A novel ABCD1 gene mutation causes adrenomyeloneuropathy presenting with spastic paraplegia: A case report

RATIONALE

X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene leading to very long chain fatty acid (VLCFA) accumulation. The disease demonstrates a spectrum of phenotypes including adrenomyeloneuropathy (AMN). We aimed to identify the genetic basis of disease in a patient presenting with AMN features in order to confirm the diagnosis, expand genetic knowledge of ABCD1 mutations, and elucidate potential genotype-phenotype associations to inform management.

PATIENT CONCERNS

A 29-year-old male presented with a 4-year history of progressive spastic paraplegia, weakness of lower limbs, fecal incontinence, sexual dysfunction, hyperreflexia, and positive Babinski and Chaddock signs.

DIAGNOSES

Neuroimaging revealed brain white matter changes and spinal cord thinning. Significantly elevated levels of hexacosanoic acid (C26:0) and tetracosanoic acid (C24:0) suggested very long chain fatty acids (VLCFA) metabolism disruption. Genetic testing identified a novel hemizygous ABCD1 mutation c.249dupC (p.F83fs). These findings confirmed a diagnosis of X-linked ALD with an AMN phenotype.

INTERVENTIONS

The patient received dietary counseling to limit VLCFA intake. Monitoring for adrenal insufficiency and consideration of Lorenzo's oil were advised. Genetic counseling and testing were offered to at-risk relatives.

OUTCOMES

At present, the patient continues to experience progressive paraplegia. Adrenal function remains normal thus far without steroid replacement. Family members have undergone predictive testing.

LESSONS

This case expands the known mutation spectrum of ABCD1-linked X-ALD, providing insight into potential genotype-phenotype correlations. A thoughtful diagnostic approach integrating clinical, biochemical and genetic data facilitated diagnosis. Findings enabled genetic counseling for at-risk relatives regarding this X-linked disorder.

Adrenomyeloneuropathy with Later Development of Cerebral Form Caused by a Hemizygous Splice-site Variant in ABCD1

Adrenomyeloneuropathy (AMN)/adrenoleukodystrophy (ALD) is an X-linked genetic disorder caused by pathogenic variants in ABCD1. We treated a 54-year-old man with slowly progressive spastic paraparesis with later development of the cerebral form. A pathogenic splice-site variant of ABCD1 (c.1489-1G>A, p.Val497Alafs*51) and elevated levels of very long-chain fatty acids were found, leading to the diagnosis of AMN. Detailed ABCD1 mRNA expression analyses revealed decreased levels of ABCD1 mRNA accompanied by deletion of the first 31 bp in exon 6. The altered mRNA transcriptional patterns associated with splice site variants are diverse and may provide important insights into ALD pathogenesis.

Intrathecal administration of mesenchymal stem cells in patients with adrenomyeloneuropathy

Background and objectives

X-linked adrenomyeloneuropathy (AMN) is an inherited neurodegenerative disorder associated with mutations in the ABCD1 gene and the accumulation of very long-chain fatty acids (VLFCAs) in plasma and tissues. Currently, there is no effective treatment for AMN. We have aimed to evaluate the therapeutic effects of mesenchymal stem cell (MSC) transplantation in patients with AMN.

Methods

This is a small cohort open-label study with patients with AMN diagnosed and treated at the University Hospital in Olsztyn, Poland. All patients met clinical, biochemical, MRI, and neuropsychological criteria for AMN. MSCs derived from Wharton jelly, 20 × 106 cells, were administered intrathecally three times every 2 months, and patients were followed up for an additional 3 months. The primary outcome measures included a blinded assessment of lower limb muscle strength with the Medical Research Council Manual Muscle Testing scale at baseline and on every month visits until the end of the study. Additional outcomes included measurements of the timed 25-feet walk (T25FW) and VLFCA serum ratio.

Results

Three male patients with AMN with an age range of 26-37 years participated in this study. All patients experienced increased muscle strength in the lower limbs at the end of the study versus baseline. The power grade increased by 25-43% at the baseline. In addition, all patients showed an improvement trend in walking speed measured with the T25FW test. Treatment with MSCs in patients with AMN appeared to be safe and well tolerated.

Discussion

The results of this study demonstrated that intrathecal administration of WJ-MSC improves motor symptoms in patients with AMN. The current findings lend support to the safety and feasibility of MSC therapy as a potentially viable treatment option for patients with AMN.

Adrenomyeloneuropathy manifesting as adrenal insufficiency and bilateral lower extremity spastic paraplegia: A case report and literature review

RATIONALE

Adrenomyeloneuropathy (AMN) is a variant type of X-linked adrenoleukodystrophy, and it is a genetic metabolic disease with strong clinical heterogeneity so that it is easily misdiagnosed and underdiagnosed. Moreover, most patients with AMN have an insidious clinical onset and slow progression. Familiarity with the pathogenesis, clinical features, diagnosis, and treatment of AMN can help identify the disease at an early stage.

PATIENT CONCERNS

We present a case of 35-year-old male, who was admitted to our hospital due to "immobility of the lower limbs for 2 years and worsening for half a year," accompanied by skin darkening and hyperpigmentation of lips, oral mucosa, and areola since puberty.

DIAGNOSIS

The level of very long-chain fatty acids was high and genetic testing depicted that exon 1 of the ABCD1 gene had a missense mutation of C.761c>T, which was diagnosed as AMN.

INTERVENTIONS

Baclofen was administered to improve muscle tension combined with glucocorticoid replacement therapy.

OUTCOMES

The condition was relieved after half a year.

LESSONS

The clinical manifestations of AMN are diverse. When patients with adrenocortical dysfunction complicated with progressive spastic paraplegia of lower limbs are involved, AMN should be highly suspected, and the determination of very long-chain fatty acids and genetic testing should be performed as soon as possible to confirm the diagnosis because early treatment can help prevent or delay the progression of the disease.

Two Single Nucleotide Deletions in the ABCD1 Gene Causing Distinct Phenotypes of X-Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a rare inborn error of the peroxisomal metabolism caused by pathologic variants in the ATP-binding cassette transporter type D, member 1 (ABCD1) gene located on the X-chromosome. ABCD1 protein, also known as adrenoleukodystrophy protein, is responsible for transport of the very long chain fatty acids (VLCFA) from cytoplasm into the peroxisomes. Therefore, altered function or lack of the ABCD1 protein leads to accumulation of VLCFA in various tissues and blood plasma leading to either rapidly progressive leukodystrophy (cerebral ALD), progressive adrenomyeloneuropathy (AMN), or isolated primary adrenal insufficiency (Addison's disease). We report two distinct single nucleotide deletions in the ABCD1 gene, c.253delC [p.Arg85Glyfs*18] in exon 1, leading to both cerebral ALD and to AMN phenotype in one family, and c.1275delA [p.Phe426Leufs*15] in exon 4, leading to AMN and primary adrenal insufficiency in a second family. For the latter variant, we demonstrate reduced mRNA expression and a complete absence of the ABCD1 protein in PBMC. Distinct mRNA and protein expression in the index patient and heterozygous carriers does not associate with VLCFA concentration in plasma, which is in line with the absence of genotype-phenotype correlation in X-ALD.

Neurocognitive and mental health impact of adrenoleukodystrophy across the lifespan: Insights for the era of newborn screening

X-linked adrenoleukodystrophy (ALD) is a rare inherited neurological disorder that poses considerable challenges for clinical management throughout the lifespan. Although males are generally more severely affected than females, the time course and presentation of clinical symptoms are otherwise difficult to predict. Opportunities to improve outcomes for individuals with ALD are rapidly expanding due to the introduction of newborn screening programs for this condition and an evolving treatment landscape. The aim of this comprehensive review is to synthesize current knowledge regarding the neurocognitive and mental health effects of ALD. This review provides investigators and clinicians with context to improve case conceptualization, inform prognostic counseling, and optimize neuropsychological and mental health care for patients and their families. Results highlight key predictive factors and brain-behavior relationships associated with the diverse manifestations of ALD. The review also discusses considerations for endpoints within clinical trials and identifies gaps to address in future research.

Novel mutations in the ABCD1 gene caused adrenomyeloneuropathy in the Chinese population

Background

As a rare genetic disease, adrenomyeloneuropathy (AMN) is the most common adult phenotype of X-linked adrenoleukodystrophy (X-ALD). Mutations in the ABCD1 gene have been identified to cause AMN.

Methods

We applied clinical evaluation, laboratory tests, and neuroimaging on three patients with progressive spastic paraparesis. In genetic analysis, we investigated ABCD1 gene mutations by whole-exome sequencing and Sanger sequencing. Bioinformatics tools were used to predict the effects of identified ABCD1 mutations on the protein.

Results

All three patients were men with adult-onset disease, mainly characterized by progressive spastic paraparesis. Among them, two patients had peripheral neuropathy and one patient had signs of adrenal insufficiency. All three patients showed cerebral involvement on brain MRI, while two patients were found with diffuse cord atrophy on spinal MRI. High-VLCFA levels in plasma, as well as C24:0/C22:0 and C26:0/C22:0 ratios, were found in all three patients. In addition, three different ABCD1 mutations were identified in three unrelated Chinese families, including one known mutation (c.1415_1416delAG) and two novel mutations (c.217C>T and c.160_170delACGCAGGAGGC). Based on the clinical assessment, radiographic, biochemical, and genetic testing, the final diagnosis was AMN in these patients with spastic paraparesis.

Conclusion

This study reported three patients with AMN and identified two novel mutations in the ABCD1 in the Chinese population. Our finding emphasized that X-ALD is an important cause of adult-onset spastic paraplegia. Thus, neuroimaging, VLCFA testing, and especially the detection of the ABCD1 gene have important implications for the etiological diagnosis of adult patients with spastic paraplegia.

MicroRNA and metabolomics signatures for adrenomyeloneuropathy disease severity

Adrenomyeloneuropathy (AMN), the slow progressive phenotype of adrenoleukodystrophy (ALD), has no clinical plasma biomarker for disease progression. This feasibility study aimed to determine whether metabolomics and micro-RNA in blood plasma provide a potential source of biomarkers for AMN disease severity. Metabolomics and RNA-seq were performed on AMN and healthy human blood plasma. Biomarker discovery and pathway analyses were performed using clustering, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and regression against patient's clinical Expanded Disability Status Score (EDSS). Fourteen AMN and six healthy control samples were analyzed. AMN showed strong disease-severity-specific metabolic and miRNA clustering signatures. Strong, significant clinical correlations were shown for 7-alpha-hydroxy-3-oxo-4-cholestenoate (7-HOCA) (r 2 = 0.83, p < 0.00001), dehydroepiandrosterone sulfate (DHEA-S; r 2 = 0.82, p < 0.00001), hypoxanthine (r 2 = 0.82, p < 0.00001), as well as miRNA-432-5p (r 2 = 0.68, p < 0.00001). KEGG pathway comparison of mild versus severe disease identified affected downstream systems: GAREM, IGF-1, CALCRL, SMAD2&3, glutathione peroxidase, LDH, and NOS. This feasibility study demonstrates that miRNA and metabolomics are a source of potential plasma biomarkers for disease severity in AMN, providing both a disease signature and individual markers with strong clinical correlations. Network analyses of affected systems implicate differentially altered vascular, inflammatory, and oxidative stress pathways, suggesting disease-severity-specific mechanisms as a function of disease severity.

Newborn Screening for X-Linked Adrenoleukodystrophy in Nebraska: Initial Experiences and Challenges

X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disease caused by pathogenic variants in ABCD1 resulting in defective peroxisomal oxidation of very long-chain fatty acids. Most male patients develop adrenal insufficiency and one of two neurologic phenotypes: a rapidly progressive demyelinating disease in mid-childhood (childhood cerebral X-ALD, ccALD) or an adult-onset spastic paraparesis (adrenomyeloneuropathy, AMN). The neurodegenerative course of ccALD can be halted if patients are treated with hematopoietic stem cell transplantation at the earliest onset of white matter disease. Newborn screening for X-ALD can be accomplished by measuring C26:0-lysophosphatidylcholine in dried blood spots. In Nebraska, X-ALD newborn screening was instituted in July 2018. Over a period of 3.3 years, 82,920 newborns were screened with 13 positive infants detected (4 males, 9 females), giving a birth prevalence of 1:10,583 in males and 1:4510 in females. All positive newborns had DNA variants in ABCD1. Lack of genotype-phenotype correlations, absence of predictive biomarkers for ccALD or AMN, and a high proportion of ABCD1 variants of uncertain significance are unique challenges in counseling families. Surveillance testing for adrenal and neurologic disease in presymptomatic X-ALD males will improve survival and overall quality of life.

Functional electrical stimulation to aid walking in patients with adrenomyeloneuropathy: A case study and observational series

Adrenomyeloneuropathy (AMN) is a rare inherited condition where affected individuals develop slowly progressive spastic paraparesis with a gradual decline in walking ability. There is no cure for AMN and treatment focuses on supportive measures and aids. One treatment option is functional electrical stimulation (FES), a treatment, approved by The National Institute for Health and Care Excellence (NICE), for managing foot drop in upper motor neuron disorders. Limited evidence exists for its use in AMN patients. We describe the effects of FES in an individual case and more broadly within a cohort of 21 patients successfully treated with FES. Patients with AMN referred for FES typically report frequent falls (71%) and foot drop (57%) as the most common barriers to walking. When using FES, walking speed at baseline (0.70 m/s [SD = 0.2]) was maintained at the 2-year review (0.68 m/s [SD = 0.2]) with a persistent orthotic effect (improvement in walking speed when device on vs. off) seen from wearing FES over the same 2-year period (11%-19%). Patient walking satisfaction (visual analogue scale: 0 - very dissatisfied; 10 - very satisfied) was also greater when comparing no-FES versus FES over the same period (Year 1: 2.5 vs. 7.7; Year 2: 2.1 vs. 6.1). FES is not effective in all patients. Twelve patients referred found no benefit from the device; although there was no clear evidence, this was related to the degree of AMN associated peripheral neuropathy. However, FES is a safe, cost-effective treatment option and should be considered, along with assessment in a multidisciplinary clinic, for all AMN patients with walking difficulties.

A case of female adrenoleukodystrophy carrier with insidious neurogenic bladder

A 65-year-old woman with mutation of the ABCD1 gene for adrenoleukodystrophy (ALD) was admitted to our hospital with a urinary tract infection. Abdominal computed tomography showed dilation of the urinary tract. Although she had noticed pollakisuria since her forties, she had not been followed up by any medical institutions until we diagnosed her as a female carrier with ALD. ALD is an X-linked pattern of inheritance that typically affects males, but many female carriers actually present slowly progressive myelopathy and neuropathy. Therefore, it is important to identify female carriers with ALD and treat them at the earliest stage possible.

Anesthetic management of pediatric patients diagnosed with X-linked adrenoleukodystrophy: A single-center experience

BACKGROUND

X-linked adrenoleukodystrophy is a progressive demyelinating disease that primarily affects males with an incidence of 1:20 000-30 000. The disease has a wide spectrum of phenotypic expression and may include adrenal insufficiency, cerebral X-linked adrenoleukodystrophy and adrenomyeloneuropathy. The condition has implications for the administration of anesthesia and reports of anesthetic management in those patients are limited at this point.

AIM

To review the perioperative care, complications and outcomes of patients diagnosed with X-linked adrenoleukodystrophy at the University of Minnesota Masonic Children's Hospital.

METHOD

After obtaining IRB approval, we performed a retrospective chart review of pediatric patients diagnosed with X-linked adrenoleukodystrophy who underwent either surgery or diagnostic/therapeutic procedures that included anesthesia services between January 2014 and December 2016. Data included demographics, American Society of Anesthesiologists classification, preoperative diagnosis, history of hematopoietic stem cell transplant, anesthetic approaches, airway management, medications used, intra- and postoperative complications, and patient disposition.

RESULTS

We identified 38 patients who had a total of 166 anesthetic encounters. The majority of patients underwent procedures in the sedation unit (75.9%) and received a total intravenous anesthetic with spontaneous ventilation via a natural airway (86.1%). Preoperative adrenal insufficiency was documented in 87.3% of the encounters. Stress-dose steroids were administered in 70.5% of the performed anesthetics. A variety of anesthetic agents were successfully used including sevoflurane, isoflurane, propofol, midazolam, ketamine, and dexmedetomidine. There were few perioperative complications noted (6.6%) and the majority were of low severity. No anesthesia-related mortality was observed.

CONCLUSIONS

With the availability of skilled pediatric anesthesia care, children with X-linked adrenoleukodystrophy can undergo procedures under anesthesia in sedation units and regular operating rooms with low overall anesthesia risk.

A novel ABCD1 gene mutation causes adrenomyeloneuropathy in a Chinese family

BACKGROUND

Adrenomyeloneuropathy (AMN) is a rare genetic disease. In this study, a case of AMN was uncovered in a Chinese family.

METHODS

Clinical manifestations were collected and observed through medical records, physical examination, laboratory tests, and magnetic resonance imaging (MRI). Generation sequencing of the ABCD1 gene was performed, and the pedigree of the family was analyzed.

RESULTS

The proband suffered from adrenocortical insufficiency at 8 years old and presented with a slowly progressive gait disorder at 21 years old. Physical examination, laboratory tests, and MRI showed that he had adult-onset AMN manifestations, including spasticity and hyperactive tendon reflexes with Hoffman and Babinski signs in the limbs, difficulty in performing the heel-to-shin test, hyperpigmentation, increased levels of adrenocorticotropic hormone and very long-chain fatty acids, decreased levels of corticosteroid and serum gesterol, and salient atrophy of the cervical and thoracic spinal cord. DNA analysis revealed a missense variant, c.290A>C (p.His97Pro) in exon 1 of the ABCD1 gene, in the proband. Sanger sequencing confirmed that the proband's mother was heterozygous for the same variant. The ABCD1 gene mutation transmitted in an X-linked inheritance manner.

CONCLUSION

A novel missense mutation in the ABCD1 gene was identified in a Chinese family, which caused an unusual manifestation of adult-onset AMN. This discovery is beneficial for the genetic counseling of patients with X-linked adrenoleukodystrophy.

Intrathecal Adeno-Associated Viral Vector-Mediated Gene Delivery for Adrenomyeloneuropathy

Mutations in the gene encoding the peroxisomal ATP-binding cassette transporter (ABCD1) cause elevations in very long-chain fatty acids (VLCFAs) and the neurodegenerative disease adrenoleukodystrophy (ALD). In most adults, this manifests as the spinal cord axonopathy adrenomyeloneuropathy (AMN). A challenge in virus-based gene therapy in AMN is how to achieve functional gene correction to the entire spinal cord while minimizing leakage into the systemic circulation, which could contribute to toxicity. In the present study, we used an osmotic pump to deliver adeno-associated viral (AAV) vector into the lumbar cerebrospinal fluid space in mice. We report that slow intrathecal delivery of recombinant AAV serotype 9 (rAAV9) achieves efficient gene transfer across the spinal cord and dorsal root ganglia as demonstrated with two different transgenes, GFP and ABCD1. In the Abcd1^-/- mouse, gene correction after continuous rAAV9-CBA-hABCD1 delivery led to a 20% decrease in VLCFA levels in spinal cord compared with controls. The major cell types transduced were astrocytes, vascular endothelial cells, and neurons. Importantly, rAAV9 delivered intrathecally by osmotic pump, in contrast to bolus injection, reduced systemic leakage into peripheral organs, particularly liver and heart tissue.

Adrenomyeloneuropathy with bulbar palsy: A rare association

Adrenomyeloneuropathy (AMN) is a variant of adrenoleukodystrophy (ALD), an X-linked recessive peroxisomal disorder associated with accumulation of very long chain fatty acids (VLCFA). Mutations of this gene lead to abnormal peroxisomal β-oxidation, which results in the harmful accumulation of VLCFAs in affected cells. Neurological symptoms occur due to progressive demyelination and destruction of cerebral white matter and primary adrenal insufficiency. Bulbar palsy in a case of AMN is very unusual. We report a case of a 22-year-old male with AMN who developed adrenal insufficiency at the age of 4 years successfully treated by gluco- and mineralocorticoids followed by features of myeloneuropathy with bulbar palsy. AMN with prominent bulbar symptoms emphasizes the diverse clinical manifestation of this disease.

Multiple endocrine disorders associated with adrenomyeloneuropathy and a novel mutation of the ABCD1 gene

INTRODUCTION

X-linked adrenomyeloneuropathy (X-AMN) is a genetic disorder that primarily affects the adrenal cortex and the nervous system. The disease shows a wide range of phenotypic expression, age of onset, and rate of progression.

PATIENT DESCRIPTION

We present a thalassemic 23-year-old man with X-AMN and multiple endocrine disorders. At age 2 years, he was diagnosed with thalassaemia intermedia, and he was receiving occasional blood transfusions and maintaining an adequate hemoglobin level without signs of extramedullar hematopoiesis or hemosiderosis. During adolescence, he was diagnosed with growth hormone deficiency, primary hypothyroidism, and primary adrenal insufficiency. In his early 20s he demonstrated progressive tetraparesis, and the diagnosis of X-AMN was confirmed by DNA analysis of the ABCD1 gene.

CONCLUSION

This patient expands the phenotype X-AMN by adding growth hormone deficiency and hypothyroidism.

Clinical and genetic aspects in twelve Korean patients with adrenomyeloneuropathy

PURPOSE

This study was designed to investigate the characteristics of Korean adrenomyeloneuropathy (AMN) patients.

MATERIALS AND METHODS

We retrospectively selected 12 Korean AMN patients diagnosed by clinical analysis and increased plasma content of very long chain fatty acids.

RESULTS

All 12 patients were men. Patient ages at symptom onset ranged from 18 to 55 years. Family history was positive in two patients. The phenotype distributions consisted of AMN without cerebral involvement in seven patients, AMN with cerebral involvement in two patients, and the spinocerebellar phenotype in three patients. Nerve conduction studies revealed abnormalities in four patients and visual evoked tests revealed abnormalities in three patients. Somatosensory evoked potential tests revealed central conduction defects in all of the tested patients. Spinal MRI showed diffuse cord atrophy or subtle signal changes in all 12 patients. Brain MRI findings were abnormal in six of the nine tested patients. These brain abnormalities reflected the clinical phenotypes. Mutational analysis identified nine different ABCD1 mutations in 10 of 11 tested patients. Among them, nine have been previously reported and shown to be associated with various phenotypes; one was a novel mutation.

CONCLUSION

In conclusion, the present study is the first to report on the clinical and mutational spectrum of Korean AMN patients, and confirms various clinical presentations and the usefulness of brain MRI scan.

Newborn screening for X-linked adrenoleukodystrophy: further evidence high throughput screening is feasible

X-linked adrenoleukodystrophy (ALD) is characterized by adrenal insufficiency and neurologic involvement with onset at variable ages. Plasma very long chain fatty acids are elevated in ALD; even in asymptomatic patients. We demonstrated previously that liquid chromatography tandem mass spectrometry measuring C26:0 lysophosphatidylcholine reliably identifies affected males. We prospectively applied this method to 4689 newborn blood spot samples; no false positives were observed. We show that high throughput neonatal screening for ALD is methodologically feasible.

Peroxisomal multifunctional protein-2 deficiency causes neuroinflammation and degeneration of Purkinje cells independent of very long chain fatty acid accumulation

Although peroxisome biogenesis and β-oxidation disorders are well known for their neurodevelopmental defects, patients with these disorders are increasingly diagnosed with neurodegenerative pathologies. In order to investigate the cellular mechanisms of neurodegeneration in these patients, we developed a mouse model lacking multifunctional protein 2 (MFP2, also called D-bifunctional protein), a central enzyme of peroxisomal β-oxidation, in all neural cells (Nestin-Mfp2(-/-)) or in oligodendrocytes (Cnp-Mfp2(-/-)) and compared these models with an already established general Mfp2 knockout. Nestin-Mfp2 but not Cnp-Mfp2 knockout mice develop motor disabilities and ataxia, similar to the general mutant. Deterioration of motor performance correlates with the demise of Purkinje cell axons in the cerebellum, which precedes loss of Purkinje cells and cerebellar atrophy. This closely mimics spinocerebellar ataxias of patients affected with mild peroxisome β-oxidation disorders. However, general knockouts have a much shorter life span than Nestin-Mfp2 knockouts which is paralleled by a disparity in activation of the innate immune system. Whereas in general mutants a strong and chronic proinflammatory reaction proceeds throughout the brain, elimination of MFP2 from neural cells results in minor neuroinflammation. Neither the extent of the inflammatory reaction nor the cerebellar degeneration could be correlated with levels of very long chain fatty acids, substrates of peroxisomal β-oxidation. In conclusion, MFP2 has multiple tasks in the adult brain, including the maintenance of Purkinje cells and the prevention of neuroinflammation but this is not mediated by its activity in oligodendrocytes nor by its role in very long chain fatty acid degradation.

Inventory and general analysis of the ATP-binding cassette (ABC) gene superfamily in maize (Zea mays L.)

The metabolic functions of ATP-binding cassette (or ABC) proteins, one of the largest families of proteins presented in all organisms, have been investigated in many protozoan, animal and plant species. To facilitate more systematic and complicated studies on maize ABC proteins in the future, we present the first complete inventory of these proteins, including 130 open reading frames (ORFs), and provide general descriptions of their classifications, basic structures, typical functions, evolution track analysis and expression profiles. The 130 ORFs were assigned to eight subfamilies based on their structures and homological features. Five of these subfamilies consist of 109 proteins, containing transmembrane domains (TM) performing as transporters. The rest three subfamilies contain 21 soluble proteins involved in various functions other than molecular transport. A comparison of ABC proteins among nine selected species revealed either convergence or divergence in each of the ABC subfamilies. Generally, plant genomes contain far more ABC genes than animal genomes. The expression profiles and evolution track of each maize ABC gene were further investigated, the results of which could provide clues for analyzing their functions. Quantitative real-time polymerase chain reaction experiments (PCR) were conducted to detect induced expression in select ABC genes under several common stresses. This investigation provides valuable information for future research on stress tolerance in plants and potential strategies for enhancing maize production under stressful conditions.