In utero copper treatment for Menkes disease associated with a severe ATP7A mutation

Chelating principles in Menkes and Wilson diseases: Choosing the right compounds in the right combinations at the right time

Dysregulation of copper homeostasis in humans is primarily found in two genetic diseases of copper transport, Menkes and Wilson diseases, which show symptoms of copper deficiency or overload, respectively. However, both diseases are copper storage disorders despite completely opposite clinical pictures. Clinically, Menkes disease is characterized by copper deficiency secondary to poor loading of copper-requiring enzymes although sufficient body copper. Copper accumulates in non-hepatic tissues, but is deficient in blood, liver, and brain. In contrast, Wilson disease is characterized by symptoms of copper toxicity secondary to accumulation of copper in several organs most notably brain and liver, and a saturated blood copper pool. It is a challenge to correct copper dyshomeostasis in either disease though copper depletion in Menkes disease is most challenging. Both diseases are caused by defective copper export from distinct cells, and we seek to give new angles and guidelines to improve treatment of these two complementary diseases. Therapy of Menkes disease with copper-histidine, thiocarbamate, nitrilotriacetate or lipoic acid is discussed. In Wilson disease combination of a hydrophilic chelator e.g. trientine or dimercaptosuccinate with a brain shuttle e.g. thiomolybdate or lipoate, is discussed. New chelating principles for copper removal or delivery are outlined.

Cerebrospinal Fluid-Directed rAAV9-rsATP7A Plus Subcutaneous Copper Histidinate Advance Survival and Outcomes in a Menkes Disease Mouse Model

Menkes disease is a lethal neurodegenerative disorder of copper metabolism caused by mutations in an evolutionarily conserved copper transporter, ATP7A. Based on our prior clinical and animal studies, we seek to develop a therapeutic approach suitable for application in affected human subjects, using the mottled-brindled (mo-br) mouse model that closely mimics the Menkes disease biochemical and clinical phenotypes. Here, we evaluate the efficacy of low-, intermediate-, and high-dose recombinant adeno-associated virus serotype 9 (rAAV9)-ATP7A delivered to the cerebrospinal fluid (CSF), in combination with subcutaneous administration of clinical-grade copper histidinate (sc CuHis, IND #34,166). Mutant mice that received high-dose (1.6 × 1010 vg) cerebrospinal fluid-directed rAAV9-rsATP7A plus sc copper histidinate showed 53.3% long-term (≥300-day) survival compared to 0% without treatment or with either treatment alone. The high-dose rAAV9-rsATP7A plus sc copper histidinate-treated mutant mice showed increased brain copper levels, normalized brain neurochemical levels, improvement of brain mitochondrial abnormalities, and normal growth and neurobehavioral outcomes. This synergistic treatment effect represents the most successful rescue to date of the mo-br mouse model. Based on these findings, and the absence of a large animal model, we propose cerebrospinal fluid-directed rAAV9-rsATP7A gene therapy plus subcutaneous copper histidinate as a potential therapeutic approach to cure or ameliorate Menkes disease.

Tandem Duplication of Exons 1-7 Neither Impairs ATP7A Expression Nor Causes a Menkes Disease Phenotype

ATP7A duplications are estimated to represent the molecular cause of Menkes disease in 4-10% of affected patients. We identified a novel duplication of ATP7A exons 1-7 discovered in the context of a challenging prenatal diagnostic situation. All other reported ATP7A duplications (n = 24) involved intragenic tandem duplications, predicted to disrupt the normal translational reading frame and produce nonfunctional ATP7A proteins. In contrast, the exon 1-7 duplication occurred at the 5' end of the ATP7A gene rather than within the gene and did not correspond to any known copy number variants. We hypothesized that, if the exon 1-7 duplication was in tandem, functional ATP7A molecules could be generated depending on promoter selection, mRNA splicing, and the proximal and distal duplication breakpoints and that Menkes disease would be averted. Here, we present detailed molecular characterization of this novel duplication, as well as 2-year postnatal clinical and biochemical correlations. The case highlights the ongoing need for cautious interpretation of prenatal genetic test results.

Novel mutations and clinical outcomes of copper-histidine therapy in Menkes disease patients

Menkes disease is a very rare X-linked copper metabolism disorder that results from an ATP7A gene mutation. With the advent of subcutaneous copper-histidine therapy, the early diagnosis of Menkes disease becomes of utmost importance for patients' prognosis. In the present study, the clinical characteristics of 12 Korean patients with Menkes disease (11 males and 1 female from 11 unrelated families) were described along with the mutation spectrum. Only 2 male patients were diagnosed in the neonatal period, and the other male patients were diagnosed at age 4.3 ± 1.9 months. The presenting signs included depigmented kinky hair, neurologic deficits, and hypotonia. Serum copper and ceruloplasmin levels were markedly decreased. Intracranial vessels were dilated with tortuosity and accompanied by regional cerebral infarctions, even at an early age. Of note, the female patient was diagnosed at age 18 months, during the evaluation for developmental delay, by characteristic MRA findings, biochemical profiles, and genetic evaluation. A total of 11 ATP7A mutations were identified, including five previously unreported mutations. Most mutations were truncated (except 1 missense mutation), including 3 frameshift, 2 nonsense, 3 large deletion, and 2 splice-site variants. The age at commencement of copper-histidine treatment was variable among patients age 7.3 ± 7.5 (0.5-27) months. Despite the treatment, seven patients died before age 5 years, and the remaining patients were severely retarded in neurodevelopment. The poor outcomes of our patients might be related to delayed therapy, but severe ATP7A mutations should be noted as well.

Molecular and biochemical characterization of Mottled-dappled, an embryonic lethal Menkes disease mouse model

Mottled-dappled (Mo-dp) is a mouse model of Menkes disease caused by a large, previously uncharacterized deletion in the 5' region of Atp7a, the mouse ortholog of ATP7A. Affected mutants die in utero at embryonic day 17, and show bending and thickening of the ribs and distortion of the pectoral and pelvic girdles and limbs. To characterize this allele, we designed a custom 4x180K microarray on the mouse X chromosome and performed comparative genomic hybridization using extracted DNA from normal and carrier Mo-dp females, and identified an approximately 9 kb deletion. We used PCR to fine-map the breakpoints and amplify a junction fragment of 630 bp. Sequencing of the junction fragment disclosed the exact breakpoint locations and that the Mo-dp deletion is precisely 8990 bp, including approximately 2 kb in the promoter region of Atp7a. Western blot analysis of Mo-dp heterozygous brains showed diminished amounts of Atp7a protein, consistent with reduced expression due to the promoter region deletion on one allele. In heterozygous females, brain copper levels tended to be lower compared to wild type whereas neurochemical analyses revealed higher dihydroxyphenylacetic acid:dihydroxyphenylglycol (DOPAC:DHPG) and dopamine:norepinephrine (DA:NE) ratios compared to normal (P=0.002 and 0.029, respectively), consistent with partial deficiency of dopamine-beta-hydroxylase, a copper-dependent enzyme. Heterozygous females showed no significant differences in body weight compared to wild type females. Our results delineate the molecular details of the Mo-dp mutation for the first time and define novel biochemical findings in heterozygous female carriers of this allele.

A novel two-nucleotide deletion in the ATP7A gene associated with delayed infantile onset of Menkes disease

BACKGROUND

Determining the relationship between clinical phenotype and genotype in genetic diseases is important in clinical practice. In general, frameshift mutations are expected to produce premature termination codons, leading to production of mutant transcripts destined for degradation by nonsense-mediated decay. In X-linked recessive diseases, male patients with frameshift mutations typically have a severe or even lethal phenotype.

PATIENT

We report a case of a 17-month-old boy with Menkes disease (NIM #309400), an X-linked recessive copper metabolism disorder caused by mutations in the ATP7A copper transporter gene. He exhibited an unexpectedly late onset and experienced milder symptoms.

STUDY AND RESULT

His genomic DNA showed a de novo two-nucleotide deletion in exon 4 of ATP7A, predicting a translational frameshift and premature stop codon, and a classic severe phenotype. Characterization of his ATP7A mRNA showed no abnormal splicing.

CONCLUSION

We speculate that translation reinitiation could occur downstream to the premature termination codon and produce a partially functional ATP7A protein. Study of the child's fibroblasts found no evidence of translation reinitiation; however, the possibility remains that this phenomenon occurred in neural tissues and influenced the clinical phenotype.

Fetal blood sampling

OBJECTIVE

We sought to review indications, technical aspects, risks, and recommendations for fetal blood sampling (FBS).

METHODS

A systematic review was performed using MEDLINE, PubMed, EMBASE, and Cochrane Library using the terms "fetal blood sampling," "percutaneous umbilical blood sampling," and "cordocentesis." The search was restricted to English-language articles published from 1966 through July 2012. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries also were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion in this document. Evidence reports and guidelines published by organizations or institutions such as the National Institutes of Health, Agency for Health Research and Quality, American Congress of Obstetricians and Gynecologists, and Society for Maternal-Fetal Medicine were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. Grade (Grading of Recommendations Assessment, Development, and Evaluation) methodology was employed for defining strength of recommendations and rating quality of evidence. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence.

RESULTS AND RECOMMENDATIONS

Ultrasound-guided FBS is the only procedure that provides direct access to the fetal circulation. When invasive testing is planned for suspected severe fetal anemia or thrombocytopenia, we recommend FBS as the procedure of choice, with availability of immediate transfusion if confirmed. We recommend against the use of FBS for indications in which other less invasive, and therefore lower risk, alternatives are available. The overall success rate of FBS is high, and blood samples can be obtained in >98% of patients. We suggest that counseling for FBS include discussion about the potential risk of FBS that may include, but may not be limited to: bleeding from puncture site (20-30%); fetal bradycardia (5-10%); pregnancy loss (≥1.3%, depending on indication, gestational age, and placental penetration); and vertical transmission of hepatitis or human immunodeficiency virus. We recommend that FBS be performed by experienced operators at centers with expertise in invasive fetal procedures when feasible.

L-threo-dihydroxyphenylserine corrects neurochemical abnormalities in a Menkes disease mouse model

OBJECTIVE

Menkes disease is a lethal neurodegenerative disorder of infancy caused by mutations in a copper-transporting adenosine triphosphatase gene, ATP7A. Among its multiple cellular tasks, ATP7A transfers copper to dopamine beta hydroxylase (DBH) within the lumen of the Golgi network or secretory granules, catalyzing the conversion of dopamine to norepinephrine. In a well-established mouse model of Menkes disease, mottled-brindled (mo-br), we tested whether systemic administration of L-threo-dihydroxyphenylserine (L-DOPS), a drug used successfully to treat autosomal recessive norepinephrine deficiency, would improve brain neurochemical abnormalities and neuropathology.

METHODS

At 8, 10, and 12 days of age, wild-type and mo-br mice received intraperitoneal injections of 200μg/g body weight of L-DOPS, or mock solution. Five hours after the final injection, the mice were euthanized, and brains were removed. We measured catecholamine metabolites affected by DBH via high-performance liquid chromatography with electrochemical detection, and assessed brain histopathology.

RESULTS

Compared to mock-treated controls, mo-br mice that received intraperitoneal L-DOPS showed significant increases in brain norepinephrine (p < 0.001) and its deaminated metabolite, dihydroxyphenylglycol (p < 0.05). The ratio of a non-beta-hydroxylated metabolite in the catecholamine biosynthetic pathway, dihydroxyphenylacetic acid, to the beta-hydroxylated metabolite, dihydroxyphenylglycol, improved equivalently to results obtained previously with brain-directed ATP7A gene therapy (p < 0.01). However, L-DOPS treatment did not arrest global brain pathology or improve somatic growth, as gene therapy had.

INTERPRETATION

We conclude that (1) L-DOPS crosses the blood-brain barrier in mo-br mice and corrects brain neurochemical abnormalities, (2) norepinephrine deficiency is not the cause of neurodegeneration in mo-br mice, and (3) L-DOPS treatment may ameliorate noradrenergic hypofunction in Menkes disease.