Genetic landscape of pediatric acute liver failure of indeterminate origin

BACKGROUND AND AIMS

Pediatric acute liver failure (PALF) is a life-threatening condition. In Europe, the main causes are viral infections (12%-16%) and inherited metabolic diseases (14%-28%). Yet, in up to 50% of cases the underlying etiology remains elusive, challenging clinical management, including liver transplantation. We systematically studied indeterminate PALF cases referred for genetic evaluation by whole-exome sequencing (WES), and analyzed phenotypic and biochemical markers, and the diagnostic yield of WES in this condition.

APPROACH AND RESULTS

With this international, multicenter observational study, patients (0-18 y) with indeterminate PALF were analyzed by WES. Data on the clinical and biochemical phenotype were retrieved and systematically analyzed.

RESULTS

In total, 260 indeterminate PALF patients from 19 countries were recruited between 2011 and 2022, of whom 59 had recurrent PALF. WES established a genetic diagnosis in 37% of cases (97/260). Diagnostic yield was highest in children with PALF in the first year of life (41%), and in children with recurrent acute liver failure (64%). Thirty-six distinct disease genes were identified. Defects in NBAS (n=20), MPV17 (n=8), and DGUOK (n=7) were the most frequent findings. When categorizing, the most frequent were mitochondrial diseases (45%), disorders of vesicular trafficking (28%), and cytosolic aminoacyl-tRNA synthetase deficiencies (10%). One-third of patients had a fatal outcome. Fifty-six patients received liver transplantation.

CONCLUSIONS

This study elucidates a large contribution of genetic causes in PALF of indeterminate origin with an increasing spectrum of disease entities. The high proportion of diagnosed cases and potential treatment implications argue for exome or in future rapid genome sequencing in PALF diagnostics.

Identification of a novel MT-ND3 variant and restoring mitochondrial function by allotopic expression of MT-ND3 gene

Mitochondrial diseases are caused by nuclear, or mitochondrial DNA (mtDNA) variants and related co-factors. Here, we report a novel m.10197G > C variant in MT-ND3 in a patient, and two other patients with m.10191 T > C. MT-ND3 variants are known to cause Leigh syndrome or mitochondrial complex I deficiency. We performed the functional analyses of the novel m.10197G > C variant that significantly lowered MT-ND3 protein levels, causing complex I assembly and activity deficiency, and reduction of ATP synthesis. We adapted a previously described re-engineering technique of delivering mitochondrial genes into mitochondria through codon optimization for nuclear expression and translation by cytoplasmic ribosomes to rescue defects arising from the MT-ND3 variants. We constructed mitochondrial targeting sequences along with the codon-optimized MT-ND3 and imported them into the mitochondria. To achieve the goal, we imported codon-optimized MT-ND3 into mitochondria in three patients with m.10197G > C and m.10191 T > C missense variants in the MT-ND3. Nuclear expression of the MT-ND3 gene partially restored protein levels, complex I deficiency, and significant improvement of ATP production indicating a functional rescue of the mutant phenotype. The codon-optimized nuclear expression of mitochondrial protein and import inside the mitochondria can supplement the requirements for ATP in energy-deficient mitochondrial disease patients.

Genetic, metabolic and clinical delineation of an MRPS23-associated mitochondrial disorder

MRPS23 is a nuclear gene encoding a mitochondrial ribosomal protein. A patient with a mitochondrial disorder was found to carry a variant in MRPS23. More cases are necessary to establish MRPS23 as a mitochondrial disease gene. Of 5134 exomes performed in our center, we identified five independent patients who had similar clinical manifestations and were homozygous for the same germline variant c.119C>T; p.P40L in MRPS23. Detailed clinical findings, mitochondrial enzyme activity assays from cultured skin fibroblasts, PCR-Sanger-sequencing, and variant age estimation were performed. Their available family members were also studied. Eight members homozygous for the MRPS23 p.P40L were identified. All were from Hmong hilltribe. Seven presented with alteration of consciousness and recurrent vomiting, while the eighth who was a younger brother of a proband was found pre-symptomatically. Patients showed delayed growth and development, hearing impairment, hypoglycemia, lactic acidosis, and liver dysfunction. In vitro assays of cultured fibroblasts showed combined respiratory chain complex deficiency with low activities of complexes I and IV. PCR-Sanger-sequencing confirmed the variant, which was estimated to have occurred 1550 years ago. These results establish the MRPS23-associated mitochondrial disorder inherited in an autosomal recessive pattern and provide insight into its clinical and metabolic features.

Strategic validation of variants of uncertain significance in ECHS1 genetic testing

BACKGROUND

Enoyl-CoA hydratase short-chain 1 (ECHS1) is an enzyme involved in the metabolism of branched chain amino acids and fatty acids. Mutations in the ECHS1 gene lead to mitochondrial short-chain enoyl-CoA hydratase 1 deficiency, resulting in the accumulation of intermediates of valine. This is one of the most common causative genes in mitochondrial diseases. While genetic analysis studies have diagnosed numerous cases with ECHS1 variants, the increasing number of variants of uncertain significance (VUS) in genetic diagnosis is a major problem.

METHODS

Here, we constructed an assay system to verify VUS function for ECHS1 gene. A high-throughput assay using ECHS1 knockout cells was performed to index these phenotypes by expressing cDNAs containing VUS. In parallel with the VUS validation system, a genetic analysis of samples from patients with mitochondrial disease was performed. The effect on gene expression in cases was verified by RNA-seq and proteome analysis.

RESULTS

The functional validation of VUS identified novel variants causing loss of ECHS1 function. The VUS validation system also revealed the effect of the VUS in the compound heterozygous state and provided a new methodology for variant interpretation. Moreover, we performed multiomics analysis and identified a synonymous substitution p.P163= that results in splicing abnormality. The multiomics analysis complemented the diagnosis of some cases that could not be diagnosed by the VUS validation system.

CONCLUSIONS

In summary, this study uncovered new ECHS1 cases based on VUS validation and omics analysis; these analyses are applicable to the functional evaluation of other genes associated with mitochondrial disease.

Perinatal lethal Gaucher disease: A case report and review of literature

Perinatal lethal Gaucher disease is a very rare variant of type 2 Gaucher disease that occurs in the neonatal period and leads to death in early infancy. The disease is characterized by hydrops fetalis or a collodion baby phenotype accompanied with progressive neurological manifestations, hepatosplenomegaly, thrombocytopenia, anemia, and failure to thrive. We report a case of perinatal lethal Gaucher disease treated with enzyme replacement therapy (ERT) who survived for 9 months and present a literature review of perinatal lethal Gaucher disease cases. The prognosis of perinatal lethal Gaucher disease is poor, and ERT is only effective in visceral manifestation. Therefore, palliative care should be recognized as a treatment option, and ERT employment needs to be discussed in this context.

Recessive NUP54 Variants Underlie Early-Onset Dystonia with Striatal Lesions

Infantile striatonigral degeneration is caused by a homozygous variant of the nuclear-pore complex (NPC) gene NUP62, involved in nucleo-cytoplasmic trafficking. By querying sequencing-datasets of patients with dystonia and/or Leigh(-like) syndromes, we identified 3 unrelated individuals with biallelic variants in NUP54. All variants clustered in the C-terminal protein region that interacts with NUP62. Associated phenotypes were similar to those of NUP62-related disease, including early-onset dystonia with dysphagia, choreoathetosis, and T2-hyperintense lesions in striatum. In silico and protein-biochemical studies gave further evidence for the argument that the variants were pathogenic. We expand the spectrum of NPC component-associated dystonic conditions with localized basal-ganglia abnormalities. ANN NEUROL 2023;93:330-335.

Severe spinal cord hypoplasia due to a novel ATAD3A compound heterozygous deletion

Biallelic deletions extending into the ATPase family AAA-domain containing protein 3A (ATAD3A) gene lead to infantile lethality with severe pontocerebellar hypoplasia (PCH). However, only 12 such cases have been reported worldwide to date, and the genotype–phenotype correlations are not well understood. We describe cases associated with the same novel biallelic deletions of the ATAD3A and ATAD3B/3A regions in Japanese siblings with severe spinal cord hypoplasia and multiple malformations, including PCH, leading to neonatal death. The ATAD3A protein is essential for normal interaction between mitochondria and endoplasmic reticulum and is important for mitochondrial biosynthesis. The cases were evaluated using whole-genome sequencing for genetic diagnosis of mitochondrial disease. Spinal cord lesions associated with biallelic compound heterozygous deletion extending into the ATAD3A gene have not been reported. In addition, the ATAD3A deletion was 19 base pairs long, which is short compared with those reported previously. This deletion introduced a frameshift, resulting in a premature termination codon, and was expected to be a null allele. The pathological findings of the atrophic spinal cord showed gliosis and tissue destruction of the gray and white matter. We describe spinal cord lesions as a new central nervous system phenotype associated with a biallelic compound heterozygous deletion extending into the ATAD3A gene. Biallelic ATAD3A deletions should be considered in cases of mitochondrial disease with spinal cord hypoplasia and PCH.

Impact of measuring heteroplasmy of a pathogenic mitochondrial DNA variant at the single-cell level in individuals with mitochondrial disease

Pathogenic mitochondrial DNA heteroplasmy has mainly been assessed with bulk sequencing in individuals with mitochondrial disease. However, the distribution of heteroplasmy at the single-cell level in skin fibroblasts obtained from individuals, together with detailed clinical and biochemical information, remains to be investigated. We used the mitochondrial DNA single-cell assay for the transposase-accessible chromatin sequencing method. Skin fibroblasts were obtained from six individuals with mitochondrial disease and pathogenic m.3243A>G variants of differing severity. Different distributions of heteroplasmy at the single-cell level were identified in skin fibroblasts from all six individuals. Four individuals with different outcomes showed similar averaged heteroplasmy rates with normal mitochondrial respiratory chain enzyme activity, while the distribution of single-cell heteroplasmy patterns differed among the individuals. This study showed different heteroplasmy distribution patterns at the single-cell level in individuals with the m.3243A>G variant, who had a similar averaged heteroplasmy rates with normal mitochondrial respiratory chain enzyme activity. Whether such different heteroplasmy distribution patterns explain the different clinical outcomes should be assessed further in future studies. Measuring heteroplasmy of pathogenic mitochondrial DNA variants at the single-cell level could be important in individuals with mitochondrial disease.

Neonatal-onset mitochondrial disease: clinical features, molecular diagnosis and prognosis

OBJECTIVE

Neonatal-onset mitochondrial disease has not been fully characterised owing to its heterogeneity. We analysed neonatal-onset mitochondrial disease in Japan to clarify its clinical features, molecular diagnosis and prognosis.

DESIGN

Retrospective observational study from January 2004 to March 2020.

SETTING

Population based.

PATIENTS

Patients (281) with neonatal-onset mitochondrial disease diagnosed by biochemical and genetic approaches.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Disease types, initial symptoms, biochemical findings, molecular diagnosis and prognosis.

RESULTS

Of the 281 patients, multisystem mitochondrial disease was found in 194, Leigh syndrome in 26, cardiomyopathy in 38 and hepatopathy in 23 patients. Of the 321 initial symptoms, 236 occurred within 2 days of birth. Using biochemical approaches, 182 patients were diagnosed by mitochondrial respiratory chain enzyme activity rate and 89 by oxygen consumption rate. The remaining 10 patients were diagnosed using a genetic approach. Genetic analysis revealed 69 patients had nuclear DNA variants in 36 genes, 11 of 15 patients had mitochondrial DNA variants in five genes and four patients had single large deletion. The Cox proportional hazards regression analysis showed the effects of Leigh syndrome (HR=0.15, 95% CI 0.04 to 0.63, p=0.010) and molecular diagnosis (HR=1.87, 95% CI 1.18 to 2.96, p=0.008) on survival.

CONCLUSIONS

Neonatal-onset mitochondrial disease has a heterogenous aetiology. The number of diagnoses can be increased, and clarity regarding prognosis can be achieved by comprehensive biochemical and molecular analyses using appropriate tissue samples.

A Japanese single-center experience of the efficacy and safety of asfotase alfa in pediatric-onset hypophosphatasia

Background

Hypophosphatasia (HPP) is a rare inherited metabolic disorder caused by mutations in the ALPL gene, which encodes tissue nonspecific alkaline phosphatase. The severity of HPP is widely diverse from the perinatal form to the adult mild form. The former represents the most severe form and was earlier associated with high mortality due to pneumonia which was caused by severe hypomineralization of the bones—such as chest deformity and fractured ribs—and muscle weakness. Enzyme replacement therapy using asfotase alfa (AA) was approved in 2015 in Japan for treating patients with HPP and has improved their pulmonary function and life prognosis. There are several practical and ethical challenges related to using orphan drugs for a rare disorder in a publicly funded healthcare system. Sharing experiences about their application is essential towards formulating guidelines to assist clinicians with decisions about their initiation and withdrawal. We report the details of AA experience in ten cases of pediatric-onset HPP in nine families from January 2015 to November 2019 (median [interquartile range] age 11.0 [7.6–12.5] years; 60% male). This is a study of a single-center cohort describing the clinical course of patients with HPP, mainly consisting of the mild childhood form of HPP, treated with AA in Japan.

Results

One case of perinatal form of HPP, two cases of benign prenatal form, and seven cases of childhood form were observed. The most common symptom at onset was pain. All patients had low serum alkaline phosphatase levels as compared to the age-matched reference range before the commencement of AA. All HPP patients seem to have responded to AA treatment, as evidenced by pain alleviation, increased height standard deviation, improvement in respiratory condition and 6-min walk test result improvement, disappearance of kidney calcification, alleviation of fatigue, and/or increases in bone mineralization. There were no serious adverse events, but all patients had an injection site reaction and skin changes at the injection sites. Genetic analysis showed that eight out of ten patients had compound heterozygosity.

Conclusions

AA may be effective in patients with mild to severe pediatric-onset forms of HPP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02230-y.

Development of Leigh syndrome with a high probability of cardiac manifestations in infantile-onset patients with m.14453G > A

The m.14453G > A mutation in MT-ND6 has been described in a few patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes or Leigh syndrome.However, the clinical spectrum and molecular characteristics are unclear.Here, we present four infantile-onset patients with m.14453G > A-associated Leigh syndrome. All four patients had brainstem lesions with basal ganglia lesions, and two patients had cardiac manifestations. Decreased ND6 protein expression and immunoreactivity were observed in patient-derived samples. There was no clear correlation between heteroplasmy levels and onset age or between heteroplasmy levels and phenotype; however, infantile onset was associated with Leigh syndrome.

Genome sequencing and RNA-seq analyses of mitochondrial complex I deficiency revealed Alu insertion-mediated deletion in NDUFV2

Isolated complex I deficiency is the most common cause of pediatric mitochondrial disease. Exome sequencing (ES) has revealed many complex I causative genes. However, there are limitations associated with identifying causative genes by ES analysis. In this study, we performed multiomics analysis to reveal the causal variants. We here report two cases with mitochondrial complex I deficiency. In both cases, ES identified a novel c.580G>A (p.Glu194Lys) variant in NDUFV2. One case additionally harbored c.427C>T (p.Arg143*), but no other variants were observed in the other case. RNA sequencing showed aberrant exon splicing of NDUFV2 in the unsolved case. Genome sequencing revealed a novel heterozygous deletion in NDUFV2, which included one exon and resulted in exon skipping. Detailed examination of the breakpoint revealed that an Alu insertion-mediated rearrangement caused the deletion. Our report reveals that combined use of transcriptome sequencing and GS was effective for diagnosing cases that were unresolved by ES.

Long-term prognosis and genetic background of cardiomyopathy in 223 pediatric mitochondrial disease patients

BACKGROUND

Cardiomyopathy is a risk factor for poor prognosis in pediatric patients with mitochondrial disease. However, other risk factors including genetic factors related to poor prognosis in mitochondrial disease has yet to be fully elucidated.

METHODS AND RESULTS

Between January 2004 and September 2019, we enrolled 223 consecutive pediatric mitochondrial disease patients aged <18 years with a confirmed genetic diagnosis, including 114 with nuclear gene mutations, 89 patients with mitochondrial DNA (mtDNA) point mutations, 11 with mtDNA single large-scale deletions and 9 with chromosomal aberrations. Cardiomyopathy at baseline was observed in 46 patients (22%). Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for all-cause mortality. Over a median follow-up of 36 months (12-77), there were 85 deaths (38%). The overall survival rate was significantly lower in patients with cardiomyopathy than in those without (p < 0.001, log-rank test). By multivariable analysis, left ventricular (LV) hypertrophy (HR = 4.6; 95% CI: 2.8-7.3), neonatal onset (HR = 2.9; 95% CI: 1.8-4.5) and chromosomal aberrations (HR = 2.9; 95% CI: 1.3-6.5) were independent predictors of all-cause mortality. Patients with LV hypertrophy with neonatal onset and/or chromosomal aberrations had higher mortality (100% in 21 patients) than those with LV hypertrophy alone (71% in 14 patients).

CONCLUSION

In pediatric patients with mitochondrial disease, cardiomyopathy was common (22%) and was associated with increased mortality. LV hypertrophy, neonatal onset and chromosomal aberrations were independent predictors of all-cause mortality. Prognosis is particularly unfavourable if LV hypertrophy is combined with neonatal onset and/or chromosomal aberrations.

Biallelic COA7-Variants Leading to Developmental Regression With Progressive Spasticity and Brain Atrophy in a Chinese Patient

Objective

The cytochrome c oxidase assembly factor 7 (COA7) gene encodes a protein localized to mitochondria that is involved in the assembly of mitochondrial respiratory chain complex IV. Here, we report the clinical, genetic and biochemical analysis of a female patient with suspected mitochondrial disorder and novel variants in COA7, that presented with a considerably different phenotype and age of onset than the five COA7 patients reported to date.

Methods

We performed trio-exome sequencing in the affected patient and both parents. To verify the pathogenicity of the detected variants in COA7, mitochondrial enzyme activities and oxygen consumption rate were investigated in fibroblasts of the patient and her parents.

Results

A Chinese girl was referred at 9 months of age with a history of developmental delay and regression since 3 months of age. In the following months, she lost previously acquired skills and developed progressive spasticity of the lower extremities. Trio-exome sequencing revealed compound heterzygous variants in COA7 (c.511G > A/p.Ala171Thr and c.566A > G/p.Asn189Ser). Functional validation experiments revealed isolated complex IV deficiency and a significantly reduced mitochondrial respiration rate in patient-derived fibroblasts.

Interpretation

Hitherto, characteristic features of COA7 patients were described as slowly progressing neuropathy and spinocerebellar ataxia, starting at the toddler age and progressing into adulthood. In contrast, our patient was reported to show developmental delay from 3 months of age, which was found to be due to a rapidly progressive encephalopathy and brain atrophy seen at 9 months of age. Unexpectedly, the genetic investigation revealed a COA7-associated mitochondrial disease, which was confirmed functionally. Thus, this report broadens the genetic and clinical spectrum of this heterogeneous mitochondriopathy and highlights the value of the presented unbiased approach.

Hepcidin Levels and Pathological Characteristics in Children with Fatty Liver Disease

PURPOSE

Hepcidin levels have previously been reported to be correlated with liver damage. However, the association between hepcidin levels and liver fibrosis in children with fatty liver disease remains unclear. This study therefore aimed to investigate the pathophysiology of fibrosis in children with fatty liver disease and its association with hepcidin levels.

METHODS

This retrospective case series included 12 boys aged 6-17 years who were diagnosed with nonalcoholic fatty liver disease (NAFLD) or nonalcoholic steatohepatitis (NASH) at the Tokyo Medical University Hospital. Sixteen liver biopsy samples from 12 subjects were analyzed. Serum hepcidin levels were assayed using enzyme-linked immunosorbent assay. Immunostaining for hepcidin was performed, and the samples were stratified by staining intensity.

RESULTS

Serum hepcidin levels were higher in pediatric NAFLD/NASH patients than in controls. Conversely, a significant inverse correlation was observed between hepcidin immunostaining and Brunt grade scores and between hepcidin scores and gamma-glutamyltranspeptidase, hyaluronic acid, and leukocyte levels. We observed inverse correlations with a high correlation coefficient of >0.4 between hepcidin immunostaining and aspartate aminotransferase, alanine aminotransferase, total bile acid, and platelet count.

CONCLUSION

There was a significant inverse correlation between hepcidin immunoreactivity and fibrosis in pediatric NAFLD patients; however, serum hepcidin levels were significantly higher, suggesting that these patients experienced a reduction in the hepcidin-producing ability of the liver in response to iron levels, leading to subsequent fibrosis. Therefore, hepcidin levels can be used as markers to identify the progression of fibrosis in patients with NAFLD.

Whole genome and exome sequencing identify NDUFV2 mutations as a new cause of progressive cavitating leukoencephalopathy

Background

Progressive cavitating leukoencephalopathy (PCL) is thought to result from mutations in nuclear genes affecting mitochondrial function and energy metabolism. To date, mutations in two subunits of complex I, NDUFS1 and NDUFV1, have been reported to be related to PCL.

Methods

Patients underwent clinical examinations, brain MRI, skin biopsy and muscle biopsy. Whole-genome or whole-exome sequencing was performed on the index patients from two unrelated families with PCL. The effects of the mutations were examined through complementation of the NDUFV2 mutation by cDNA expression.

Results

The common clinical features of the patients in this study were recurring episodes of acute or subacute developmental regression that appeared in the first years of life, followed by gradual remissions and prolonged periods of stability. MRI showed leukoencephalopathy with multiple cavities. Three novel NDUFV2 missense mutations were identified in these families. Complex I deficiency was confirmed in affected individuals’ fibroblasts and a muscle biopsy. Functional and structural analyses revealed that these mutations affect the structural stability and function of the NDUFV2 protein, indicating that defective NDUFV2 function is responsible for the phenotypes in these individuals.

Conclusions

Here, we report the clinical presentations, neuroimaging and molecular and functional analyses of novel mutations in NDUFV2 in two sibling pairs of two Chinese families presenting with PCL. We hereby expand the knowledge on the clinical phenotypes associated with mutations in NDUFV2 and the genotypes causative for PCL.

Prenatal diagnosis of severe mitochondrial diseases caused by nuclear gene defects: a study in Japan

Prenatal diagnoses of mitochondrial diseases caused by defects in nuclear DNA (nDNA) or mitochondrial DNA have been reported in several countries except for Japan. The present study aimed to clarify the status of prenatal genetic diagnosis of mitochondrial diseases caused by nDNA defects in Japan. A comprehensive genomic analysis was performed to diagnose more than 400 patients, of which, 13 families (16 cases) had requested prenatal diagnoses. Eight cases diagnosed with wild type homozygous or heterozygous variants same as either of the heterozygous parents continued the pregnancy and delivered healthy babies. Another eight cases were diagnosed with homozygous, compound heterozygous, or hemizygous variants same as the proband. Of these, seven families chose to terminate the pregnancy, while one decided to continue the pregnancy. Neonatal- or infantile-onset mitochondrial diseases show severe phenotypes and lead to lethality. Therefore, such diseases could be candidates for prenatal diagnosis with careful genetic counseling, and prenatal testing could be a viable option for families.

Whole exome sequencing identifies a novel homozygous MECR mutation in a Chinese patient with childhood-onset dystonia and basal ganglia abnormalities, without optic atrophy

Childhood-onset dystonia with optic atrophy and basal ganglia abnormalities is an extremely rare autosomal recessive mitochondrial disease caused by biallelic mutations in MECR. Using whole-exome sequencing, we identified a novel homozygous MECR mutation (c.910G > T, p.Asp304Tyr) in a Chinese patient with childhood-onset dystonia and basal ganglia abnormalities, without optic atrophy. With lipoic acid treatment, the disease progression was under control, and neither visual impairment nor optic atrophy was observed. To our knowledge, this is the first study about MECR-related mitochondrial disease in a Chinese patient and the first to report that supplementation with lipoic acid is a possible effective therapeutic strategy for this disease.

A novel homozygous variant in MICOS13/QIL1 causes hepato-encephalopathy with mitochondrial DNA depletion syndrome

BACKGROUND

Mitochondrial DNA depletion syndrome (MTDPS) is part of a group of mitochondrial diseases characterized by a reduction in mitochondrial DNA copy number. Most MTDPS is caused by mutations in genes that disrupt deoxyribonucleotide metabolism.

METHODS

We performed the whole-exome sequencing of a hepato-encephalopathy patient with MTDPS and functional analyses to determine the clinical significance of the identified variant.

RESULTS

Here, whole-exome sequencing of a patient presenting with hepato-encephalopathy and MTDPS identified a novel homozygous frameshift variant, c.13_29del (p.Trp6Profs*71) in MICOS13. MICOS13 (also known as QIL1, MIC13, or C19orf70) is a component of the MICOS complex, which plays crucial roles in the maintenance of cristae junctions at the mitochondrial inner membrane. We found loss of MICOS13 protein and fewer cristae structures in the mitochondria of fibroblasts derived from the patient. Stable expression of a wild-type MICOS13 cDNA in the patients fibroblasts using a lentivirus system rescued mitochondrial respiratory chain complex deficiencies.

CONCLUSION

Our findings suggest that the novel c.13_29del (p.Trp6Profs*71) MICOS13 variant causes hepato-encephalopathy with MTDPS. We propose that MICOS13 is classified as the cause of MTDPS.

Effectiveness of low-dose riboflavin as a prophylactic agent in pediatric migraine

BACKGROUND

Riboflavin may prevent migraine episodes; however, there is limited evidence of its effectiveness in pediatric populations. This study investigated the effectiveness of riboflavin and clinical predictors of response in children with migraines.

METHODS

We retrospectively reviewed data from 68 Japanese children with migraines, of whom 52 also exhibited another type of headache. Patients received 10 or 40 mg/day of riboflavin. We evaluated the average migraine frequency per month as a baseline and after 3 months of riboflavin therapy to determine the effectiveness and clinical predictors of response.

RESULTS

The frequency of migraine episodes was significantly lower at 3 months than at baseline (median, [interquartile range], 5.2 (3-7) vs. 4.0 (2-5); p < 0.01). Twenty-five patients (36.7%) showed 50% or greater reduction in episode frequency (responders), while 18 (26.5%) showed a 25%-50% reduction. We compared responders (n = 25) and non-responders (n = 43) and found no significant differences in sex, familial history, riboflavin dose, migraine type (i.e., presence or absence of aura), age at headache onset, or age at consultation. However, non-responders were more likely to have co-morbid non-migraine headaches (odds ratio, 4.11; 95% confidence interval [CI], 1.27-13.33; p = 0.02); this variable was also significant in a multivariate analysis (adjusted odds ratio, 3.8; 95% CI, 1.16-12.6; p = 0.03). Of the co-morbid headache types, only tension headaches were significant (odds ratio, 0.176; 95% CI, 0.04-0.73; p = 0.013). No adverse effects of riboflavin were identified.

CONCLUSIONS

Low-dose riboflavin is safe and modestly effective for migraines in children. It may be especially beneficial for children without other co-morbid headache types.

Clinical and molecular basis of hepatocerebral mitochondrial DNA depletion syndrome in Japan: evaluation of outcomes after liver transplantation

BACKGROUND

Hepatocerebral mitochondrial DNA depletion syndrome (MTDPS) is a disease caused by defects in mitochondrial DNA maintenance and leads to liver failure and neurological complications during infancy. Liver transplantation (LT) remains controversial due to poor outcomes associated with extrahepatic symptoms. The purposes of this study were to clarify the current clinical and molecular features of hepatocerebral MTDPS and to evaluate the outcomes of LT in MTDPS patients in Japan.

RESULTS

We retrospectively assessed the clinical and genetic findings, as well as the clinical courses, of 23 hepatocerebral MTDPS patients from a pool of 999 patients who were diagnosed with mitochondrial diseases between 2007 and 2019. Causative genes were identified in 18 of 23 patients: MPV17 (n = 13), DGUOK (n = 3), POLG (n = 1), and MICOS13 (n = 1). Eight MPV17-deficient patients harbored c.451dupC and all three DGUOK-deficient patients harbored c.143-307_170del335. The most common initial manifestation was failure to thrive (n = 13, 56.5%). The most frequent liver symptom was cholestasis (n = 21, 91.3%). LT was performed on 12 patients, including nine MPV17-deficient and two DGUOK-deficient patients. Among the 12 transplanted patients, five, including one with mild intellectual disability, survived; while seven who had remarkable neurological symptoms before LT died. Five of the MPV17-deficient survivors had either c.149G > A or c.293C > T.

CONCLUSIONS

MPV17 was the most common genetic cause of hepatocerebral MTDPS. The outcome of LT for MTDPS was not favorable, as previously reported, however, patients harboring MPV17 mutations associated with mild phenotypes such as c.149G > A or c.293C > T, and exhibiting no marked neurologic manifestations before LT, had a better prognosis after LT.

Therapeutic effect of N-carbamylglutamate in CPS1 deficiency

The detoxification of ammonia to urea requires a functional hepatic urea cycle, which consists of six enzymes and two mitochondrial membrane transporters. The initial step of the urea cycle is catalyzed by carbamyl phosphate synthetase 1 (CPS1). CPS1 deficiency (CPS1D) is a rare autosomal recessive disorder. N-Carbamylglutamate (NCG), a deacylase-resistant analogue of N-acetylglutamate, can activate CPS1. We describe the therapeutic course of a patient suffering from neonatal onset CPS1D with compound heterozygosity for the c.2359C > T (p.Arg787*) and c.3559G > T (p.Val1187Phe) variants in CPS1, treated with NCG. She presented with hyperammonemia, which reached 944 μmol/L at the age of 2 days. The ammonia concentration decreased after treatment with continuous hemodiafiltration, NCG, sodium benzoate, sodium phenylbutyrate, L-arginine, vitamin cocktail (vitamin B1, vitamin B12, vitamin C, vitamin E, biotin), l-carnitine, coenzyme Q10, and parenteral nutrition. Her ammonia and glutamine levels remained low; thus, protein intake was increased to 1.2 g/kg/day. Furthermore, the amount of sodium benzoate and sodium phenylbutyrate were reduced. She remained metabolically stable and experienced no metabolic crisis following treatment with oral NCG, sodium benzoate, sodium phenylbutyrate, citrulline, vitamin cocktail, l-carnitine, and coenzyme Q10 until she underwent liver transplantation at 207 days of age. She had no neurological complications at the age of 15 months. Ammonia and glutamine levels of the patient were successfully maintained at a low level via NCG treatment with increased protein intake, which led to normal neurological development. Thus, undiagnosed urea cycle disorders should be treated rapidly with acute therapy including NCG, which should be maintained until a genetic diagnosis is reached. It is essential to prevent metabolic crises in patients with CPS1D until liver transplantation to improve their prognoses.

Mortality of Japanese patients with Leigh syndrome: Effects of age at onset and genetic diagnosis

Leigh syndrome is a major phenotype of mitochondrial diseases in children. With new therapeutic options being proposed, assessing the mortality and clinical condition of Leigh syndrome patients is crucial for evaluating therapeutics. As data are scarce in Japan, we analysed the mortality rate and clinical condition of Japanese Leigh syndrome patients that we diagnosed since 2007. Data from 166 Japanese patients diagnosed with Leigh syndrome from 2007 to 2017 were reviewed. Patients' present status, method of ventilation and feeding, and degree of disability as of April 2018 was analysed. Overall, 124 (74.7%) were living, 40 (24.1%) were deceased, and 2 (1.2%) were lost to follow-up. Median age of living patients was 8 years (1-39 years). Median length of disease course was 91 months for living patients and 23.5 months for deceased patients. Nearly 90% of deaths occurred by age 6. Mortality rate of patients with onset before 6 months of age was significantly higher than that of onset after 6 months. All patients with neonatal onset were either deceased or bedridden. MT-ATP6 deficiency caused by m.8993T>G mutation and MT-ND5 deficiency induced a severe form of Leigh syndrome. Patients with NDUFAF6, ECHS1, and SURF1 deficiency had relatively mild symptoms and better survival. The impact of onset age on prognosis varied across the genetic diagnoses. The clinical condition of many patients was poor; however, few did not require mechanical ventilation or tube-feeding and were not physically dependent. Early disease onset and genetic diagnosis may have prognostic value.

Hearing impairment improved after treatment with asfotase alfa in a case of perinatal hypophosphatasia

Hearing impairment is a neurological symptom of hypophosphatasia (HPP), which leads to a reduced quality of life. However, the pathomechanism of hearing impairment and the effects of asfotase alfa enzyme replacement therapy on hearing function in HPP have not been clarified. Here we report a case and present clinical data of a patient with perinatal HPP whose hearing impairment improved after asfotase alfa treatment.

Efficacy of bezafibrate in two patients with mitochondrial trifunctional protein deficiency

Mitochondrial trifunctional protein (TFP) deficiency is a rare inherited metabolic disorder caused by defects in fatty acid β-oxidation (FAO) of long-chain fatty acids, leading to impaired energy production. Fasting avoidance, fatty acid-restricted diets, and supplementation with medium-chain triglycerides are recommended as a treatment, but there are no pharmaceutical treatments available with strong evidence of efficacy. Bezafibrate, which enhances the transcription of FAO enzymes, is a promising therapeutic option for FAO disorders (FAODs). The effectiveness of bezafibrate for FAODs has been reported in some clinical trials, but few clinical studies have investigated its in vivo efficacy toward TFP deficiency.

Herein, we describe two Japanese patients with TFP deficiency. Patient 1 presented with recurrent myalgia since the age of 5 years. Laboratory findings showed increased serum levels of long-chain fatty acids and reduced expression of TFPα and TFPβ in his skin fibroblasts. Based on these findings, he was diagnosed with the myopathic type of TFP deficiency. Patient 2 suddenly exhibited cardiopulmonary arrest one day after birth. Elevated levels of creatine kinase and long-chain acylcarnitines were observed. Genetic analysis identified compound heterozygous variants in HADHB (c.1175C>T/c.1364T>G). He was diagnosed with the lethal type of TFP deficiency. Although both patients were treated with dietary therapy and l-carnitine supplementation, they experienced frequent myopathic attacks associated with respiratory infections and exercise. After the initiation of bezafibrate, their myopathic manifestations were markedly reduced, leading to an improvement in quality of life without any side effects.

Our clinical findings indicate that bezafibrate combined with other treatments such as dietary therapy may be effective in improving myopathic manifestations in TFP deficiency.

A homozygous variant in NDUFA8 is associated with developmental delay, microcephaly, and epilepsy due to mitochondrial complex I deficiency

Mitochondrial complex I deficiency is caused by pathogenic variants in mitochondrial and nuclear genes associated with complex I structure and assembly. We report the case of a patient with　NDUFA8-related mitochondrial disease. The patient presented with developmental delay, microcephaly, and epilepsy. His fibroblasts showed apparent biochemical defects in mitochondrial complex I. Whole-exome sequencing revealed that the patient carried a homozygous variant in NDUFA8. His fibroblasts showed a reduction in the protein expression level of not only NDUFA8, but also the other complex I subunits, consistent with assembly defects. The enzyme activity of complex I and oxygen consumption rate were restored by reintroducing wild-typeNDUFA8 cDNA into patient fibroblasts. The functional properties of the variant in NDUFA8 were also investigated using NDUFA8 knockout cells expressing wild-type or mutated NDUFA8 cDNA. These experiments further supported the pathogenicity of the variant in complex I assembly. This is the first report describing that the loss of NDUFA8, which has not previously been associated with mitochondrial disease, causes severe defect in the assembly of mitochondrial complex I, leading to progressive neurological and developmental abnormalities.

Two cases of a non-progressive hepatic form of glycogen storage disease type IV with atypical liver pathology

Glycogen storage disease type IV (GSD IV) is a rare inborn metabolic disorder characterized by the accumulation of amylopectin-like glycogen in the liver or other organs. The hepatic subtype may appear normal at birth but rapidly develops to liver cirrhosis in infancy. Liver pathological findings help diagnose the hepatic form of the disease, supported by analyses of enzyme activity and GBE1 gene variants. Pathology usually shows periodic acid-Schiff (PAS) positive hepatocytes resistant to diastase. We report two cases of hepatic GSD IV with pathology showing PAS positive hepatocytes that were mostly digested by diastase, which differ from past cases. Gene analysis was critical for the diagnosis. Both cases were found to have the same variants c.288delA (p.Gly97GlufsTer46) and c.1825G > A (p.Glu609Lys). These findings suggest that c.1825G > A variant might be a common variant in the non-progressive hepatic form of GSD IV.

A familial case of overgrowth syndrome caused by a 9q22.3 microdeletion in a mother and daughter

Microdeletions in the 9q22.3 chromosomal region can cause macrosomia with characteristic features, including prenatal-onset overgrowth, metopic craniosynostosis, hydrocephalus, developmental delay, and intellectual disability, in addition to manifestations of nevoid basal cell carcinoma syndrome (NBCCS). Haploinsufficiency of PTCH1 may be responsible for accelerated overgrowth, but the mechanism of macrosomia remains to be elucidated. We report a familial case with a 9q22.3 microdeletion, manifesting with prenatal-onset overgrowth in a mother and post-natal overgrowth in her daughter. Although both were clinically diagnosed with NBCCS, they had characteristic features of 9q22.3 microdeletion, especially the daughter. Microarray comparative genomic hybridization analysis revealed a 4.0 Mb deletion of chromosome 9q22.3 in both individuals. Among the 11 reported patients of overgrowth and/or macrosomia, a 550 Kb region encompassing PTCH1, C9orf3, FANCC, and 5 miRNAs is the most commonly deleted region. The let-7 family miRNAs, which are involved in diverse cellular processes including growth and tumor processes, were identified in the deleted regions in 10 of 11 patients. Characteristic features of 9q22.3 microdeletion might be associated with decreased expression of let-7.

Successful treatment of infantile-onset ACAD9-related cardiomyopathy with a combination of sodium pyruvate, beta-blocker, and coenzyme Q10

Mitochondrial acyl-CoA dehydrogenase 9 (ACAD9) deficiency is one of the common causes of respiratory chain complex I deficiency, which is characterized by cardiomyopathy, lactic acidemia, and muscle weakness. Infantile cardiomyopathy is the most common phenotype and is usually lethal by the age of 5 years. Riboflavin treatment is known to be effective in ~65% of the patients; however, the remaining are unresponsive to riboflavin and are in need of additional treatment measures. In this report, we describe a patient with ACAD9 deficiency who developed progressive cardiomyopathy at 8 months of age. As the patient's left ventricular ejection fraction (LVEF) kept decreasing to 45.4% at 1 year 8 months, sodium pyruvate treatment was introduced together with a beta-blocker and coenzyme Q10. This resulted in a steady improvement, with full and sustained normalization of cardiac function without riboflavin. The therapy, therefore, might be a useful addition for the treatment of ACAD9 deficiency.

Antiepileptic drug-induced psychosis associated with MTHFR C677T: a case report

Background

Various antiepileptic drugs can potentially cause psychiatric side effects in patients with epilepsy, but the precise mechanism of these actions remains unknown. In recent years, the common polymorphism C677T in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has attracted attention for its role in the onset of psychiatric diseases. MTHFR and several vitamins (as cofactors) are crucial for remethylation of homocysteine via folate and homocysteine metabolism. We report a case of a Japanese patient who presented with reversible schizophrenia-like symptoms during antiepileptic drug therapy.

Case presentation

Our patient had frontal lobe epilepsy and had been treated with several antiepileptic drugs since the age of 13 years. He developed auditory hallucinations and multiple personalities at 17 years of age, several months after the initiation of phenytoin and phenobarbital, despite these antiepileptic drugs being used within the therapeutic ranges. Genetic analysis revealed that he was homozygous for the C677T polymorphism of MTHFR. Hyperhomocysteinemia, hypomethionemia, and multiple vitamin deficiencies, including folate, riboflavin, and pyridoxal, were identified at the age of 23 years. Vitamin supplementation and alteration of the antiepileptic drugs improved his psychotic symptoms. Multiple vitamin deficiencies with homozygous MTHFR C677T should be considered in patients presenting with schizophrenia-like symptoms during antiepileptic drug therapy.

Conclusions

To the best of our knowledge, this is the first report of antiepileptic drug-induced psychosis associated with homozygous C677T and multiple vitamin deficiencies. Our findings will contribute to the elucidation of the pathogenesis of the psychiatric side effects of antiepileptic drugs and lead to improved medical management for patients with epilepsy.

MELAS syndrome with m.4450 G > A mutation in mitochondrial tRNAMet gene

Mutations in the mitochondrial tRNA^Met gene have been reported in only five patients to date, all of whom presented with muscle weakness and exercise intolerance as signs of myopathy. We herein report the case of a 12-year-old girl with focal epilepsy since the age of eight years. At age 11, the patient developed sudden visual disturbances and headaches accompanied by recurrent, stroke-like episodes with lactic acidosis (pH 7.279, lactic acid 11.6 mmol/L). The patient frequently developed a delirious state, exhibited regression of intellectual ability. Brain magnetic resonance imaging revealed high-intensity signals on T2-weighted images of the left occipital lobe. Mitochondrial gene analysis revealed a heteroplasmic m.4450G > A mutation in the mitochondrial tRNA^Met. The heteroplasmic rate of the m.4450G > A mutation in blood, skin, urinary sediment, hair, saliva, and nail samples were 20, 38, 59, 41, 27, and 35%, respectively. The patient's fibroblast showed an approximately 53% reduction in the oxygen consumption rate, compared to a control, and decreased complex I and IV activities. Stroke-like episodes, lactic acidosis, encephalopathy with brain magnetic resonance imaging findings, and declined mitochondrial function were consistent with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. To our knowledge, the findings associated with this first patient with MELAS syndrome harboring the m.4450G > A mutation in mitochondrial tRNA^Met expand the phenotypic spectrum of tRNA^Met gene.

Mitochondrial ribosomal protein PTCD3 mutations cause oxidative phosphorylation defects with Leigh syndrome

Pentatricopeptide repeat domain proteins are a large family of RNA-binding proteins involved in mitochondrial RNA editing, stability, and translation. Mitochondrial translation machinery defects are an expanding group of genetic diseases in humans. We describe a patient who presented with low birth weight, mental retardation, and optic atrophy. Brain MRI showed abnormal bilateral signals at the basal ganglia and brainstem, and the patient was diagnosed as Leigh syndrome. Exome sequencing revealed two potentially loss-of-function variants [c.415-2A>G, and c.1747_1748insCT (p.Phe583Serfs*3)] in PTCD3 (also known as MRPS39). PTCD3, a member of the pentatricopeptide repeat domain protein family, is a component of the small mitoribosomal subunit. The patient had marked decreases in mitochondrial complex I and IV levels and activities, oxygen consumption and ATP biosynthesis, and generalized mitochondrial translation defects in fibroblasts. Quantitative proteomic analysis revealed decreased levels of the small mitoribosomal subunits. Complementation experiments rescued oxidative phosphorylation complex I and IV levels and activities, ATP biosynthesis, and MT-RNR1 rRNA transcript level, providing functional validation of the pathogenicity of identified variants. This is the first report of an association of PTCD3 mutations with Leigh syndrome along with combined oxidative phosphorylation deficiencies caused by defects in the mitochondrial translation machinery.

Effectiveness of plasma lyso-Gb3 as a biomarker for selecting high-risk patients with Fabry disease from multispecialty clinics for genetic analysis

PURPOSE

Plasma globotriaosylsphingosine (lyso-Gb3) is a promising secondary screening biomarker for Fabry disease. Here, we examined its applicability as a primary screening biomarker for classic and late-onset Fabry disease in males and females.

METHODS

Between 1 July 2014 and 31 December 2015, we screened 2,359 patients (1,324 males) referred from 168 Japanese specialty clinics (cardiology, nephrology, neurology, and pediatrics), based on clinical symptoms suggestive of Fabry disease. We used the plasma lyso-Gb3 concentration, α-galactosidase A (α-Gal A) activity, and analysis of the α-Gal A gene (GLA) for primary and secondary screens, respectively.

RESULTS

Of 8 males with elevated lyso-Gb3 levels (≥2.0 ng ml-1) and low α-Gal A activity (≤4.0 nmol h-1 ml-1), 7 presented a GLA mutation (2 classic and 5 late-onset). Of 14 females with elevated lyso-Gb3, 7 displayed low α-Gal A activity (5 with GLA mutations; 4 classic and 1 late-onset) and 7 exhibited normal α-Gal A activity (1 with a classic GLA mutation and 3 with genetic variants of uncertain significance).

CONCLUSION

Plasma lyso-Gb3 is a potential primary screening biomarker for classic and late-onset Fabry disease probands.

Mutations in TOP3A Cause a Bloom Syndrome-like Disorder

Bloom syndrome, caused by biallelic mutations in BLM, is characterized by prenatal-onset growth deficiency, short stature, an erythematous photosensitive malar rash, and increased cancer predisposition. Diagnostically, a hallmark feature is the presence of increased sister chromatid exchanges (SCEs) on cytogenetic testing. Here, we describe biallelic mutations in TOP3A in ten individuals with prenatal-onset growth restriction and microcephaly. TOP3A encodes topoisomerase III alpha (TopIIIα), which binds to BLM as part of the BTRR complex, and promotes dissolution of double Holliday junctions arising during homologous recombination. We also identify a homozygous truncating variant in RMI1, which encodes another component of the BTRR complex, in two individuals with microcephalic dwarfism. The TOP3A mutations substantially reduce cellular levels of TopIIIα, and consequently subjects' cells demonstrate elevated rates of SCE. Unresolved DNA recombination and/or replication intermediates persist into mitosis, leading to chromosome segregation defects and genome instability that most likely explain the growth restriction seen in these subjects and in Bloom syndrome. Clinical features of mitochondrial dysfunction are evident in several individuals with biallelic TOP3A mutations, consistent with the recently reported additional function of TopIIIα in mitochondrial DNA decatenation. In summary, our findings establish TOP3A mutations as an additional cause of prenatal-onset short stature with increased cytogenetic SCEs and implicate the decatenation activity of the BTRR complex in their pathogenesis.

Loss of the Mitochondrial Fatty Acid β-Oxidation Protein Medium-Chain Acyl-Coenzyme A Dehydrogenase Disrupts Oxidative Phosphorylation Protein Complex Stability and Function

Medium-chain acyl-Coenzyme A dehydrogenase (MCAD) is involved in the initial step of mitochondrial fatty acid β-oxidation (FAO). Loss of function results in MCAD deficiency, a disorder that usually presents in childhood with hypoketotic hypoglycemia, vomiting and lethargy. While the disruption of mitochondrial fatty acid metabolism is the primary metabolic defect, secondary defects in mitochondrial oxidative phosphorylation (OXPHOS) may also contribute to disease pathogenesis. Therefore, we examined OXPHOS activity and stability in MCAD-deficient patient fibroblasts that have no detectable MCAD protein. We found a deficit in mitochondrial oxygen consumption, with reduced steady-state levels of OXPHOS complexes I, III and IV, as well as the OXPHOS supercomplex. To examine the mechanisms involved, we generated an MCAD knockout (KO) using human 143B osteosarcoma cells. These cells also exhibited defects in OXPHOS complex function and steady-state levels, as well as disrupted biogenesis of newly-translated OXPHOS subunits. Overall, our findings suggest that the loss of MCAD is associated with a reduction in steady-state OXPHOS complex levels, resulting in secondary defects in OXPHOS function which may contribute to the pathology of MCAD deficiency.

The comparative anatomy of the folds, fossae, and adhesions around the duodenojejunal flexure in mammals

BACKGROUND

Anatomical knowledge of the duodenojejunal flexure is necessary for abdominal surgeries, and also important for physiologic studies about the duodenum. But little is known about the anatomy of this region in mammals. Here, we examined comparative anatomy to understand the anatomical formation of the duodenojejunal flexure in mammals.

MATERIALS AND METHODS

The areas around the duonenojejunal flexure were ob-served in mouse, rat, dog, pig, and human, and the anatomical structures around the duodenojejunal junction in the animals were compared with those in human.

RESULTS

The superior and inferior duodenal folds, and the superior and inferior duodenal fossae were identified in all examined humans. In pig, the structures were not clearly identified because the duodenum strongly adhered to the retroperitoneum and to the mesocolon. In mouse, rat, and dog, only the plica duodenocolica, which is regarded as the animal counterpart of the superior duo-denal fold in human, was identified, and other folds or fossae were not observed, probably because the duodenum was not fixed to the parietal peritoneum in those animals. Transection of the plica duodenocolica could return the normally rotated intestine back to the state of non-rotation in rat.

CONCLUSIONS

This study showed the anatomical similarities and dissimilarities of the duodenojejunal flexure among the mammals. Anatomical knowledge of the area is useful for duodenal and pancreatic surgeries, and for animal studies about the duodenum. (Folia Morphol 2018; 77, 2: 286-292).

Clinical validity of biochemical and molecular analysis in diagnosing Leigh syndrome: a study of 106 Japanese patients

Leigh syndrome (LS) is a progressive neurodegenerative disorder of infancy and early childhood. It is clinically diagnosed by typical manifestations and characteristic computed tomography (CT) or magnetic resonance imaging (MRI) studies. Unravelling mitochondrial respiratory chain (MRC) dysfunction behind LS is essential for deeper understanding of the disease, which may lead to the development of new therapies and cure. The aim of this study was to evaluate the clinical validity of various diagnostic tools in confirming MRC disorder in LS and Leigh-like syndrome (LL). The results of enzyme assays, molecular analysis, and cellular oxygen consumption rate (OCR) measurements were examined. Of 106 patients, 41 were biochemically and genetically verified, and 34 had reduced MRC activity but no causative mutations. Seven patients with normal MRC complex activities had mutations in the MT-ATP6 gene. Five further patients with normal activity in MRC were identified with causative mutations. Conversely, 12 out of 60 enzyme assays performed for genetically verified patients returned normal results. No biochemical or genetic background was confirmed for 19 patients. OCR was reduced in ten out of 19 patients with negative enzyme assay results. Inconsistent enzyme assay results between fibroblast and skeletal muscle biopsy samples were observed in 33% of 37 simultaneously analyzed cases. These data suggest that highest diagnostic rate is reached using a combined enzymatic and genetic approach, analyzing more than one type of biological materials where suitable. Microscale oxygraphy detected MRC impairment in 50% cases with no defect in MRC complex activities.

Practical characteristics of adaptive design in phase 2 and 3 clinical trials

WHAT IS KNOWN AND OBJECTIVE

Adaptive design methods are expected to be ethical, reflect real medical practice, increase the likelihood of research and development success and reduce the allocation of patients into ineffective treatment groups by the early termination of clinical trials. However, the comprehensive details regarding which types of clinical trials will include adaptive designs remain unclear. We examined the practical characteristics of adaptive design used in clinical trials.

METHODS

We conducted a literature search of adaptive design clinical trials published from 2012 to 2015 using PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials, with common search terms related to adaptive design. We systematically assessed the types and characteristics of adaptive designs and disease areas employed in the adaptive design trials.

RESULTS AND DISCUSSION

Our survey identified 245 adaptive design clinical trials. The number of trials by the publication year increased from 2012 to 2013 and did not greatly change afterwards. The most frequently used adaptive design was group sequential design (n = 222, 90.6%), especially for neoplasm or cardiovascular disease trials. Among the other types of adaptive design, adaptive dose/treatment group selection (n = 21, 8.6%) and adaptive sample-size adjustment (n = 19, 7.8%) were frequently used. The adaptive randomization (n = 8, 3.3%) and adaptive seamless design (n = 6, 2.4%) were less frequent. Adaptive dose/treatment group selection and adaptive sample-size adjustment were frequently used (up to 23%) in "certain infectious and parasitic diseases," "diseases of nervous system," and "mental and behavioural disorders" in comparison with "neoplasms" (<6.6%). For "mental and behavioural disorders," adaptive randomization was used in two trials of eight trials in total (25%). Group sequential design and adaptive sample-size adjustment were used frequently in phase 3 trials or in trials where study phase was not specified, whereas the other types of adaptive designs were used more in phase 2 trials. Approximately 82% (202 of 245 trials) resulted in early termination at the interim analysis. Among the 202 trials, 132 (54% of 245 trials) had fewer randomized patients than initially planned. This result supports the motive to use adaptive design to make study durations shorter and include a smaller number of subjects.

WHAT IS NEW AND CONCLUSION

We found that adaptive designs have been applied to clinical trials in various therapeutic areas and interventions. The applications were frequently reported in neoplasm or cardiovascular clinical trials. The adaptive dose/treatment group selection and sample-size adjustment are increasingly common, and these adaptations generally follow the Food and Drug Administration's (FDA's) recommendations.

A Comprehensive Genomic Analysis Reveals the Genetic Landscape of Mitochondrial Respiratory Chain Complex Deficiencies

Mitochondrial disorders have the highest incidence among congenital metabolic disorders characterized by biochemical respiratory chain complex deficiencies. It occurs at a rate of 1 in 5,000 births, and has phenotypic and genetic heterogeneity. Mutations in about 1,500 nuclear encoded mitochondrial proteins may cause mitochondrial dysfunction of energy production and mitochondrial disorders. More than 250 genes that cause mitochondrial disorders have been reported to date. However exact genetic diagnosis for patients still remained largely unknown. To reveal this heterogeneity, we performed comprehensive genomic analyses for 142 patients with childhood-onset mitochondrial respiratory chain complex deficiencies. The approach includes whole mtDNA and exome analyses using high-throughput sequencing, and chromosomal aberration analyses using high-density oligonucleotide arrays. We identified 37 novel mutations in known mitochondrial disease genes and 3 mitochondria-related genes (MRPS23, QRSL1, and PNPLA4) as novel causative genes. We also identified 2 genes known to cause monogenic diseases (MECP2 and TNNI3) and 3 chromosomal aberrations (6q24.3-q25.1, 17p12, and 22q11.21) as causes in this cohort. Our approaches enhance the ability to identify pathogenic gene mutations in patients with biochemically defined mitochondrial respiratory chain complex deficiencies in clinical settings. They also underscore clinical and genetic heterogeneity and will improve patient care of this complex disorder.

Mitochondria play a crucial role in ATP biosynthesis and comprise proteins encoded in both the nuclear and mitochondrial genomes. Although more than 250 mitochondrial disease-causing genes have been reported, the exact genetic causes in patients remain largely unknown. Here, we aimed to provide further insights into the pathogenic mechanisms of mitochondrial disorders. We investigated the genes encoded in the nuclear and mitochondrial genomes using comprehensive genomic analysis in 142 patients with mitochondrial respiratory chain complex deficiencies. We identified 3 novel disease-causing mitochondria-related genes (MRPS23, QRSL1, and PNPLA4) as well as other disease-causing genes and novel pathogenic mutations in known mitochondrial disease-causing genes. All pathogenic mutations in this study are validated by genetic and/or functional evidence. Our findings, including the achievement of firm genetic diagnoses for 49 of 142 patients (34.5%), were higher than the general diagnosis rate of approximately 25% and demonstrated the value of comprehensive genomic analysis. Accordingly, we have shed light on the genetic heterogeneity underlying mitochondrial disorders.

Effects of parathyroid hormone-related protein on systemic and regional hemodynamics in conscious rats. A comparison with human parathyroid hormone

PTHrp was discovered as a humoral hypercalcemic factor of malignancy and has been shown to bind the same receptor as PTH in rat bone cells, canine renal membranes, and rabbit renal microvessels. We investigated the global effect of human PTH(hPTH) and PTHrp on systemic and regional hemodynamics in conscious rats. The hypotensive response to PTHrp was more potent than that to hPTH. Although hPTH (15 micrograms/kg/min, i.v.) caused a significant increase in cardiac output, whereas PTHrp (5 micrograms/kg/min, i.v.) caused no change in cardiac output despite a similar hypotensive effect to hPTH, the effects of PTHrp and hPTHrp on regional hemodynamics were quite similar, and both peptides had a prominent vasodilatory effect on the coronary and hepatic arteries. Therefore, PTHrp appears to have an important role in blood pressure and regional hemodynamics as does hPTH.