Clinical outcomes of patients with mut-type methylmalonic acidemia identified through expanded newborn screening in China.

BACKGROUND: Isolated methylmalonic acidemia, an autosomal recessive disorder of propionate metabolism, is usually caused by mutations in the methylmalonyl-CoA mutase gene (mut-type). Because no universal consensus was made on whether mut-type methylmalonic acidemia should be included in newborn screening (NBS), we aimed to compare the outcome of this disorder detected by NBS with that detected clinically and investigate the influence of NBS on the disease course. DESIGN & METHODS: In this study, 168 patients with mut-type methylmalonic acidemia diagnosed by NBS were compared to 210 patients diagnosed after disease onset while NBS was not performed. Clinical data of these patients from 7 metabolic centers in China were analyzed retrospectively, including initial manifestations, biochemical metabolites, the responsiveness of vitamin B12 therapy, and gene variation, to explore different factors on the long-term outcome. RESULTS: By comparison of the clinically-diagnosed patients, NBS-detected patients showed younger age at diagnosis, less incidence of disease onset, better responsiveness of vitamin B12, younger age at start of treatment, lower levels of biochemical features before and after treatment, and better long-term prognosis (P < 0.01). Onset of disease, blood C3/C2 ratio and unresponsiveness of vitamin B12 were more positively associated with poor outcomes of patients whether identified by NBS. Moreover, the factors above as well as older age at start of treatment were positively associated with mortality. CONCLUSIONS: This research highly demonstrated NBS could prevent major disease-related events and allow an earlier treatment initiation. As a key prognostic factor, NBS is beneficial for improving the overall survival of infants with mut-type methylmalonic acidemia.

Screening of 1.17 million newborns for inborn errors of metabolism using tandem mass spectrometry in Shanghai, China: A 19-year report.

BACKGROUND: Inborn errors of metabolism (IEMs) frequently result in progressive and irreversible clinical consequences if not be diagnosed or treated timely. The tandem mass spectrometry (MS/MS)-based newborn screening (NBS) facilitates early diagnosis and treatment of IEMs. The aim of this study was to determine the characteristics of IEMs and the successful deployment and application of MS/MS screening over a 19-year time period in Shanghai, China, to inform national NBS policy. METHODS: The amino acids and acylcarnitines in dried blood spots from 1,176,073 newborns were assessed for IEMs by MS/MS. The diagnosis of IEMs was made through a comprehensive consideration of clinical features, biochemical performance and genetic testing results. The levels of MS/MS testing parameters were compared between various IEM subtypes and genotypes. RESULTS: A total of 392 newborns were diagnosed with IEMs from January 2003 to June 2022. There were 196 newborns with amino acid disorders (50.00%, 1: 5910), 115 newborns with organic acid disorders (29.59%, 1: 10,139), and 81 newborns with fatty acid oxidation disorders (20.41%; 1:14,701). Phenylalanine hydroxylase deficiency, methylmalonic acidemia and primary carnitine deficiency were the three most common disorders. Some hotspot variations in eight IEM genes (PAH, SLC22A5, MMACHC, MMUT, MAT1A, MCCC2, ACADM, ACAD8), 35 novel variants and some genotype-biochemical phenotype associations were identified. CONCLUSIONS: A total of 28 types of IEMs were identified, with an overall incidence of 1: 3000 in Shanghai, China. Our study offered clinical guidance for the implementation of MS/MS-based NBS and genetic counseling for IEMs in this city.

Long-term follow-up of Chinese patients with methylmalonic acidemia of the cblC and mut subtypes.

BACKGROUND: Methylmalonic acidemia (MMA) is the most common organic acidemia in China, with cblC (cblC-MMA) and mut (mut-MMA) being the predominant subtypes. The present study aimed to investigate the prognostic manifestations and their possible influence in patients with these two subtypes. METHODS: A national multicenter retrospective study of patients with cblC-MMA and mut-MMA between 2004 and 2022 was performed. We compared the clinical features between patients with two subtypes or diagnosed with or without newborn screening (NBS) and further explored the potentially influential factors on the prognosis. RESULTS: The 1617 enrolled MMA patients included 81.6% cblC-MMA patients and 18.4% mut-MMA patients, with an overall poor prognosis rate of 71.9%. These two subtypes of patients showed great differences in poor prognostic manifestations. The role of NBS in better outcomes was more pronounced in cblC-MMA patients. Predictors of outcomes are "pre-treatment onset", "NBS", variants of c.80A > G and c.482G > A and baseline levels of propionylcarnitine and homocysteine for cblC-MMA; "pre-treatment onset", "responsive to vitB12", variants of c.914T > C and baseline propionylcarnitine and propionylcarnitine/acetylcarnitine ratio for mut-MMA. Besides, prognostic biochemical indicators have diagnostic value for poor outcomes in mut-MMA. CONCLUSIONS: The study provided potential predictors of the long-term outcome of patients with cblC-MMA and mut-MMA. IMPACT: Predictors of outcomes are "pre-treatment onset", "NBS", MMACHC variants of c.80A > G and c.482G > A and baseline propionylcarnitine and homocysteine for cblC-MMA, "pre-treatment onset", "responsive to vitB12", MMUT variants of c.914T > C and baseline propionylcarnitine and propionylcarnitine/acetylcarnitine ratio for mut-MMA. This study with larger sample sizes effectively validated the prediction power and emphasized the importance of NBS in improving the outcomes of both MMA subtypes. The study enhances understanding of the phenotypic and prognostic variations of MMA disease and the predictors will help in the improvement of diagnosis and treatment strategies to achieve a better prognosis for MMA.

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.

Genetic and phenotypic spectrum of non-21-hydroxylase-deficiency primary adrenal insufficiency in childhood: data from 111 Chinese patients.

BACKGROUND: Primary adrenal insufficiency (PAI) is a rare but life-threatening condition. Differential diagnosis of numerous causes of PAI requires a thorough understanding of the condition. METHODS: To describe the genetic composition and presentations of PAI. The following data were collected retrospectively from 111 patients with non-21OHD with defined genetic diagnoses: demographic information, onset age, clinical manifestations, laboratory findings and genetic results. Patients were divided into four groups based on the underlying pathogenesis: (1) impaired steroidogenesis, (2) adrenal hypoplasia, (3) resistance to adrenocorticotropic hormone (ACTH) and (4) adrenal destruction. The age of onset was compared within the groups. RESULTS: Mutations in the following genes were identified: NR0B1 (n=39), STAR (n=33), CYP11B1 (n=12), ABCD1 (n=8), CYP17A1 (n=5), HSD3B2 (n=4), POR (n=4), MRAP (n=2), MC2R (n=1), CYP11A1 (n=1), LIPA (n=1) and SAMD9 (n=1). Frequent clinical manifestations included hyperpigmentation (73.0%), dehydration (49.5%), vomiting (37.8%) and abnormal external genitalia (23.4%). Patients with adrenal hypoplasia typically presented manifestations earlier than those with adrenal destruction but later than those with impaired steroidogenesis (both p<0.01). The elevated ACTH (92.6%) and decreased cortisol (73.5%) were the most common laboratory findings. We generated a differential diagnosis flowchart for PAI using the following clinical features: 17-hydroxyprogesterone, very-long-chain fatty acid, external genitalia, hypertension and skeletal malformation. This flowchart identified 84.8% of patients with PAI before next-generation DNA sequencing. CONCLUSIONS: STAR and NR0B1 were the most frequently mutated genes in patients with non-21OHD PAI. Age of onset and clinical characteristics were dependent on aetiology. Combining clinical features and molecular tests facilitates accurate diagnosis.

Evaluation of the clinical, biochemical, genotype and prognosis of mut-type methylmalonic acidemia in 365 Chinese cases.

BACKGROUND: Methylmalonic acidemia (MMA), which results from defects in methylmalonyl-CoA mutase (mut type) or its cofactor, is the most common inherited organic acid metabolic disease in China. This study aimed to investigate the phenotype and genotype of mut-type MMA in Chinese patients. METHODS: We recruited 365 patients with mut-type MMA; investigated their disease onset, newborn screening (NBS) status, biochemical metabolite levels, gene variations and prognosis; and explored the relationship between phenotype and genotype. RESULTS: There were 152 patients diagnosed by tandem mass spectrometry (MS/MS) expanded NBS, 209 patients diagnosed because of disease onset without NBS and 4 cases diagnosed because of sibling diagnosis. The median age of onset was 15 days old, with a variety of symptoms without specificity. Urinary levels of methylmalonic acid and methylcitric acid (MCA) decreased after treatment. Regarding the prognosis, among the 152 patients with NBS, 50.6% were healthy, 30.3% had neurocognitive impairment and/or movement disorders and 13.8% died. Among the 209 patients without NBS, 15.3% were healthy, 45.9% had neurocognitive impairment and/or movement disorders and 33.0% died. In total, 179 variants were detected in the MMUT gene, including 52 novel variations. c.729_730insTT, c.1106G>A, c.323G>A, c.914T>C and c.1663G>A were the five most frequent variations. The c.1663G>A variation led to a milder phenotype and better prognosis. CONCLUSION: There is a wide spectrum of variations in the MMUT gene with several common variations. Although the overall prognosis of mut-type MMA was poor, participation in MS/MS expanded NBS, vitamin B12 responsive and late onset are favourable factors for the prognosis.

Clinical characteristics and genetic analysis of six children with carnitine palmitoyltransferase 2 deficiency. / å ­ä¾‹è‚‰ç¢±æ£•æ¦ˆé °åŸºè½¬ç§»é ¶2ç¼ºä¹ç—‡æ‚£å„¿ä¸´åºŠç‰¹å¾åŠåŸºå› å˜å¼‚åˆ†æž.

OBJECTIVES: To investigate the clinical characteristic and genetic variants of children with carnitine palmitoyltransferase 2 (CPT2) deficiency. METHODS: The clinical and genetic data of 6 children with CPT2 deficiency were retrospectively analyzed. The blood acylcarnitines and genetic variants were detected with tandem mass spectrometry and whole-exon gene sequencing, respectively. RESULTS: There were 4 males and 2 females with a mean age of 32 months (15 d-9 years) at diagnosis. One case was asymptomatic and with normal laboratory test results, 2 had delayed onset, and 3 were of infantile type. Three cases were diagnosed at neonatal screening, and 3 cases presented with clinical manifestations of fever, muscle weakness, and increased muscle enzymes. Five children presented with decreased free carnitine and elevated levels of palmitoyl and octadecenoyl carnitines. CPT2 gene variants were detected at 8 loci in 6 children (4 harboring biallelic mutations and 2 harboring single locus mutations), including 3 known variants (p.R631C, p.T589M, and p.D255G) and 5 newly reported variants (p.F352L, p.R498L, p.F434S, p.A515P, and c.153-2A>G). It was predicted by PolyPhen2 and SIFT software that c.153-2A>G and p.F352L were suspected pathogenic variants, while p.R498L, p.F434S and p.A515P were variants of unknown clinical significance. CONCLUSIONS: The clinical phenotypes of CPT2 deficiency are diverse. An early diagnosis can be facilitated by neonatal blood tandem mass spectrometry screening and genetic testing, and most patients have good prognosis after a timely diagnosis and treatment.

Clinical characteristics and genotypes of 201 patients with mucopolysaccharidosis type II in China: A retrospective, observational study.

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal storage disease caused by a disease-associated variant in the IDS gene, which encodes iduronate 2-sulfatase (IDS). We aimed to characterize the clinical characteristics and genotypes of the largest cohort of Chinese patients with MPS II and so gain a deeper understanding of natural disease progression. Patients with confirmed MPS II and without treatment were included. The disease was classified as severe in patients with neurological impairment, and as attenuated in patients aged >6 years without neurological impairment. Of the 201 male patients, 78.1% had severe MPS II. Cognitive regression occurred before age 6 years in 94.3% of patients. Of 122 IDS variants identified, 37 were novel. Among the large gene alteration types identified, only the frequency of IDS-IDS2 recombination was significantly higher in severe versus attenuated MPS II (P = 0.032). Some identified point variants could inform the understanding of genotype-phenotype correlations. In conclusion, this study showed that classification of the disease as attenuated should only be made in patients aged >6 years. Our findings expand the understanding of the genotype-phenotype relationship, inform the diagnostic process, and provide an indication of the likely prognosis.

Improving variant prioritization in exome analysis by entropy-weighted ensemble of multiple tools.

Variant prioritization is a crucial step in the analysis of exome and genome sequencing. Multiple phenotype-driven tools have been developed to automate the variant prioritization process, but the efficacy of these tools in clinical setting with fuzzy phenotypic information and whether ensemble of these tools could outperform single algorithm remains to be assessed. A large rare disease cohort with heterogeneous phenotypic information, including a primary cohort of 1614 patients and a replication cohort of 1904 patients referred to exome sequencing, were recruited to assess the efficacy of variant prioritization and their ensemble. Three freely available tools-Exomiser, Xrare, and DeepPVP-and their ensemble were evaluated. The performance of all three tools was influenced by the attributes of phenotypic input. When combining these three tools by weighted-sum entropy method (EWE3), the ensemble outperformed any single algorithm, achieving a rate of 78% diagnostic variants in top 3 (13% improvement over current best performer, compared to Exomiser: 63%, Xrare: 65%, and DeepPVP: 51%), 88% in top 10 and 96% in top 30. The results were replicated in another independent cohort. Our study supports using entropy-weighted ensemble of multiple tools to improve variant prioritization and accelerate molecular diagnosis in exome/genome sequencing.

[Long-term outcome of hematopoietic stem cell transplantation in two children with Mucopolysaccharidosis].

OBJECTIVE: To explore the long-term efficacy of allogeneic hematopoietic stem cell transplantation (alloHSCT) in patients with Mucopolysaccharidosis (MPS), which has rarely been reported in China. METHODS: A 18-month-old boy and a 23-month-old girl undergoing alloHSCT for MPS VI and MPS IH Shanghai Children's Medical Center on March 30, 2006 and September 6, 2006 were selected as the study subjects. A busulfan-based myeloablative regimen was used as the conditioning regimen. Peripheral stem cells were respectively collected from a human leucocyte antigen (HLA) matched sibling carrier donor and a HLA 9/10 matched unrelated donor. Both patients were followed up for more than 15 years. The functions of internal organs before and after the transplantation were compared, and child 1 was also compared with his untreated brother and healthy brother. RESULTS: Both children have achieved full donor chimerism after the transplantation, and their enzymatic activities have remained stable. The enzymatic activity of the child 1 was slightly lower than normal but similar to that of his carrier donor, whilst that of the child 2 was normal. Both children have attended schools with good academic performance. Compared with his untreated brother, the respiratory function and hearing of child 1 have significantly improved. However, his orthopedic and cardiac disorders have still remained and required medical intervention. For child 2, her obstructive pulmonary disease was resolved and cognitive development was well preserved after the HSCT. Her heart disease has become stabilized and even improved with time, though her corneal clouding and skeletal malformation still required surgery. CONCLUSION: MPS patients can sustain long-term and stable enzymatic activities after successful alloHSCT. Compared with untreated patients, their health can be significantly improved, along with considerably prolonged survival, though the long-term efficacy of HSCT for different organs may vary to a certain extent.

[Consensus on laboratory diagnosis of congenital adrenal hyperplasia due to 21 hydroxylase deficiency].

21 hydroxylase deficiency (21-OHD), the most common form of congenital adrenal hyperplasia, is caused by defects in CYP21A2 gene, which encodes the cytochrome P450 oxidase (P450C21) involved in glucocorticoid and mineralocorticoid synthesis. The diagnosis of 21-OHD is based on the comprehensive evaluation of clinical manifestation, biochemical alteration and molecular genetics results. Due to the complex structure of CYP21A2, special techniques are required to perform delicate analysis to avoid the interference of its pseudogene. Recently, the state-of-the-art diagnostic methods were applied to the clinic gradually, including the steroid hormone profiling and third generation sequencing. To standardize the laboratory diagnosis of 21-OHD, this consensus was drafted on the basis of the extensive knowledge, the updated progress and the published consensuses and guidelines worldwide by expert discussion organized by Rare Diseases Group of Pediatric Branch of Chinese Medical Association, Medical Genetics Branch of Chinese Medical Doctor Association, Birth Defect Prevention and Molecular Genetics Branch of China Maternal and Child Health Association. and Molecular Diagnosis Branch of Shanghai Medical Association.

[Analysis of disease spectrum for abnormal 3-hydroxyisovalerylcarnitine metabolism identified through newborn screening and clinical diagnosis].

OBJECTIVE: To explore the disease spectrum for abnormal 3-hydroxyisovalerylcarnitine (C5OH) metabolism identified through newborn screening and clinical diagnosis patients and the key points for differential diagnosis so as to raise the awareness of pediatricians for such diseases. METHODS: Clinical data of 85 neonates with abnormal C5OH metabolism identified from February 2004 to January 2022 at Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were collected. Their clinical manifestations and results of tandem mass spectrometry (MS/MS), gas chromatography mass spectrometry (GC-MS) and genetic testing were retrospectively analyzed. RESULTS: Among the 85 cases, 46 (54.1%) were identified by neonate screening, whilst 39 (45.9%) were clinically diagnosed patients. Five diseases were diagnosed, including 28 cases with multiple carboxylase deficiency (MCD, 32.9%), 29 cases with 3-methylcrotonyl-coenzymeAcarboxylasedeficiency (MCCD, 34.1%), 4 cases with 3-methylglutaconic acid (3-MGA, 4.7%), 7 cases with 3-hydroxy-3-methylglutaric acid (3-HMG, 8.2%), and 17 cases with beta-ketothiolase deficiency (BKD, 20.0%). The disorders were characterized by sudden onset, anorexia, vomiting, diarrhea, abnormal breathing, consciousness disorder, spasm and developmental delay. CONCLUSION: Among newborns with abnormal C5OH metabolism, MCCD is the most common disorder, which was followed by BKD and MCD. For patients with abnormal C5OH metabolism, MCD is the most common, followed by BKD and 3-HMG. C5OH related diseases have great heterogeneity. Combination of blood acylcarnitine levels, urinary organic acid levels and genetic testing based on clinical characteristics can help to attain the diagnosis.

Diagnosis and follow-up of glycogen storage disease (GSD) type VI from the largest GSD center in China.

Glycogen storage disease (GSD) Type VI is a glycogenolysis disorder caused by variants of PYGL. Knowledge about this disease is limited because only approximately 50 cases have been reported. We investigated the clinical profiles, molecular diagnosis, and treatment outcomes in patients with GSD VI from 2000 to 2021. The main initial clinical features of this cohort include hepatomegaly, short stature, elevated liver transaminases, hypertriglyceridemia, fasting hypoglycemia, and hyperuricemia. After uncooked cornstarch treatment, the stature and biochemical parameters improved significantly (p < 0.05). However, hyperuricemia recurred in most patients during adolescence. Among the 56 GSD VI patients, 54 biallelic variants and two single allelic variants of PYGL were identified, of which 43 were novel. There were two hotspot variants, c.1621-258_2178-23del and c.2467C>T p.(Gln823*), mainly in patients from Southwest and South China. c.1621-258_2178-23del is a 3.6 kb deletion that results in an out-of-frame deletion r.1621_2177del and an in-frame deletion r.1621_2265del. Our data show for the first time that long-term monitoring of uric acid is recommended for older GSD VI patients. This study also broadens the variant spectrum of PYGL and indicates that there are two hot-spot variants in China.

Investigation of GALNS variants and genotype-phenotype correlations in a large cohort of patients with mucopolysaccharidosis type IVA.

Mucopolysaccharidosis type IVA (MPS IVA) is a rare autosomal recessive disorder resulting from the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) caused by pathogenic variants in the GALNS gene. A systematic analysis for genotype-phenotype correlation is essential due to hundreds of variants generating different levels of residual GALNS activity and causing a wide degree of clinical manifestation effects. Here, we retrospectively analyzed clinical and genetic data of 108 unrelated patients with MPS IVA to investigate the variants spectrum of GALNS and assess their clinical effects. In this cohort, 82 patients were classified as severe, 14 as intermediate, and 12 as mild. One hundred and one GALNS variants were identified, of which 47 were novel. Most patients with at least one GALNS null variant were classified as severe phenotype (92%, 33/36). Missense variants mapped to different residues of GALNS protein resulted in different phenotypes in patients with MPS IVA. Ninety-two percent of patients with two missense variants mapped to buried residues were classified as severe (92%, 24/26), while at least one missense variant mapped to surface residues was identified in patients with biallelic missense variants presenting intermediate MPS IVA (78%, 7/9) and presenting mild MPS IVA (86%, 6/7). Our study contributes to a better understanding of the molecular spectrum of GALNS variants and their clinical implications. Based on the data herein reported, we generated a systematic flowchart correlating the GALNS variants to assist in phenotype prediction and classification of patients with MPS IVA.

Resource utilization of medical waste under COVID-19: Waste mask used as crude oil fluidity improver.

The disposal of medical waste has become an increasing environmental issue since the COVID-19 epidemic outbreaks. Conventional disposal methods have produced waste of fossil resources and environmental problems. In this study, the waste medical mask-derived materials were tested as viscosity reducer and pour point depressant to evaluate the possibility of being used as crude oil fluidity improver. The results show that the materials derived from the three parts of the waste medical mask can reduce the viscosity and pour point of each crude oil samples from different oilfields in China. The middle layer of the medical mask (PP-2) displays the highest efficiency, and the viscosity reduction rate and maximum pour point reduction reaches 81% and 8.3 °C at 500 ppm, respectively. A probable mechanism of improving rheological properties of the crude oil samples by the medical mask-derived materials was further proposed after the differential scanning calorimetry (DSC) analysis and the wax crystal morphology analysis. We hope this work could provide a way to solve the current environmental issues under COVID-19.

[The progress, challenges and opportunities of neonatal genome screening].

Neonatal screening is one of the crucial parts of the tertiary prevention strategy to reduce congenital disability. Traditional neonatal screening, mainly focusing on genetic metabolic diseases, has limitations in disease types and requires genetic testing for further validation and accurate typing. Currently, conducting genetic screening based on biochemical metabolite screening has become the trend in neonatal screening. This article synthesizes the current state of neonatal genome screening at home and abroad. Herein, the comprehensive concepts of "SNV Plus" (single nucleotide variation plus) and "CNV Plus" (copy number variation plus) have been proposed to develop a new technology that can detect the gene structure of SNV and CNV simultaneously and improve the level of neonatal genome screening based on characteristics of the pathogenic gene structure.

Clinical, biochemical, and genotype-phenotype correlations of 118 patients with Niemann-Pick disease Types A/B.

Niemann-Pick disease Types A and B (NPA/B) are autosomal recessive disorders caused by variants in the sphingomyelin phosphodiesterase-1 (SMPD1) gene. This study aimed to describe and characterize a cohort of 118 patients diagnosed with NPA/B based on clinical, biochemical, and molecular findings, and to identify sound correlations between laboratory findings and clinical presentations. Decreased peripheral leukocyte acid sphingomyelinase activity levels and increased plasma 7-ketocholesterol levels were significantly correlated with disease onset and severity of the clinical course. We identified 92 different sequence SMPD1 variants, including 41 novel variants, in 118 NPA/B patients (19 NPA, 24 intermediate type, 75 NPB). The most prevalent mutation was p.Arg602His, which accounted for 9.3% of the alleles. Patients homozygous for p.Arg602His or p.Asn522Ser showed a late-onset form of the NPB phenotype. The homozygous SMPD1 variant p.Tyr500His correlated with the early-onset NPB clinical form. Additionally, homozygous variants p.His284SerfsX18, p.Phe465Ser, and p.Ser486Arg were associated with the neuronopathic NPA clinical form. The homozygous variant p.Arg3AlafsX74 was associated with the intermediate clinical form. Our study contributes to the understanding of the natural history of NPA/B and assists in the development of efficacious treatments for patients afflicted with this devastating lysosomal storage disorder.

De Novo Mutations of CCNK Cause a Syndromic Neurodevelopmental Disorder with Distinctive Facial Dysmorphism.

Neurodevelopment is a transcriptionally orchestrated process. Cyclin K, a regulator of transcription encoded by CCNK, is thought to play a critical role in the RNA polymerase II-mediated activities. However, dysfunction of CCNK has not been linked to genetic disorders. In this study, we identified three unrelated individuals harboring de novo heterozygous copy number loss of CCNK in an overlapping 14q32.3 region and one individual harboring a de novo nonsynonymous variant c.331A>G (p.Lys111Glu) in CCNK. These four individuals, though from different ethnic backgrounds, shared a common phenotype of developmental delay and intellectual disability (DD/ID), language defects, and distinctive facial dysmorphism including high hairline, hypertelorism, thin eyebrows, dysmorphic ears, broad nasal bridge and tip, and narrow jaw. Functional assay in zebrafish larvae showed that Ccnk knockdown resulted in defective brain development, small eyes, and curly spinal cord. These defects were partially rescued by wild-type mRNA coding CCNK but not the mRNA with the identified likely pathogenic variant c.331A>G, supporting a causal role of CCNK variants in neurodevelopmental disorders. Taken together, we reported a syndromic neurodevelopmental disorder with DD/ID and facial characteristics caused by CCNK variations, possibly through a mechanism of haploinsufficiency.

Diagnostic yield of additional exome sequencing after the detection of long continuous stretches of homozygosity (LCSH) in SNP arrays.

Long continuous stretches of homozygosity (LCSH) are associated with risk of recessive disorders. Though LCSH can be detected by SNP microarrays, additional testing is necessary to clarify the clinical significance. This study is to assess the yield of additional exome sequencing (ES) after LCSH detection and inform the likelihood of eventual diagnosis. In 2226 patients referred to SNP microarrays, 35 patients met the criteria of indicative LCSH. These patients were recruited and went through additional ES. The diagnostic yield was analyzed, and the LCSH pattern was compared between eventually diagnosed cases and those undiagnosed. The results showed additional ES attained a diagnostic yield of 31.4% (11/35), but only one-third of the yield (11.4%, 4/35) was relevant to LCSH. In contrast, two-thirds of the diagnostic variants (20%, 7/35) were de novo or dominantly inherited, irrelevant to the original LCSH finding. No particular LCSH pattern, including the chromosomal coverage or LCSH size, was found to associate with the diagnostic outcome. We concluded that additional ES after LCSH detection could reveal diagnostic variants, but it is strongly recommended to consider all possible inheritance mode, as the diagnostic variants may be irrelevant to the original LCSH finding.

Gene expression profiles in the brain of phenylketonuria mouse model reversed by the low phenylalanine diet therapy.

To gain insight into the potential protective mechanisms of low phenylalanine diet (LPD) in phenylketonuria (PKU), gene expression profiles were studied in the cerebral cortex and hippocampus of a PKU mouse model (BTBR-Pahenu2). PKU mice were fed with low Phe diet (LPD-PKU group) and normal diet (PKU group). Wild-type mice were treated with normal diet (WT group) as control. After 12 weeks, we detected gene expression in the cerebral cortex and hippocampus of the three groups by RNA-sequencing, and then screened the differentially-expressed genes (DEGs) among the groups by bioinformatics analyses. We found that the transcriptional profiles of both cerebral cortex and hippocampus changed markedly between PKU and WT mice. Furthermore, LPD changed the transcriptional profiles of the cerebral cortex and the hippocampus of PKU mice significantly, especially in the cerebral cortex, with overlaps of genes that changed with the disease and altered by LPD treatment. In the cerebral cortex, hundreds of DEGs enriched in a wide spectrum of biological processes, molecular function, and cellular component, including nervous system development, axon development and guidance, calcium ion binding, modulation of chemical synaptic transmission, and regulation of protein kinase activity. In the hippocampus, the overlapping genes were enriched in positive regulation of long term synaptic, negative regulation of excitatory postsynaptic potential, positive regulation of synapse assembly. Our results showed that genes impaired in PKU and then rescued by LPD might indicate the potential protective capability of LPD in the PKU brain.