντρα διεθνώς. Η μελέτη αυτή περιγράφει την ανάπτυξη και την πρώτη εφαρμογή της μεθόδου των μικροσυστοιχιών DNA για τη μελέτη της μιτοχονδριακής γονιδιακής έκφρασης. Κατασκευάστηκε μια μικροσυστοιχία, αποτελούμενη από 501 γονίδια πυρηνικού DNA σχετιζόμενα με τη δομή, τη βιοσύνθεση και τη λειτουργία του μιτοχονδρίου. Για την αξιολόγηση της μεθόδου χρησιμοποιήθηκαν ανθρώπινα μυϊκά κύτταρα in vitro για τη διερεύνηση της επίδρασης των γλυκοκορτικοειδών στη μιτοχονδριακή λειτουργία, με απώτερο στόχο την κατανόηση των μοριακών μηχανισμών της μυοπάθειας από στεροειδή. Σημαντικές μεταβολές παρατηρήθηκαν στην έκφραση γονιδίων που συμμετέχουν στην πρωτεϊνοσύνθεση, το μεταβολισμό των λιπαρών οξέων, το οξειδωτικό stress και την απόπτωση, μεταξύ άλλων, ενώ σημαντικότερη ήταν η επαγωγή της μεταγραφής της μονοαμινοξειδάσης Α (ΜΑΟ-Α). Η ΜΑΟ-Α είναι το σημαντικότερο ένζυμο μεταβολισμού των κατεχολαμινών και άλλων νευρομεταβιβαστών, του οποίου ο ρόλος στο σκελετικό μυ παραμένει αδιευκρίνιστος. Η παρούσα μελέτη περιγράφει τη διέγερση της μεταγραφής, της μετάφρασης και της ενζυμικής δραστικότητας της ΜΑΟ-Α μετά από έκθεση μυϊκών κυττάρων σε γλυκοκορτικοειδή, με επακόλουθη αύξηση της παραγωγής υπεροξειδίου του υδρογόνου. Ο μεταβολικός αυτός δρόμος μπορεί να οδηγεί σε αύξηση του οξειδωτικού stress και κυτταρική βλάβη, συμβάλλοντας στην αιτιοπαθογένεια της μυοπάθειας από στεροειδή. Η εμπειρία από αυτήν την πρώτη εφαρμογή, οδήγησε στη βελτίωση του σχεδιασμού και την κατασκευή μιας νέας μιτοχονδριακής μικροσυστοιχίας με 1135 γονίδια σχετιζόμενα με το μιτοχόνδριο, συμπεριλαμβανομένων αυτών που κωδικοποιούνται από το μιτοχονδριακό DNA. Πιστεύουμε, πως η μιτοχονδριακή μικροσυστοιχία αποτελεί ένα αξιόπιστο και πρωτοποριακό εργαλείο για τη μελέτη της μιτοχονδριακής γονιδιωματικής

Glucocorticoid receptor (GR) has intrinsic, GRa-independent transcriptional activity

The human glucocorticoid receptor (GR) gene produces C-terminal GRβ and GRα isoforms through alternative use of specific exons 9β and α, respectively. We explored the transcriptional activity of GRβ on endogenous genes by developing HeLa cells stably expressing EGFP-GRβ or EGFP. Microarray analyses revealed that GRβ had intrinsic gene-specific transcriptional activity, regulating mRNA expression of a large number of genes negatively or positively. Majority of GRβ-responsive genes was distinct from those modulated by GRα, while GRβ and GRα mutually modulated each other’s transcriptional activity in a subpopulation of genes. We did not observe in HCT116 cells nuclear translocation of GRβ and activation of this receptor by RU 486, a synthetic steroid previously reported to bind GRβ and to induce nuclear translocation. Our results indicate that GRβ has intrinsic, GRα-independent, gene-specific transcriptional activity, in addition to its previously reported dominant negative effect on GRα-induced transactivation of GRE-driven promoters

Glucocorticoid receptor (GR) beta has intrinsic, GR alpha-independent transcriptional activity

The human glucocorticoid receptor (GR) gene produces C-terminal GR beta and GR alpha isoforms through alternative use of specific exons 9 beta and alpha, respectively. We explored the transcriptional activity of GR beta on endogenous genes by developing HeLa cells stably expressing EGFP-GR beta or EGFP. Microarray analyses revealed that GR beta had intrinsic gene-specific transcriptional activity, regulating mRNA expression of a large number of genes negatively or positively. Majority of GR beta-responsive genes was distinct from those modulated by GR alpha, while GR beta and GR alpha mutually modulated each other’s transcriptional activity in a subpopulation of genes. We did not observe in HCT116 cells nuclear translocation of GR beta and activation of this receptor by RU 486, a synthetic steroid previously reported to bind GR beta and to induce nuclear translocation. Our results indicate that GR beta has intrinsic, GR alpha-independent, gene-specific transcriptional activity, in addition to its previously reported dominant negative effect on GR alpha-induced transactivation of GRE-driven promoters. Published by Elsevier Inc

Allele-specific silencing of the dominant disease allele in sialuria by RNA interference

Dominant disease alleles are attractive therapeutic targets for allele-specific gene silencing by small interfering RNA (siRNA). Sialuria is a dominant disorder caused by missense mutations in the allosteric site of GNE, coding for the rate-limiting enzyme of sialic acid biosynthesis, UDP-GlcNAc 2-epimerase/ManNAc kinase. The resultant loss of feedback inhibition of GNE-epimerase activity by CMP-sialic acid causes excessive production of free sialic acid. For this study we employed synthetic siRNAs specifically targeting the dominant GNE mutation c.797G>A (p.R266Q) in sialuria fibroblasts. We demonstrated successful siRNA-mediated down-regulation of the mutant allele by allele-specific real-time PCR. Importantly, mutant allele-specific silencing resulted in a significant decrease of free sialic acid, to within the normal range. Feedback inhibition of GNE-epimerase activity by CMP-sialic acid recovered after silencing demonstrating specificity of this effect. These findings indicate that allele-specific silencing of a mutated allele is a viable therapeutic strategy for autosomal dominant diseases, including sialuria.—Klootwijk, R. D., Savelkoul, P. J. M., Ciccone, C., Manoli, I., Caplen, N. J., Krasnewich, D. M., Gahl, W. A., Huizing, M. Allele-specific silencing of the dominant disease allele in sialuria by RNA interference