Clinical and Molecular Genetic Analysis with Methylmalonic Acidemia Combined with Homocystinuria.

BACKGROUND: Based on research, c.609G>A (p.W203X) is a universal mutation site for MMACHC in methylmalonic acidemia (MMA) combined with homocystinuria, cblC type (cblC disease), and c.467G>A (p.G156D) mutation in families with such disease have not yet been reported. To conduct clinical and molecular genetic analysis of a family with cblC disease. METHODS: This work followed the Declaration of Helsinki. All testing methods were performed under the informed consent of our children patients' parents. A second-generation cblC family with 5 members, was selected as the research subject, including sick siblings and parents and an older sister with normal phenotype, given newborn screening for acylcarnitine spectrum via liquid chromatography tandem mass spectrometry (LC-MS/MS), and diagnosed through combining urine organic acid with homocysteine detection via gas chromatography-mass spectrometry (GC-MS) with second-generation gene sequencing technology. The peripheral blood of five family members was collected for genomic DNA extraction, and the changes were screened in disease-related MMACHC sequence via PCR and direct DNA sequencing. RESULTS: The family conformed to the autosomal recessive inheritance, the proband and younger sister were cblC patients, diagnosed in February and at 22d given relevant treatment. The proband died, whereas the younger sister received follow-up treatment. Their parents and sister had normal phenotype. In 2 cases, there was compound heterozygous mutation in MMACHC called c.609G>A (p.W203X) nonsense mutation and c.467G>A (p.G156D) missense mutation in exon 4, while the father with normal phenotype had heterozygous mutation c.609G>A in exon 4 coding area. In its protein, the 203rd amino acid changed from tryptophan to a stop codon (p.W203 x). The normal mother and sister had a heterozygous mutation c.467G>A in exon 4 coding area. In its protein, the 156th amino acid changed from glycine to aspartic acid (p.G156D). CONCLUSIONS: The cblC family results from c.609G>A (p.W203X) and c.467G>A (p.G156D) compound heterozygous mutations in MMACHC, which has a pathogenic impact.

Result of a Pilot External Quality Assessment Scheme for Clinical Diagnosis of Inherited Metabolic Disorders in China.

BACKGROUND: We aimed to evaluate the diagnostic capabilities of Chinese laboratories for inherited metabolic disorders (IMDs) using gas chromatography-mass spectrometry (GC-MS) on urine samples. Meanwhile, based on the result of the pilot external quality assessment (EQA) scheme, we hope to establish a standardized and reliable procedure for future EQA practice. METHODS: We recruited laboratories that participated in the EQA of quantitative analysis of urinary organic acids with GC-MS before joining the surveys. In each survey, a set of five real urine samples was distributed to each participant. The participants should analyze the sample by GC-MS and report the "analytical result", "the most likely diagnosis", and "recommendation for further tests" to the NCCL before the deadline. RESULTS: A total of 21 laboratories participated in the scheme. The pass rates were 94.4% in 2020 and 89.5% in 2021. For all eight IMDs tested, the analytical proficiency rates ranged from 84.7% - 100%, and the interpretational performance rate ranged from 88.2% - 97.0%. The performance on hyperphenylalaninemia (HPA), 3-methylcrotonyl-CoA carboxylase deficiency (MCCD), and ethylmalonic encephalopathy (EE) samples were not satisfactory. CONCLUSIONS: In general, the participants of this pilot EQA scheme are equipped with the basic capability for qualitative organic acid analysis and interpretation of the results. Limited by the small size of laboratories and samples involved, this activity could not fully reflect the state of clinical practice of Chinese laboratories. NCCL will improve the EQA scheme and implement more EQA activities in the future.

Results of a Pilot External Quality Assessment Scheme for Genetic Testing of Newborns with Spinal Muscular Atrophy.

BACKGROUND: This study aims to evaluate the ability of laboratories to perform spinal muscular atrophy (SMA) genetic testing in newborns based on dried blood spot (DBS) samples, and to provide reference data and advance preparation for establishing the pilot external quality assessment (EQA) scheme for SMA genetic testing of newborns in China. METHODS: The pilot EQA scheme contents and evaluation principles of this project were designed by National Center for Clinical Laboratories (NCCL), National Health Commission. Two surveys were carried out in 2022, and 5 batches of blood spots were submitted to the participating laboratory each time. All participating laboratories conducted testing upon receiving samples, and test results were submitted to NCCL within the specified date. RESULTS: The return rates were 75.0% (21/28) and 95.2% (20/21) in the first and second surveys, respectively. The total return rate of the two examinations was 83.7% (41/49). Nineteen laboratories (19/21, 90.5%) had a full score passing on the first survey, while in the second survey twenty laboratories (20/20, 100%) scored full. CONCLUSIONS: This pilot EQA survey provides a preliminary understanding of the capability of SMA genetic testing for newborns across laboratories in China. A few laboratories had technical or operational problems in testing. It is, therefore, of importance to strengthen laboratory management and to improve testing capacity for the establishment of a national EQA scheme for newborn SMA genetic testing.

Whole-exome sequencing analysis to identify novel potential pathogenetic NPC1 mutations in two Chinese families with Niemann-Pick disease type C.

BACKGROUND: Niemann-Pick disease type C (NPC) is an autosomal recessive lipid storage disorder, affecting the nervous system and the internal organs. It is characterized by the presence of foam cells in bone marrow, liver, and spleen biopsies. Although many mutations in NPC1 have been identified to be related to disease onset, the relationship between genotype and phenotype remains unclear. To elucidate the genetic heterogeneity of NPC, we described the clinical manifestations and possible genetic pathogenesis of two patients from unrelated families with NPC. METHODS: DNA was extracted from the peripheral blood of the two patients and their families and from healthy individuals. Whole-exome sequencing followed by Sanger sequencing was performed to verify the mutations identified in their families. RESULTS: We identified four mutations in NPC1 in the two patients from different families: c.1290delC (p.F431Lfs*18)/c.2807G > A(p.G936D) in family A and c.3604_3605insA (p.I1202Nfs*56)/c.881 + 3A > G in family B from their parents. Bioinformatics analysis predicted these mutations to be deleterious, suggesting that mutations in exons are highly conservative. The patient in family A presented with a developmental delay that was different from the typical symptoms of developmental regression in family B. CONCLUSION: Our study identified three novel mutations and one known mutation in NPC1 and evaluated their pathogenicity, enriching the NPC1 mutation and phenotype spectrum and providing a new basis for the genetic and prenatal diagnosis of this disease.

Chinese newborn screening for the incidence of G6PD deficiency and variant of G6PD gene from 2013 to 2017.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the most common X-linked enzymopathies caused by G6PD gene variant. We aimed to provide the characteristics of G6PD deficiency and G6PD gene variant distribution in a large Chinese newborn screening population. We investigated the prevalence of G6PD in China from 2013 to 2017. Then, we examined G6PD activity and G6PD gene in representative Chinese birth cohort to explore the distribution of G6PD gene variant in 2016. We then performed multicolor melting curve analysis to classify G6PD gene variants in 10,357 neonates with activity-confirmed G6PD deficiency, and DNA Sanger sequencing for G6PD coding exons if hot site variants were not found. The screened population, organizations, and provinces of G6PD deficiency were increased from 2013 to 2017 in China. The top five frequency of G6PD gene variants were c.1376G>T, c.1388G>A, c.95A>G, c.1024C>T, and c.871G>A and varied in different provinces, with regional and ethnic features, and four pathogenic variant sites (c.152C>T, c.290A>T, c.697G>C, and c.1285A>G) were first reported. G6PD deficiency mainly occurs in South China, and the frequency of G6PD gene variant varies in different regions and ethnicities.

Fabrication and phase transition of long-range-ordered, high-density GST nanoparticle arrays.

We use a monolayer of self-assembled polystyrene (PS) spheres (220 nm in diameter) as a reactive ion etching (RIE) mask to fabricate large-scale (more than 1 cm(2)), long-range-ordered, high-density Ge(1)Sb(2)Te(4) (GST) phase-change material nanoparticle arrays. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images show that periodic and isolated GST nanoparticle arrays 30-80 nm high and 150-200 nm bottom diameter were formed. Phase transitions of the GST films and nanoparticle arrays were studied by subjecting the samples to high-resolution transmission electron microscopy (HRTEM) electron-beam radiation. Nanocrystals between 2 and 5 nm in diameter were observed for GST nanoparticle arrays due to the large surface-to-volume ratio. The density of the GST arrays can reach as high as 10(9) cm(-2), which can lead to the realization of future high-density phase-change random access memory (PCRAM).