Estimation of hereditary fructose intolerance prevalence in the Chinese population

Characterization of a human induced pluripotent stem cell line (FDCHi015-A) derived from PBMCs of a patient harbouring ALDOB mutation

Hereditary fructose intolerance (HFI) is an autosomal recessive metabolic disease associated with a mutation in the aldolase B gene on chromosome 9q31. In this study, we generated a human-induced pluripotent stem cell (hiPSC) line, FDCHi015-A, from peripheral blood mononuclear cells (PBMCs) of a patient carrying the compound heterozygous mutations c.360_364delCAAA and c.1013C > T in exons 4 and 9 of the ALDOB gene, respectively. The iPSCs with the confirmed patient-specific mutation demonstrate pluripotency markers expression, a normal karyotype, and the ability to differentiate into derivatives of three germ layers.

Fructose-1,6-bisphosphatase deficiency: estimation of prevalence in the Chinese population and analysis of genotype-phenotype association

Objective

Fructose-1,6-bisphosphatase deficiency (FBP1D) is a rare inborn error due to mutations in the FBP1 gene. The genetic spectrum of FBP1D in China is unknown, also nonspecific manifestations confuse disease diagnosis. We systematically estimated the FBP1D prevalence in Chinese and explored genotype-phenotype association.

Methods

We collected 101 FBP1 variants from our cohort and public resources, and manually curated pathogenicity of these variants. Ninety-seven pathogenic or likely pathogenic variants were used in our cohort to estimate Chinese FBP1D prevalence by three methods: 1) carrier frequency, 2) permutation and combination, 3) Bayesian framework. Allele frequencies (AFs) of these variants in our cohort, China Metabolic Analytics Project (ChinaMAP) and gnomAD were compared to reveal the different hotspots in Chinese and other populations. Clinical and genetic information of 122 FBP1D patients from our cohort and published literature were collected to analyze the genotype-phenotypes association. Phenotypes of 68 hereditary fructose intolerance (HFI) patients from our previous study were used to compare the phenotypic differences between these two fructose metabolism diseases.

Results

The estimated Chinese FBP1D prevalence was 1/1,310,034. In the Chinese population, c.490G>A and c.355G>A had significantly higher AFs than in the non-Finland European population, and c.841G>A had significantly lower AF value than in the South Asian population (all p values < 0.05). The genotype-phenotype association analyses showed that patients carrying homozygous c.841G>A were more likely to present increased urinary glycerol, carrying two CNVs (especially homozygous exon1 deletion) were often with hepatic steatosis, carrying compound heterozygous variants were usually with lethargy, and carrying homozygous variants were usually with ketosis and hepatic steatosis (all p values < 0.05). By comparing to phenotypes of HFI patients, FBP1D patients were more likely to present hypoglycemia, metabolic acidosis, and seizures (all p-value < 0.05).

Conclusion

The prevalence of FBP1D in the Chinese population is extremely low. Genetic sequencing could effectively help to diagnose FBP1D.

PICOTEES: a privacy-preserving online service of phenotype exploration for genetic-diagnostic variants from Chinese children cohorts

The growth in biomedical data resources has raised potential privacy concerns and risks of genetic information leakage. For instance, exome sequencing aids clinical decisions by comparing data through web services, but it requires significant trust between users and providers. To alleviate privacy concerns, the most commonly used strategy is to anonymize sensitive data. Unfortunately, studies have shown that anonymization is insufficient to protect against reidentification attacks. Recently, privacy-preserving technologies have been applied to preserve application utility while protecting the privacy of biomedical data. We present the PICOTEES framework, a privacy-preserving online service of phenotype exploration for genetic-diagnostic variants (https://birthdefectlab.cn:3000/). PICOTEES enables privacy-preserving queries of the phenotype spectrum for a single variant by utilizing trusted execution environment technology, which can protect the privacy of the user's query information, backend models, and data, as well as the final results. We demonstrate the utility and performance of PICOTEES by exploring a bioinformatics dataset. The dataset is from a cohort containing 20,909 genetic testing patients with 3,152,508 variants from the Children's Hospital of Fudan University in China, dominated by the Chinese Han population (>99.9%). Our query results yield a large number of unreported diagnostic variants and previously reported pathogenicity.

Sweet ending: When genetics prevent a dramatic CDG diagnostic mistake

Herein, we described the case of a newborn male, from consanguineous parents, who developed, at day 11 of life, an obstructive hydrocephalus resulting from bilateral cerebellar hemorrhage without evident cause. Then, at 1 month, he developed a fulminant hepatitis with hyperammonia, hyperlactatemia and metabolic acidosis. Infectious and first line metabolic explorations were normal. Screening for congenital disorder of glycosylation (CDG) was performed using capillary electrophoresis and western blot of serum transferrin. Abnormal results were evocative of mannose-phosphate isomerase deficiency (MPI-CDG or CDG-Ib) as it can be responsible for fulminant hepatitis, digestive disease, developmental delay, and coagulopathy. However, trio whole exome sequencing revealed a pathogenic variant at the homozygous state in ALDOB, responsible for hereditary fructose intolerance (HFI), an inherited metabolic disorder with excellent prognosis under a fructose-free diet. HFI had not been previously evoked in view of the absence of diet diversification, but meticulous inquiry revealed that parents systematically added white sugar to the bottle milk of their child, unintentionally triggering potentially fatal HFI decompensations. Early genetic analysis upsetted both diagnosis and prognosis for this infant who had excellent development after fructose removal. This full-of-surprises diagnostic approach illustrates the importance of an integrative collaboration between clinicians, biochemists, and geneticists.

Identification of a novel mutation in the ALDOB gene in hereditary fructose intolerance

OBJECTIVES

Hereditary fructose intolerance (HFI) is caused by aldolase B enzyme deficiency. There has been no report about HFI from Iran and the type of mutations has not been reported in the Iranian population so far.

CASE PRESENTATION

Herein we report a 2 year old girl presented with failure to thrive, hepatomegaly, and liver dysfunction. The primary impression has been hepatic glycogen storage disease type 1 or 6. This diagnosis was not confirmed by laboratory data and liver biopsy. Therefore, targeted-gene sequencing (TGS) covering 450 genes involved in inborn errors in metabolic diseases was performed. The results of TGS showed a rare novel homozygous pathogenic variant c.944del (p.Gly315ValfsTer15) in the ALDOB gene.

CONCLUSIONS

This report introduces a novel variant that expands the mutational spectrum of the ALDOB gene in patients with HFI.