Application of next generation sequencing in the screening of monogenic diseases in China,2021:a consensus among Chinese newborn screening experts

Newborn screening(NBS)refers to a maternal and newborn healthcare technology,in which special examinations of congenital and genetic diseases that could seriously impact the health of newborns,are implemented during the neonatal period to provide early diagnosis and treatment[1].With a history of more than 60 years,NBS has advanced greatly due to technological progress resulting in significant improvement in the number of diseases covered by NBS and in screening efficiency[2-7].

A multicenter prospective study of next-generation sequencing-based newborn screening for monogenic genetic diseases in China

Background Newborn screening(NBS)is an important and successful public health program that helps improve the long-term clinical outcomes of newborns by providing early diagnosis and treatment of certain inborn diseases.The develop-ment of next-generation sequencing(NGS)technology provides new opportunities to expand current newborn screening methodologies.Methods We designed a a newborn genetic screening(NBGS)panel targeting 135 genes associated with 75 inborn disorders by multiplex PCR combined with NGS.With this panel,a large-scale,multicenter,prospective multidisease analysis was conducted on dried blood spot(DBS)profiles from 21,442 neonates nationwide.Results We presented the positive detection rate and carrier frequency of diseases and related variants in different regions;and 168(0.78%)positive cases were detected.Glucose-6-Phosphate Dehydrogenase deficiency(G6PDD)and phenylketonuria(PKU)had higher prevalence rates,which were significantly different in different regions.The positive detection of G6PD variants was quite common in south China,whereas PAH variants were most commonly identified in north China.In addi-tion,NBGS identified 3 cases with DUOX2 variants and one with SLC25A13 variants,which were normal in conventional NBS,but were confirmed later as abnormal in repeated biochemical testing after recall.Eighty percent of high-frequency gene carriers and 60%of high-frequency variant carriers had obvious regional differences.On the premise that there was no significant difference in birth weight and gestational age,the biochemical indicators of SLC22A5 c.1400C>G and ACADSB c.1165A>G carriers were significantly different from those of non-carriers.Conclusions We demonstrated that NBGS is an effective strategy to identify neonates affected with treatable diseases as a supplement to current NBS methods.Our data also showed that the prevalence of diseases has significant regional charac-teristics,which provides a theoretical basis for screening diseases in different regions.

FMR1 allele frequencies in 51,000 newborns:a large-scale population study in China

Background Fragile X syndrome(FXS).caused by CGG-repeat expansion in FMR1 promoter,is one of the most common causes of mental retardation.Individuals with full mutation and premutation alleles have a high risk of psychophysiological disorder and of having affected offspring.Frequencies of FMR1 alleles in general newborns have been reported in Caucasians but have not been investigated in the large-scale population in the mainland of China.Methods The sizes of FMRI CGG-repeats were analyzed in 51,661 newborns(28,114 males and 23,547 females)and also in a cohort of 33 children diagnosed with developmental delay using GC-rich polymerase chain reaction(PCR)and triple repeat primed PCR.Results The frequency of CGG repeats>100 was 1/9371 in males and 1/5887 in females,and the frequency of CGG repeats>54 was 1/1561 in males and 1/1624 in females.FMRJ full mutation and premutation were identified in 27.27%of children who had Ages and Stages Questionnaire scores less than two standard deviations from the cutoff value.Conclusions Our study revealed the prevalence of FXS in China and improved the sample databases of FXS,suggesting that the prevalence of FXS in Chinese is higher than estimated previously and that FXS screening can be advised to high-risk families.

Novel ACADVL variants resulting in mitochondrial defects in long-chain acyl-CoA dehydrogenase deficiency

The pathogenesis of very-long-chain acyl-CoA dehydrogenase(VLCAD)deficiency is highly heterogeneous and still unclear.Additional novel variants have been recently detected in the population.The molecular and cellular effects of these previously unreported variants are still poorly understood and require further characterization.To address this problem,we have evaluated the various functions and biochemical consequences of six novel missense variants that lead to mild VLCAD deficiency.Marked deficiencies in fatty acid oxidation(FAO)and other mitochondrial defects were observed in cells carrying one of these six variants(c.541 C>T,c.863 T>G,c.895 A>G,c.1238 T>C,c.1276 G>A,and c.1505 T>A),including reductions in mitochondrial respiratory-chain function and adenosine teriphosphate(ATP)production,and increased levels of mitochondrial reactive oxygen species(ROS).Intriguingly,higher apoptosis levels were found in cells carrying the mutant VLCAD under glucose-limited stress.Moreover,the stability of the mutant homodimer was disturbed,and major conformational changes in each mutant VLCAD structure were predicted by molecular dynamics(MD)simulation.The data presented here may provide valuable information for improving management of diagnosis and treatment of VLCAD deficiency and for a better understanding of the general molecular bases of disease variability.