May Malicdan - Academia.edu (original) (raw)

Papers by May Malicdan

Objective: Assess long-term safety, tolerability, pharmacokinetics, and biochemical effect of Man... more Objective: Assess long-term safety, tolerability, pharmacokinetics, and biochemical effect of ManNAc in subjects with GNE myopathy and identify clinical endpoints suitable for subsequent clinical trials. Background: GNE myopathy is a rare, autosomal recessive myopathy caused by mutations in GNE, the gene encoding the rate-limiting enzyme in sialic acid biosynthesis. The disease manifests as an adult-onset myopathy characterized by progressive skeletal muscle weakness and atrophy. There is no approved therapy for this disease. Hyposialylation of muscle glycoproteins mediates the pathophysiology of the disease. ManNAc, an uncharged monosaccharide and the first committed precursor in sialic acid biosynthesis, is an oral therapeutic candidate that prevents muscle weakness in the mouse model of GNE myopathy. A first-in-human, randomized, placebo-controlled, double-blind, single-ascending dose study (NCT01634750) showed ManNAc is safe and restored sialic acid production in GNE myopathy patients. Design/Methods: A Phase 2, open-label, single-center study (NCT02346461) enrolled twelve subjects with genetically-confirmed GNE myopathy. Subjects received oral ManNAc at 6 grams twice daily (12 grams/day) and were evaluated at baseline, 3, 6, 12, 18, 24 and 30 months. Results: Long-term administration of ManNAc at 6 grams twice daily is safe but was associated with decreased gastrointestinal tolerability. ManNAc resulted in a sustained increase in levels of plasma free sialic acid (Neu5Ac). Comparison of serial-sampled plasma ManNAc and Neu5Ac at 6 grams BID and 4 grams TID daily showed increased bioavailability with TID dosing. Biochemical efficacy was assessed by increase in muscle sialylation after 3 months of ManNAc administration. Measures of muscle strength (including quantitative muscle assessment), function, and patient-reported outcomes were evaluated for suitability to test clinical efficacy in future trials. Conclusions: The findings of this study support further development of ManNAc as a therapy for GNE myopathy. A multicenter, randomized, placebo-controlled, double-blind trial of ManNAc in subjects with GNE myopathy is planned. Disclosure: Dr. Carillo-Carrasco has received research support from Leadiant Biosciences. Dr. Huizing has received compensation for serving on the Board of Directors of Leadiant. Dr. Huizing has received royalty, license fees, or contractual rights payments from Leadiant. Dr. Leoyklang has nothing to disclose. Dr. Quintana has nothing to disclose. Dr. Shrader has nothing to disclose. Dr. Bradley has nothing to disclose. Dr. Slota has nothing to disclose. Dr. Perreault has nothing to disclose. Dr. Class has nothing to disclose. Dr. Ciccone has nothing to disclose. Dr. Parks has nothing to disclose. Dr. Joe has nothing to disclose. Dr. Heiss has nothing to disclose. Dr. Berry has nothing to disclose. Dr. Malicdan has received royalty, license fees, or contractual rights payments from Leadiant Biosciences. Dr. Malicdan has received research support from Leadiant Biosciences. Dr. Gahl has received royalty, license fees, or contractual rights payments from Leadiant Biosciences. Dr. Gahl has received research support from Leadiant Biosciences.

npj Genomic Medicine

Autophagy regulates the degradation of damaged organelles and protein aggregates, and is critical... more Autophagy regulates the degradation of damaged organelles and protein aggregates, and is critical for neuronal development, homeostasis, and maintenance, yet few neurodevelopmental disorders have been associated with pathogenic variants in genes encoding autophagy-related proteins. We report three individuals from two unrelated families with a neurodevelopmental disorder characterized by speech and motor impairment, and similar facial characteristics. Rare, conserved, bi-allelic variants were identified in ATG4D, encoding one of four ATG4 cysteine proteases important for autophagosome biogenesis, a hallmark of autophagy. Autophagosome biogenesis and induction of autophagy were intact in cells from affected individuals. However, studies evaluating the predominant substrate of ATG4D, GABARAPL1, demonstrated that three of the four ATG4D patient variants functionally impair ATG4D activity. GABARAPL1 is cleaved or “primed” by ATG4D and an in vitro GABARAPL1 priming assay revealed decreas...

Myocardin-Related Transcription Factor B (MRTFB) is an important transcriptional regulator which ... more Myocardin-Related Transcription Factor B (MRTFB) is an important transcriptional regulator which promotes the activity of an estimated 300 genes during different stages of development. Here we report two pediatric probands withde novovariants inMRTFB(R104G and A91P) and mild dysmorphic features, intellectual disability, global developmental delays, speech apraxia, and impulse control issues. As theMRTFBprotein is highly conserved between vertebrate and invertebrate model organisms, we generated a humanizedDrosophilamodel expressing the humanMRTFBprotein in the same spatial and temporal pattern as the fly gene. Expression of the humanMRTFBR104Gvariant using amrtf-T2A-GAL4line proved to be embryonic lethal. Additional phenotypes were also identified by expressing theMRTFBR104GandMRTFBA91Pvariant in a subset ofDrosophilatissues. Notably, expression within wing tissues resulted in an expansion of intervein tissue, wing vein thickening, shortening or loss of wing veins, and blistering. T...

Respiratory Research

Background HPS-1 is a genetic type of Hermansky-Pudlak syndrome (HPS) with highly penetrant pulmo... more Background HPS-1 is a genetic type of Hermansky-Pudlak syndrome (HPS) with highly penetrant pulmonary fibrosis (HPSPF), a restrictive lung disease that is similar to idiopathic pulmonary fibrosis (IPF). Hps1ep/ep (pale ear) is a naturally occurring HPS-1 mouse model that exhibits high sensitivity to bleomycin-induced pulmonary fibrosis (PF). Traditional methods of administering bleomycin as an intratracheal (IT) route to induce PF in this model often lead to severe acute lung injury and high mortality rates, complicating studies focusing on pathobiological mechanisms or exploration of therapeutic options for HPSPF. Methods To develop a murine model of HPSPF that closely mimics the progression of human pulmonary fibrosis, we investigated the pulmonary effects of systemic delivery of bleomycin in Hps1ep/ep mice using a subcutaneous minipump and compared results to oropharyngeal delivery of bleomycin. Results Our study revealed that systemic delivery of bleomycin induced limited, acute...

The American Journal of Human Genetics, 2019

Optimal lysosome function requires maintenance of an acidic pH maintained by proton pumps in comb... more Optimal lysosome function requires maintenance of an acidic pH maintained by proton pumps in combination with a counterion transporter such as the Cl À /H þ exchanger, CLCN7 (ClC-7), encoded by CLCN7. The role of ClC-7 in maintaining lysosomal pH has been controversial. In this paper, we performed clinical and genetic evaluations of two children of different ethnicities. Both children had delayed myelination and development, organomegaly, and hypopigmentation, but neither had osteopetrosis. Whole-exome and-genome sequencing revealed a de novo c.2144A>G variant in CLCN7 in both affected children. This p.Tyr715Cys variant, located in the C-terminal domain of ClC-7, resulted in increased outward currents when it was heterologously expressed in Xenopus oocytes. Fibroblasts from probands displayed a lysosomal pH approximately 0.2 units lower than that of control cells, and treatment with chloroquine normalized the pH. Primary fibroblasts from both probands also exhibited markedly enlarged intracellular vacuoles; this finding was recapitulated by the overexpression of human p.Tyr715Cys CLCN7 in control fibroblasts, reflecting the dominant, gain-of-function nature of the variant. A mouse harboring the knock-in Clcn7 variant exhibited hypopigmentation, hepatomegaly resulting from abnormal storage, and enlarged vacuoles in cultured fibroblasts. Our results show that p.Tyr715Cys is a gain-of-function CLCN7 variant associated with developmental delay, organomegaly, and hypopigmentation resulting from lysosomal hyperacidity, abnormal storage, and enlarged intracellular vacuoles. Our data supports the hypothesis that the ClC-7 antiporter plays a critical role in maintaining lysosomal pH.

American journal of human genetics, Jan 4, 2018

The conserved oligomeric Golgi (COG) complex is involved in intracellular vesicular transport, an... more The conserved oligomeric Golgi (COG) complex is involved in intracellular vesicular transport, and is composed of eight subunits distributed in two lobes, lobe A (COG1-4) and lobe B (COG5-8). We describe fourteen individuals with Saul-Wilson syndrome, a rare form of primordial dwarfism with characteristic facial and radiographic features. All affected subjects harbored heterozygous de novo variants in COG4, giving rise to the same recurrent amino acid substitution (p.Gly516Arg). Affected individuals' fibroblasts, whose COG4 mRNA and protein were not decreased, exhibited delayed anterograde vesicular trafficking from the ER to the Golgi and accelerated retrograde vesicular recycling from the Golgi to the ER. This altered steady-state equilibrium led to a decrease in Golgi volume, as well as morphologic abnormalities with collapse of the Golgi stacks. Despite these abnormalities of the Golgi apparatus, protein glycosylation in sera and fibroblasts from affected subjects was not no...

American journal of medical genetics. Part A, 2017

Joubert syndrome is a neurodevelopmental disorder, characterized by malformation of the mid and h... more Joubert syndrome is a neurodevelopmental disorder, characterized by malformation of the mid and hindbrain leading to the pathognomonic molar tooth appearance of the brainstem and cerebellum on axial MRI. Core clinical manifestations include hypotonia, tachypnea/apnea, ataxia, ocular motor apraxia, and developmental delay of varying degrees. In addition, a subset of patients has retinal dystrophy, chorioretinal colobomas, hepatorenal fibrocystic disease, and polydactyly. Joubert syndrome exhibits genetic heterogeneity, with mutations identified in more than 30 genes, including INPP5E, a gene encoding inositol polyphosphate 5-phosphatase E, which is important in the development and stability of the primary cilium. Here, we report the detailed clinical phenotypes of two sisters with a novel homozygous variant in INPP5E (NM_019892.4: c.1565G>C, NP_063945.2: p.Gly552Ala), expanding the phenotype associated with Joubert syndrome type 1. Expression studies using patient-derived fibrobla...

Human mutation, Oct 4, 2017

Aminoacyl-tRNA synthetases (ARSs) are ubiquitously expressed enzymes that ligate amino acids onto... more Aminoacyl-tRNA synthetases (ARSs) are ubiquitously expressed enzymes that ligate amino acids onto tRNA molecules. Genes encoding ARSs have been implicated in myriad dominant and recessive disease phenotypes. Glycyl-tRNA synthetase (GARS) is a bifunctional ARS that charges tRNA(Gly) in the cytoplasm and mitochondria. GARS variants have been associated with dominant Charcot-Marie-Tooth disease but have not been convincingly implicated in recessive phenotypes. Here, we describe a patient from the NIH Undiagnosed Diseases Program with a multisystem, developmental phenotype. Whole-exome sequence analysis revealed that the patient is compound heterozygous for one frameshift (p.Glu83Ilefs*6) and one missense (p.Arg310Gln) GARS variant. Using in vitro and in vivo functional studies, we show that both GARS variants cause a loss-of-function effect: the frameshift variant results in depleted protein levels and the missense variant reduces GARS tRNA charging activity. In support of GARS variant...

Molecular genetics & genomic medicine, 2017

GNE myopathy is a rare genetic disease characterized by progressive muscle atrophy and weakness. ... more GNE myopathy is a rare genetic disease characterized by progressive muscle atrophy and weakness. It is caused by biallelic mutations in the GNE gene that encodes for the bifunctional enzyme, uridine diphosphate (UDP)-N-acetylglucosamine (GlcNAc) 2-epimerase/N-acetylmannosamine (ManNAc) kinase. Typical characteristics of GNE myopathy include progressive myopathy, first involving anterior tibialis muscle and sparing the quadriceps, and rimmed vacuoles on muscle biopsy. Identifying biallelic mutations by sequencing of the GNE gene confirms the diagnosis of GNE myopathy. In a subset of patients, diagnostic confirmation is challenged by the identification of mutations in only one allele, suggesting mutations in deep intronic regions or regulatory regions. We performed targeted sequencing and copy number variant (CNV) analysis of GNE in two siblings who clinically presented with GNE myopathy. Further molecular and biochemical studies were done to characterize the effect of a previously un...

Molecular genetics and metabolism, Mar 18, 2016

Combined alpha-delta platelet storage pool deficiency is characterized by the absence or reductio... more Combined alpha-delta platelet storage pool deficiency is characterized by the absence or reduction in the number of both alpha granules and dense bodies. This disorder can have variable severity as well as a variable inheritance pattern. We describe two patients from unrelated families with combined alpha-delta storage pool deficiency due to mutations in GFI1B, a zinc finger protein known to act as a transcriptional repressor of various genes. We demonstrate that this disease is associated with either a heterozygous mutation (de novo or familial) abrogating the binding of the zinc fingers with the promoter of its target genes, or by hypomorphic biallelic mutations in GFI1B leading to autosomal recessive inheritance.

American journal of medical genetics. Part A, Jan 4, 2017

Joubert syndrome is a ciliopathy characterized by a specific constellation of central nervous sys... more Joubert syndrome is a ciliopathy characterized by a specific constellation of central nervous system malformations that result in the pathognomonic "molar tooth sign" on imaging. More than 27 genes are associated with Joubert syndrome, but some patients do not have mutations in any of these genes. Celsr1, Celsr2, and Celsr3 are the mammalian orthologues of the drosophila planar cell polarity protein, flamingo; they play important roles in neural development, including axon guidance, neuronal migration, and cilium polarity. Here, we report bi-allelic mutations in CELSR2 in a Joubert patient with cortical heterotopia, microophthalmia, and growth hormone deficiency. © 2017 Wiley Periodicals, Inc.

Human mutation, Nov 23, 2016

Joubert and Meckel-Gruber syndromes (JS and MGS) are ciliopathies with overlapping features. JS p... more Joubert and Meckel-Gruber syndromes (JS and MGS) are ciliopathies with overlapping features. JS patients manifest the "molar tooth sign" on brain imaging and variable eye, kidney and liver disease. MGS presents with polycystic kidneys, occipital encephalocele and polydactyly; it is typically perinatally fatal. Both syndromes are genetically heterogeneous; some genes cause either syndrome. Here, we report two brothers married to unrelated women. The first brother had three daughters with JS and a son with polycystic kidneys who died at birth. The second brother's wife had a fetal demise due to MGS. Whole exome sequencing identified TMEM231 NM_001077416.2: c.784G>A; p.(Asp262Asn) in all children and the wife of the first brother; the second brother's wife had a c.406T>G;p.(Trp136Gly) change. In-depth analysis uncovered a rare gene conversion event in TMEM231, leading to loss of exon 4, in all the affected children of first brother. We believe that the combinati...

Orphanet journal of rare diseases, May 14, 2016

Mutations of TCF4, which encodes a basic helix-loop-helix transcription factor, cause Pitt-Hopkin... more Mutations of TCF4, which encodes a basic helix-loop-helix transcription factor, cause Pitt-Hopkins syndrome (PTHS) via multiple genetic mechanisms. TCF4 is a complex locus expressing multiple transcripts by alternative splicing and use of multiple promoters. To address the relationship between mutation of these transcripts and phenotype, we report a three-generation family segregating mild intellectual disability with a chromosomal translocation disrupting TCF4. Using whole genome sequencing, we detected a complex unbalanced karyotype disrupting TCF4 (46,XY,del(14)(q23.3q23.3)del(18)(q21.2q21.2)del(18)(q21.2q21.2)inv(18)(q21.2q21.2)t(14;18)(q23.3;q21.2)(14pter®14q23.3::18q21.2®18q21.2::18q21.1®18qter;18pter®18q21.2::14q23.3®14qter). Subsequent transcriptome sequencing, qRT-PCR and nCounter analyses revealed that cultured skin fibroblasts and peripheral blood had normal expression of genes along chromosomes 14 or 18 and no marked changes in expression of genes other than TCF4. Affect...

Journal of Medical Genetics, 2016

TV, MCVM, YMC, WAG and MG-A have contributed equally. Contributors TV performed most molecular da... more TV, MCVM, YMC, WAG and MG-A have contributed equally. Contributors TV performed most molecular data experiments, analysed the data, generated figures and wrote the manuscript. MCVM performed most cell biology experiments, provided direction for the project, analysed the data, generated figures and wrote the manuscript. YMC performed western blot experiments. PMZ performed electron microscopy and data analysis. JS performed data analysis and helped generate tables. JG performed cloning experiments, production of lentivirus and manuscript writing. ARC contributed to interpretation of data. JB coordinated admitting the patients, gathering data from patients and contributed to manuscript writing. RF assisted in screening for mutations in our patient cohort, and contributed in manuscript writing. BPB, WMZ and EAW gathered and analysed ophthalmological data from patients and contributed to manuscript writing. CKZ and AP gathered and analysed neuropsychiatric and neuroimaging data from patients and contributed to manuscript writing. MMB contributed to cell culture experiments. MV, JCM, MK, SMA and NISC Comparative Sequencing Program contributed to tools for data analysis and manuscript writing. MH contributed in manuscript writing and assisted in data analysis. CT gathered and analysed neurological data from patients, and contributed to project direction and manuscript writing. WAG provided direction for the project, obtained funding, guided data collection and interpretation and contributed to manuscript writing. MG-A principal investigator of clinical trial NCT00068224, designed the research, recruited patients, performed clinical and molecular data analysis, provided direction for the project and wrote the manuscript.

European journal of human genetics : EJHG, Aug 17, 2016

Protein-losing enteropathy (PLE) is a clinical disorder of protein loss from the gastrointestinal... more Protein-losing enteropathy (PLE) is a clinical disorder of protein loss from the gastrointestinal system that results in hypoproteinemia and malnutrition. This condition is associated with a wide range of gastrointestinal disorders. Recently, a unique syndrome of congenital PLE associated with biallelic mutations in the DGAT1 gene has been reported in a single family. We hypothesize that mutations in this gene are responsible for undiagnosed cases of PLE in infancy. Here we investigated three children in two families presenting with severe diarrhea, hypoalbuminemia and PLE, using clinical studies, homozygosity mapping, and exome sequencing. In one family, homozygosity mapping using SNP arrays revealed the DGAT1 gene as the best candidate gene for the proband. Sequencing of all the exons including flanking regions and promoter regions of the gene identified a novel homozygous missense variant, p.(Leu295Pro), in the highly conserved membrane-bound O-acyl transferase (MBOAT) domain of ...

Biomarkers in Medicine, 2014

Aim: The exact pathomechanism of GNE myopathy remains elusive, but likely involves aberrant sialy... more Aim: The exact pathomechanism of GNE myopathy remains elusive, but likely involves aberrant sialylation. We explored sialylation status of blood-based glycans as potential disease markers. Methods: We employed immunoblotting, lectin histochemistry and mass spectrometry. Results: GNE myopathy muscle showed hyposialylation of predominantly O-linked glycans. The O-linked glycome of patients' plasma compared with controls showed increased amounts of desialylated Thomsen–Friedenreich (T)-antigen, and/or decreased amounts of its sialylated form, ST-antigen. Importantly, all patients had increased T/ST ratios compared with controls. These ratios were normalized in a patient treated with intravenous immunoglobulins as a source of sialic acid. Discussion: GNE myopathy clinical trial data will reveal whether T/ST ratios correlate to muscle function. Conclusion: Plasma T/ST ratios are a robust blood-based biomarker for GNE myopathy, and may also help explain the pathology and course of the...

Clinical Journal of the American Society of Nephrology, 2013

Summary Background and objectives Elevated serum vitamin D with hypercalciuria can result in neph... more Summary Background and objectives Elevated serum vitamin D with hypercalciuria can result in nephrocalcinosis and nephrolithiasis. This study evaluated the cause of excess 1,25-dihydroxycholecalciferol (1α,25(OH)2D3) in the development of those disorders in two individuals. Design, setting, participants, & measurements Two patients with elevated vitamin D levels and nephrocalcinosis or nephrolithiasis were investigated at the National Institutes of Health (NIH) Clinical Center and the NIH Undiagnosed Diseases Program, by measuring calcium, phosphate, and vitamin D metabolites, and by performing CYP24A1 mutation analysis. Results Both patients exhibited hypercalciuria, hypercalcemia, low parathyroid hormone, elevated vitamin D (1α,25(OH)2D3), normal 25-OHD3, decreased 24,25(OH)2D, and undetectable activity of 1,25(OH)2D-24-hydroxylase (CYP24A1), the enzyme that inactivates 1α,25(OH)2D3. Both patients had bi-allelic mutations in CYP24A1 leading to loss of function of this enzyme. On t...

Brain : a journal of neurology, 2014

Patients with GNE myopathy, a progressive and debilitating disease caused by a genetic defect in ... more Patients with GNE myopathy, a progressive and debilitating disease caused by a genetic defect in sialic acid biosynthesis, rely on supportive care and eventually become wheelchair-bound. To elucidate whether GNE myopathy is treatable at a progressive stage of the disease, we examined the efficacy of sialic acid supplementation on symptomatic old GNE myopathy mice that have ongoing, active muscle degeneration. We examined the therapeutic effect of a less metabolized sialic acid compound (6'-sialyllactose) or free sialic acid (N-acetylneuraminic acid) by oral, continuous administration to 50-week-old GNE myopathy mice for 30 weeks. To evaluate effects on their motor performance in living mice, spontaneous locomotion activity on a running wheel was measured chronologically at 50, 65, 72 and 80 weeks of age. The size, force production, and pathology of isolated gastrocnemius muscle were analysed at the end point. Sialic acid level in skeletal muscle was also measured. Spontaneous lo...