Phosphoethanolamine Elevation in Plasma of Spinal Muscular Atrophy Type 1 Patients

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by degeneration or loss of lower motor neurons. The survival of motor neuron (SMN) 1 gene, which produces the SMN protein, has been identified as a responsible gene for the disease. SMN is ubiquitously expressed in any tissue and may play an important role on the metabolism in the human body. However, no appropriate biomarkers reflecting the alteration in the metabolism in SMA have been identified.

METHODS

Low-molecular-weight metabolites were extracted from plasma of 20 human infants (9 SMA type 1 patients and 11 controls) and 9 infant mice (5 SMA-model mice, 4 control mice), and derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide. Finally, the derivatized products were applied to Gas Chromatography/Mass Spectrometry apparatus. To confirm the metabolite abnormality in SMA type 1 patients, we performed SMN-silencing experiment using a hepatocyte-derived cell line (HepG2).

RESULTS

We performed a comprehensive metabolomics analysis of plasma from the patients with SMA type 1 and controls, and found that phosphoethanolamine (PEA) was significantly higher in the patients than in the controls. HepG2 experiment also showed that SMN-silencing increased PEA levels. However, comprehensive metabolomics analysis of plasma from SMA-model mice and control mice showed different profile compared to human plasma; there was no increase of PEA even in the SMA-model mice plasma.

CONCLUSION

Our data suggested that PEA was one of the possible biomarkers of human SMA reflecting metabolic abnormalities due to the SMN protein deficiency.

Newborn Screening for Spinal Muscular Atrophy: DNA Preparation from Dried Blood Spot and DNA Polymerase Selection in PCR

BACKGROUND

Polymerase chain reaction (PCR) analysis using DNA from dried blood spot (DBS) samples on filter paper is a critical technique for spinal muscular atrophy (SMA) newborn screening. However, DNA extraction from DBS is time-consuming, and elimination of PCR inhibitors from DBS is almost impossible.

METHODS

Exon 7 of the two homologous SMA-related genes, survival motor neuron (SMN) 1 and SMN2, of five SMA patients and five controls were amplified by PCR with a punched-out circle of the DBS paper. Two types of DNA preparation methods were tested; DNA-extraction (extracted DNA was added in a PCR tube) and non-DNA-extraction (a punched-out DBS circle was placed in a PCR tube). As for the DNA polymerases, two different enzymes were compared; TaKaRa Ex Taq™ and KOD FX Neo™. To test the diagnostic quality of PCR products, RFLP (Restriction fragment length polymorphism) analysis with DraI digestion was performed, differentiating SMN1 and SMN2.

RESULTS

In PCR using extracted DNA, sufficient amplification was achieved with TaKaRa Ex Taq™ and KOD FX Neo™, and there was no significant difference in amplification efficiency between them. In direct PCR with a punched-out DBS circle, sufficient amplification was achieved when KOD FX Neo™ polymerase was used, while there was no amplification with TaKaRa Ex Taq™. RFLP analysis of the direct PCR products with KOD FX Neo™ clearly separated SMN1 and SMN2 sequences and proved the presence of both of SMN1 and SMN2 in controls, and only SMN2 in SMA patients, suggesting that the direct PCR products with KOD FX Neo™ were of sufficient diagnostic quality for SMA testing.

CONCLUSION

Direct PCR with DNA polymerases like KOD FX NeoTM has potential to be widely used in SMA newborn screening in the near future as it obviates the DNA extraction process from DBS and can precisely amplify the target sequences in spite of the presence of PCR inhibitors.

Spinal Muscular Atrophy: Advanced Version of Screening System with Real-Time mCOP-PCR and PCR-RFLP for SMN1 Deletion

BACKGROUND

Spinal Muscular Atrophy (SMA) is a common autosomal recessive neuromuscular disease characterized by defects of lower motor neurons. More than 95% of SMA patients show homozygous deletion for the survival motor neuron 1 (SMN1) gene. For the screening of SMN1 deletion using dried blood spot (DBS), we developed a new combined system with real-time "modified competitive oligonucleotide priming"-polymerase chain reaction (mCOP-PCR) and PCR restriction fragment length polymorphism (PCR-RFLP). Although our real-time mCOP-PCR method is secured enough to be gene-specific, its amplification efficiency is not as good because the reverse primers carry a nucleotide mismatched with the sequence of the pre-amplified product. The mismatch has consequently been generated in the process of introducing a restriction enzyme site in the pre-amplified products for PCR-RFLP.

METHOD

DBS samples of the subjects were stored at room temperature for a period of less than one year. Each subject had already been genotyped by the first PCR-RFLP using fresh blood DNA. SMN1/SMN2 exon 7 was collectively amplified using conventional PCR (targeted pre-amplification). Pre-amplified products were used as template in the real-time mCOP-PCR, and, on the other hand, were digested with DraI enzyme (PCR-RFLP). To improve the amplification efficiency of mCOP-PCR, one nucleotide change was introduced in the original reverse primers (SMN1-COP and SMN2-COP) to eliminate the mismatched nucleotide.

RESULTS

The real-time mCOP-PCR with a new primer (SMN1-COP-DRA or SMN2-COP-DRA) more rapidly and specifically amplified SMN1 and SMN2, and clearly demonstrated SMN1 deletion in an SMA patient. With the new primers, the amplification efficiencies of real-time mCOP-PCR were improved and the Cq values of SMN1 (+) and SMN2 (+) samples were significantly lowered.

CONCLUSION

In the advanced version of our screening system for homozygous SMN1 deletion using DBS, the real-time mCOP-PCR with newly-designed reverse primers demonstrated the presence or absence of SMN1 and SMN2 within a shorter time, and the results were easily tested by PCR-RFLP. This rapid and accurate screening system will be useful for detection of newborn infants with SMA.

Spinal Muscular Atrophy: New Screening System with Real-Time mCOP-PCR and PCR-RFLP for SMN1 Deletion

BACKGROUND

Spinal Muscular Atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration or loss of lower motor neurons. More than 95% of SMA patients show homozygous deletion for the survival motor neuron 1 (SMN1) gene. For the screening of SMN1 deletion, it is necessary to differentiate SMN1 from its highly homologous gene, SMN2. We developed a modified competitive oligonucleotide priming-PCR (mCOP-PCR) method using dried blood spot (DBS)-DNA, in which SMN1 and SMN2-specific PCR products are detected with gel-electrophoresis. Next, we added a targeted pre-amplification step prior to the mCOP-PCR step, to avoid unexpected, non-specific amplification. The pre-amplification step enabled us to combine mCOP-PCR and real-time PCR. In this study, we combined real-time mCOP-PCR and PCR-restriction fragment length polymorphism (PCR-RFLP) to develop a new screening system for detection of SMN1 deletion.

METHODS

DBS samples of the subjects were stored at room temperature for a period of less than one year. Each subject had already been genotyped by the first PCR-RFLP using fresh blood DNA. SMN1/SMN2 exon 7 was collectively amplified using conventional PCR (targeted pre-amplification), the products of which were then used as a template in the real-time PCR with mCOP-primer sets. To confirm the results, the pre-amplified products were subject to the second PCR-RFLP.

RESULTS

The real-time mCOP-PCR separately amplified SMN1 and SMN2 exon7, and clearly demonstrated SMN1 deletion in an SMA patient. The results of the real-time mCOP-PCR using DBS-DNA were completely consistent with those of the first and second PCR-RFLP analysis.

CONCLUSION

In our new system for detection of SMN1 deletion, real-time mCOP-PCR rapidly proved the presence or absence of SMN1 and SMN2, and the results were easily tested by PCR-RFLP. This solid genotyping system will be useful for SMA screening.

Nested PCR Amplification Secures DNA Template Quality and Quantity in Real-time mCOP-PCR Screening for SMA

BACKGROUND

Spinal Muscular Atrophy (SMA) is a common autosomal recessive disorder caused by SMN1 gene deletion. SMA has been considered an incurable disease. However, a newly-developed antisense oligonucleotide drug, nusinersen, brings about a good outcome to SMA patients in the clinical trials. Now, a screening for SMA is required for early diagnosis and early treatment so as to give a better clinical outcome to the patients. We have invented a new technology, mCOP-PCR, for SMA screening using dried blood spot (DBS) on the filter paper. One of the problems encountered in SMA screening is poor quality and quantity of DNA extracted from DBS.

METHODS

DNA was extracted from DBS of six individuals. Fresh blood DNA of each individual had already been genotyped using PCR/RFLP. The fragments including the sequence of SMN1/SMN2 exon 7 were pre-amplified with conventional PCR. To determine which pre-amplified product is a better template for the real-time mCOP-PCR, we did pre-amplification with a single PCR or pre-amplification with a nested PCR.

RESULTS

The real-time mCOP-PCR using pre-amplified products with a single PCR brought about ambiguous results in some SMN1-carrying individuals. However, the results of real-time mCOP-PCR following pre-amplification with a nested PCR were completely matched with those of PCR-RFLP.

CONCLUSION

In our study on the real-time mCOP-PCR screening system for SMA, a nested PCR secured the DNA template quality and quantity, leading to unambiguous results of SMA screening.

SMA Diagnosis: Detection of SMN1 Deletion with Real-Time mCOP-PCR System Using Fresh Blood DNA

BACKGROUND

Spinal muscular atrophy (SMA) is one of the most common autosomal recessive disorders. The symptoms are caused by defects of lower motor neurons in the spinal cord. More than 95% of SMA patients are homozygous for survival motor neuron 1 (SMN1) deletion. We previously developed a screening system for SMN1 deletion based on a modified competitive oligonucleotide priming-PCR (mCOP-PCR) technique using dried blood spot (DBS) on filter paper. This system is convenient for mass screening in the large population and/or first-tier diagnostic method of the patients in the remote areas. However, this system was still time-consuming and effort-taking, because it required pre-amplification procedure to avoid non-specific amplification and gel-electrophoresis to detect the presence or absence of SMN1 deletion. When the fresh blood samples are used instead of DBS, or when the gel-electrophoresis is replaced by real-time PCR, we may have a simpler and more rapid diagnostic method for SMA.

AIM

To establish a simpler and more rapid diagnostic method of SMN1 deletion using fresh blood DNA.

METHODS

DNA samples extracted from fresh blood and stored at 4 ℃ for 1 month. The samples were assayed using a real-time mCOP-PCR system without pre-amplification procedures. DNA samples had already been genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP), showing the presence or absence of SMN1 exon 7. The DNA samples were directly subjected to the mCOP-PCR step. The amplification of mCOP-PCR was monitored in a real-time PCR apparatus.

RESULTS

The genotyping results of the real-time mCOP-PCR system using fresh blood DNA were completely matched with those of PCR-RFLP. In this real-time mCOP-PCR system using fresh blood-DNA, it took only four hours from extraction of DNA to detection of the presence or absence of SMN1 deletion, while it took more than 12 hours in PCR-RFLP.

CONCLUSION

Our real-time mCOP-PCR system using fresh blood DNA was rapid and accurate, suggesting it may be useful for the first-tier diagnostic method of SMA.

Gender Effects on the Clinical Phenotype in Japanese Patients with Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by a mutation in SMN1. SMA is classified into three subtypes (types 1, 2, 3) based on achieved motor milestones. Although NAIP and SMN2 are widely accepted as SMA-modifying factors, gender-related modifying factors or gender effects on the clinical phenotype are still controversial.

METHODS

A total of 122 Japanese patients with SMA, of which SMN1 was homozygously deleted, were analyzed from the perspective of the achieved motor milestone, NAIP status and SMN2 copy number.

RESULTS

A predominance of male patients was observed in SMA type 3 (the walker group) without NAIP-deletion or with high SMN2 copy number (3 or 4 copies).

CONCLUSION

We suggest the presence of gender-related modifiers on disease severity in SMA patients. The modifiers may contribute only in the presence of NAIP and a high copy number of SMN2.

New, Improved Version of the mCOP-PCR Screening System for Detection of Spinal Muscular Atrophy Gene (SMN1) Deletion

BACKGROUND

Spinal muscular atrophy (SMA) is a frequent autosomal recessive disorder, characterized by lower motor neuron loss in the spinal cord. More than 95% of SMA patients show homozygous survival motor neuron 1 (SMN1) deletion. We previously developed a screening system for SMN1 deletion based on a modified competitive oligonucleotide priming-PCR (mCOP-PCR) technique. However, non-specific amplification products were observed with mCOP-PCR, which might lead to erroneous interpretation of the screening results.

AIM

To establish an improved version of the mCOP-PCR screening system without non-specific amplification.

METHODS

DNA samples were assayed using a new version of the mCOP-PCR screening system. DNA samples had already been genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP), showing the presence or absence of SMN1 exon 7. The new mCOP-PCR method contained a targeted pre-amplification step of the region, including an SMN1-specific nucleotide, prior to the mCOP-PCR step. mCOP-PCR products were electrophoresed on agarose gels.

RESULTS

No non-specific amplification products were detected in electrophoresis gels with the new mCOP-PCR screening system.

CONCLUSION

An additional targeted pre-amplification step eliminated non-specific amplification from mCOP-PCR screening.

Metabolic patterns in three types of phagocytizing cells

Some chemical and metabolic characteristics of polymorphonuclear leukocytes and monocytes from peritoneal exudates of the guinea pig, and of alveolar macrophages from the same animal, have been compared. Changes in the metabolic patterns of these three types of cell have been followed during the act of phagocytosis. The effect of conventional inhibitors of metabolism, and of anaerobiosis on the phagocytic ability of each of the three cell types mentioned has also been determined. From these studies it was found that alveolar macrophages depend to a considerable degree upon oxidative phosphorylation to provide energy for phagocytosis. The other two types of cell depend only on glycolysis as the source of metabolic energy for that function. In some experiments aimed at obtaining information on the possible role of complex lipids in the function of the cell membrane, it was noted that phagocytosis stimulated the incorporation of inorganic phosphate-P³² into the phosphatides of both types of cell from peritoneal exudates—whether these were free-swimming or adherent to a surface. This phenomenon has not yet been detected in the case of alveolar macrophages.

Passive transfer of immunity to typhoid by macrophages

Saito, Kazuhisa (Keio University School of Medicine, Tokyo, Japan), Masayasu Nakano, Takehisa Akiyama, and Daizo Ushiba. Passive transfer of immunity to typhoid by macrophages. J. Bacteriol. 84:500-507. 1962.-Cultured peritoneal macrophages collected from mice which had been injected intravenously with intact macrophages of mice immunized with live vaccine were found to exert inhibitory action against intracellular virulent Salmonella enteritidis. This inhibition was quantitatively inferior to that exhibited by peritoneal macrophages from the donors, i.e., mice actively immunized with live vaccine. After an intravenous injection of P(32)-labeled macrophages into mice, almost no radioactivity could be recovered in the peritoneal exudate cells of the recipients; about 50% of the radioactivity was recovered from the liver, spleen, and mesenteric lymph nodes. Therefore, the inhibitory action of the recipient's peritoneal macrophages against intracellular multiplication was attributed to the capacity of the recipient's own macrophages and not to that of the donor's macrophages. Tissue-cultured macrophages from recipients of sonic-treated cells did not exhibit inhibition against intracellular, virulent S. enteritidis, although the recipients were resistant to intraperitoneal infection with the same strain.

Inhibition of Salmonella enteritidis ingested in mononuclear phagocytes from liver and subcutaneous tissue of mice immunized with live vaccine

Sato, Ichiei (School of Medicine, Gunma University, Maebashi, Japan), Tokumitsu Tanaka, Kazuko Saito, and Susumu Mitsuhashi. Inhibition of Salmonella enteritidis ingested in mononuclear phagocytes from liver and subcutaneous tissue of mice immunized with live vaccine. J. Bacteriol. 83:1306-1312. 1962.-In our earlier studies it was shown that mice hyperimmunized with live vaccine of Salmonella enteritidis resisted intravenous challenge with 1,000 MLD of virulent strain 116-54 of S. enteritidis. Survivors of this challenge completely resisted additional intravenous challenge with 10,000 MLD of the same organism. Mononuclear phagocytes obtained from the abdominal cavity of mice immunized with live vaccine of S. enteritidis inhibited intracellular multiplication of virulent strain 116-54, regardless of the presence of antibody in the cell-culture medium. In the present study, mononuclear phagocytes were obtained in a nearly pure state from liver or subcutaneous tissue of mice and were maintained in vitro in good condition. These cells also resisted cellular degeneration caused by intracellular existence of virulent strain 116-54, regardless of the presence of antibody in the cell-culture medium. In contrast, cells obtained from normal mice or mice immunized with dead vaccine were subject to degeneration.

LYSOSOMAL ACID HYDROLASES AND HYPERREACTIVITY TO ENDOTOXIN IN MICE INFECTED WITH BCG

Experiments are reported dealing with the correlation between activities of lysosomal acid hydrolases and hyperreactivity to endotoxin induced by BCG infection. Acid hydrolases were determined quantitatively in peritoneal MP, liver homogenate, and plasma of normal and hyperreactive mice. Mice infected with BCG not only exhibited a hyperreactive state to lethal effect of endotoxin, but also responded to endotoxin by rapid increase of acid hydrolases, especially of β-glucuronidase, in the plasma; whereas control mice responded to endotoxin by almost no change in plasma acid hydrolases. The extent of increase of β-glucuronidase in plasma of hyperreactive mice was shown to correlate fairly well with the degree of hyperreactivity to the lethal effect of endotoxin. Desensitization of such animals with endotoxin was found to cause a decreased response of plasma β-glucuronidase parallel with decreased mortality. A large amount of PPD exerted the similar effect to that of endotoxin in hyperreactive mice. Furthermore, the effect of PPD was decreased by desensitization of such animals with endotoxin, a fact which suggests contamination of PPD with endotoxin.

LYSOSOMAL ACID HYDROLASES IN MICE INFECTED WITH BCG

Experiments are reported dealing with the increase of lysosomal acid hydrolases induced by BCG infection. Acid hydrolases were determined quantitatively in peritoneal MP, liver homogenate, and plasma of normal and BCG-infected mice. A significant increase of acid phosphatase, beta-glucuronidase, and cathepsin was found in MP and liver homogenate of BCG-infected mice. In plasma also a significant increase of acid phosphatase and beta-glucuronidase was noticed. The results of the determination of the enzymes in centrifugally separated subcellular fractions of liver homogenate indicated clearly that the acid hydrolases associated mainly with the "large granular" fraction, which consists of mitochondria, lysosomes, and microsomes and that infection with BCG caused significant increase of the enzymes specifically in this fraction. Differences in the pattern of location among centrifugally separated fraction of liver homogenate were observed between acid phosphatase and the other two acid hydrolases. MP cultured in vitro doubled their acid phosphatases content within 24 hours, whereas beta-glucuronidase rather decreased in the same cells.